blob: cc174dfc7c969e728995de3d34daa4ac8d2833cd [file] [log] [blame]
/*
* Copyright 2016 The WebRTC Project Authors. All rights reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#ifndef RTC_BASE_COPYONWRITEBUFFER_H_
#define RTC_BASE_COPYONWRITEBUFFER_H_
#include <stdint.h>
#include <algorithm>
#include <cstring>
#include <string>
#include <type_traits>
#include <utility>
#include "rtc_base/buffer.h"
#include "rtc_base/checks.h"
#include "rtc_base/refcountedobject.h"
#include "rtc_base/scoped_ref_ptr.h"
namespace rtc {
class CopyOnWriteBuffer {
public:
// An empty buffer.
CopyOnWriteBuffer();
// Copy size and contents of an existing buffer.
CopyOnWriteBuffer(const CopyOnWriteBuffer& buf);
// Move contents from an existing buffer.
CopyOnWriteBuffer(CopyOnWriteBuffer&& buf);
// Construct a buffer from a string, convenient for unittests.
CopyOnWriteBuffer(const std::string& s);
// Construct a buffer with the specified number of uninitialized bytes.
explicit CopyOnWriteBuffer(size_t size);
CopyOnWriteBuffer(size_t size, size_t capacity);
// Construct a buffer and copy the specified number of bytes into it. The
// source array may be (const) uint8_t*, int8_t*, or char*.
template <typename T,
typename std::enable_if<
internal::BufferCompat<uint8_t, T>::value>::type* = nullptr>
CopyOnWriteBuffer(const T* data, size_t size)
: CopyOnWriteBuffer(data, size, size) {}
template <typename T,
typename std::enable_if<
internal::BufferCompat<uint8_t, T>::value>::type* = nullptr>
CopyOnWriteBuffer(const T* data, size_t size, size_t capacity)
: CopyOnWriteBuffer(size, capacity) {
if (buffer_) {
std::memcpy(buffer_->data(), data, size);
}
}
// Construct a buffer from the contents of an array.
template <typename T,
size_t N,
typename std::enable_if<
internal::BufferCompat<uint8_t, T>::value>::type* = nullptr>
CopyOnWriteBuffer(const T (&array)[N]) // NOLINT: runtime/explicit
: CopyOnWriteBuffer(array, N) {}
~CopyOnWriteBuffer();
// Get a pointer to the data. Just .data() will give you a (const) uint8_t*,
// but you may also use .data<int8_t>() and .data<char>().
template <typename T = uint8_t,
typename std::enable_if<
internal::BufferCompat<uint8_t, T>::value>::type* = nullptr>
const T* data() const {
return cdata<T>();
}
// Get writable pointer to the data. This will create a copy of the underlying
// data if it is shared with other buffers.
template <typename T = uint8_t,
typename std::enable_if<
internal::BufferCompat<uint8_t, T>::value>::type* = nullptr>
T* data() {
RTC_DCHECK(IsConsistent());
if (!buffer_) {
return nullptr;
}
CloneDataIfReferenced(buffer_->capacity());
return buffer_->data<T>();
}
// Get const pointer to the data. This will not create a copy of the
// underlying data if it is shared with other buffers.
template <typename T = uint8_t,
typename std::enable_if<
internal::BufferCompat<uint8_t, T>::value>::type* = nullptr>
const T* cdata() const {
RTC_DCHECK(IsConsistent());
if (!buffer_) {
return nullptr;
}
return buffer_->data<T>();
}
size_t size() const {
RTC_DCHECK(IsConsistent());
return buffer_ ? buffer_->size() : 0;
}
size_t capacity() const {
RTC_DCHECK(IsConsistent());
return buffer_ ? buffer_->capacity() : 0;
}
CopyOnWriteBuffer& operator=(const CopyOnWriteBuffer& buf) {
RTC_DCHECK(IsConsistent());
RTC_DCHECK(buf.IsConsistent());
if (&buf != this) {
buffer_ = buf.buffer_;
}
return *this;
}
CopyOnWriteBuffer& operator=(CopyOnWriteBuffer&& buf) {
RTC_DCHECK(IsConsistent());
RTC_DCHECK(buf.IsConsistent());
buffer_ = std::move(buf.buffer_);
return *this;
}
bool operator==(const CopyOnWriteBuffer& buf) const;
bool operator!=(const CopyOnWriteBuffer& buf) const {
return !(*this == buf);
}
uint8_t& operator[](size_t index) {
RTC_DCHECK_LT(index, size());
return data()[index];
}
uint8_t operator[](size_t index) const {
RTC_DCHECK_LT(index, size());
return cdata()[index];
}
// Replace the contents of the buffer. Accepts the same types as the
// constructors.
template <typename T,
typename std::enable_if<
internal::BufferCompat<uint8_t, T>::value>::type* = nullptr>
void SetData(const T* data, size_t size) {
RTC_DCHECK(IsConsistent());
if (!buffer_) {
buffer_ = size > 0 ? new RefCountedObject<Buffer>(data, size) : nullptr;
} else if (!buffer_->HasOneRef()) {
buffer_ = new RefCountedObject<Buffer>(data, size, buffer_->capacity());
} else {
buffer_->SetData(data, size);
}
RTC_DCHECK(IsConsistent());
}
template <typename T,
size_t N,
typename std::enable_if<
internal::BufferCompat<uint8_t, T>::value>::type* = nullptr>
void SetData(const T (&array)[N]) {
SetData(array, N);
}
void SetData(const CopyOnWriteBuffer& buf) {
RTC_DCHECK(IsConsistent());
RTC_DCHECK(buf.IsConsistent());
if (&buf != this) {
buffer_ = buf.buffer_;
}
}
// Append data to the buffer. Accepts the same types as the constructors.
template <typename T,
typename std::enable_if<
internal::BufferCompat<uint8_t, T>::value>::type* = nullptr>
void AppendData(const T* data, size_t size) {
RTC_DCHECK(IsConsistent());
if (!buffer_) {
buffer_ = new RefCountedObject<Buffer>(data, size);
RTC_DCHECK(IsConsistent());
return;
}
CloneDataIfReferenced(
std::max(buffer_->capacity(), buffer_->size() + size));
buffer_->AppendData(data, size);
RTC_DCHECK(IsConsistent());
}
template <typename T,
size_t N,
typename std::enable_if<
internal::BufferCompat<uint8_t, T>::value>::type* = nullptr>
void AppendData(const T (&array)[N]) {
AppendData(array, N);
}
void AppendData(const CopyOnWriteBuffer& buf) {
AppendData(buf.data(), buf.size());
}
// Sets the size of the buffer. If the new size is smaller than the old, the
// buffer contents will be kept but truncated; if the new size is greater,
// the existing contents will be kept and the new space will be
// uninitialized.
void SetSize(size_t size);
// Ensure that the buffer size can be increased to at least capacity without
// further reallocation. (Of course, this operation might need to reallocate
// the buffer.)
void EnsureCapacity(size_t capacity);
// Resets the buffer to zero size without altering capacity. Works even if the
// buffer has been moved from.
void Clear();
// Swaps two buffers.
friend void swap(CopyOnWriteBuffer& a, CopyOnWriteBuffer& b) {
std::swap(a.buffer_, b.buffer_);
}
private:
// Create a copy of the underlying data if it is referenced from other Buffer
// objects.
void CloneDataIfReferenced(size_t new_capacity);
// Pre- and postcondition of all methods.
bool IsConsistent() const { return (!buffer_ || buffer_->capacity() > 0); }
// buffer_ is either null, or points to an rtc::Buffer with capacity > 0.
scoped_refptr<RefCountedObject<Buffer>> buffer_;
};
} // namespace rtc
#endif // RTC_BASE_COPYONWRITEBUFFER_H_