前言
swoole 中数据的接受与发送(例如 reactor 线程接受客户端消息、发送给客户端的消息、接受到的来自 worker 的消息、要发送给 worker 的消息等等)都要涉及到缓冲区，swoole 中的缓冲区实现是 swBuffer，实际上是一个单链表。
swBuffer 的数据结构
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swBuffer数据结构中trunk_num是链表元素的个数，trunk_size是swBuffer缓冲区创建时，链表元素约定的大小(实际大小不一定是这个值)，length是实际上缓冲区占用的内存总大小。 -
swBuffer_trunk中的type有三种，分别应用于：缓存数据、发送文件、提醒连接关闭三种情景。length指的是元素的内存大小。
enum swBufferChunk{ SW_CHUNK_DATA, SW_CHUNK_SENDFILE, SW_CHUNK_CLOSE,};typedef struct _swBuffer_trunk{ uint32_t type; uint32_t length; uint32_t offset; union { void *ptr; struct { uint32_t val1; uint32_t val2; } data; } store; uint32_t size; void (*destroy)(struct _swBuffer_trunk *chunk); struct _swBuffer_trunk *next;} swBuffer_trunk;typedef struct _swBuffer{ int fd; uint8_t trunk_num; //trunk数量 uint16_t trunk_size; uint32_t length; swBuffer_trunk *head; swBuffer_trunk *tail;} swBuffer; swBuffer 的创建
swBuffer 的创建很简单，只是初始化整个 swBuffer 的 header 头元素而已：
swBuffer* swBuffer_new(int trunk_size){ swBuffer *buffer = sw_malloc(sizeof(swBuffer)); if (buffer == NULL) { swWarn("malloc for buffer failed. Error: %s[%d]", strerror(errno), errno); return NULL; } bzero(buffer, sizeof(swBuffer)); buffer->trunk_size = trunk_size; return buffer;} swBuffer 内存的申请
swBuffer 内存的申请逻辑也很简单，按照传入的 size 参数为链表元素申请内存，初始化成员变量，然后将链表元素放到链表的尾部即可：
int swBuffer_append(swBuffer *buffer, void *data, uint32_t size){ swBuffer_trunk *chunk = swBuffer_new_trunk(buffer, SW_CHUNK_DATA, size); if (chunk == NULL) { return SW_ERR; } buffer->length += size; chunk->length = size; memcpy(chunk->store.ptr, data, size); swTraceLog(SW_TRACE_BUFFER, "trunk_n=%d|size=%d|trunk_len=%d|trunk=%p", buffer->trunk_num, size, chunk->length, chunk); return SW_OK;}swBuffer_trunk *swBuffer_new_trunk(swBuffer *buffer, uint32_t type, uint32_t size){ swBuffer_trunk *chunk = sw_malloc(sizeof(swBuffer_trunk)); if (chunk == NULL) { swWarn("malloc for trunk failed. Error: %s[%d]", strerror(errno), errno); return NULL; } bzero(chunk, sizeof(swBuffer_trunk)); //require alloc memory if (type == SW_CHUNK_DATA && size > 0) { void *buf = sw_malloc(size); if (buf == NULL) { swWarn("malloc(%d) for data failed. Error: %s[%d]", size, strerror(errno), errno); sw_free(chunk); return NULL; } chunk->size = size; chunk->store.ptr = buf; } chunk->type = type; buffer->trunk_num ++; if (buffer->head == NULL) { buffer->tail = buffer->head = chunk; } else { buffer->tail->next = chunk; buffer->tail = chunk; } return chunk;} 获取 swBuffer 的元素
从 swBuffer 缓冲区拿数据只能从 head 中获取：
#define swBuffer_get_trunk(buffer) (buffer->head)
swBuffer 元素的 pop
获取了缓冲区的元素之后，就要相应删除 head 链表元素:
void swBuffer_pop_trunk(swBuffer *buffer, swBuffer_trunk *chunk){ if (chunk->next == NULL) { buffer->head = NULL; buffer->tail = NULL; buffer->length = 0; buffer->trunk_num = 0; } else { buffer->head = chunk->next; buffer->length -= chunk->length; buffer->trunk_num--; } if (chunk->type == SW_CHUNK_DATA) { sw_free(chunk->store.ptr); } if (chunk->destroy) { chunk->destroy(chunk); } sw_free(chunk);} swBuffer 缓冲区的销毁
int swBuffer_free(swBuffer *buffer){ volatile swBuffer_trunk *chunk = buffer->head; void * *will_free_trunk; //free the point while (chunk != NULL) { if (chunk->type == SW_CHUNK_DATA) { sw_free(chunk->store.ptr); } will_free_trunk = (void *) chunk; chunk = chunk->next; sw_free(will_free_trunk); } sw_free(buffer); return SW_OK;}