First cut at a higher-level api

lmdb-sys/Cargo.toml

@@ -12,6 +12,9 @@ build = "build.rs"
 
 name = "lmdb-sys"
 
+[dependencies.rust-bindgen]
+rust-bindgen = "*"
+
 [build-dependencies.pkg-config]
 pkg-config = "*"
 

lmdb-sys/build.rs

@@ -13,6 +13,6 @@ fn main() {
         gcc::compile_library("liblmdb.a",
                              &Default::default(),
                              &[mdb.join("mdb.c").as_str().unwrap(),
-                               mdb.join("midl.c").as_str().unwrap()])
+                               mdb.join("midl.c").as_str().unwrap()]);
     }
 }

lmdb-sys/mdb

@@ -1 +1 @@
-Subproject commit 9a8eb95674c7b500cfe5f44d03493ff76c9fc0c1
+Subproject commit 9cc04f604f80f033d712f5f1faeb4ed97ca74f40

lmdb-sys/src/constants.rs

@@ -1,4 +1,4 @@
-use libc::c_uint;
+use libc::{c_int, c_uint};
 
 bitflags! {
     #[doc="Environment Options"]
@@ -120,39 +120,39 @@ bitflags! {
             #[doc="Keys are strings to be compared in reverse order, from the end"]
             #[doc="of the strings to the beginning. By default, Keys are treated as strings and"]
             #[doc="compared from beginning to end."]
-            const MDB_REVERSEKEY = 0x02,
+            const MDB_REVERSEKEY = 0x02, // 2
 
             #[doc="Duplicate keys may be used in the database. (Or, from another perspective,"]
             #[doc="keys may have multiple data items, stored in sorted order.) By default"]
             #[doc="keys must be unique and may have only a single data item."]
-            const MDB_DUPSORT = 0x04,
+            const MDB_DUPSORT = 0x04, // 4
 
             #[doc="Keys are binary integers in native byte order. Setting this option"]
             #[doc="requires all keys to be the same size, typically sizeof(int)"]
             #[doc="or sizeof(size_t)."]
-            const MDB_INTEGERKEY = 0x08,
+            const MDB_INTEGERKEY = 0x08, // 8
 
             #[doc="This flag may only be used in combination with `MDB_DUPSORT`. This option"]
             #[doc="tells the library that the data items for this database are all the same"]
             #[doc="size, which allows further optimizations in storage and retrieval. When"]
             #[doc="all data items are the same size, the `MDB_GET_MULTIPLE` and `MDB_NEXT_MULTIPLE`"]
             #[doc="cursor operations may be used to retrieve multiple items at once."]
-            const MDB_DUPFIXED = 0x10,
+            const MDB_DUPFIXED = 0x10, // 16
 
             #[doc="This option specifies that duplicate data items are also integers, and"]
             #[doc="should be sorted as such."]
-            const MDB_INTEGERDUP = 0x20,
+            const MDB_INTEGERDUP = 0x20, // 32
 
             #[doc="This option specifies that duplicate data items should be compared as"]
             #[doc="strings in reverse order."]
-            const MDB_REVERSEDUP = 0x40,
+            const MDB_REVERSEDUP = 0x40, // 64
-
-            #[doc="Create the named database if it doesn't exist. This option is not"]
-            #[doc="allowed in a read-only transaction or a read-only environment."]
-            const MDB_CREATE = 0x40000,
     }
 }
 
+/// Create the named database if it doesn't exist. This option is not
+/// allowed in a read-only transaction or a read-only environment.
+pub const MDB_CREATE: c_uint = 0x40000;
+
 bitflags! {
     #[doc="Write Options"]
     #[deriving(Show)]
@@ -180,15 +180,6 @@ bitflags! {
         #[doc="record followed by an insert."]
         const MDB_CURRENT = 0x40,
 
-        #[doc="Reserve space for data of the given size, but"]
-        #[doc="don't copy the given data. Instead, return a pointer to the"]
-        #[doc="reserved space, which the caller can fill in later - before"]
-        #[doc="the next update operation or the transaction ends. This saves"]
-        #[doc="an extra memcpy if the data is being generated later."]
-        #[doc="LMDB does nothing else with this memory, the caller is expected"]
-        #[doc="to modify all of the space requested."]
-        const MDB_RESERVE = 0x10000,
-
         #[doc="Append the given key/data pair to the end of the"]
         #[doc="database. No key comparisons are performed. This option allows"]
         #[doc="fast bulk loading when keys are already known to be in the"]
@@ -200,3 +191,81 @@ bitflags! {
         const MDB_APPENDDUP = 0x40000,
     }
 }
+
+/// Reserve space for data of the given size, but don't copy the given data. Instead, return a
+/// pointer to the reserved space, which the caller can fill in later - before the next update
+/// operation or the transaction ends. This saves an extra memcpy if the data is being generated
+/// later. LMDB does nothing else with this memory, the caller is expected to modify all of the
+/// space requested.
+pub const MDB_RESERVE: c_uint = 0x10000;
+
+
+///////////////////////////////////////////////////////////////////////////////////////////////////
+//// Return Codes
+///////////////////////////////////////////////////////////////////////////////////////////////////
+
+/// Successful result.
+pub const MDB_SUCCESS: c_int = 0;
+
+/// key/data pair already exists.
+pub const MDB_KEYEXIST: c_int = -30799;
+
+/// key/data pair not found (EOF).
+pub const MDB_NOTFOUND: c_int = -30798;
+
+/// Requested page not found - this usually indicates corruption.
+pub const MDB_PAGE_NOTFOUND: c_int = -30797;
+
+/// Located page was wrong type.
+pub const MDB_CORRUPTED: c_int = -30796;
+
+/// Update of meta page failed or environment had fatal error.
+pub const MDB_PANIC	: c_int = -30795;
+
+/// Environment version mismatch.
+pub const MDB_VERSION_MISMATCH: c_int = -30794;
+
+/// File is not a valid LMDB file.
+pub const MDB_INVALID: c_int = -30793;
+
+/// Environment mapsize reached.
+pub const MDB_MAP_FULL: c_int = -30792;
+
+/// Environment maxdbs reached.
+pub const MDB_DBS_FULL: c_int = -30791;
+
+/// Environment maxreaders reached.
+pub const MDB_READERS_FULL: c_int = -30790;
+
+/// Too many TLS keys in use - Windows only.
+pub const MDB_TLS_FULL: c_int = -30789;
+
+/// Txn has too many dirty pages.
+pub const MDB_TXN_FULL: c_int = -30788;
+
+/// Cursor stack too deep - internal error.
+pub const MDB_CURSOR_FULL: c_int = -30787;
+
+/// Page has not enough space - internal error.
+pub const MDB_PAGE_FULL: c_int = -30786;
+
+/// Database contents grew beyond environment mapsize.
+pub const MDB_MAP_RESIZED: c_int = -30785;
+
+/// MDB_INCOMPATIBLE: Operation and DB incompatible, or DB flags changed.
+pub const MDB_INCOMPATIBLE: c_int = -30784;
+
+/// Invalid reuse of reader locktable slot.
+pub const MDB_BAD_RSLOT: c_int = -30783;
+
+/// Transaction cannot recover - it must be aborted.
+pub const MDB_BAD_TXN: c_int = -30782;
+
+/// Unsupported size of key/DB name/data, or wrong DUPFIXED size.
+pub const MDB_BAD_VALSIZE: c_int = -30781;
+
+/// The specified DBI was changed unexpectedly.
+pub const MDB_BAD_DBI: c_int = -30780;
+
+/// The last defined error code.
+pub const MDB_LAST_ERRCODE: c_int = MDB_BAD_DBI;

lmdb-sys/src/lib.rs

@@ -1,202 +1,12 @@
-//! Provides extern declarations for `liblmdb`. Additionally, this crate provides `liblmdb` as a
+#![allow(dead_code, uppercase_variables, non_camel_case_types)]
-//! native Cargo dependency.
+#![feature(phase,globs)]
 
-#![allow(non_camel_case_types)]
+#[phase(plugin)] extern crate bindgen;
 extern crate libc;
 
-use libc::{c_int, c_uint, c_void, c_char, size_t};
+use libc::{size_t, mode_t};
+pub use constants::*;
 
-pub type mdb_mode_t = libc::mode_t;
+mod constants;
-pub type mdb_filehandle_t = libc::c_int;
 
-pub type MDB_dbi = c_uint;
+bindgen!("../mdb/libraries/liblmdb/lmdb.h", match="lmdb.h", link="lmdb")
-
-pub type MDB_rel_func = extern fn(*mut MDB_val, *mut c_void, *mut c_void, *mut c_void);
-pub type MDB_msg_func = extern fn(*const c_char, *mut c_void) -> c_int;
-pub type MDB_cmp_func = extern fn(*const MDB_val, *const MDB_val) -> c_int;
-
-#[repr(C)]
-pub struct MDB_val {
-    pub mv_size: size_t,
-    pub mv_data: *mut c_void,
-}
-
-#[repr(C)]
-pub struct MDB_env;
-
-#[repr(C)]
-pub struct MDB_txn;
-
-#[repr(C)]
-pub struct MDB_cursor;
-
-#[repr(C)]
-pub struct MDB_stat {
-    ms_psize: c_uint,
-    ms_depth: c_uint,
-    ms_branch_pages: size_t,
-    ms_leaf_pages: size_t,
-    ms_overflow_pages: size_t,
-    ms_entries: size_t
-}
-
-#[repr(C)]
-pub struct MDB_envinfo {
-    me_mapaddr: *const c_void,
-    me_mapsize: size_t,
-    me_last_pgno: size_t,
-    me_last_txnid: size_t,
-    me_maxreaders: c_uint,
-    me_numreaders: c_uint
-}
-
-#[repr(C)]
-pub enum MDB_cursor_op {
-    /// Position at first key/data item.
-    MDB_FIRST,
-    /// Position at first data item of current key. Only for `MDB_DUPSORT`.
-    MDB_FIRST_DUP,
-    /// Position at key/data pair. Only for `MDB_DUPSORT`.
-    MDB_GET_BOTH,
-    /// position at key, nearest data. Only for `MDB_DUPSORT`.
-    MDB_GET_BOTH_RANGE,
-    /// Return key/data at current cursor position.
-    MDB_GET_CURRENT,
-    /// Return key and up to a page of duplicate data items from current cursor position. Move
-    /// cursor to prepare for `MDB_NEXT_MULTIPLE`. Only for `MDB_DUPFIXED`.
-    MDB_GET_MULTIPLE,
-    /// Position at last key/data item.
-    MDB_LAST,
-    /// Position at last data item of current key. Only for `MDB_DUPSORT`.
-    MDB_LAST_DUP,
-    /// Position at next data item.
-    MDB_NEXT,
-    /// Position at next data item of current key. Only for `MDB_DUPSORT`.
-    MDB_NEXT_DUP,
-    /// Return key and up to a page of duplicate data items from next cursor position. Move cursor
-    /// to prepare for `MDB_NEXT_MULTIPLE`. Only for `MDB_DUPFIXED`.
-    MDB_NEXT_MULTIPLE,
-    /// Position at first data item of next key.
-    MDB_NEXT_NODUP,
-    /// Position at previous data item.
-    MDB_PREV,
-    /// Position at previous data item of current key. Only for `MDB_DUPSORT`.
-    MDB_PREV_DUP,
-    /// Position at last data item of previous key.
-    MDB_PREV_NODUP,
-    /// Position at specified key.
-    MDB_SET,
-    /// Position at specified key, return key + data.
-    MDB_SET_KEY,
-    /// Position at first key greater than or equal to specified key.
-    MDB_SET_RANGE,
-}
-
-// Return codes
-pub const MDB_SUCCESS: c_int = 0;
-pub const MDB_KEYEXIST: c_int = -30799;
-pub const MDB_NOTFOUND: c_int = -30798;
-pub const MDB_PAGE_NOTFOUND: c_int = -30797;
-pub const MDB_CORRUPTED: c_int = -30796;
-pub const MDB_PANIC: c_int = -30795;
-pub const MDB_VERSION_MISMATCH: c_int = -30794;
-pub const MDB_INVALID: c_int = -30793;
-pub const MDB_MAP_FULL: c_int = -30792;
-pub const MDB_DBS_FULL: c_int = -30791;
-pub const MDB_READERS_FULL: c_int = -30790;
-pub const MDB_TLS_FULL: c_int = -30789;
-pub const MDB_TXN_FULL: c_int = -30788;
-pub const MDB_CURSOR_FULL: c_int = -30787;
-pub const MDB_PAGE_FULL: c_int = -30786;
-pub const MDB_MAP_RESIZED: c_int = -30785;
-pub const MDB_INCOMPATIBLE: c_int = -30784;
-pub const MDB_BAD_RSLOT: c_int = -30783;
-pub const MDB_BAD_TXN: c_int = -30782;
-pub const MDB_BAD_VALSIZE: c_int = -30781;
-pub const MDB_BAD_DBI: c_int = -30780;
-
-// Write flags
-pub const MDB_NOOVERWRITE: c_uint = 0x10;
-pub const MDB_NODUPDATA: c_uint = 0x20;
-pub const MDB_CURRENT: c_uint = 0x40;
-pub const MDB_RESERVE: c_uint = 0x10000;
-pub const MDB_APPEND: c_uint = 0x20000;
-pub const MDB_APPENDDUP: c_uint = 0x40000;
-pub const MDB_MULTIPLE: c_uint = 0x80000;
-
-// Database flags
-pub const MDB_REVERSEKEY: c_uint = 0x02;
-pub const MDB_DUPSORT: c_uint = 0x04;
-pub const MDB_INTEGERKEY: c_uint = 0x08;
-pub const MDB_DUPFIXED: c_uint = 0x10;
-pub const MDB_INTEGERDUP: c_uint = 0x20;
-pub const MDB_REVERSEDUP: c_uint =  0x40;
-pub const MDB_CREATE: c_uint = 0x40000;
-
-// Environment flags
-pub const MDB_FIXEDMAP: c_uint =  0x01;
-pub const MDB_NOSUBDIR: c_uint = 0x4000;
-pub const MDB_NOSYNC: c_uint = 0x10000;
-pub const MDB_RDONLY: c_uint = 0x20000;
-pub const MDB_NOMETASYNC: c_uint = 0x40000;
-pub const MDB_WRITEMAP: c_uint = 0x80000;
-pub const MDB_MAPASYNC: c_uint = 0x100000;
-pub const MDB_NOTLS: c_uint = 0x200000;
-pub const MDB_NOLOCK: c_uint =  0x400000;
-pub const MDB_NORDAHEAD: c_uint = 0x800000;
-pub const MDB_NOMEMINIT: c_uint =  0x1000000;
-
-extern {
-    pub fn mdb_version(major: *mut c_int, minor: *mut c_int, patch: *mut c_int) -> *mut c_char;
-    pub fn mdb_strerror(err: c_int) -> *mut c_char;
-    pub fn mdb_env_create(env: *mut *mut MDB_env) -> c_int;
-    pub fn mdb_env_open(env: *mut MDB_env, path: *const c_char, flags: c_uint, mode: mdb_mode_t) -> c_int;
-    pub fn mdb_env_copy(env: *mut MDB_env, path: *const c_char) -> c_int;
-    pub fn mdb_env_copyfd(env: *mut MDB_env, fd: mdb_filehandle_t) -> c_int;
-    pub fn mdb_env_copy2(env: *mut MDB_env, path: *const c_char, flags: c_uint) -> c_int;
-    pub fn mdb_env_copyfd2(env: *mut MDB_env, fd: mdb_filehandle_t, flags: c_uint) -> c_int;
-    pub fn mdb_env_stat(env: *mut MDB_env, stat: *mut MDB_stat) -> c_int;
-    pub fn mdb_env_info(env: *mut MDB_env, stat: *mut MDB_envinfo) -> c_int;
-    pub fn mdb_env_sync(env: *mut MDB_env, force: c_int) -> c_int;
-    pub fn mdb_env_close(env: *mut MDB_env);
-    pub fn mdb_env_set_flags(env: *mut MDB_env, flags: c_uint, onoff: c_int) -> c_int;
-    pub fn mdb_env_get_flags(env: *mut MDB_env, flags: *mut c_uint) -> c_int;
-    pub fn mdb_env_get_path(env: *mut MDB_env, path: *const *const c_char) -> c_int;
-    pub fn mdb_env_get_fd(env: *mut MDB_env, fd: *mut mdb_filehandle_t) -> c_int;
-    pub fn mdb_env_set_mapsize(env: *mut MDB_env, size: size_t) -> c_int;
-    pub fn mdb_env_set_maxreaders(env: *mut MDB_env, readers: c_uint) -> c_int;
-    pub fn mdb_env_get_maxreaders(env: *mut MDB_env, readers: *mut c_uint) -> c_int;
-    pub fn mdb_env_set_maxdbs(env: *mut MDB_env, dbs: MDB_dbi) -> c_int;
-    pub fn mdb_env_get_maxkeysize(env: *mut MDB_env) -> c_int;
-    pub fn mdb_txn_begin(env: *mut MDB_env, parent: *mut MDB_txn, flags: c_uint, txn: *mut *mut MDB_txn) -> c_int;
-    pub fn mdb_txn_env(txn: *mut MDB_txn) -> *mut MDB_env;
-    pub fn mdb_txn_commit(txn: *mut MDB_txn) -> c_int;
-    pub fn mdb_txn_abort(txn: *mut MDB_txn);
-    pub fn mdb_txn_reset(txn: *mut MDB_txn);
-    pub fn mdb_txn_renew(txn: *mut MDB_txn) -> c_int;
-    pub fn mdb_dbi_open(txn: *mut MDB_txn, name: *const c_char, flags: c_uint, dbi: *mut MDB_dbi) -> c_int;
-    pub fn mdb_stat(txn: *mut MDB_txn, dbi: MDB_dbi, stat: *mut MDB_stat) -> c_int;
-    pub fn mdb_dbi_flags(txn: *mut MDB_txn, dbi: MDB_dbi, flags: *mut c_uint) -> c_int;
-    pub fn mdb_dbi_close(txn: *mut MDB_env, dbi: MDB_dbi);
-    pub fn mdb_drop(txn: *mut MDB_txn, dbi: MDB_dbi, del: c_int) -> c_int;
-    pub fn mdb_set_compare(txn: *mut MDB_txn, dbi: MDB_dbi, cmp: *mut MDB_cmp_func) -> c_int;
-    pub fn mdb_set_dupsort(txn: *mut MDB_txn, dbi: MDB_dbi, cmp: *mut MDB_cmp_func) -> c_int;
-    pub fn mdb_set_relfunc(txn: *mut MDB_txn, dbi: MDB_dbi, rel: *mut MDB_rel_func) -> c_int;
-    pub fn mdb_set_relctx(txn: *mut MDB_txn, dbi: MDB_dbi, ctx: *mut c_void) -> c_int;
-    pub fn mdb_get(txn: *mut MDB_txn, dbi: MDB_dbi, key: *mut MDB_val, data: *mut MDB_val) -> c_int;
-    pub fn mdb_put(txn: *mut MDB_txn, dbi: MDB_dbi, key: *mut MDB_val, data: *mut MDB_val, flags: c_uint) -> c_int;
-    pub fn mdb_del(txn: *mut MDB_txn, dbi: MDB_dbi, key: *mut MDB_val, data: *mut MDB_val) -> c_int;
-    pub fn mdb_cursor_open(txn: *mut MDB_txn, dbi: MDB_dbi, cursor: *mut *mut MDB_cursor) -> c_int;
-    pub fn mdb_cursor_close(cursor: *mut MDB_cursor);
-    pub fn mdb_cursor_renew(txn: *mut MDB_txn, cursor: *mut MDB_cursor) -> c_int;
-    pub fn mdb_cursor_txn(cursor: *mut MDB_cursor) -> *mut MDB_txn;
-    pub fn mdb_cursor_dbi(cursor: *mut MDB_cursor) -> MDB_dbi;
-    pub fn mdb_cursor_get(cursor: *mut MDB_cursor, key: *mut MDB_val, data: *mut MDB_val, op: MDB_cursor_op) -> c_int;
-    pub fn mdb_cursor_put(cursor: *mut MDB_cursor, key: *mut MDB_val, data: *mut MDB_val, flags: c_uint) -> c_int;
-    pub fn mdb_cursor_del(cursor: *mut MDB_cursor, flags: c_uint) -> c_int;
-    pub fn mdb_cursor_count(cursor: *mut MDB_cursor, countp: *mut size_t) -> c_int;
-    pub fn mdb_cmp(txn: *mut MDB_txn, dbi: MDB_dbi, a: *const MDB_val, b: *const MDB_val) -> c_int;
-    pub fn mdb_dcmp(txn: *mut MDB_txn, dbi: MDB_dbi, a: *const MDB_val, b: *const MDB_val) -> c_int;
-    pub fn mdb_reader_list(env: *mut MDB_env, func: *mut MDB_msg_func, ctx: *mut c_void) -> c_int;
-    pub fn mdb_reader_check(env: *mut MDB_env, dead: *mut c_int) -> c_int;
-}

src/cursor.rs

@@ -1,61 +1,36 @@
-use libc::{c_void, size_t};
+use libc::{c_void, size_t, c_uint};
 use std::{mem, ptr, raw};
 use std::kinds::marker;
 
 use database::Database;
 use error::{LmdbResult, lmdb_result};
 use ffi;
-use ffi::{MDB_cursor, mdb_cursor_open, MDB_cursor_op, MDB_val};
+use ffi::{MDB_cursor, mdb_cursor_open, MDB_val, WriteFlags};
-use flags::WriteFlags;
 use transaction::Transaction;
 
-/// A cursor for navigating within a database.
-pub struct Cursor<'txn> {
-    cursor: *mut MDB_cursor,
-    _no_sync: marker::NoSync,
-    _no_send: marker::NoSend,
-    _contravariant: marker::ContravariantLifetime<'txn>,
-}
 
-#[unsafe_destructor]
+/// An LMDB cursor.
-impl <'txn> Drop for Cursor<'txn> {
+pub trait Cursor<'txn> {
-    fn drop(&mut self) {
+    /// Returns a raw pointer to the underlying LMDB cursor.
-        unsafe { ffi::mdb_cursor_close(self.cursor) }
+    ///
-    }
+    /// The caller **must** ensure that the pointer is not used after the lifetime of the cursor.
+    fn cursor(&self) -> *mut MDB_cursor;
 }
 
-impl <'txn> Cursor<'txn> {
+pub trait ReadCursor<'txn> : Cursor<'txn> {
-
-    /// Creates a new cursor into the given database in the given transaction. Prefer using
-    /// `Transaction::open_cursor()`.
-    #[doc(hidden)]
-    pub fn new(txn: &'txn Transaction, db: Database) -> LmdbResult<Cursor<'txn>> {
-        let mut cursor: *mut MDB_cursor = ptr::null_mut();
-        unsafe { try!(lmdb_result(mdb_cursor_open(txn.txn(), db.dbi(), &mut cursor))); }
-        Ok(Cursor {
-            cursor: cursor,
-            _no_sync: marker::NoSync,
-            _no_send: marker::NoSend,
-            _contravariant: marker::ContravariantLifetime::<'txn>,
-        })
-    }
-
-    pub fn cursor(&self) -> *mut MDB_cursor {
-        self.cursor
-    }
 
     /// Retrieves a key/data pair from the cursor. Depending on the cursor op, the current key is
     /// returned.
-    pub fn get(&self,
+    fn get(&self,
                key: Option<&[u8]>,
                data: Option<&[u8]>,
-               op: MDB_cursor_op)
+               op: c_uint)
                -> LmdbResult<(Option<&'txn [u8]>, &'txn [u8])> {
         unsafe {
             let mut key_val = slice_to_val(key);
             let mut data_val = slice_to_val(data);
             let key_ptr = key_val.mv_data;
-            try!(lmdb_result(ffi::mdb_cursor_get(self.cursor,
+            try!(lmdb_result(ffi::mdb_cursor_get(self.cursor(),
                                                  &mut key_val,
                                                  &mut data_val,
                                                  op)));
@@ -64,10 +39,13 @@ impl <'txn> Cursor<'txn> {
             Ok((key_out, data_out))
         }
     }
+}
+
+pub trait WriteCursor<'txn> : ReadCursor<'txn> {
 
     /// Puts a key/data pair into the database. The cursor will be positioned at the new data item,
     /// or on failure usually near it.
-    pub fn put(&self,
+    fn put(&self,
            key: &[u8],
            data: &[u8],
            flags: WriteFlags)
@@ -92,13 +70,94 @@ impl <'txn> Cursor<'txn> {
     ///
     /// `MDB_NODUPDATA` may be used to delete all data items for the current key, if the database
     /// was opened with `MDB_DUPSORT`.
-    pub fn del(&self, flags: WriteFlags) -> LmdbResult<()> {
+    fn del(&self, flags: WriteFlags) -> LmdbResult<()> {
         unsafe {
             lmdb_result(ffi::mdb_cursor_del(self.cursor(), flags.bits()))
         }
     }
 }
 
+/// A read-only cursor for navigating items within a database.
+pub struct RoCursor<'txn> {
+    cursor: *mut MDB_cursor,
+    _no_sync: marker::NoSync,
+    _no_send: marker::NoSend,
+    _contravariant: marker::ContravariantLifetime<'txn>,
+}
+
+impl <'txn> Cursor<'txn> for RoCursor<'txn> {
+    fn cursor(&self) -> *mut MDB_cursor {
+        self.cursor
+    }
+}
+
+impl <'txn> ReadCursor<'txn> for RoCursor<'txn> { }
+
+#[unsafe_destructor]
+impl <'txn> Drop for RoCursor<'txn> {
+    fn drop(&mut self) {
+        unsafe { ffi::mdb_cursor_close(self.cursor) }
+    }
+}
+
+impl <'txn> RoCursor<'txn> {
+
+    /// Creates a new read-only cursor in the given database and transaction. Prefer using
+    /// `Transaction::open_cursor()`.
+    #[doc(hidden)]
+    pub fn new(txn: &'txn Transaction, db: Database) -> LmdbResult<RoCursor<'txn>> {
+        let mut cursor: *mut MDB_cursor = ptr::null_mut();
+        unsafe { try!(lmdb_result(mdb_cursor_open(txn.txn(), db.dbi(), &mut cursor))); }
+        Ok(RoCursor {
+            cursor: cursor,
+            _no_sync: marker::NoSync,
+            _no_send: marker::NoSend,
+            _contravariant: marker::ContravariantLifetime::<'txn>,
+        })
+    }
+}
+
+/// A read-only cursor for navigating items within a database.
+pub struct RwCursor<'txn> {
+    cursor: *mut MDB_cursor,
+    _no_sync: marker::NoSync,
+    _no_send: marker::NoSend,
+    _contravariant: marker::ContravariantLifetime<'txn>,
+}
+
+impl <'txn> Cursor<'txn> for RwCursor<'txn> {
+    fn cursor(&self) -> *mut MDB_cursor {
+        self.cursor
+    }
+}
+
+impl <'txn> ReadCursor<'txn> for RwCursor<'txn> { }
+impl <'txn> WriteCursor<'txn> for RwCursor<'txn> { }
+
+#[unsafe_destructor]
+impl <'txn> Drop for RwCursor<'txn> {
+    fn drop(&mut self) {
+        unsafe { ffi::mdb_cursor_close(self.cursor) }
+    }
+}
+
+impl <'txn> RwCursor<'txn> {
+
+    /// Creates a new read-only cursor in the given database and transaction. Prefer using
+    /// `WriteTransaction::open_write_cursor()`.
+    #[doc(hidden)]
+    pub fn new(txn: &'txn Transaction, db: Database) -> LmdbResult<RwCursor<'txn>> {
+        let mut cursor: *mut MDB_cursor = ptr::null_mut();
+        unsafe { try!(lmdb_result(mdb_cursor_open(txn.txn(), db.dbi(), &mut cursor))); }
+        Ok(RwCursor {
+            cursor: cursor,
+            _no_sync: marker::NoSync,
+            _no_send: marker::NoSend,
+            _contravariant: marker::ContravariantLifetime::<'txn>,
+        })
+    }
+}
+
 unsafe fn slice_to_val(slice: Option<&[u8]>) -> MDB_val {
     match slice {
         Some(slice) =>
@@ -120,53 +179,52 @@ unsafe fn val_to_slice<'a>(val: MDB_val) -> &'a [u8] {
 #[cfg(test)]
 mod test {
 
-    use libc::{c_void, size_t};
+    use libc::{c_void, size_t, c_uint};
     use std::{io, ptr};
 
+    use transaction::*;
     use environment::*;
     use error::{LmdbResult, lmdb_result};
-    use flags::*;
+    use ffi::*;
-    use ffi;
-    use ffi::{MDB_cursor_op, MDB_val};
     use super::*;
 
     #[test]
     fn test_get() {
         let dir = io::TempDir::new("test").unwrap();
         let env = Environment::new().open(dir.path(), io::USER_RWX).unwrap();
+        let db = env.open_db(None).unwrap();
 
-        let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+        let mut txn = env.begin_write_txn().unwrap();
-        let db = txn.open_db(None, DatabaseFlags::empty()).unwrap();
         txn.put(db, b"key1", b"val1", WriteFlags::empty()).unwrap();
         txn.put(db, b"key2", b"val2", WriteFlags::empty()).unwrap();
         txn.put(db, b"key3", b"val3", WriteFlags::empty()).unwrap();
 
-        let cursor = txn.open_cursor(db).unwrap();
+        let cursor = txn.open_read_cursor(db).unwrap();
         assert_eq!((Some(b"key1"), b"val1"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_FIRST).unwrap());
+                   cursor.get(None, None, MDB_FIRST).unwrap());
         assert_eq!((Some(b"key1"), b"val1"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_GET_CURRENT).unwrap());
+                   cursor.get(None, None, MDB_GET_CURRENT).unwrap());
         assert_eq!((Some(b"key2"), b"val2"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_NEXT).unwrap());
+                   cursor.get(None, None, MDB_NEXT).unwrap());
         assert_eq!((Some(b"key1"), b"val1"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_PREV).unwrap());
+                   cursor.get(None, None, MDB_PREV).unwrap());
         assert_eq!((Some(b"key3"), b"val3"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_LAST).unwrap());
+                   cursor.get(None, None, MDB_LAST).unwrap());
         assert_eq!((None, b"val2"),
-                   cursor.get(Some(b"key2"), None, MDB_cursor_op::MDB_SET).unwrap());
+                   cursor.get(Some(b"key2"), None, MDB_SET).unwrap());
         assert_eq!((Some(b"key3"), b"val3"),
-                   cursor.get(Some(b"key3"), None, MDB_cursor_op::MDB_SET_KEY).unwrap());
+                   cursor.get(Some(b"key3"), None, MDB_SET_KEY).unwrap());
         assert_eq!((Some(b"key3"), b"val3"),
-                   cursor.get(Some(b"key2\0"), None, MDB_cursor_op::MDB_SET_RANGE).unwrap());
+                   cursor.get(Some(b"key2\0"), None, MDB_SET_RANGE).unwrap());
     }
 
     #[test]
     fn test_get_dup() {
         let dir = io::TempDir::new("test").unwrap();
         let env = Environment::new().open(dir.path(), io::USER_RWX).unwrap();
+        let db = env.create_db(None, MDB_DUPSORT).unwrap();
 
-        let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+        let mut txn = env.begin_write_txn().unwrap();
-        let db = txn.open_db(None, MDB_DUPSORT).unwrap();
         txn.put(db, b"key1", b"val1", WriteFlags::empty()).unwrap();
         txn.put(db, b"key1", b"val2", WriteFlags::empty()).unwrap();
         txn.put(db, b"key1", b"val3", WriteFlags::empty()).unwrap();
@@ -174,45 +232,45 @@ mod test {
         txn.put(db, b"key2", b"val2", WriteFlags::empty()).unwrap();
         txn.put(db, b"key2", b"val3", WriteFlags::empty()).unwrap();
 
-        let cursor = txn.open_cursor(db).unwrap();
+        let cursor = txn.open_read_cursor(db).unwrap();
         assert_eq!((Some(b"key1"), b"val1"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_FIRST).unwrap());
+                   cursor.get(None, None, MDB_FIRST).unwrap());
         assert_eq!((None, b"val1"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_FIRST_DUP).unwrap());
+                   cursor.get(None, None, MDB_FIRST_DUP).unwrap());
         assert_eq!((Some(b"key1"), b"val1"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_GET_CURRENT).unwrap());
+                   cursor.get(None, None, MDB_GET_CURRENT).unwrap());
         assert_eq!((Some(b"key2"), b"val1"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_NEXT_NODUP).unwrap());
+                   cursor.get(None, None, MDB_NEXT_NODUP).unwrap());
         assert_eq!((Some(b"key2"), b"val2"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_NEXT_DUP).unwrap());
+                   cursor.get(None, None, MDB_NEXT_DUP).unwrap());
         assert_eq!((Some(b"key2"), b"val3"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_NEXT_DUP).unwrap());
+                   cursor.get(None, None, MDB_NEXT_DUP).unwrap());
-        assert!(cursor.get(None, None, MDB_cursor_op::MDB_NEXT_DUP).is_err());
+        assert!(cursor.get(None, None, MDB_NEXT_DUP).is_err());
         assert_eq!((Some(b"key2"), b"val2"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_PREV_DUP).unwrap());
+                   cursor.get(None, None, MDB_PREV_DUP).unwrap());
         assert_eq!((None, b"val3"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_LAST_DUP).unwrap());
+                   cursor.get(None, None, MDB_LAST_DUP).unwrap());
         assert_eq!((Some(b"key1"), b"val3"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_PREV_NODUP).unwrap());
+                   cursor.get(None, None, MDB_PREV_NODUP).unwrap());
         assert_eq!((None, b"val1"),
-                   cursor.get(Some(b"key1"), None, MDB_cursor_op::MDB_SET).unwrap());
+                   cursor.get(Some(b"key1"), None, MDB_SET).unwrap());
         assert_eq!((Some(b"key2"), b"val1"),
-                   cursor.get(Some(b"key2"), None, MDB_cursor_op::MDB_SET_KEY).unwrap());
+                   cursor.get(Some(b"key2"), None, MDB_SET_KEY).unwrap());
         assert_eq!((Some(b"key2"), b"val1"),
-                   cursor.get(Some(b"key1\0"), None, MDB_cursor_op::MDB_SET_RANGE).unwrap());
+                   cursor.get(Some(b"key1\0"), None, MDB_SET_RANGE).unwrap());
         assert_eq!((None, b"val3"),
-                   cursor.get(Some(b"key1"), Some(b"val3"), MDB_cursor_op::MDB_GET_BOTH).unwrap());
+                   cursor.get(Some(b"key1"), Some(b"val3"), MDB_GET_BOTH).unwrap());
         assert_eq!((None, b"val1"),
-                   cursor.get(Some(b"key2"), Some(b"val"), MDB_cursor_op::MDB_GET_BOTH_RANGE).unwrap());
+                   cursor.get(Some(b"key2"), Some(b"val"), MDB_GET_BOTH_RANGE).unwrap());
     }
 
     #[test]
     fn test_get_dupfixed() {
         let dir = io::TempDir::new("test").unwrap();
         let env = Environment::new().open(dir.path(), io::USER_RWX).unwrap();
+        let db = env.create_db(None, MDB_DUPSORT | MDB_DUPFIXED).unwrap();
 
-        let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+        let mut txn = env.begin_write_txn().unwrap();
-        let db = txn.open_db(None, MDB_DUPSORT | MDB_DUPFIXED).unwrap();
         txn.put(db, b"key1", b"val1", WriteFlags::empty()).unwrap();
         txn.put(db, b"key1", b"val2", WriteFlags::empty()).unwrap();
         txn.put(db, b"key1", b"val3", WriteFlags::empty()).unwrap();
@@ -220,12 +278,12 @@ mod test {
         txn.put(db, b"key2", b"val5", WriteFlags::empty()).unwrap();
         txn.put(db, b"key2", b"val6", WriteFlags::empty()).unwrap();
 
-        let cursor = txn.open_cursor(db).unwrap();
+        let cursor = txn.open_read_cursor(db).unwrap();
         assert_eq!((Some(b"key1"), b"val1"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_FIRST).unwrap());
+                   cursor.get(None, None, MDB_FIRST).unwrap());
         assert_eq!((None, b"val1val2val3"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_GET_MULTIPLE).unwrap());
+                   cursor.get(None, None, MDB_GET_MULTIPLE).unwrap());
-        assert!(cursor.get(None, None, MDB_cursor_op::MDB_NEXT_MULTIPLE).is_err());
+        assert!(cursor.get(None, None, MDB_NEXT_MULTIPLE).is_err());
     }
 
     /// Checks assumptions about which get operations return keys.
@@ -249,22 +307,22 @@ mod test {
         fn sets_key(cursor: &Cursor,
                     key: Option<&[u8]>,
                     data: Option<&[u8]>,
-                    op: MDB_cursor_op)
+                    op: c_uint)
                     -> LmdbResult<bool> {
             unsafe {
                 let mut key_val = slice_to_val(key);
                 let mut data_val = slice_to_val(data);
                 let key_ptr = key_val.mv_data;
-                try!(lmdb_result(ffi::mdb_cursor_get(cursor.cursor(),
+                try!(lmdb_result(mdb_cursor_get(cursor.cursor(),
                                                 &mut key_val,
                                                 &mut data_val,
                                                 op)));
                 Ok(key_ptr != key_val.mv_data)
             }
         }
+        let db = env.create_db(None, MDB_DUPSORT | MDB_DUPFIXED).unwrap();
 
-        let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+        let mut txn = env.begin_write_txn().unwrap();
-        let db = txn.open_db(None, MDB_DUPSORT | MDB_DUPFIXED).unwrap();
         txn.put(db, b"key1", b"val1", WriteFlags::empty()).unwrap();
         txn.put(db, b"key1", b"val2", WriteFlags::empty()).unwrap();
         txn.put(db, b"key1", b"val3", WriteFlags::empty()).unwrap();
@@ -275,48 +333,48 @@ mod test {
         txn.put(db, b"key3", b"val8", WriteFlags::empty()).unwrap();
         txn.put(db, b"key3", b"val9", WriteFlags::empty()).unwrap();
 
-        let cursor = txn.open_cursor(db).unwrap();
+        let cursor = txn.open_read_cursor(db).unwrap();
-        assert!(sets_key(&cursor, None, None, MDB_cursor_op::MDB_FIRST).unwrap());
+        assert!(sets_key(&cursor, None, None, MDB_FIRST).unwrap());
-        assert!(!sets_key(&cursor, None, None, MDB_cursor_op::MDB_FIRST_DUP).unwrap());
+        assert!(!sets_key(&cursor, None, None, MDB_FIRST_DUP).unwrap());
-        assert!(!sets_key(&cursor, Some(b"key2"), Some(b"val5"), MDB_cursor_op::MDB_GET_BOTH).unwrap());
+        assert!(!sets_key(&cursor, Some(b"key2"), Some(b"val5"), MDB_GET_BOTH).unwrap());
-        assert!(!sets_key(&cursor, Some(b"key2"), Some(b"val"), MDB_cursor_op::MDB_GET_BOTH_RANGE).unwrap());
+        assert!(!sets_key(&cursor, Some(b"key2"), Some(b"val"), MDB_GET_BOTH_RANGE).unwrap());
-        assert!(sets_key(&cursor, None, None, MDB_cursor_op::MDB_GET_CURRENT).unwrap());
+        assert!(sets_key(&cursor, None, None, MDB_GET_CURRENT).unwrap());
-        assert!(!sets_key(&cursor, None, None, MDB_cursor_op::MDB_GET_MULTIPLE).unwrap());
+        assert!(!sets_key(&cursor, None, None, MDB_GET_MULTIPLE).unwrap());
-        assert!(sets_key(&cursor, None, None, MDB_cursor_op::MDB_LAST).unwrap());
+        assert!(sets_key(&cursor, None, None, MDB_LAST).unwrap());
-        assert!(!sets_key(&cursor, None, None, MDB_cursor_op::MDB_LAST_DUP).unwrap());
+        assert!(!sets_key(&cursor, None, None, MDB_LAST_DUP).unwrap());
-        sets_key(&cursor, None, None, MDB_cursor_op::MDB_FIRST).unwrap();
+        sets_key(&cursor, None, None, MDB_FIRST).unwrap();
-        assert!(sets_key(&cursor, None, None, MDB_cursor_op::MDB_NEXT).unwrap());
+        assert!(sets_key(&cursor, None, None, MDB_NEXT).unwrap());
-        assert!(sets_key(&cursor, None, None, MDB_cursor_op::MDB_NEXT_DUP).unwrap());
+        assert!(sets_key(&cursor, None, None, MDB_NEXT_DUP).unwrap());
-        sets_key(&cursor, None, None, MDB_cursor_op::MDB_FIRST).unwrap();
+        sets_key(&cursor, None, None, MDB_FIRST).unwrap();
-        assert!(sets_key(&cursor, None, None, MDB_cursor_op::MDB_NEXT_MULTIPLE).unwrap());
+        assert!(sets_key(&cursor, None, None, MDB_NEXT_MULTIPLE).unwrap());
-        assert!(sets_key(&cursor, None, None, MDB_cursor_op::MDB_NEXT_NODUP).unwrap());
+        assert!(sets_key(&cursor, None, None, MDB_NEXT_NODUP).unwrap());
-        assert!(sets_key(&cursor, None, None, MDB_cursor_op::MDB_PREV).unwrap());
+        assert!(sets_key(&cursor, None, None, MDB_PREV).unwrap());
-        sets_key(&cursor, None, None, MDB_cursor_op::MDB_LAST).unwrap();
+        sets_key(&cursor, None, None, MDB_LAST).unwrap();
-        assert!(sets_key(&cursor, None, None, MDB_cursor_op::MDB_PREV_DUP).unwrap());
+        assert!(sets_key(&cursor, None, None, MDB_PREV_DUP).unwrap());
-        assert!(sets_key(&cursor, None, None, MDB_cursor_op::MDB_PREV_NODUP).unwrap());
+        assert!(sets_key(&cursor, None, None, MDB_PREV_NODUP).unwrap());
-        assert!(!sets_key(&cursor, Some(b"key2"), None, MDB_cursor_op::MDB_SET).unwrap());
+        assert!(!sets_key(&cursor, Some(b"key2"), None, MDB_SET).unwrap());
-        assert!(sets_key(&cursor, Some(b"key2"), None, MDB_cursor_op::MDB_SET_KEY).unwrap());
+        assert!(sets_key(&cursor, Some(b"key2"), None, MDB_SET_KEY).unwrap());
-        assert!(sets_key(&cursor, Some(b"key2"), None, MDB_cursor_op::MDB_SET_RANGE).unwrap());
+        assert!(sets_key(&cursor, Some(b"key2"), None, MDB_SET_RANGE).unwrap());
     }
 
     #[test]
     fn test_put_del() {
         let dir = io::TempDir::new("test").unwrap();
         let env = Environment::new().open(dir.path(), io::USER_RWX).unwrap();
+        let db = env.open_db(None).unwrap();
 
-        let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+        let mut txn = env.begin_write_txn().unwrap();
-        let db = txn.open_db(None, DatabaseFlags::empty()).unwrap();
+        let cursor = txn.open_write_cursor(db).unwrap();
-        let cursor = txn.open_cursor(db).unwrap();
 
         cursor.put(b"key1", b"val1", WriteFlags::empty()).unwrap();
         cursor.put(b"key2", b"val2", WriteFlags::empty()).unwrap();
         cursor.put(b"key3", b"val3", WriteFlags::empty()).unwrap();
 
         assert_eq!((Some(b"key3"), b"val3"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_GET_CURRENT).unwrap());
+                   cursor.get(None, None, MDB_GET_CURRENT).unwrap());
 
         cursor.del(WriteFlags::empty()).unwrap();
         assert_eq!((Some(b"key2"), b"val2"),
-                   cursor.get(None, None, MDB_cursor_op::MDB_LAST).unwrap());
+                   cursor.get(None, None, MDB_LAST).unwrap());
     }
 }

src/database.rs

@@ -2,37 +2,43 @@ use std::kinds::marker;
 use std::ptr;
 
 use error::{LmdbResult, lmdb_result};
-use ffi::{MDB_dbi, mdb_dbi_open};
+use ffi::*;
-use flags::DatabaseFlags;
+use transaction::{Transaction, ReadTransaction, WriteTransaction};
-use transaction::Transaction;
 
 /// A handle to an individual database in an environment.
 ///
 /// A database handle denotes the name and parameters of a database in an environment. The database
 /// may not exist in the environment (for instance, if the database is opened during a transaction
 /// that has not yet committed).
+#[deriving(Clone, Copy)]
 pub struct Database<'env> {
     dbi: MDB_dbi,
     _marker: marker::ContravariantLifetime<'env>,
 }
 
-impl <'env> Copy for Database<'env> { }
-
 impl <'env> Database<'env> {
 
-    /// Opens a database in the given transaction. Prefer using `Transaction::open_db`.
+    pub unsafe fn open<'env>(txn: &ReadTransaction<'env>,
-    #[doc(hidden)]
+                             name: Option<&str>)
-    pub fn new(txn: &Transaction<'env>,
+                             -> LmdbResult<Database<'env>> {
+        let c_name = name.map(|n| n.to_c_str());
+        let name_ptr = if let Some(ref c_name) = c_name { c_name.as_ptr() } else { ptr::null() };
+        let mut dbi: MDB_dbi = 0;
+        try!(lmdb_result(mdb_dbi_open(txn.txn(), name_ptr, 0, &mut dbi)));
+        Ok(Database { dbi: dbi,
+                      _marker: marker::ContravariantLifetime::<'env> })
+    }
+
+    pub unsafe fn create<'env>(txn: &WriteTransaction<'env>,
                                name: Option<&str>,
                                flags: DatabaseFlags)
                                -> LmdbResult<Database<'env>> {
         let c_name = name.map(|n| n.to_c_str());
         let name_ptr = if let Some(ref c_name) = c_name { c_name.as_ptr() } else { ptr::null() };
         let mut dbi: MDB_dbi = 0;
-        unsafe {
+        try!(lmdb_result(mdb_dbi_open(txn.txn(), name_ptr, flags.bits() | MDB_CREATE, &mut dbi)));
-            try!(lmdb_result(mdb_dbi_open(txn.txn(), name_ptr, flags.bits(), &mut dbi)));
+        Ok(Database { dbi: dbi,
-        }
+                      _marker: marker::ContravariantLifetime::<'env> })
-        Ok(Database { dbi: dbi, _marker: marker::ContravariantLifetime::<'env> })
     }
 
     /// Returns the underlying LMDB database handle.

src/environment.rs

@@ -1,19 +1,19 @@
 use libc::{c_uint, size_t, mode_t};
 use std::io::FilePermission;
 use std::ptr;
+use std::sync::Mutex;
 
+use error::{LmdbResult, lmdb_result};
 use database::Database;
-use error::{LmdbError, LmdbResult, lmdb_result};
+use ffi::*;
-use ffi;
+use transaction::{RoTransaction, RwTransaction, Transaction, TransactionExt};
-use ffi::MDB_env;
-use flags::EnvironmentFlags;
-use transaction::Transaction;
 
 /// An LMDB environment.
 ///
 /// An environment supports multiple databases, all residing in the same shared-memory map.
 pub struct Environment {
     env: *mut MDB_env,
+    dbi_open_mutex: Mutex<()>,
 }
 
 impl Environment {
@@ -36,11 +36,65 @@ impl Environment {
         self.env
     }
 
-    /// Create a transaction for use with the environment.
+    /// Opens a handle to an LMDB database.
     ///
-    /// `flags` must either be empty, or `MDB_RDONLY` in order to specify a read-only transaction.
+    /// If `name` is `None`, then the returned handle will be for the default database.
-    pub fn begin_txn<'a>(&'a self, flags: EnvironmentFlags) -> LmdbResult<Transaction<'a>> {
+    ///
-        Transaction::new(self, flags)
+    /// If `name` is not `None`, then the returned handle will be for a named database. In this
+    /// case the environment must be configured to allow named databases through
+    /// `EnvironmentBuilder::set_max_dbs`.
+    ///
+    /// The returned database handle may be shared among transactions.
+    pub fn open_db<'env>(&'env self, name: Option<&str>) -> LmdbResult<Database<'env>> {
+        let mutex = self.dbi_open_mutex.lock();
+        let txn = try!(self.begin_read_txn());
+        let db = unsafe { try!(Database::open(&txn, name)) };
+        try!(txn.commit());
+        drop(mutex);
+        Ok(db)
+    }
+
+    /// Opens a handle to an LMDB database, opening the database if necessary.
+    ///
+    /// If the database is already created, the given option flags will be added to it.
+    ///
+    /// If `name` is `None`, then the returned handle will be for the default database.
+    ///
+    /// If `name` is not `None`, then the returned handle will be for a named database. In this
+    /// case the environment must be configured to allow named databases through
+    /// `EnvironmentBuilder::set_max_dbs`.
+    ///
+    /// The returned database handle may be shared among transactions.
+    pub fn create_db<'env>(&'env self,
+                           name: Option<&str>,
+                           flags: DatabaseFlags)
+                           -> LmdbResult<Database<'env>> {
+        let mutex = self.dbi_open_mutex.lock();
+        let txn = try!(self.begin_write_txn());
+        let db = unsafe { try!(Database::create(&txn, name, flags)) };
+        try!(txn.commit());
+        drop(mutex);
+        Ok(db)
+    }
+
+    pub fn get_db_flags<'env>(&'env self, db: Database<'env>) -> LmdbResult<DatabaseFlags> {
+        let txn = try!(self.begin_read_txn());
+        let mut flags: c_uint = 0;
+        unsafe {
+            try!(lmdb_result(mdb_dbi_flags(txn.txn(), db.dbi(), &mut flags)));
+        }
+        Ok(DatabaseFlags::from_bits(flags).unwrap())
+    }
+
+    /// Create a read-only transaction for use with the environment.
+    pub fn begin_read_txn<'env>(&'env self) -> LmdbResult<RoTransaction<'env>> {
+        RoTransaction::new(self)
+    }
+
+    /// Create a read-write transaction for use with the environment. This method will block while
+    /// there are any other read-write transactions open on the environment.
+    pub fn begin_write_txn<'env>(&'env self) -> LmdbResult<RwTransaction<'env>> {
+        RwTransaction::new(self)
     }
 
     /// Flush data buffers to disk.
@@ -50,7 +104,7 @@ impl Environment {
     /// the environment was opened with `MDB_NOSYNC` or in part `MDB_NOMETASYNC`.
     pub fn sync(&self, force: bool) -> LmdbResult<()> {
         unsafe {
-            lmdb_result(ffi::mdb_env_sync(self.env(), if force { 1 } else { 0 }))
+            lmdb_result(mdb_env_sync(self.env(), if force { 1 } else { 0 }))
         }
     }
 
@@ -66,13 +120,13 @@ impl Environment {
     /// handle value. Usually it's better to set a bigger `EnvironmentBuilder::set_max_dbs`, unless
     /// that value would be large.
     pub unsafe fn close_db(&self, db: Database) {
-        ffi::mdb_dbi_close(self.env, db.dbi())
+        mdb_dbi_close(self.env, db.dbi())
     }
 }
 
 impl Drop for Environment {
     fn drop(&mut self) {
-        unsafe { ffi::mdb_env_close(self.env) }
+        unsafe { mdb_env_close(self.env) }
     }
 }
 
@@ -81,7 +135,7 @@ impl Drop for Environment {
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
 /// Options for opening or creating an environment.
-#[deriving(Show, PartialEq, Eq)]
+#[deriving(Show, PartialEq, Eq, Copy, Clone)]
 pub struct EnvironmentBuilder {
     flags: EnvironmentFlags,
     max_readers: Option<c_uint>,
@@ -95,26 +149,27 @@ impl EnvironmentBuilder {
     pub fn open(&self, path: &Path, mode: FilePermission) -> LmdbResult<Environment> {
         let mut env: *mut MDB_env = ptr::null_mut();
         unsafe {
-            lmdb_try!(ffi::mdb_env_create(&mut env));
+            lmdb_try!(mdb_env_create(&mut env));
             if let Some(max_readers) = self.max_readers {
-                lmdb_try_with_cleanup!(ffi::mdb_env_set_maxreaders(env, max_readers),
+                lmdb_try_with_cleanup!(mdb_env_set_maxreaders(env, max_readers),
-                                       ffi::mdb_env_close(env))
+                                       mdb_env_close(env))
             }
             if let Some(max_dbs) = self.max_dbs {
-                lmdb_try_with_cleanup!(ffi::mdb_env_set_maxdbs(env, max_dbs),
+                lmdb_try_with_cleanup!(mdb_env_set_maxdbs(env, max_dbs),
-                                       ffi::mdb_env_close(env))
+                                       mdb_env_close(env))
             }
             if let Some(map_size) = self.map_size {
-                lmdb_try_with_cleanup!(ffi::mdb_env_set_mapsize(env, map_size),
+                lmdb_try_with_cleanup!(mdb_env_set_mapsize(env, map_size),
-                                       ffi::mdb_env_close(env))
+                                       mdb_env_close(env))
             }
-            lmdb_try_with_cleanup!(ffi::mdb_env_open(env,
+            lmdb_try_with_cleanup!(mdb_env_open(env,
                                                      path.to_c_str().as_ptr(),
                                                      self.flags.bits(),
                                                      mode.bits() as mode_t),
-                                   ffi::mdb_env_close(env));
+                                   mdb_env_close(env));
         }
-        Ok(Environment { env: env })
+        Ok(Environment { env: env,
+                         dbi_open_mutex: Mutex::new(()) })
     }
 
     pub fn set_flags(&mut self, flags: EnvironmentFlags) -> &mut EnvironmentBuilder {
@@ -169,7 +224,7 @@ mod test {
 
     use std::io;
 
-    use flags;
+    use ffi::*;
     use super::*;
 
     #[test]
@@ -177,7 +232,7 @@ mod test {
         let dir = io::TempDir::new("test").unwrap();
 
         // opening non-existent env with read-only should fail
-        assert!(Environment::new().set_flags(flags::MDB_RDONLY)
+        assert!(Environment::new().set_flags(MDB_RDONLY)
                                   .open(dir.path(), io::USER_RWX)
                                   .is_err());
 
@@ -185,7 +240,7 @@ mod test {
         assert!(Environment::new().open(dir.path(), io::USER_RWX).is_ok());
 
         // opening env with read-only should not fail
-        assert!(Environment::new().set_flags(flags::MDB_RDONLY)
+        assert!(Environment::new().set_flags(MDB_RDONLY)
                                   .open(dir.path(), io::USER_RWX)
                                   .is_ok());
     }
@@ -197,23 +252,44 @@ mod test {
 
         {
             // Mutable env, mutable txn
-            assert!(env.begin_txn(flags::EnvironmentFlags::empty()).is_ok());
+            assert!(env.begin_write_txn().is_ok());
         } {
             // Mutable env, read-only txn
-            assert!(env.begin_txn(flags::MDB_RDONLY).is_ok());
+            assert!(env.begin_read_txn().is_ok());
         } {
             // Read-only env, mutable txn
-            let env = Environment::new().set_flags(flags::MDB_RDONLY)
+            let env = Environment::new().set_flags(MDB_RDONLY)
                                         .open(dir.path(), io::USER_RWX)
                                         .unwrap();
-            assert!(env.begin_txn(flags::EnvironmentFlags::empty()).is_err());
+            assert!(env.begin_write_txn().is_err());
         } {
             // Read-only env, read-only txn
-            let env = Environment::new().set_flags(flags::MDB_RDONLY)
+            let env = Environment::new().set_flags(MDB_RDONLY)
+                                        .open(dir.path(), io::USER_RWX)
+                                        .unwrap();
+            assert!(env.begin_read_txn().is_ok());
+        }
+    }
+
+    #[test]
+    fn test_open_db() {
+        let dir = io::TempDir::new("test").unwrap();
+        let env = Environment::new().set_max_dbs(10)
                                     .open(dir.path(), io::USER_RWX)
                                     .unwrap();
-            assert!(env.begin_txn(flags::MDB_RDONLY).is_ok());
+        assert!(env.open_db(None).is_ok());
+        assert!(env.open_db(Some("testdb")).is_err());
     }
+
+    #[test]
+    fn test_create_db() {
+        let dir = io::TempDir::new("test").unwrap();
+        let env = Environment::new().set_max_dbs(10)
+                                    .open(dir.path(), io::USER_RWX)
+                                    .unwrap();
+        assert!(env.open_db(Some("testdb")).is_err());
+        assert!(env.create_db(Some("testdb"), DatabaseFlags::empty()).is_ok());
+        assert!(env.open_db(Some("testdb")).is_ok())
     }
 
     #[test]
@@ -223,7 +299,7 @@ mod test {
             let env = Environment::new().open(dir.path(), io::USER_RWX).unwrap();
             assert!(env.sync(true).is_ok());
         } {
-            let env = Environment::new().set_flags(flags::MDB_RDONLY)
+            let env = Environment::new().set_flags(MDB_RDONLY)
                                         .open(dir.path(), io::USER_RWX)
                                         .unwrap();
             assert!(env.sync(true).is_ok());

src/lib.rs

@@ -14,13 +14,13 @@ pub use cursor::Cursor;
 pub use database::Database;
 pub use environment::{Environment, EnvironmentBuilder};
 pub use error::{LmdbResult, LmdbError};
-pub use transaction::Transaction;
+pub use transaction::{ReadTransaction, WriteTransaction, RoTransaction, RwTransaction};
 
 macro_rules! lmdb_try {
     ($expr:expr) => ({
         match $expr {
-            ffi::MDB_SUCCESS => (),
+            ::ffi::MDB_SUCCESS => (),
-            err_code => return Err(::std::error::FromError::from_error(LmdbError::from_err_code(err_code))),
+            err_code => return Err(::std::error::FromError::from_error(::LmdbError::from_err_code(err_code))),
         }
     })
 }
@@ -28,10 +28,10 @@ macro_rules! lmdb_try {
 macro_rules! lmdb_try_with_cleanup {
     ($expr:expr, $cleanup:expr) => ({
         match $expr {
-            ffi::MDB_SUCCESS => (),
+            ::ffi::MDB_SUCCESS => (),
             err_code => {
                 let _ = $cleanup;
-                return Err(::std::error::FromError::from_error(LmdbError::from_err_code(err_code)))
+                return Err(::std::error::FromError::from_error(::LmdbError::from_err_code(err_code)))
             },
         }
     })
@@ -42,5 +42,3 @@ mod database;
 mod environment;
 mod error;
 mod transaction;
-
-pub mod flags;

src/transaction.rs

@@ -3,94 +3,35 @@ use std::{mem, ptr, raw};
 use std::kinds::marker;
 use std::io::BufWriter;
 
-use cursor::Cursor;
+use cursor::{RoCursor, RwCursor};
-use database::Database;
 use environment::Environment;
+use database::Database;
 use error::{LmdbResult, lmdb_result};
 use ffi;
 use ffi::MDB_txn;
-use flags::{DatabaseFlags, EnvironmentFlags, WriteFlags, MDB_RESERVE};
+use ffi::{DatabaseFlags, EnvironmentFlags, WriteFlags, MDB_RDONLY, MDB_RESERVE};
 
 /// An LMDB transaction.
 ///
 /// All database operations require a transaction.
-pub struct Transaction<'env> {
+pub trait Transaction<'env> {
-    txn: *mut MDB_txn,
-    _no_sync: marker::NoSync,
-    _no_send: marker::NoSend,
-    _contravariant: marker::ContravariantLifetime<'env>,
-}
-
-#[unsafe_destructor]
-impl <'env> Drop for Transaction<'env> {
-    fn drop(&mut self) {
-        unsafe { ffi::mdb_txn_abort(self.txn) }
-    }
-}
-
-impl <'env> Transaction<'env> {
-
-    /// Creates a new transaction in the given environment. Prefer using `Environment::begin_txn`.
-    #[doc(hidden)]
-    pub fn new(env: &'env Environment, flags: EnvironmentFlags) -> LmdbResult<Transaction<'env>> {
-        let mut txn: *mut MDB_txn = ptr::null_mut();
-        unsafe {
-            try!(lmdb_result(ffi::mdb_txn_begin(env.env(),
-                                                ptr::null_mut(),
-                                                flags.bits(),
-                                                &mut txn)));
-            Ok(Transaction {
-                txn: txn,
-                _no_sync: marker::NoSync,
-                _no_send: marker::NoSend,
-                _contravariant: marker::ContravariantLifetime::<'env>,
-            })
-        }
-    }
 
     /// Returns a raw pointer to the underlying LMDB transaction.
     ///
     /// The caller **must** ensure that the pointer is not used after the lifetime of the
     /// transaction.
-    pub fn txn(&self) -> *mut MDB_txn {
+    fn txn(&self) -> *mut MDB_txn;
-        self.txn
-    }
-
-    /// Opens a handle to a database.
-    ///
-    /// If `name` is `None`, then the returned handle will be for the default database.
-    ///
-    /// If `name` is not `None`, then the returned handle will be for a named database. In this
-    /// case the environment must be configured to allow named databases through
-    /// `EnvironmentBuilder::set_max_dbs`.
-    ///
-    /// The database handle will be private to the current transaction until the transaction is
-    /// successfully committed. If the transaction is aborted the database handle will be closed
-    /// automatically. After a successful commit the database handle will reside in the shared
-    /// environment, and may be used by other transactions.
-    ///
-    /// A transaction that uses this function must finish (either commit or abort) before any other
-    /// transaction may use the function.
-    pub fn open_db(&self, name: Option<&str>, flags: DatabaseFlags) -> LmdbResult<Database<'env>> {
-        Database::new(self, name, flags)
 }
 
-    /// Gets the option flags for the given database in the transaction.
+/// Transaction extension methods.
-    pub fn db_flags(&self, db: Database) -> LmdbResult<DatabaseFlags> {
+pub trait TransactionExt<'env> : Transaction<'env> {
-        let mut flags: c_uint = 0;
-        unsafe {
-            try!(lmdb_result(ffi::mdb_dbi_flags(self.txn, db.dbi(), &mut flags)));
-        }
-
-        Ok(DatabaseFlags::from_bits_truncate(flags))
-    }
 
     /// Commits the transaction.
     ///
     /// Any pending operations will be saved.
-    pub fn commit(self) -> LmdbResult<()> {
+    fn commit(self) -> LmdbResult<()> {
         unsafe {
-            let result = lmdb_result(ffi::mdb_txn_commit(self.txn()));
+            let result = lmdb_result(::ffi::mdb_txn_commit(self.txn()));
             mem::forget(self);
             result
         }
@@ -99,22 +40,30 @@ impl <'env> Transaction<'env> {
     /// Aborts the transaction.
     ///
     /// Any pending operations will not be saved.
-    pub fn abort(self) {
+    fn abort(self) {
-        // Abort is called in the destructor
+        // Abort should be performed in transaction destructors.
     }
+}
+
+impl<'env, T> TransactionExt<'env> for T where T: Transaction<'env> {}
+
+/// A read-only LMDB transaction.
+///
+/// All database read operations require a transaction.
+pub trait ReadTransaction<'env> : Transaction<'env> {
 
     /// Gets an item from a database.
     ///
     /// This function retrieves the data associated with the given key in the database. If the
     /// database supports duplicate keys (`MDB_DUPSORT`) then the first data item for the key will
     /// be returned. Retrieval of other items requires the use of `Transaction::cursor_get`.
-    pub fn get<'txn>(&'txn self, database: Database, key: &[u8]) -> LmdbResult<&'txn [u8]> {
+    fn get<'txn>(&'txn self, database: Database, key: &[u8]) -> LmdbResult<&'txn [u8]> {
-        let mut key_val: ffi::MDB_val = ffi::MDB_val { mv_size: key.len() as size_t,
+        let mut key_val: ::ffi::MDB_val = ::ffi::MDB_val { mv_size: key.len() as size_t,
                                                        mv_data: key.as_ptr() as *mut c_void };
-        let mut data_val: ffi::MDB_val = ffi::MDB_val { mv_size: 0,
+        let mut data_val: ::ffi::MDB_val = ::ffi::MDB_val { mv_size: 0,
                                                         mv_data: ptr::null_mut() };
         unsafe {
-            try!(lmdb_result(ffi::mdb_get(self.txn(),
+            try!(lmdb_result(::ffi::mdb_get(self.txn(),
                                           database.dbi(),
                                           &mut key_val,
                                           &mut data_val)));
@@ -127,12 +76,38 @@ impl <'env> Transaction<'env> {
         }
     }
 
+    /// Open a new read-only cursor on the given database.
+    fn open_read_cursor<'txn>(&'txn self, db: Database) -> LmdbResult<RoCursor<'txn>> {
+        RoCursor::new(self, db)
+    }
+
+    /// Gets the option flags for the given database in the transaction.
+    fn db_flags(&self, db: Database) -> LmdbResult<DatabaseFlags> {
+        let mut flags: c_uint = 0;
+        unsafe {
+            try!(lmdb_result(ffi::mdb_dbi_flags(self.txn(), db.dbi(), &mut flags)));
+        }
+
+        Ok(DatabaseFlags::from_bits_truncate(flags))
+    }
+}
+
+/// A read-write LMDB transaction.
+///
+/// All database operations require a transaction.
+pub trait WriteTransaction<'env> : ReadTransaction<'env> {
+
+    /// Open a new read-write cursor on the given database.
+    fn open_write_cursor<'txn>(&'txn mut self, db: Database) -> LmdbResult<RwCursor<'txn>> {
+        RwCursor::new(self, db)
+    }
+
     /// Stores an item into a database.
     ///
     /// This function stores key/data pairs in the database. The default behavior is to enter the
     /// new key/data pair, replacing any previously existing key if duplicates are disallowed, or
     /// adding a duplicate data item if duplicates are allowed (`MDB_DUPSORT`).
-    pub fn put(&mut self,
+    fn put(&mut self,
            database: Database,
            key: &[u8],
            data: &[u8],
@@ -152,8 +127,8 @@ impl <'env> Transaction<'env> {
     }
 
     /// Returns a `BufWriter` which can be used to write a value into the item at the given key
-    /// and with the given length.
+    /// and with the given length. The buffer must be completely filled by the caller.
-    pub fn put_zero_copy<'txn>(&'txn mut self,
+    fn reserve<'txn>(&'txn mut self,
                          database: Database,
                          key: &[u8],
                          len: size_t,
@@ -168,7 +143,7 @@ impl <'env> Transaction<'env> {
                                           database.dbi(),
                                           &mut key_val,
                                           &mut data_val,
-                                          (flags | MDB_RESERVE).bits())));
+                                          flags.bits() | MDB_RESERVE)));
             let slice: &'txn mut [u8] =
                 mem::transmute(raw::Slice {
                     data: data_val.mv_data as *const u8,
@@ -187,7 +162,7 @@ impl <'env> Transaction<'env> {
     /// for the key will be deleted. Otherwise, if the data parameter is `Some` only the matching
     /// data item will be deleted. This function will return `MDB_NOTFOUND` if the specified key/data
     /// pair is not in the database.
-    pub fn del(&mut self,
+    fn del(&mut self,
                database: Database,
                key: &[u8],
                data: Option<&[u8]>)
@@ -205,16 +180,101 @@ impl <'env> Transaction<'env> {
                                              .unwrap_or(ptr::null_mut())))
         }
     }
+}
 
-    /// Open a new cursor over the database.
+/// An LMDB read-only transaction.
-    ///
+pub struct RoTransaction<'env> {
-    /// Takes a mutable reference to the transaction since cursors can mutate the transaction, which
+    txn: *mut MDB_txn,
-    /// will invalidates values read during the transaction.
+    _no_sync: marker::NoSync,
-    pub fn open_cursor<'txn>(&'txn mut self, db: Database) -> LmdbResult<Cursor<'txn>> {
+    _no_send: marker::NoSend,
-        Cursor::new(self, db)
+    _contravariant: marker::ContravariantLifetime<'env>,
+}
+
+#[unsafe_destructor]
+impl <'env> Drop for RoTransaction<'env> {
+    fn drop(&mut self) {
+        unsafe { ffi::mdb_txn_abort(self.txn) }
+    }
+}
+
+impl <'env> RoTransaction<'env> {
+
+    /// Creates a new read-only transaction in the given environment. Prefer using
+    /// `Environment::begin_ro_txn`.
+    #[doc(hidden)]
+    pub fn new(env: &'env Environment) -> LmdbResult<RoTransaction<'env>> {
+        let mut txn: *mut MDB_txn = ptr::null_mut();
+        unsafe {
+            try!(lmdb_result(ffi::mdb_txn_begin(env.env(),
+                                                ptr::null_mut(),
+                                                MDB_RDONLY.bits(),
+                                                &mut txn)));
+            Ok(RoTransaction {
+                txn: txn,
+                _no_sync: marker::NoSync,
+                _no_send: marker::NoSend,
+                _contravariant: marker::ContravariantLifetime::<'env>,
+            })
+        }
+    }
+}
+
+impl <'env> Transaction<'env> for RoTransaction<'env> {
+    fn txn(&self) -> *mut MDB_txn {
+        self.txn
+    }
+}
+
+//impl <'env> TransactionExt<'env> for RoTransaction<'env> { }
+impl <'env> ReadTransaction<'env> for RoTransaction<'env> { }
+
+/// An LMDB read-write transaction.
+pub struct RwTransaction<'env> {
+    txn: *mut MDB_txn,
+    _no_sync: marker::NoSync,
+    _no_send: marker::NoSend,
+    _contravariant: marker::ContravariantLifetime<'env>,
+}
+
+#[unsafe_destructor]
+impl <'env> Drop for RwTransaction<'env> {
+    fn drop(&mut self) {
+        unsafe { ffi::mdb_txn_abort(self.txn) }
+    }
+}
+
+impl <'env> RwTransaction<'env> {
+
+    /// Creates a new read-write transaction in the given environment. Prefer using
+    /// `Environment::begin_ro_txn`.
+    #[doc(hidden)]
+    pub fn new(env: &'env Environment) -> LmdbResult<RwTransaction<'env>> {
+        let mut txn: *mut MDB_txn = ptr::null_mut();
+        unsafe {
+            try!(lmdb_result(ffi::mdb_txn_begin(env.env(),
+                                                ptr::null_mut(),
+                                                EnvironmentFlags::empty().bits(),
+                                                &mut txn)));
+            Ok(RwTransaction {
+                txn: txn,
+                _no_sync: marker::NoSync,
+                _no_send: marker::NoSend,
+                _contravariant: marker::ContravariantLifetime::<'env>,
+            })
+        }
     }
 }
 
+impl <'env> Transaction<'env> for RwTransaction<'env> {
+    fn txn(&self) -> *mut MDB_txn {
+        self.txn
+    }
+}
+
+//impl <'env> TransactionExt<'env> for RwTransaction<'env> { }
+impl <'env> ReadTransaction<'env> for RwTransaction<'env> { }
+impl <'env> WriteTransaction<'env> for RwTransaction<'env> { }
+
 #[cfg(test)]
 mod test {
 
@@ -222,44 +282,23 @@ mod test {
     use std::sync::{Arc, Barrier, Future};
 
     use environment::*;
-    use flags::*;
+    use super::*;
+    use ffi::*;
 
-    #[test]
-    fn test_open_db() {
-        let dir = io::TempDir::new("test").unwrap();
-        let env = Environment::new().set_max_dbs(10)
-                                    .open(dir.path(), io::USER_RWX)
-                                    .unwrap();
-        {
-            let txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
-            assert!(txn.open_db(None, DatabaseFlags::empty()).is_ok());
-            assert!(txn.commit().is_ok());
-        } {
-            let txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
-            assert!(txn.open_db(Some("testdb"), DatabaseFlags::empty()).is_err())
-        } {
-            let txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
-            txn.open_db(Some("testdb"), MDB_CREATE).unwrap();
-            assert!(txn.commit().is_ok());
-        } {
-            let txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
-            assert!(txn.open_db(Some("testdb"), DatabaseFlags::empty()).is_ok())
-        }
-    }
 
     #[test]
     fn test_put_get_del() {
         let dir = io::TempDir::new("test").unwrap();
         let env = Environment::new().open(dir.path(), io::USER_RWX).unwrap();
+        let db = env.open_db(None).unwrap();
 
-        let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+        let mut txn = env.begin_write_txn().unwrap();
-        let db = txn.open_db(None, DatabaseFlags::empty()).unwrap();
         txn.put(db, b"key1", b"val1", WriteFlags::empty()).unwrap();
         txn.put(db, b"key2", b"val2", WriteFlags::empty()).unwrap();
         txn.put(db, b"key3", b"val3", WriteFlags::empty()).unwrap();
         txn.commit().unwrap();
 
-        let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+        let mut txn = env.begin_write_txn().unwrap();
         assert_eq!(b"val1", txn.get(db, b"key1").unwrap());
         assert_eq!(b"val2", txn.get(db, b"key2").unwrap());
         assert_eq!(b"val3", txn.get(db, b"key3").unwrap());
@@ -270,19 +309,19 @@ mod test {
     }
 
     #[test]
-    fn test_put_zero_copy() {
+    fn test_reserve() {
         let dir = io::TempDir::new("test").unwrap();
         let env = Environment::new().open(dir.path(), io::USER_RWX).unwrap();
+        let db = env.open_db(None).unwrap();
 
-        let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+        let mut txn = env.begin_write_txn().unwrap();
-        let db = txn.open_db(None, DatabaseFlags::empty()).unwrap();
         {
-            let mut writer = txn.put_zero_copy(db, b"key1", 4, WriteFlags::empty()).unwrap();
+            let mut writer = txn.reserve(db, b"key1", 4, WriteFlags::empty()).unwrap();
             writer.write(b"val1").unwrap();
         }
         txn.commit().unwrap();
 
-        let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+        let mut txn = env.begin_write_txn().unwrap();
         assert_eq!(b"val1", txn.get(db, b"key1").unwrap());
         assert!(txn.get(db, b"key").is_err());
 
@@ -299,15 +338,15 @@ mod test {
                                        .unwrap());
 
         let db1 = {
-            let txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+            let db = env.create_db(Some("db"), DatabaseFlags::empty()).unwrap();
-            let db = txn.open_db(Some("db"), MDB_CREATE).unwrap();
+            let txn = env.begin_write_txn().unwrap();
             txn.commit().unwrap();
             db
         };
 
         let db2 = {
-            let txn = env.begin_txn(MDB_RDONLY).unwrap();
+            let db = env.open_db(Some("db")).unwrap();
-            let db = txn.open_db(Some("db"), DatabaseFlags::empty()).unwrap();
+            let txn = env.begin_read_txn().unwrap();
             txn.commit().unwrap();
             db
         };
@@ -316,7 +355,7 @@ mod test {
         assert!(db1.dbi() == db2.dbi());
 
         {
-            let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+            let mut txn = env.begin_write_txn().unwrap();
             txn.put(db1, b"key1", b"val1", WriteFlags::empty()).unwrap();
             assert!(txn.commit().is_ok());
         }
@@ -324,7 +363,7 @@ mod test {
         unsafe { env.close_db(db1) };
 
         {
-            let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+            let mut txn = env.begin_write_txn().unwrap();
             assert!(txn.put(db1, b"key2", b"val2", WriteFlags::empty()).is_err());
         }
     }
@@ -332,15 +371,11 @@ mod test {
     #[test]
     fn test_concurrent_readers_single_writer() {
         let dir = io::TempDir::new("test").unwrap();
-        let env = Arc::new(Environment::new().open(dir.path(), io::USER_RWX).unwrap());
+        let env: Arc<Environment> = Arc::new(Environment::new().open(dir.path(), io::USER_RWX).unwrap());
-
-        let open_db_txn = env.begin_txn(MDB_RDONLY).unwrap();
-        let db = open_db_txn.open_db(None, DatabaseFlags::empty()).unwrap();
-        open_db_txn.commit().unwrap();
 
         let n = 10u; // Number of concurrent readers
         let barrier = Arc::new(Barrier::new(n + 1));
-        let mut futures = Vec::with_capacity(n);
+        let mut futures: Vec<Future<bool>> = Vec::with_capacity(n);
 
         let key = b"key";
         let val = b"val";
@@ -349,22 +384,24 @@ mod test {
             let reader_env = env.clone();
             let reader_barrier = barrier.clone();
 
-            futures.push(Future::spawn(proc() {
+            futures.push(Future::spawn(move|| {
+                let db = reader_env.open_db(None).unwrap();
                 {
-                    let txn = reader_env.begin_txn(MDB_RDONLY).unwrap();
+                    let txn = reader_env.begin_read_txn().unwrap();
                     assert!(txn.get(db, key).is_err());
                     txn.abort();
                 }
                 reader_barrier.wait();
                 reader_barrier.wait();
                 {
-                    let txn = reader_env.begin_txn(MDB_RDONLY).unwrap();
+                    let txn = reader_env.begin_read_txn().unwrap();
                     txn.get(db, key).unwrap() == val
                 }
             }));
         }
 
-        let mut txn = env.begin_txn(EnvironmentFlags::empty()).unwrap();
+        let db = env.open_db(None).unwrap();
+        let mut txn = env.begin_write_txn().unwrap();
         barrier.wait();
         txn.put(db, key, val, WriteFlags::empty()).unwrap();
         txn.commit().unwrap();
@@ -378,12 +415,8 @@ mod test {
         let dir = io::TempDir::new("test").unwrap();
         let env = Arc::new(Environment::new().open(dir.path(), io::USER_RWX).unwrap());
 
-        let open_db_txn = env.begin_txn(MDB_RDONLY).unwrap();
-        let db = open_db_txn.open_db(None, DatabaseFlags::empty()).unwrap();
-        open_db_txn.commit().unwrap();
-
         let n = 10u; // Number of concurrent writers
-        let mut futures = Vec::with_capacity(n);
+        let mut futures: Vec<Future<bool>> = Vec::with_capacity(n);
 
         let key = "key";
         let val = "val";
@@ -391,8 +424,9 @@ mod test {
         for i in range(0, n) {
             let writer_env = env.clone();
 
-            futures.push(Future::spawn(proc() {
+            futures.push(Future::spawn(move|| {
-                let mut txn = writer_env.begin_txn(EnvironmentFlags::empty()).unwrap();
+                let db = writer_env.open_db(None).unwrap();
+                let mut txn = writer_env.begin_write_txn().unwrap();
                 txn.put(db,
                         format!("{}{}", key, i).as_bytes(),
                         format!("{}{}", val, i).as_bytes(),
@@ -403,7 +437,8 @@ mod test {
         }
         assert!(futures.iter_mut().all(|b| b.get()));
 
-        let txn = env.begin_txn(MDB_RDONLY).unwrap();
+        let db = env.open_db(None).unwrap();
+        let txn = env.begin_read_txn().unwrap();
 
         for i in range(0, n) {
             assert_eq!(