On Wed, Nov 24, 2010 at 5:18 PM, M. Mohan Kumar <mo...@in.ibm.com> wrote:
> Add qemu_read_full function
>
> Signed-off-by: M. Mohan Kumar <mo...@in.ibm.com>
> ---
> osdep.c | 29 +++++++++++++++++++++++++++++
> qemu-common.h | 2 ++
> 2 files changed, 31 insertions(+), 0 deletions(-)
>
> diff --git a/osdep.c b/osdep.c
> index 327583b..7046b32 100644
> --- a/osdep.c
> +++ b/osdep.c
> @@ -127,6 +127,35 @@ ssize_t qemu_write_full(int fd, const void *buf, size_t
> count)
> }
>
> /*
> + * A variant of read(2) which handles interrupted read.
> + * Simlar to qemu_write_full function
> + *
> + * Return the number of bytes read.
> + *
> + */
Two points worth noting in the comment (stolen from qemu_write_full):
1. "This function don't work with non-blocking fd's."
2. "Set errno if fewer than `count' bytes are read." Normal QEMU
style would be to return -errno, so it's important to point out this
exception to the rule.
> +ssize_t qemu_read_full(int fd, void *buf, size_t count)
> +{
> + ssize_t ret = 0;
> + ssize_t total = 0;
> +
> + while (count) {
> + ret = read(fd, buf, count);
> + if (ret < 0) {
> + if (errno == EINTR) {
> + continue;
> + }
> + break;
> + }
> +
> + count -= ret;
> + buf += ret;
> + total += ret;
> + }
> +
> + return total;
> +}
On EOF read(2) will return 0. Right now we don't handle this case and
go into an infinite loop.
Stefan
