fread.c revision 266692 
1/*
2 * Copyright (c) 2000-2001 Proofpoint, Inc. and its suppliers.
3 *      All rights reserved.
4 * Copyright (c) 1990, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This code is derived from software contributed to Berkeley by
8 * Chris Torek.
9 *
10 * By using this file, you agree to the terms and conditions set
11 * forth in the LICENSE file which can be found at the top level of
12 * the sendmail distribution.
13 */
14
15#include <sm/gen.h>
16SM_RCSID("@(#)$Id: fread.c,v 1.29 2013-11-22 20:51:42 ca Exp $")
17#include <string.h>
18#include <errno.h>
19#include <sm/io.h>
20#include <sm/assert.h>
21#include "local.h"
22
23/*
24**  SM_IO_READ -- read data from the file pointer
25**
26**	Parameters:
27**		fp -- file pointer to read from
28**		timeout -- time to complete the read
29**		buf -- location to place read data
30**		size -- size of each chunk of data
31**
32**	Returns:
33**		Failure: returns 0 (zero) _and_ sets errno
34**		Success: returns the number of whole chunks read.
35**
36**	A read returning 0 (zero) is only an indication of error when errno
37**	has been set.
38*/
39
40size_t
41sm_io_read(fp, timeout, buf, size)
42	SM_FILE_T *fp;
43	int timeout;
44	void *buf;
45	size_t size;
46{
47	register size_t resid = size;
48	register char *p;
49	register int r;
50
51	SM_REQUIRE_ISA(fp, SmFileMagic);
52
53	if (fp->f_read == NULL)
54	{
55		errno = ENODEV;
56		return 0;
57	}
58
59	/*
60	**  The ANSI standard requires a return value of 0 for a count
61	**  or a size of 0.  Peculiarily, it imposes no such requirements
62	**  on fwrite; it only requires read to be broken.
63	*/
64
65	if (resid == 0)
66		return 0;
67	if (fp->f_r < 0)
68		fp->f_r = 0;
69	p = buf;
70	while ((int) resid > (r = fp->f_r))
71	{
72		(void) memcpy((void *) p, (void *) fp->f_p, (size_t) r);
73		fp->f_p += r;
74		/* fp->f_r = 0 ... done in sm_refill */
75		p += r;
76		resid -= r;
77		if ((fp->f_flags & SMNOW) != 0 && r > 0)
78		{
79			/*
80			**  Take whatever we have available. Spend no more time
81			**  trying to get all that has been requested.
82			**  This is needed on some file types (such as
83			**  SASL) that would jam when given extra, untimely
84			**  reads.
85			*/
86
87			fp->f_r -= r;
88			return size - resid;
89		}
90		if (sm_refill(fp, timeout) != 0)
91		{
92			/* no more input: return partial result */
93			return size - resid;
94		}
95	}
96	(void) memcpy((void *) p, (void *) fp->f_p, resid);
97	fp->f_r -= resid;
98	fp->f_p += resid;
99	return size;
100}
101