数据结构:
struct ustream_buf {
struct ustream_buf *next;
char *data; /** 指向上次操作buff开始地址 */
char *tail; /** 指向未使用buff开始地址 */
char *end; /** 指向buf结束地址 */
char head[]; /** 指向buf开始地址 */
};
struct ustream_buf_list {
struct ustream_buf *head; /** 指向第1块ustream_buf */
struct ustream_buf *data_tail; /** 指向未使用的ustream_buf */
struct ustream_buf *tail; /** 指向最后的ustream_buf */
int (*alloc)(struct ustream *s, struct ustream_buf_list *l);
int data_bytes; /** 已用存储空间大小 */
int min_buffers; /** 可存储最小的ustream_buf块个数 */
int max_buffers; /** 可存储最大的ustream_buf块个数 */
int buffer_len; /** 每块ustream_buf块存储空间大小 */
int buffers; /** ustream_buf块个数 */
};
struct ustream {
struct ustream_buf_list r, w;
struct uloop_timeout state_change;
struct ustream *next;
/*
* notify_read: (optional)
* called by the ustream core to notify that new data is available
* for reading.
* must not free the ustream from this callback
*/
void (*notify_read)(struct ustream *s, int bytes_new);
/*
* notify_write: (optional)
* called by the ustream core to notify that some buffered data has
* been written to the stream.
* must not free the ustream from this callback
*/
void (*notify_write)(struct ustream *s, int bytes);
/*
* notify_state: (optional)
* called by the ustream implementation to notify that the read
* side of the stream is closed (eof is set) or there was a write
* error (write_error is set).
* will be called again after the write buffer has been emptied when
* the read side has hit EOF.
*/
void (*notify_state)(struct ustream *s);
/*
* write:
* must be defined by ustream implementation, accepts new write data.
* 'more' is used to indicate that a subsequent call will provide more
* data (useful for aggregating writes)
* returns the number of bytes accepted, or -1 if no more writes can
* be accepted (link error)
*/
int (*write)(struct ustream *s, const char *buf, int len, bool more);
/*
* free: (optional)
* defined by ustream implementation, tears down the ustream and frees data
*/
void (*free)(struct ustream *s);
/*
* set_read_blocked: (optional)
* defined by ustream implementation, called when the read_blocked flag
* changes
*/
void (*set_read_blocked)(struct ustream *s);
/*
* poll: (optional)
* defined by the upstream implementation, called to request polling for
* available data.
* returns true if data was fetched.
*/
bool (*poll)(struct ustream *s);
/*
* ustream user should set this if the input stream is expected
* to contain string data. the core will keep all data 0-terminated.
*/
bool string_data; /** 此ustream是否为字符串,true-是;false-否 */
bool write_error; /** 写出错,true-是;false-否 */
bool eof, eof_write_done;
enum read_blocked_reason read_blocked;
};
struct ustream_fd {
struct ustream stream;
struct uloop_fd fd;
};
初始/销毁
/**
* ustream_fd_init: create a file descriptor ustream (uses uloop)
*/
void ustream_fd_init(struct ustream_fd *s, int fd);
/**
* ustream_init_defaults: fill default callbacks and options
*/
void ustream_init_defaults(struct ustream *s);
/**
* ustream_free: free all buffers and data associated with a ustream
*/
void ustream_free(struct ustream *s);
写入read buffer
:
/*
* ustream_reserve: allocate rx buffer space
* 分配len大小的read buffer可用内存空间,与ustream_fill_read()配合使用
*
* len: hint for how much space is needed (not guaranteed to be met)
* maxlen: pointer to where the actual buffer size is going to be stored
*/
char *ustream_reserve(struct ustream *s, int len, int *maxlen);
/**
* ustream_fill_read: mark rx buffer space as filled
* 设置被ustream_reseve()分配read buffer后写入的数据大小,
* 回调notify_read()接口,表示有数据可读
*/
void ustream_fill_read(struct ustream *s, int len);
读出read buffer
(一般在notify_read()
回调接口使用):
/*
* ustream_get_read_buf: get a pointer to the next read buffer data
* 获取新一次写入的内容,与ustream_consume()配置使用
*/
char *ustream_get_read_buf(struct ustream *s, int *buflen);
/**
* ustream_consume: remove data from the head of the read buffer
*/
void ustream_consume(struct ustream *s, int len);
操作write buffer
,尽最大能力调用write()
回调用接口写入,如果超出能力将把未写入的数据存储在write buffer
中。
/*
* ustream_write: add data to the write buffer
*/
int ustream_write(struct ustream *s, const char *buf, int len, bool more);
int ustream_printf(struct ustream *s, const char *format, ...);
int ustream_vprintf(struct ustream *s, const char *format, va_list arg);
把在write buffer
中的数据写入实际地方,调用write()
回调接口和notify_write()
回调接口。一般在描述符的poll
操作中调用,表示当描述符变为可写时立即把上一次未写入的内容进行写入操作。
/*
* ustream_write_pending: attempt to write more data from write buffers
* returns true if all write buffers have been emptied.
*/
bool ustream_write_pending(struct ustream *s);
**粗体** _斜体_ [链接](http://example.com) `代码` - 列表 > 引用
。你还可以使用@
来通知其他用户。