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rocksdb/third-party/fbson/FbsonStream.h

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/*
* Copyright (c) 2014, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD-style license found in the
* LICENSE file in the root directory of this source tree. An additional grant
* of patent rights can be found in the PATENTS file in the same directory.
*
*/
/*
* This header file defines FbsonInBuffer and FbsonOutStream classes.
*
* ** Input Buffer **
* FbsonInBuffer is a customer input buffer to wrap raw character buffer. Its
* object instances are used to create std::istream objects interally.
*
* ** Output Stream **
* FbsonOutStream is a custom output stream classes, to contain the FBSON
* serialized binary. The class is conveniently used to specialize templates of
* FbsonParser and FbsonWriter.
*
* @author Tian Xia <tianx@fb.com>
*/
#ifndef FBSON_FBSONSTREAM_H
#define FBSON_FBSONSTREAM_H
#ifndef __STDC_FORMAT_MACROS
#define __STDC_FORMAT_MACROS
#endif
#include <inttypes.h>
#include <iostream>
namespace fbson {
// lengths includes sign
#define MAX_INT_DIGITS 11
#define MAX_INT64_DIGITS 20
#define MAX_DOUBLE_DIGITS 23 // 1(sign)+16(significant)+1(decimal)+5(exponent)
/*
* FBSON's implementation of input buffer
*/
class FbsonInBuffer : public std::streambuf {
public:
FbsonInBuffer(const char* str, uint32_t len) {
// this is read buffer and the str will not be changed
// so we use const_cast (ugly!) to remove constness
char* pch(const_cast<char*>(str));
setg(pch, pch, pch + len);
}
};
/*
* FBSON's implementation of output stream.
*
* This is a wrapper of a char buffer. By default, the buffer capacity is 1024
* bytes. We will double the buffer if realloc is needed for writes.
*/
class FbsonOutStream : public std::ostream {
public:
explicit FbsonOutStream(uint32_t capacity = 1024)
: head_(nullptr), size_(0), capacity_(capacity), alloc_(true) {
if (capacity_ == 0) {
capacity_ = 1024;
}
head_ = (char*)malloc(capacity_);
}
FbsonOutStream(char* buffer, uint32_t capacity)
: head_(buffer), size_(0), capacity_(capacity), alloc_(false) {
assert(buffer && capacity_ > 0);
}
~FbsonOutStream() {
if (alloc_) {
free(head_);
}
}
void put(char c) { write(&c, 1); }
void write(const char* c_str) { write(c_str, (uint32_t)strlen(c_str)); }
void write(const char* bytes, uint32_t len) {
if (len == 0)
return;
if (size_ + len > capacity_) {
realloc(len);
}
memcpy(head_ + size_, bytes, len);
size_ += len;
}
// write the integer to string
void write(int i) {
// snprintf automatically adds a NULL, so we need one more char
if (size_ + MAX_INT_DIGITS + 1 > capacity_) {
realloc(MAX_INT_DIGITS + 1);
}
int len = snprintf(head_ + size_, MAX_INT_DIGITS + 1, "%d", i);
assert(len > 0);
size_ += len;
}
// write the 64bit integer to string
void write(int64_t l) {
// snprintf automatically adds a NULL, so we need one more char
if (size_ + MAX_INT64_DIGITS + 1 > capacity_) {
realloc(MAX_INT64_DIGITS + 1);
}
int len = snprintf(head_ + size_, MAX_INT64_DIGITS + 1, "%" PRIi64, l);
assert(len > 0);
size_ += len;
}
// write the double to string
void write(double d) {
// snprintf automatically adds a NULL, so we need one more char
if (size_ + MAX_DOUBLE_DIGITS + 1 > capacity_) {
realloc(MAX_DOUBLE_DIGITS + 1);
}
int len = snprintf(head_ + size_, MAX_DOUBLE_DIGITS + 1, "%.15g", d);
assert(len > 0);
size_ += len;
}
pos_type tellp() const { return size_; }
void seekp(pos_type pos) { size_ = (uint32_t)pos; }
const char* getBuffer() const { return head_; }
pos_type getSize() const { return tellp(); }
private:
void realloc(uint32_t len) {
assert(capacity_ > 0);
capacity_ *= 2;
while (capacity_ < size_ + len) {
capacity_ *= 2;
}
if (alloc_) {
char* new_buf = (char*)::realloc(head_, capacity_);
assert(new_buf);
head_ = new_buf;
} else {
char* new_buf = (char*)::malloc(capacity_);
assert(new_buf);
memcpy(new_buf, head_, size_);
head_ = new_buf;
alloc_ = true;
}
}
private:
char* head_;
uint32_t size_;
uint32_t capacity_;
bool alloc_;
};
} // namespace fbson
#endif // FBSON_FBSONSTREAM_H