.TH LIBSHA2_SUM_FD 3 2019-02-09 libjson
.SH NAME
libsha2_sum_fd \- Hash a file with a SHA 2 algorithm
.SH SYNOPSIS
.nf
#include <libsha2.h>

enum libsha2_algorithm {
	LIBSHA2_224,     /* SHA-224     */
	LIBSHA2_256,     /* SHA-256     */
	LIBSHA2_384,     /* SHA-384     */
	LIBSHA2_512,     /* SHA-512     */
	LIBSHA2_512_224, /* SHA-512/224 */
	LIBSHA2_512_256  /* SHA-512/256 */
};

int libsha2_sum_fd(int \fIfd\fP, enum libsha2_algorithm \fIalgorithm\fP, char *restrict \fIhashsum\fP);
.fi
.PP
Link with
.IR \-lsha2 .
.SH DESCRIPTION
The
.BR libsha2_sum_fd ()
function hashes the file with the
file descriptor
.I fd
with the selected
.IR algorithm .
The resulting hash is stored in binary
format in
.IR hashsum .
The user must make sure that
.I hashsum
is sufficiently large, which means at
least the return value of the
.BR libsha2_algorithm_output_size (3)
function.
.PP
The
.BR libsha2_behex_lower (3)
and
.BR libsha2_behex_upper (3)
functions can be used to convert the
result to hexadecimal format.
.SH RETURN VALUE
The
.BR libsha2_sum_fd ()
function returns 0 upon successful completion,
otherwise -1 is returned and
.I errno
is set appropriately.
.SH ERRORS
The
.BR libsha2_sum_fd ()
function may fail for any reason specified for the
.BR read (3)
and
.BR libsha2_init (3)
functions.
.SH EXAMPLES
None.
.SH APPLICATION USAGE
None.
.SH RATIONALE
None.
.SH FUTURE DIRECTIONS
None.
.SH NOTES
None.
.SH BUGS
None.
.SH SEE ALSO
.BR libsha2_algorithm_output_size (3),
.BR libsha2_behex_lower (3),
.BR libsha2_behex_upper (3),
.BR libsha2_init (3)