Add support for open_for_read_only APIs (#402)

src/db.rs

@@ -21,7 +21,7 @@ use crate::{
     WriteBatch, WriteOptions,
 };
 
-use libc::{self, c_char, c_int, c_void, size_t};
+use libc::{self, c_char, c_int, c_uchar, c_void, size_t};
 use std::collections::BTreeMap;
 use std::ffi::{CStr, CString};
 use std::fmt;
@@ -50,20 +50,35 @@ unsafe impl Send for DB {}
 // use within the rocksdb library is generally behind a const reference
 unsafe impl Sync for DB {}
 
+// Specifies whether open DB for read only.
+enum AccessType {
+    ReadWrite,
+    ReadOnly { error_if_log_file_exist: bool },
+}
+
 impl DB {
-    /// Open a database with default options.
+    /// Opens a database with default options.
     pub fn open_default<P: AsRef<Path>>(path: P) -> Result<DB, Error> {
         let mut opts = Options::default();
         opts.create_if_missing(true);
         DB::open(&opts, path)
     }
 
-    /// Open the database with the specified options.
+    /// Opens the database with the specified options.
     pub fn open<P: AsRef<Path>>(opts: &Options, path: P) -> Result<DB, Error> {
         DB::open_cf(opts, path, None::<&str>)
     }
 
-    /// Open a database with the given database options and column family names.
+    /// Opens the database for read only with the specified options.
+    pub fn open_for_read_only<P: AsRef<Path>>(
+        opts: &Options,
+        path: P,
+        error_if_log_file_exist: bool,
+    ) -> Result<DB, Error> {
+        DB::open_cf_for_read_only(opts, path, None::<&str>, error_if_log_file_exist)
+    }
+
+    /// Opens a database with the given database options and column family names.
     ///
     /// Column families opened using this function will be created with default `Options`.
     pub fn open_cf<P, I, N>(opts: &Options, path: P, cfs: I) -> Result<DB, Error>
@@ -76,11 +91,51 @@ impl DB {
             .into_iter()
             .map(|name| ColumnFamilyDescriptor::new(name.as_ref(), Options::default()));
 
-        DB::open_cf_descriptors(opts, path, cfs)
+        DB::open_cf_descriptors_internal(opts, path, cfs, AccessType::ReadWrite)
     }
 
-    /// Open a database with the given database options and column family descriptors.
+    /// Opens a database for read only with the given database options and column family names.
+    pub fn open_cf_for_read_only<P, I, N>(
+        opts: &Options,
+        path: P,
+        cfs: I,
+        error_if_log_file_exist: bool,
+    ) -> Result<DB, Error>
+    where
+        P: AsRef<Path>,
+        I: IntoIterator<Item = N>,
+        N: AsRef<str>,
+    {
+        let cfs = cfs
+            .into_iter()
+            .map(|name| ColumnFamilyDescriptor::new(name.as_ref(), Options::default()));
+
+        DB::open_cf_descriptors_internal(
+            opts,
+            path,
+            cfs,
+            AccessType::ReadOnly {
+                error_if_log_file_exist,
+            },
+        )
+    }
+
+    /// Opens a database with the given database options and column family descriptors.
     pub fn open_cf_descriptors<P, I>(opts: &Options, path: P, cfs: I) -> Result<DB, Error>
+    where
+        P: AsRef<Path>,
+        I: IntoIterator<Item = ColumnFamilyDescriptor>,
+    {
+        DB::open_cf_descriptors_internal(opts, path, cfs, AccessType::ReadWrite)
+    }
+
+    /// Internal implementation for opening RocksDB.
+    fn open_cf_descriptors_internal<P, I>(
+        opts: &Options,
+        path: P,
+        cfs: I,
+        access_type: AccessType,
+    ) -> Result<DB, Error>
     where
         P: AsRef<Path>,
         I: IntoIterator<Item = ColumnFamilyDescriptor>,
@@ -100,9 +155,7 @@ impl DB {
         let mut cf_map = BTreeMap::new();
 
         if cfs.is_empty() {
-            unsafe {
-                db = ffi_try!(ffi::rocksdb_open(opts.inner, cpath.as_ptr() as *const _));
-            }
+            db = DB::open_raw(opts, cpath, access_type)?;
         } else {
             let mut cfs_v = cfs;
             // Always open the default column family.
@@ -119,27 +172,25 @@ impl DB {
                 .map(|cf| CString::new(cf.name.as_bytes()).unwrap())
                 .collect();
 
-            let mut cfnames: Vec<_> = c_cfs.iter().map(|cf| cf.as_ptr()).collect();
+            let cfnames: Vec<_> = c_cfs.iter().map(|cf| cf.as_ptr()).collect();
 
             // These handles will be populated by DB.
             let mut cfhandles: Vec<_> = cfs_v.iter().map(|_| ptr::null_mut()).collect();
 
-            let mut cfopts: Vec<_> = cfs_v
+            let cfopts: Vec<_> = cfs_v
                 .iter()
                 .map(|cf| cf.options.inner as *const _)
                 .collect();
 
-            unsafe {
-                db = ffi_try!(ffi::rocksdb_open_column_families(
-                    opts.inner,
-                    cpath.as_ptr(),
-                    cfs_v.len() as c_int,
-                    cfnames.as_mut_ptr(),
-                    cfopts.as_mut_ptr(),
-                    cfhandles.as_mut_ptr(),
-                ));
-            }
-
+            db = DB::open_cf_raw(
+                opts,
+                cpath,
+                &cfs_v,
+                &cfnames,
+                &cfopts,
+                &mut cfhandles,
+                access_type,
+            )?;
             for handle in &cfhandles {
                 if handle.is_null() {
                     return Err(Error::new(
@@ -164,6 +215,63 @@ impl DB {
         })
     }
 
+    fn open_raw(
+        opts: &Options,
+        cpath: CString,
+        access_type: AccessType,
+    ) -> Result<*mut ffi::rocksdb_t, Error> {
+        let db = unsafe {
+            match access_type {
+                AccessType::ReadOnly {
+                    error_if_log_file_exist,
+                } => ffi_try!(ffi::rocksdb_open_for_read_only(
+                    opts.inner,
+                    cpath.as_ptr() as *const _,
+                    error_if_log_file_exist as c_uchar,
+                )),
+                AccessType::ReadWrite => {
+                    ffi_try!(ffi::rocksdb_open(opts.inner, cpath.as_ptr() as *const _))
+                }
+            }
+        };
+        Ok(db)
+    }
+
+    fn open_cf_raw(
+        opts: &Options,
+        cpath: CString,
+        cfs_v: &[ColumnFamilyDescriptor],
+        cfnames: &[*const c_char],
+        cfopts: &[*const ffi::rocksdb_options_t],
+        cfhandles: &mut Vec<*mut ffi::rocksdb_column_family_handle_t>,
+        access_type: AccessType,
+    ) -> Result<*mut ffi::rocksdb_t, Error> {
+        let db = unsafe {
+            match access_type {
+                AccessType::ReadOnly {
+                    error_if_log_file_exist,
+                } => ffi_try!(ffi::rocksdb_open_for_read_only_column_families(
+                    opts.inner,
+                    cpath.as_ptr(),
+                    cfs_v.len() as c_int,
+                    cfnames.as_ptr(),
+                    cfopts.as_ptr(),
+                    cfhandles.as_mut_ptr(),
+                    error_if_log_file_exist as c_uchar,
+                )),
+                AccessType::ReadWrite => ffi_try!(ffi::rocksdb_open_column_families(
+                    opts.inner,
+                    cpath.as_ptr(),
+                    cfs_v.len() as c_int,
+                    cfnames.as_ptr(),
+                    cfopts.as_ptr(),
+                    cfhandles.as_mut_ptr(),
+                )),
+            }
+        };
+        Ok(db)
+    }
+
     pub fn list_cf<P: AsRef<Path>>(opts: &Options, path: P) -> Result<Vec<String>, Error> {
         let cpath = to_cpath(path)?;
         let mut length = 0;
@@ -958,6 +1066,48 @@ impl fmt::Debug for DB {
     }
 }
 
+#[test]
+fn test_open_for_read_only() {
+    let path = "_rust_rocksdb_test_open_for_read_only";
+    {
+        let db = DB::open_default(path).unwrap();
+        db.put(b"k1", b"v1").unwrap();
+    }
+    {
+        let opts = Options::default();
+        let error_if_log_file_exist = false;
+        let db = DB::open_for_read_only(&opts, path, error_if_log_file_exist).unwrap();
+        assert_eq!(db.get(b"k1").unwrap().unwrap(), b"v1");
+        assert!(db.put(b"k2", b"v2").is_err());
+    }
+    let opts = Options::default();
+    assert!(DB::destroy(&opts, path).is_ok());
+}
+
+#[test]
+fn test_open_cf_for_read_only() {
+    let path = "_rust_rocksdb_test_open_cf_for_read_only";
+    let cfs = vec!["cf1"];
+    {
+        let mut opts = Options::default();
+        opts.create_if_missing(true);
+        opts.create_missing_column_families(true);
+        let db = DB::open_cf(&opts, path, cfs.clone()).unwrap();
+        let cf1 = db.cf_handle("cf1").unwrap();
+        db.put_cf(cf1, b"k1", b"v1").unwrap();
+    }
+    {
+        let opts = Options::default();
+        let error_if_log_file_exist = false;
+        let db = DB::open_cf_for_read_only(&opts, path, cfs, error_if_log_file_exist).unwrap();
+        let cf1 = db.cf_handle("cf1").unwrap();
+        assert_eq!(db.get_cf(cf1, b"k1").unwrap().unwrap(), b"v1");
+        assert!(db.put_cf(cf1, b"k2", b"v2").is_err());
+    }
+    let opts = Options::default();
+    assert!(DB::destroy(&opts, path).is_ok());
+}
+
 #[test]
 fn external() {
     let path = "_rust_rocksdb_externaltest";