前言

swoole 中數(shù)據(jù)的接受與發(fā)送(例如 reactor 線程接受客戶(hù)端消息、發(fā)送給客戶(hù)端的消息、接受到的來(lái)自 worker 的消息、要發(fā)送給 worker 的消息等等)都要涉及到緩沖區(qū)，swoole 中的緩沖區(qū)實(shí)現(xiàn)是 swBuffer，實(shí)際上是一個(gè)單鏈表。

swBuffer 的數(shù)據(jù)結(jié)構(gòu)

• swBuffer 數(shù)據(jù)結(jié)構(gòu)中 trunk_num 是鏈表元素的個(gè)數(shù)，trunk_size 是 swBuffer 緩沖區(qū)創(chuàng)建時(shí)，鏈表元素約定的大小(實(shí)際大小不一定是這個(gè)值)，length 是實(shí)際上緩沖區(qū)占用的內(nèi)存總大小。
• swBuffer_trunk 中的 type 有三種，分別應(yīng)用于：緩存數(shù)據(jù)、發(fā)送文件、提醒連接關(guān)閉三種情景。length 指的是元素的內(nèi)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數(shù)量
    uint16_t trunk_size;
    uint32_t length;
    swBuffer_trunk *head;
    swBuffer_trunk *tail;
} swBuffer;

swBuffer 的創(chuàng)建

swBuffer 的創(chuàng)建很簡(jiǎn)單，只是初始化整個(gè) swBuffer 的 header 頭元素而已：

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 內(nèi)存的申請(qǐng)

swBuffer 內(nèi)存的申請(qǐng)邏輯也很簡(jiǎn)單，按照傳入的 size 參數(shù)為鏈表元素申請(qǐng)內(nèi)存，初始化成員變量，然后將鏈表元素放到鏈表的尾部即可：

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;
}

獲取 swBuffer 的元素

從 swBuffer 緩沖區(qū)拿數(shù)據(jù)只能從 head 中獲取：

#define swBuffer_get_trunk(buffer)   (buffer->head)

swBuffer 元素的 pop

獲取了緩沖區(qū)的元素之后，就要相應(yīng)刪除 head 鏈表元素:

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 緩沖區(qū)的銷(xiāo)毀

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;
}