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BGETHF.C
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1989-08-30
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115 lines
/* Copyright (c) 1989 Citadel */
/* All Rights Reserved */
/* #ident "bgethf.c 1.1 - 89/07/03" */
#include <errno.h>
/* #include <string.h> */
#include "blkio_.h"
/*man---------------------------------------------------------------------------
NAME
bgethf - get a header field from a block file
SYNOPSIS
#include <blkio.h>
int bgethf(bp, offset, buf, bufsize)
BLKFILE *bp;
size_t offset;
void *buf;
size_t bufsize;
DESCRIPTION
The bgethf function reads a field from the header in the block file
associated with BLKFILE pointer bp into buf. The field begins offset
characters from the beginning of the header and is bufsize characters
long. buf must point to a storage area at least bufsize characters
long.
bgethf will fail if one or more of the following is true:
[EINVAL] bp is not a valid BLKFILE pointer.
[EINVAL] bn or bufsize is less than 1.
[EINVAL] buf is the NULL pointer.
[BEBOUND] offset + bufsize extends beyond the boundary
of the header.
[BEBOUND] End of file not on block boundary.
[BEEOF] bp is empty.
[BENOPEN] bp is not open for reading.
SEE ALSO
bgeth, bgetbf, bputhf.
DIAGNOSTICS
Upon successful completion, a value of 0 is returned. Otherwise, a
value of -1 is returned, and errno set to indicate the error.
------------------------------------------------------------------------------*/
int bgethf(bp, offset, buf, bufsize)
BLKFILE * bp;
size_t offset;
void * buf;
size_t bufsize;
{
int rs = 0;
errno = 0;
/* validate arguments */
if (!b_valid(bp)) {
errno = EINVAL;
return -1;
}
if ((buf == NULL) || (bufsize < 1)) {
errno = EINVAL;
return -1;
}
/* check if not open for reading */
if (!(bp->flags & BIOREAD)) {
errno = BENOPEN;
return -1;
}
/* check if block boundary is crossed */
if ((offset + bufsize) > bp->hdrsize) {
errno = BEBOUND;
return -1;
}
/* check if header not yet written */
if (bp->endblk < 1) {
errno = BEEOF;
return -1;
}
/* check if not buffered */
if (bp->bufcnt == 0) {
rs = b_ugetf(bp, (size_t)0, offset, buf, bufsize);
if (rs == -1) {
BEPRINT;
return -1;
}
errno = 0;
return 0;
}
/* check if buffer is not loaded */
if (!(b_block_p(bp, (size_t)0)->flags & BLKREAD)) {
/* read header from file */
b_block_p(bp, (size_t)0)->bn = 0;
rs = b_get(bp, (size_t)0);
if (rs == -1) {
BEPRINT;
return -1;
}
}
/* copy from block buffer into buf */
memcpy(buf, (void *)((char *)b_blkbuf(bp, (size_t)0) + offset), bufsize);
errno = 0;
return 0;
}