Q1ngbo commented on code in PR #3062:
URL: https://github.com/apache/brpc/pull/3062#discussion_r2273393570
##########
src/butil/iobuf.cpp:
##########
@@ -1976,6 +1976,259 @@ size_t IOBufCutter::cutn(void* out, size_t n) {
}
}
+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::alloc(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) << "invaild 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) {
+ if (_block_size == 0) {
+ iobuf::release_tls_block(_cur_block);
+ } else {
+ _cur_block->dec_ref();
+ _block_size = 0;
+ }
+ _cur_block = NULL;
+ }
+ if (_cur_ref.block != NULL) {
+ _cur_ref.block->dec_ref();
+ }
+ _cur_ref.offset = 0;
+ _cur_ref.length = 0;
+ _cur_ref.block = NULL;
+}
+
+void SingleIOBuf::target_block_inc_ref(void* b) {
+ IOBuf::Block* block = (IOBuf::Block*)b;
+ block->inc_ref();
+}
+
+void SingleIOBuf::target_block_dec_ref(void* b) {
+ IOBuf::Block* block = (IOBuf::Block*)b;
+ block->dec_ref();
+}
+
+bool SingleIOBuf::assign(const IOBuf& buf, uint32_t msg_size) {
+ if (BAIDU_UNLIKELY(buf.length() < msg_size)) {
+ LOG(ERROR) << "Fail to dump_mult_iobuf msg_size:" << msg_size
+ << " from source iobuf of size:" << buf.length();
+ return false;
+ }
+ reset();
+ if (BAIDU_UNLIKELY(msg_size == 0)) {
+ return true;
+ }
+ const IOBuf::BlockRef& ref = buf._front_ref();
+ if (ref.length >= msg_size) {
+ _cur_ref.offset = ref.offset;
+ _cur_ref.length = msg_size;
+ _cur_ref.block = ref.block;
+ _cur_ref.block->inc_ref();
+ return true;
+ } else {
+ IOBuf::Block* b = alloc_block_by_size(msg_size);
+ if (!b) {
+ return false;
+ }
+ char* out = b->data + b->size;
+ const size_t nref = buf.backing_block_num();
+ uint32_t last_len = msg_size;
+ for (size_t i = 0; i < nref && last_len > 0; ++i) {
+ const IOBuf::BlockRef& r = buf._ref_at(i);
+ uint32_t n = std::min(r.length, last_len);
+ iobuf::cp(out, r.block->data + r.offset, n);
+ last_len -= n;
+ out += n;
+ }
+ _cur_ref.offset = b->size;
+ _cur_ref.length = msg_size;
+ _cur_ref.block = b;
+ b->size += msg_size;
+ _cur_ref.block->inc_ref();
+ return true;
+ }
+ return false;
+}
+
+void SingleIOBuf::append_to(IOBuf* buf) const {
Review Comment:
在flatbuffers中用户使用fbs文件定义message格式（类似于proto）。所以在用户应用程序中创建请求时可以按消息大小分配内存。构造出的消息内容保存在SingleIOBuf中，最终它会通过SingleIOBuf::append_to添加到IOBuf中发送出去。brpc接收到的消息同样保存在IOBuf中。因此在解析请求时，将调用SingleIOBuf::assign将IOBuf
assign给SingleIOBuf,
如果IOBuf的单个Block能容纳整个message，则直接将该Block赋值给SingleIOBuf，否则会根据消息大小重新申请足够大的Block，再从传入的IOBuf中拷贝数据。
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