zqz/platform-external-webrtc
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Define rtc::BufferT, like rtc::Buffer but for any trivial type

Browse Source 
And redefine rtc::Buffer as

  using Buffer = BufferT<uint8_t>;

(In the long run, I'd like to remove the type alias and rename the
template to just rtc::Buffer, but that requires all current users of
Buffer to start saying Buffer<uint8_t> instead, and since Buffer is
used in the API, we can't do that in one step.)

The immediate reason for the new template is that we'd like to use
BufferT<int16_t> in the AudioDecoder interface.

BUG=webrtc:5801

Review-Url: https://codereview.webrtc.org/1929903002
Cr-Commit-Position: refs/heads/master@{#12564}
This commit is contained in:
kwiberg
2016-04-29 08:00:22 -07:00
committed by Commit bot
parent ef8b61e110
commit a4ac4786a8
7 changed files with 252 additions and 156 deletions
Download Patch File Download Diff File Expand all files Collapse all files

252
webrtc/base/buffer.h
View File

@ -13,79 +13,114 @@
#include <cstring>
#include <memory>
#include <type_traits>
#include <utility>
#include "webrtc/base/array_view.h"
#include "webrtc/base/checks.h"
#include "webrtc/base/constructormagic.h"
namespace rtc {
namespace internal {
// (Internal; please don't use outside this file.) ByteType<T>::t is int if T
// is uint8_t, int8_t, or char; otherwise, it's a compilation error. Use like
// this:
//
// template <typename T, typename ByteType<T>::t = 0>
// void foo(T* x);
//
// to let foo<T> be defined only for byte-sized integers.
template <typename T>
struct ByteType {
private:
static int F(uint8_t*);
static int F(int8_t*);
static int F(char*);
public:
using t = decltype(F(static_cast<T*>(nullptr)));
// (Internal; please don't use outside this file.) Determines if elements of
// type U are compatible with a BufferT<T>. For most types, we just ignore
// top-level const and forbid top-level volatile and require T and U to be
// otherwise equal, but all byte-sized integers (notably char, int8_t, and
// uint8_t) are compatible with each other. (Note: We aim to get rid of this
// behavior, and treat all types the same.)
template <typename T, typename U>
struct BufferCompat {
static constexpr bool value =
!std::is_volatile<U>::value &&
((std::is_integral<T>::value && sizeof(T) == 1)
? (std::is_integral<U>::value && sizeof(U) == 1)
: (std::is_same<T, typename std::remove_const<U>::type>::value));
};
} // namespace internal
// Basic buffer class, can be grown and shrunk dynamically.
// Unlike std::string/vector, does not initialize data when expanding capacity.
class Buffer {
// Unlike std::string/vector, does not initialize data when increasing size.
template <typename T>
class BufferT {
// We want T's destructor and default constructor to be trivial, i.e. perform
// no action, so that we don't have to touch the memory we allocate and
// deallocate. And we want T to be trivially copyable, so that we can copy T
// instances with std::memcpy. This is precisely the definition of a trivial
// type.
static_assert(std::is_trivial<T>::value, "T must be a trivial type.");
// This class relies heavily on being able to mutate its data.
static_assert(!std::is_const<T>::value, "T may not be const");
public:
Buffer(); // An empty buffer.
Buffer(Buffer&& buf); // Move contents from an existing buffer.
// An empty BufferT.
BufferT() : size_(0), capacity_(0), data_(nullptr) {
RTC_DCHECK(IsConsistent());
}
// Construct a buffer with the specified number of uninitialized bytes.
explicit Buffer(size_t size);
Buffer(size_t size, size_t capacity);
// Disable copy construction and copy assignment, since copying a buffer is
// expensive enough that we want to force the user to be explicit about it.
BufferT(const BufferT&) = delete;
BufferT& operator=(const BufferT&) = delete;
// 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 internal::ByteType<T>::t = 0>
Buffer(const T* data, size_t size)
: Buffer(data, size, size) {}
BufferT(BufferT&& buf)
: size_(buf.size()),
capacity_(buf.capacity()),
data_(std::move(buf.data_)) {
RTC_DCHECK(IsConsistent());
buf.OnMovedFrom();
}
template <typename T, typename internal::ByteType<T>::t = 0>
Buffer(const T* data, size_t size, size_t capacity)
: Buffer(size, capacity) {
std::memcpy(data_.get(), data, size);
// Construct a buffer with the specified number of uninitialized elements.
explicit BufferT(size_t size) : BufferT(size, size) {}
BufferT(size_t size, size_t capacity)
: size_(size),
capacity_(std::max(size, capacity)),
data_(new T[capacity_]) {
RTC_DCHECK(IsConsistent());
}
// Construct a buffer and copy the specified number of elements into it.
template <typename U,
typename std::enable_if<
internal::BufferCompat<T, U>::value>::type* = nullptr>
BufferT(const U* data, size_t size) : BufferT(data, size, size) {}
template <typename U,
typename std::enable_if<
internal::BufferCompat<T, U>::value>::type* = nullptr>
BufferT(U* data, size_t size, size_t capacity) : BufferT(size, capacity) {
static_assert(sizeof(T) == sizeof(U), "");
std::memcpy(data_.get(), data, size * sizeof(U));
}
// Construct a buffer from the contents of an array.
template <typename T, size_t N, typename internal::ByteType<T>::t = 0>
Buffer(const T(&array)[N])
: Buffer(array, N) {}
template <typename U,
size_t N,
typename std::enable_if<
internal::BufferCompat<T, U>::value>::type* = nullptr>
BufferT(U (&array)[N]) : BufferT(array, N) {}
~Buffer();
// 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 internal::ByteType<T>::t = 0>
const T* data() const {
// Get a pointer to the data. Just .data() will give you a (const) T*, but if
// T is a byte-sized integer, you may also use .data<U>() for any other
// byte-sized integer U.
template <typename U = T,
typename std::enable_if<
internal::BufferCompat<T, U>::value>::type* = nullptr>
const U* data() const {
RTC_DCHECK(IsConsistent());
return reinterpret_cast<T*>(data_.get());
return reinterpret_cast<U*>(data_.get());
}
template <typename T = uint8_t, typename internal::ByteType<T>::t = 0>
T* data() {
template <typename U = T,
typename std::enable_if<
internal::BufferCompat<T, U>::value>::type* = nullptr>
U* data() {
RTC_DCHECK(IsConsistent());
return reinterpret_cast<T*>(data_.get());
return reinterpret_cast<U*>(data_.get());
}
size_t size() const {
@ -98,7 +133,7 @@ class Buffer {
return capacity_;
}
Buffer& operator=(Buffer&& buf) {
BufferT& operator=(BufferT&& buf) {
RTC_DCHECK(IsConsistent());
RTC_DCHECK(buf.IsConsistent());
size_ = buf.size_;
@ -108,94 +143,120 @@ class Buffer {
return *this;
}
bool operator==(const Buffer& buf) const {
bool operator==(const BufferT& buf) const {
RTC_DCHECK(IsConsistent());
return size_ == buf.size() && memcmp(data_.get(), buf.data(), size_) == 0;
if (size_ != buf.size_) {
return false;
}
if (std::is_integral<T>::value) {
// Optimization.
return std::memcmp(data_.get(), buf.data_.get(), size_ * sizeof(T)) == 0;
}
for (size_t i = 0; i < size_; ++i) {
if (data_[i] != buf.data_[i]) {
return false;
}
}
return true;
}
bool operator!=(const Buffer& buf) const { return !(*this == buf); }
bool operator!=(const BufferT& buf) const { return !(*this == buf); }
uint8_t& operator[](size_t index) {
T& operator[](size_t index) {
RTC_DCHECK_LT(index, size_);
return data()[index];
}
uint8_t operator[](size_t index) const {
T operator[](size_t index) const {
RTC_DCHECK_LT(index, size_);
return data()[index];
}
// The SetData functions replace the contents of the buffer. They accept the
// same input types as the constructors.
template <typename T, typename internal::ByteType<T>::t = 0>
void SetData(const T* data, size_t size) {
template <typename U,
typename std::enable_if<
internal::BufferCompat<T, U>::value>::type* = nullptr>
void SetData(const U* data, size_t size) {
RTC_DCHECK(IsConsistent());
size_ = 0;
AppendData(data, size);
}
template <typename T, size_t N, typename internal::ByteType<T>::t = 0>
void SetData(const T(&array)[N]) {
template <typename U,
size_t N,
typename std::enable_if<
internal::BufferCompat<T, U>::value>::type* = nullptr>
void SetData(const U (&array)[N]) {
SetData(array, N);
}
void SetData(const Buffer& buf) { SetData(buf.data(), buf.size()); }
void SetData(const BufferT& buf) { SetData(buf.data(), buf.size()); }
// Replace the data in the buffer with at most |max_bytes| of data, using the
// function |setter|, which should have the following signature:
// size_t setter(ArrayView<T> view)
// Replace the data in the buffer with at most |max_elements| of data, using
// the function |setter|, which should have the following signature:
// size_t setter(ArrayView<U> view)
// |setter| is given an appropriately typed ArrayView of the area in which to
// write the data (i.e. starting at the beginning of the buffer) and should
// return the number of bytes actually written. This number must be <=
// |max_bytes|.
template <typename T = uint8_t, typename F,
typename internal::ByteType<T>::t = 0>
size_t SetData(size_t max_bytes, F&& setter) {
// return the number of elements actually written. This number must be <=
// |max_elements|.
template <typename U = T,
typename F,
typename std::enable_if<
internal::BufferCompat<T, U>::value>::type* = nullptr>
size_t SetData(size_t max_elements, F&& setter) {
RTC_DCHECK(IsConsistent());
size_ = 0;
return AppendData<T>(max_bytes, std::forward<F>(setter));
return AppendData<U>(max_elements, std::forward<F>(setter));
}
// The AppendData functions adds data to the end of the buffer. They accept
// The AppendData functions add data to the end of the buffer. They accept
// the same input types as the constructors.
template <typename T, typename internal::ByteType<T>::t = 0>
void AppendData(const T* data, size_t size) {
template <typename U,
typename std::enable_if<
internal::BufferCompat<T, U>::value>::type* = nullptr>
void AppendData(const U* data, size_t size) {
RTC_DCHECK(IsConsistent());
const size_t new_size = size_ + size;
EnsureCapacity(new_size);
std::memcpy(data_.get() + size_, data, size);
static_assert(sizeof(T) == sizeof(U), "");
std::memcpy(data_.get() + size_, data, size * sizeof(U));
size_ = new_size;
RTC_DCHECK(IsConsistent());
}
template <typename T, size_t N, typename internal::ByteType<T>::t = 0>
void AppendData(const T(&array)[N]) {
template <typename U,
size_t N,
typename std::enable_if<
internal::BufferCompat<T, U>::value>::type* = nullptr>
void AppendData(const U (&array)[N]) {
AppendData(array, N);
}
void AppendData(const Buffer& buf) { AppendData(buf.data(), buf.size()); }
void AppendData(const BufferT& buf) { AppendData(buf.data(), buf.size()); }
// Append at most |max_bytes| of data to the end of the buffer, using the
// function |setter|, which should have the following signature:
// size_t setter(ArrayView<T> view)
// Append at most |max_elements| to the end of the buffer, using the function
// |setter|, which should have the following signature:
// size_t setter(ArrayView<U> view)
// |setter| is given an appropriately typed ArrayView of the area in which to
// write the data (i.e. starting at the former end of the buffer) and should
// return the number of bytes actually written. This number must be <=
// |max_bytes|.
template <typename T = uint8_t, typename F,
typename internal::ByteType<T>::t = 0>
size_t AppendData(size_t max_bytes, F&& setter) {
// return the number of elements actually written. This number must be <=
// |max_elements|.
template <typename U = T,
typename F,
typename std::enable_if<
internal::BufferCompat<T, U>::value>::type* = nullptr>
size_t AppendData(size_t max_elements, F&& setter) {
RTC_DCHECK(IsConsistent());
const size_t old_size = size_;
SetSize(old_size + max_bytes);
T *base_ptr = data<T>() + old_size;
size_t written_bytes =
setter(rtc::ArrayView<T>(base_ptr, max_bytes));
SetSize(old_size + max_elements);
U* base_ptr = data<U>() + old_size;
size_t written_elements = setter(rtc::ArrayView<U>(base_ptr, max_elements));
RTC_CHECK_LE(written_bytes, max_bytes);
size_ = old_size + written_bytes;
RTC_CHECK_LE(written_elements, max_elements);
size_ = old_size + written_elements;
RTC_DCHECK(IsConsistent());
return written_bytes;
return written_elements;
}
// Sets the size of the buffer. If the new size is smaller than the old, the
@ -214,8 +275,8 @@ class Buffer {
RTC_DCHECK(IsConsistent());
if (capacity <= capacity_)
return;
std::unique_ptr<uint8_t[]> new_data(new uint8_t[capacity]);
std::memcpy(new_data.get(), data_.get(), size_);
std::unique_ptr<T[]> new_data(new T[capacity]);
std::memcpy(new_data.get(), data_.get(), size_ * sizeof(T));
data_ = std::move(new_data);
capacity_ = capacity;
RTC_DCHECK(IsConsistent());
@ -229,7 +290,7 @@ class Buffer {
}
// Swaps two buffers. Also works for buffers that have been moved from.
friend void swap(Buffer& a, Buffer& b) {
friend void swap(BufferT& a, BufferT& b) {
using std::swap;
swap(a.size_, b.size_);
swap(a.capacity_, b.capacity_);
@ -262,11 +323,12 @@ class Buffer {
size_t size_;
size_t capacity_;
std::unique_ptr<uint8_t[]> data_;
RTC_DISALLOW_COPY_AND_ASSIGN(Buffer);
std::unique_ptr<T[]> data_;
};
// By far the most common sort of buffer.
using Buffer = BufferT<uint8_t>;
} // namespace rtc
#endif // WEBRTC_BASE_BUFFER_H_