vfs_readv.c 文件参考

浏览源代码.

函数
static char *	pread_buf_and_check (int fd, const struct iovec *iov, int iovcnt, ssize_t *totalbytesread, off_t *offset)
ssize_t	vfs_readv (int fd, const struct iovec *iov, int iovcnt, off_t *offset)
	供系统调用 更多...
ssize_t	readv (int fd, const struct iovec *iov, int iovcnt)

函数说明

pread_buf_and_check()

static char * pread_buf_and_check ( int  fd, const struct iovec *  iov, int  iovcnt, ssize_t *  totalbytesread, off_t *  offset  )

static

在文件 vfs_readv.c 第 42 行定义.

{
    char *buf = NULL;
    size_t buflen = 0;
    int i;
 
    if ((iov == NULL) || (iovcnt > IOV_MAX)) {
        *totalbytesread = VFS_ERROR;
        return NULL;
    }
 
    for (i = 0; i < iovcnt; ++i) {
        if (SSIZE_MAX - buflen < iov[i].iov_len) {
            set_errno(EINVAL);
            return NULL;
        }
        buflen += iov[i].iov_len;
    }
 
    if (buflen == 0) {
        *totalbytesread = 0;
        return NULL;
    }
 
#ifdef LOSCFG_KERNEL_VM
    buf = (char *)LOS_VMalloc(buflen * sizeof(char));
#else
    buf = (char *)malloc(buflen * sizeof(char));
#endif
    if (buf == NULL) {
        set_errno(ENOMEM);
        *totalbytesread = VFS_ERROR;
        return buf;
    }
 
    *totalbytesread = (offset == NULL) ? read(fd, buf, buflen)
                                       : pread(fd, buf, buflen, *offset);
    if ((*totalbytesread == VFS_ERROR) || (*totalbytesread == 0)) {
#ifdef LOSCFG_KERNEL_VM
        LOS_VFree(buf);
#else
        free(buf);
#endif
        return NULL;
    }
 
    return buf;
}

函数调用图:

这是这个函数的调用关系图:

readv()

ssize_t readv	(	int	fd,
		const struct iovec *	iov,
		int	iovcnt
	)

在文件 vfs_readv.c 第 144 行定义.

{
    return vfs_readv(fd, iov, iovcnt, NULL);
}

函数调用图:

vfs_readv()

ssize_t vfs_readv	(	int	fd,
		const struct iovec *	iov,
		int	iovcnt,
		off_t *	offset
	)

供系统调用

在文件 vfs_readv.c 第 91 行定义.

{
    int i;
    int ret;
    char *buf = NULL;
    char *curbuf = NULL;
    ssize_t bytestoread;
    ssize_t totalbytesread = 0;
    ssize_t bytesleft;
 
    buf = pread_buf_and_check(fd, iov, iovcnt, &totalbytesread, offset);
    if (buf == NULL) {
        return totalbytesread;
    }
 
    curbuf = buf;
    bytesleft = totalbytesread;
    for (i = 0; i < iovcnt; ++i) {
        bytestoread = iov[i].iov_len;
        if (bytestoread == 0) {
            continue;
        }
 
        if (bytesleft <= bytestoread) {
            ret = LOS_CopyFromKernel(iov[i].iov_base, bytesleft, curbuf, bytesleft);
            bytesleft = ret;
            goto out;
        }
 
        ret = LOS_CopyFromKernel(iov[i].iov_base, bytestoread, curbuf, bytestoread);
        if (ret != 0) {
            bytesleft = bytesleft - (bytestoread - ret);
            goto out;
        }
        bytesleft -= bytestoread;
        curbuf += bytestoread;
    }
 
out:
#ifdef LOSCFG_KERNEL_VM
    LOS_VFree(buf);
#else
    free(buf);
#endif
    if ((i == 0) && (ret == iov[i].iov_len)) {
        /* failed in the first iovec copy, and 0 bytes copied */
        set_errno(EFAULT);
        return VFS_ERROR;
    }
 
    return totalbytesread - bytesleft;
}

函数调用图:

这是这个函数的调用关系图: