Q1ngbo commented on code in PR #3062: URL: https://github.com/apache/brpc/pull/3062#discussion_r2287675769
########## src/butil/single_iobuf.cpp: ########## @@ -0,0 +1,279 @@ +// Licensed to the Apache Software Foundation (ASF) under one +// or more contributor license agreements. See the NOTICE file +// distributed with this work for additional information +// regarding copyright ownership. The ASF licenses this file +// to you under the Apache License, Version 2.0 (the +// "License"); you may not use this file except in compliance +// with the License. You may obtain a copy of the License at +// +// http://www.apache.org/licenses/LICENSE-2.0 +// +// Unless required by applicable law or agreed to in writing, +// software distributed under the License is distributed on an +// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY +// KIND, either express or implied. See the License for the +// specific language governing permissions and limitations +// under the License. + +// SingleIOBuf - A continuous zero-copied buffer + +#include "butil/logging.h" // CHECK, LOG +#include "butil/iobuf.h" +#include "butil/iobuf_inl.h" +#include "butil/single_iobuf.h" + +namespace butil { + +SingleIOBuf::SingleIOBuf() + : _cur_block(NULL) + , _block_size(0) { + _cur_ref.offset = 0; + _cur_ref.length = 0; + _cur_ref.block = NULL; +} + +SingleIOBuf::SingleIOBuf(const IOBuf::BlockRef& ref) { + _cur_block = NULL; + _block_size = 0; + if (ref.block) { + _cur_ref = ref; + _cur_ref.block->inc_ref(); + } +} + +SingleIOBuf::SingleIOBuf(const SingleIOBuf& other) { + _cur_block = NULL; + _block_size = 0; + if (other._cur_ref.block != NULL) { + _cur_ref = other._cur_ref; + _cur_ref.block->inc_ref(); + } +} + +SingleIOBuf::~SingleIOBuf() { + reset(); +} + +SingleIOBuf& SingleIOBuf::operator=(const SingleIOBuf& rhs) { + reset(); + _block_size = 0; + if (rhs._cur_ref.block != NULL) { + _cur_ref = rhs._cur_ref; + _cur_ref.block->inc_ref(); + } + return *this; +} + +void SingleIOBuf::swap(SingleIOBuf& other) { + IOBuf::BlockRef tmp_ref = _cur_ref; + _cur_ref = other._cur_ref; + other._cur_ref = tmp_ref; + IOBuf::Block* tmp_ptr = other._cur_block; + other._cur_block = _cur_block; + _cur_block = tmp_ptr; + uint32_t tmp_size = other._block_size; + other._block_size = _block_size; + _block_size = tmp_size; +} + +void* SingleIOBuf::allocate(uint32_t size) { + IOBuf::Block* b = alloc_block_by_size(size); + if (!b) { + return NULL; + } + _cur_ref.offset = b->size; + _cur_ref.length = size; + _cur_ref.block = b; + b->size += size; + b->inc_ref(); + return b->data + _cur_ref.offset; +} + +void SingleIOBuf::deallocate(void* p) { + if (_cur_ref.block) { + if (_cur_ref.block->data + _cur_ref.offset == (char*)p) { + reset(); + } + } +} + +IOBuf::Block* SingleIOBuf::alloc_block_by_size(uint32_t data_size) { + if (_cur_block != NULL) { + if (_cur_block->left_space() >= data_size) { + return _cur_block; + } else { + _cur_block->dec_ref(); + _cur_block = NULL; + } + } + uint32_t total_size = data_size + sizeof(IOBuf::Block); + if (total_size <= IOBuf::DEFAULT_BLOCK_SIZE) { + _cur_block = iobuf::acquire_tls_block(); + if (_cur_block != NULL) { + if (_cur_block->left_space() >= data_size) { + return _cur_block; + } else { + _cur_block->dec_ref(); + _cur_block = NULL; + } + } + _cur_block = iobuf::create_block(); + } else { + _cur_block = iobuf::create_block(total_size); + _block_size = total_size; + } + if (BAIDU_UNLIKELY(!_cur_block)) { + errno = ENOMEM; + _block_size = 0; + return NULL; + } + return _cur_block; +} + +void SingleIOBuf::memcpy_downward(void* old_p, uint32_t old_size, + void* new_p, uint32_t new_size, + uint32_t in_use_back, uint32_t in_use_front) { + memcpy((u_char*)new_p + new_size - in_use_back, (u_char*)old_p + old_size - in_use_back, + in_use_back); + memcpy(new_p, old_p, in_use_front); +} + +void* SingleIOBuf::reallocate_downward(uint32_t new_size, uint32_t in_use_back, + uint32_t in_use_front) { + IOBuf::BlockRef& ref = _cur_ref; + if (BAIDU_UNLIKELY(new_size <= ref.length)) { + LOG(ERROR) << "invalid new size:" << new_size; + errno = EINVAL; + return NULL; + } + if (BAIDU_UNLIKELY(ref.block == NULL)) { + LOG(ERROR) << "SingleIOBuf reallocate_downward failed. Block cannot be null!"; + errno = EINVAL; + return NULL; + } + char* old_p = ref.block->data + ref.offset; + uint32_t old_size = ref.length; + IOBuf::Block* b = alloc_block_by_size(new_size); + if (!b) { + return NULL; + } + char* new_p = b->data + b->size; + memcpy_downward(old_p, old_size, + new_p, new_size, + in_use_back, in_use_front); + ref.block->dec_ref(); + _cur_ref.offset = b->size; + _cur_ref.length = new_size; + _cur_ref.block = b; + b->size += new_size; + b->inc_ref(); + return new_p; +} + +const void* SingleIOBuf::get_begin() const { + if (_cur_ref.block) { + return _cur_ref.block->data + _cur_ref.offset; + } + return NULL; +} + +uint32_t SingleIOBuf::get_length() const { + return _cur_ref.length; +} + +void SingleIOBuf::reset() { + if (_cur_block) { Review Comment: _cur_block表示的是SingleIOBuf 自己负责分配/释放的block。_cur_ref.block可以认为是当前实际存储数据的block。 在当前reset()实现中，如果在assign里同步更新_cur_block，会导致在后续reset中错误地dec_ref同一块block两次。 -- This is an automated message from the Apache Git Service. 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