AVIOInterruptCB结构体分析

1 AVIOInterruptCB结构体定义

在/usr/include/libavformat/avio.h中有如下的结构体定义，根据头文件中的注释：这是一个回调函数和参数的结构体。有些函数是在阻塞的，用这个回调函数来检查是否中断这个阻塞函数，如果回调函数返回1，那么这个正在阻塞的操作将被中止。那么就用这个结构体里的参数opaque来回调其中的callback函数。如果阻塞函数被中断了，那么阻塞函数的返回值为AVERROR_EXIT。

1/**
2 * Callback for checking whether to abort blocking functions.
3 * AVERROR_EXIT is returned in this case by the interrupted
4 * function. During blocking operations, callback is called with
5 * opaque as parameter. If the callback returns 1, the
6 * blocking operation will be aborted.
7 *
8 * No members can be added to this struct without a major bump, if
9 * new elements have been added after this struct in AVFormatContext
10 * or AVIOContext.
11 */
12typedef struct AVIOInterruptCB {
13    int (*callback)(void*);
14    void *opaque;
15} AVIOInterruptCB;