stdio.c 文件参考

浏览源代码.

函数
off_t	_lseek (int fd, off_t offset, int whence)
off64_t	_lseek64 (int fd, int offsetHigh, int offsetLow, off64_t *result, int whence)

函数说明

_lseek()

off_t _lseek	(	int	fd,
		off_t	offset,
		int	whence
	)

在文件 stdio.c 第 38 行定义.

{
    int ret;
    struct file *filep = NULL;
 
    /* Get the file structure corresponding to the file descriptor. */
    ret = fs_getfilep(fd, &filep);
    if (ret < 0) {
        /* The errno value has already been set */
        return (off_t)-get_errno();
    }
 
    /* libc seekdir function should set the whence to SEEK_SET, so we can discard
     * the whence argument here */
    if (filep->f_oflags & O_DIRECTORY) {
        /* defensive coding */
        if (filep->f_dir == NULL) {
            return (off_t)-EINVAL;
        }
        if (offset == 0) {
            rewinddir(filep->f_dir);
        } else {
            seekdir(filep->f_dir, offset);
        }
        ret = telldir(filep->f_dir);
        if (ret < 0) {
            return (off_t)-get_errno();
        }
        return ret;
    }
 
    /* Then let file_seek do the real work */
    ret = file_seek(filep, offset, whence);
    if (ret < 0) {
        return -get_errno();
    }
    return ret;
}

这是这个函数的调用关系图:

_lseek64()

off64_t _lseek64	(	int	fd,
		int	offsetHigh,
		int	offsetLow,
		off64_t *	result,
		int	whence
	)

在文件 stdio.c 第 77 行定义.

{
    off64_t ret;
    struct file *filep = NULL;
    off64_t offset = ((off64_t)offsetHigh << 32) + (uint)offsetLow; /* 32: offsetHigh is high 32 bits */
 
    /* Get the file structure corresponding to the file descriptor. */
    ret = fs_getfilep(fd, &filep);
    if (ret < 0) {
        /* The errno value has already been set */
        return (off64_t)-get_errno();
    }
 
    /* libc seekdir function should set the whence to SEEK_SET, so we can discard
     * the whence argument here */
    if (filep->f_oflags & O_DIRECTORY) {
        /* defensive coding */
        if (filep->f_dir == NULL) {
            return (off64_t)-EINVAL;
        }
        if (offsetLow == 0) {
            rewinddir(filep->f_dir);
        } else {
            seekdir(filep->f_dir, offsetLow);
        }
        ret = telldir(filep->f_dir);
        if (ret < 0) {
            return (off64_t)-get_errno();
        }
        goto out;
    }
 
    /* Then let file_seek do the real work */
    ret = file_seek64(filep, offset, whence);
    if (ret < 0) {
        return (off64_t)-get_errno();
    }
 
out:
    *result = ret;
 
    return 0;
}

这是这个函数的调用关系图: