tdlight/tdutils/td/utils/buffer.cpp

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//
// Copyright Aliaksei Levin (levlam@telegram.org), Arseny Smirnov (arseny30@gmail.com) 2014-2019
//
// Distributed under the Boost Software License, Version 1.0. (See accompanying
// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
//
#include "td/utils/buffer.h"
#include "td/utils/port/thread_local.h"
#include <cstddef>
#include <new>
// fixes https://bugs.llvm.org/show_bug.cgi?id=33723 for clang >= 3.6 + c++11 + libc++
#if TD_CLANG && _LIBCPP_VERSION
#define TD_OFFSETOF __builtin_offsetof
#else
#define TD_OFFSETOF offsetof
#endif
namespace td {
TD_THREAD_LOCAL BufferAllocator::BufferRawTls *BufferAllocator::buffer_raw_tls; // static zero-initialized
std::atomic<size_t> BufferAllocator::buffer_mem;
size_t BufferAllocator::get_buffer_mem() {
return buffer_mem;
}
BufferAllocator::WriterPtr BufferAllocator::create_writer(size_t size) {
if (size < 512) {
size = 512;
}
return create_writer_exact(size);
}
BufferAllocator::WriterPtr BufferAllocator::create_writer_exact(size_t size) {
return WriterPtr(create_buffer_raw(size));
}
BufferAllocator::WriterPtr BufferAllocator::create_writer(size_t size, size_t prepend, size_t append) {
auto ptr = create_writer(size + prepend + append);
ptr->begin_ += prepend;
ptr->end_ += prepend + size;
return ptr;
}
BufferAllocator::ReaderPtr BufferAllocator::create_reader(size_t size) {
if (size < 512) {
return create_reader_fast(size);
}
auto ptr = create_writer_exact(size);
ptr->end_ += (size + 7) & -8;
return create_reader(ptr);
}
BufferAllocator::ReaderPtr BufferAllocator::create_reader_fast(size_t size) {
size = (size + 7) & -8;
init_thread_local<BufferRawTls>(buffer_raw_tls);
auto buffer_raw = buffer_raw_tls->buffer_raw.get();
if (buffer_raw == nullptr || buffer_raw->data_size_ - buffer_raw->end_.load(std::memory_order_relaxed) < size) {
buffer_raw = create_buffer_raw(4096 * 4);
buffer_raw_tls->buffer_raw = std::unique_ptr<BufferRaw, BufferAllocator::BufferRawDeleter>(buffer_raw);
}
buffer_raw->end_.fetch_add(size, std::memory_order_relaxed);
buffer_raw->ref_cnt_.fetch_add(1, std::memory_order_acq_rel);
return ReaderPtr(buffer_raw);
}
BufferAllocator::ReaderPtr BufferAllocator::create_reader(const WriterPtr &raw) {
raw->was_reader_ = true;
raw->ref_cnt_.fetch_add(1, std::memory_order_acq_rel);
return ReaderPtr(raw.get());
}
BufferAllocator::ReaderPtr BufferAllocator::create_reader(const ReaderPtr &raw) {
raw->ref_cnt_.fetch_add(1, std::memory_order_acq_rel);
return ReaderPtr(raw.get());
}
void BufferAllocator::dec_ref_cnt(BufferRaw *ptr) {
int left = ptr->ref_cnt_.fetch_sub(1, std::memory_order_acq_rel);
if (left == 1) {
auto buf_size = max(sizeof(BufferRaw), TD_OFFSETOF(BufferRaw, data_) + ptr->data_size_);
buffer_mem -= buf_size;
ptr->~BufferRaw();
delete[] ptr;
}
}
BufferRaw *BufferAllocator::create_buffer_raw(size_t size) {
size = (size + 7) & -8;
auto buf_size = TD_OFFSETOF(BufferRaw, data_) + size;
if (buf_size < sizeof(BufferRaw)) {
buf_size = sizeof(BufferRaw);
}
buffer_mem += buf_size;
auto *buffer_raw = reinterpret_cast<BufferRaw *>(new char[buf_size]);
new (buffer_raw) BufferRaw();
buffer_raw->data_size_ = size;
buffer_raw->begin_ = 0;
buffer_raw->end_ = 0;
buffer_raw->ref_cnt_.store(1, std::memory_order_relaxed);
buffer_raw->has_writer_.store(true, std::memory_order_relaxed);
buffer_raw->was_reader_ = false;
return buffer_raw;
}
void BufferBuilder::append(BufferSlice slice) {
if (append_inplace(slice.as_slice())) {
return;
}
append_slow(std::move(slice));
}
void BufferBuilder::append(Slice slice) {
if (append_inplace(slice)) {
return;
}
append_slow(BufferSlice(slice));
}
void BufferBuilder::prepend(BufferSlice slice) {
if (prepend_inplace(slice.as_slice())) {
return;
}
prepend_slow(std::move(slice));
}
void BufferBuilder::prepend(Slice slice) {
if (prepend_inplace(slice)) {
return;
}
prepend_slow(BufferSlice(slice));
}
BufferSlice BufferBuilder::extract() {
if (to_append_.empty() && to_prepend_.empty()) {
return buffer_writer_.as_buffer_slice();
}
size_t total_size = 0;
for_each([&](auto &&slice) { total_size += slice.size(); });
BufferWriter writer(0, 0, total_size);
for_each([&](auto &&slice) {
writer.prepare_append().truncate(slice.size()).copy_from(slice.as_slice());
writer.confirm_append(slice.size());
});
*this = {};
return writer.as_buffer_slice();
}
bool BufferBuilder::append_inplace(Slice slice) {
if (!to_append_.empty()) {
return false;
}
auto dest = buffer_writer_.prepare_append();
if (dest.size() < slice.size()) {
return false;
}
dest.remove_suffix(dest.size() - slice.size());
dest.copy_from(slice);
buffer_writer_.confirm_append(slice.size());
return true;
}
void BufferBuilder::append_slow(BufferSlice slice) {
to_append_.push_back(std::move(slice));
}
bool BufferBuilder::prepend_inplace(Slice slice) {
if (!to_prepend_.empty()) {
return false;
}
auto dest = buffer_writer_.prepare_prepend();
if (dest.size() < slice.size()) {
return false;
}
dest.remove_prefix(dest.size() - slice.size());
dest.copy_from(slice);
buffer_writer_.confirm_prepend(slice.size());
return true;
}
void BufferBuilder::prepend_slow(BufferSlice slice) {
to_prepend_.push_back(std::move(slice));
}
} // namespace td