Redis rio的代码很少，基本上包了一个虚基类:
struct _rio {
void (*update_cksum)(struct _rio *, const void *buf, size_t len);
/* The current checksum */
uint64_t cksum;
/* Backend-specific vars. */
union {
struct {
sds ptr;
off_t pos;
} buffer;
struct {
FILE *fp;
off_t buffered; /* Bytes written since last fsync. */
off_t autosync; // buffered超过这个值自动更新，默认为0
} file;
} io;
};
API如下:
static inline size_t rioWrite(rio *r, const void *buf, size_t len) ; // 调用 rio->write,同时更新checksum
static inline size_t rioRead(rio *r, void *buf, size_t len) // 调用 rio->read,同时更新checksum
static inline off_t rioTell(rio *r); //直接调用rio->tell
void rioInitWithFile(rio *r, FILE *fp); // 初始化rio->io->file
void rioInitWithBuffer(rio *r, sds s); // 初始化rio->io->buffer
// 以下几个是High Level Interface,用于写AOF文件
size_t rioWriteBulkCount(rio *r, char prefix, int count);
size_t rioWriteBulkString(rio *r, const char *buf, size_t len);
size_t rioWriteBulkLongLong(rio *r, long long l);
size_t rioWriteBulkDouble(rio *r, double d);
// 更新crc64 checksum
void rioGenericUpdateChecksum(rio *r, const void *buf, size_t len);
// 设置自动sync的字节数
void rioSetAutoSync(rio *r, off_t bytes);
