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119 lines
3.7 KiB
119 lines
3.7 KiB
#ifndef AVIO_H
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#define AVIO_H
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/*
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** 文件读写模块定义的数据结构和函数声明
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*/
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#define URL_EOF (-1)
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typedef int64_t offset_t;
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/* 文件访问的权限的定义 */
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#define URL_RDONLY 0
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#define URL_WRONLY 1
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#define URL_RDWR 2
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/*
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** URL上下文：表示一个输入（文件或者套接字流 ）
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** URLContext 结构表示程序运行的当前广义文件协议使用的上下文，着重于所有广义文件协议共有的
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** 属性(并且是在程序运行时才能确定其值)和关联其他结构的字段
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*/
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typedef struct URLContext
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{
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// 具体的协议
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struct URLProtocol *prot;
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int flags;
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int max_packet_size; // if non zero, the stream is packetized with this max packet size
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void *priv_data; // 对于file，则是一个文件句柄，如果是其他的协议，就可能是其他东西
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char filename[1]; // specified filename
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} URLContext;
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/*
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** URL协议（针对文件或者套接字流的操作）
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** URLProtocol 定义广义的文件协议，着重于功能函数
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** 一种广义的文件协议对应一个 URLProtocol 结构，
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** 本例删掉了 pipe，udp，tcp等输入协议，仅保留一个 file 协议
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*/
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typedef struct URLProtocol
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{
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const char *name;
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int(*url_open)(URLContext *h, const char *filename, int flags);
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int(*url_read)(URLContext *h, unsigned char *buf, int size);
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int(*url_write)(URLContext *h, unsigned char *buf, int size);
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offset_t(*url_seek)(URLContext *h, offset_t pos, int whence);
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int(*url_close)(URLContext *h);
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struct URLProtocol *next;
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} URLProtocol;
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/*
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** 广义上的，带缓冲的文件
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*/
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typedef struct ByteIOContext
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{
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// 数据缓冲区
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unsigned char *buffer;
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// 缓冲区大小
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int buffer_size;
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// 有效的字节范围
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unsigned char *buf_ptr, *buf_end;
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// 其他
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void *opaque;
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// 读取数据
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int (*read_buf)(void *opaque, uint8_t *buf, int buf_size);
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// 写入数据
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int (*write_buf)(void *opaque, uint8_t *buf, int buf_size);
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// 调整buffer指针
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offset_t(*seek)(void *opaque, offset_t offset, int whence);
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// 位置
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offset_t pos; // position in the file of the current buffer
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// 是不是必须要刷新
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int must_flush; // true if the next seek should flush
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// 是否到达文件尾部
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int eof_reached; // true if eof reached
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// 是否可写
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int write_flag; // true if open for writing
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// 最大的数据包的大小
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int max_packet_size;
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// 错误码
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int error; // contains the error code or 0 if no error happened
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} ByteIOContext;
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int url_open(URLContext **h, const char *filename, int flags);
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int url_read(URLContext *h, unsigned char *buf, int size);
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int url_write(URLContext *h, unsigned char *buf, int size);
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offset_t url_seek(URLContext *h, offset_t pos, int whence);
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int url_close(URLContext *h);
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int url_get_max_packet_size(URLContext *h);
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int register_protocol(URLProtocol *protocol);
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int init_put_byte(ByteIOContext *s,
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unsigned char *buffer,
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int buffer_size,
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int write_flag,
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void *opaque,
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int(*read_buf)(void *opaque, uint8_t *buf, int buf_size),
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int(*write_buf)(void *opaque, uint8_t *buf, int buf_size),
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offset_t(*seek)(void *opaque, offset_t offset, int whence));
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offset_t url_fseek(ByteIOContext *s, offset_t offset, int whence);
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void url_fskip(ByteIOContext *s, offset_t offset);
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offset_t url_ftell(ByteIOContext *s);
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offset_t url_fsize(ByteIOContext *s);
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int url_feof(ByteIOContext *s);
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int url_ferror(ByteIOContext *s);
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int url_fread(ByteIOContext *s, unsigned char *buf, int size); // get_buffer
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int get_byte(ByteIOContext *s);
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unsigned int get_le32(ByteIOContext *s);
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unsigned int get_le16(ByteIOContext *s);
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int url_setbufsize(ByteIOContext *s, int buf_size);
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int url_fopen(ByteIOContext *s, const char *filename, int flags);
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int url_fclose(ByteIOContext *s);
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int url_open_buf(ByteIOContext *s, uint8_t *buf, int buf_size, int flags);
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int url_close_buf(ByteIOContext *s);
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#endif
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