fastdfs函数tracker_query_storage_update1分析

粘贴第一个函数

tracker_query_storage_update1(pTrackerServer, &storageServer, file_id);

函数解析：函数名：tracker_query_storage_update1，参数：in（pTrackerServer），in（file_id) ，out（storageServer）。
函数意义：传入:pTrackerServer,和file_id，返回storageServer

---

粘贴第二个函数

int tracker_query_storage_update1(ConnectionInfo *pTrackerServer,ConnectionInfo *pStorageServer,const char *file_id){    `FDFS_SPLIT_GROUP_NAME_AND_FILENAME`(file_id)    return tracker_query_storage_update(pTrackerServer,     pStorageServer, group_name, filename);}

函数意义：将函数tracker_query_storage_update1传进来的file_id进行剥离。

---

剥离函数：

#define FDFS_SPLIT_GROUP_NAME_AND_FILENAME(file_id) \    char new_file_id[FDFS_GROUP_NAME_MAX_LEN + 128]; \    char *group_name; \    char *filename; \    char *pSeperator; \    \    snprintf(new_file_id, sizeof(new_file_id), "%s", file_id); \    pSeperator = strchr(new_file_id, FDFS_FILE_ID_SEPERATOR); \    if (pSeperator == NULL) \    { \        return EINVAL; \    } \    \    *pSeperator = '\0'; \    group_name = new_file_id; \    filename =  pSeperator + 1; \

将file_id剥离出：group_name，例如：group1
剥离出：filename，例如：/M00/00/01/wKgBIFVjCM*.jpg

---

粘贴函数

#define tracker_query_storage_update(pTrackerServer, pStorageServer, group_name, filename) tracker_do_query_storage(pTrackerServer, pStorageServer, RACKER_PROTO_CMD_SERVICE_QUERY_UPDATE,group_name, filename)

函数解析：
/**
* query storage server to update (delete file or set meta data)
* params:
* pTrackerServer: tracker server
* pStorageServer: return storage server
* group_name: the group name of storage server
* ilename: filename on storage server
* return: 0 success, !=0 fail, return the error code
**/

int tracker_do_query_storage(ConnectionInfo *pTrackerServer, ConnectionInfo *pStorageServer, const byte cmd, const char *group_name, const char *filename){    TrackerHeader *pHeader;//定义头部结构体    ConnectionInfo *conn;    bool new_connection;//是否为新的连接    char out_buff[sizeof(TrackerHeader) + FDFS_GROUP_NAME_MAX_LEN + 128];    char in_buff[sizeof(TrackerHeader) + TRACKER_QUERY_STORAGE_FETCH_BODY_LEN];    char *pInBuff;    int64_t in_bytes;    int result;    int filename_len;    CHECK_CONNECTION(pTrackerServer, conn, result, new_connection);//检查连接是否正常，不正常，建立新连接    memset(pStorageServer, 0, sizeof(ConnectionInfo));    pStorageServer->sock = -1;    memset(out_buff, 0, sizeof(out_buff));    pHeader = (TrackerHeader *)out_buff;    snprintf(out_buff + sizeof(TrackerHeader), sizeof(out_buff) - sizeof(TrackerHeader),  "%s", group_name);    filename_len = snprintf(out_buff + sizeof(TrackerHeader) + FDFS_GROUP_NAME_MAX_LEN,sizeof(out_buff) - sizeof(TrackerHeader) - FDFS_GROUP_NAME_MAX_LEN,  "%s", filename);//拷贝filename 到out_buff,返回拷贝的字节数。//以下是构建头部数据[long2buff](http://blog.csdn.net/akakakak250/article/details/45672019)    long2buff(FDFS_GROUP_NAME_MAX_LEN + filename_len, pHeader->pkg_len);    pHeader->cmd = cmd;    if ((result=tcpsenddata_nb(conn->sock, out_buff, \        sizeof(TrackerHeader) + FDFS_GROUP_NAME_MAX_LEN + filename_len, g_fdfs_network_timeout)) != 0)//成功返回0    {        logError("file: "__FILE__", line: %d, " \            "send data to tracker server %s:%d fail, "             "errno: %d, error info: %s", __LINE__, \            pTrackerServer->ip_addr, \            pTrackerServer->port, \            result, STRERROR(result));    }    else    {        pInBuff = in_buff;        result = fdfs_recv_response(conn, \            &pInBuff, sizeof(in_buff), &in_bytes);    }//in_byte,返回字节数。fdfs_recv_response，里面有两个函数，一个是获取头，和数据    if (new_connection)    {        tracker_disconnect_server_ex(conn, result != 0);    }    if (result != 0)    {        return result;    }    if (in_bytes != TRACKER_QUERY_STORAGE_FETCH_BODY_LEN)//in_bytes是固定大小    {        logError("file: "__FILE__", line: %d, " \            "tracker server %s:%d response data " \            "length: %"PRId64" is invalid, " \            "expect length: %d", __LINE__, \            pTrackerServer->ip_addr, \            pTrackerServer->port, in_bytes, \            TRACKER_QUERY_STORAGE_FETCH_BODY_LEN);        return EINVAL;    }    memcpy(pStorageServer->ip_addr, in_buff + \            FDFS_GROUP_NAME_MAX_LEN, IP_ADDRESS_SIZE-1);//获取storage的ip    pStorageServer->port = (int)buff2long(in_buff + \            FDFS_GROUP_NAME_MAX_LEN + IP_ADDRESS_SIZE - 1);//获取storage的port    return 0;}

整体解释：根据传入pTrackerServer, file_id，查询storageServer, 返回ip，port。

刚接触fastdfs不是很熟，有不对的地方提出，共同进步