1 /*
2  * Copyright (c) 2000-2001 Sendmail, 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>
16 SM_RCSID("@(#)$Id: setvbuf.c,v 1.30 2001/02/28 20:25:18 rodney Exp $")
17 #include <stdlib.h>
18 #include <errno.h>
19 #include <fcntl.h>
20 #include <sm/io.h>
21 #include <sm/heap.h>
22 #include <sm/assert.h>
23 #include <sm/conf.h>
24 #include "local.h"
25 
26 /*
27 **  SM_IO_SETVBUF -- set the buffering type for a file
28 **
29 **  Set one of the different kinds of buffering, optionally including
30 **  a buffer.
31 **  If 'size' is == 0 then an "optimal" size will be selected.
32 **  If 'buf' is == NULL then space will be allocated at 'size'.
33 **
34 **	Parameters:
35 **		fp -- the file that buffering is to be changed for
36 **		timeout -- time allowed for completing the function
37 **		buf -- buffer to use
38 **		mode -- buffering method to use
39 **		size -- size of 'buf'
40 **
41 **	Returns:
42 **		Failure: SM_IO_EOF
43 **		Success: 0 (zero)
44 */
45 
46 int
47 sm_io_setvbuf(fp, timeout, buf, mode, size)
48 	SM_FILE_T *fp;
49 	int timeout;
50 	char *buf;
51 	int mode;
52 	size_t size;
53 {
54 	int ret, flags;
55 	size_t iosize;
56 	int ttyflag;
57 	int fd;
58 	struct timeval to;
59 
60 	SM_REQUIRE_ISA(fp, SmFileMagic);
61 
62 	/*
63 	**  Verify arguments.  The `int' limit on `size' is due to this
64 	**  particular implementation.  Note, buf and size are ignored
65 	**  when setting SM_IO_NBF.
66 	*/
67 
68 	if (mode != SM_IO_NBF)
69 		if ((mode != SM_IO_FBF && mode != SM_IO_LBF &&
70 		    mode != SM_IO_NOW) || (int) size < 0)
71 			return SM_IO_EOF;
72 
73 	/*
74 	**  Write current buffer, if any.  Discard unread input (including
75 	**  ungetc data), cancel line buffering, and free old buffer if
76 	**  malloc()ed.  We also clear any eof condition, as if this were
77 	**  a seek.
78 	*/
79 
80 	ret = 0;
81 	SM_CONVERT_TIME(fp, fd, timeout, &to);
82 	(void) sm_flush(fp, &timeout);
83 	if (HASUB(fp))
84 		FREEUB(fp);
85 	fp->f_r = fp->f_lbfsize = 0;
86 	flags = fp->f_flags;
87 	if (flags & SMMBF)
88 	{
89 		sm_free((void *) fp->f_bf.smb_base);
90 		fp->f_bf.smb_base = NULL;
91 	}
92 	flags &= ~(SMLBF | SMNBF | SMMBF | SMOPT | SMNPT | SMFEOF | SMNOW |
93 		   SMFBF);
94 
95 	/* If setting unbuffered mode, skip all the hard work. */
96 	if (mode == SM_IO_NBF)
97 		goto nbf;
98 
99 	/*
100 	**  Find optimal I/O size for seek optimization.  This also returns
101 	**  a `tty flag' to suggest that we check isatty(fd), but we do not
102 	**  care since our caller told us how to buffer.
103 	*/
104 
105 	flags |= sm_whatbuf(fp, &iosize, &ttyflag);
106 	if (size == 0)
107 	{
108 		buf = NULL;	/* force local allocation */
109 		size = iosize;
110 	}
111 
112 	/* Allocate buffer if needed. */
113 	if (buf == NULL)
114 	{
115 		if ((buf = sm_malloc(size)) == NULL)
116 		{
117 			/*
118 			**  Unable to honor user's request.  We will return
119 			**  failure, but try again with file system size.
120 			*/
121 
122 			ret = SM_IO_EOF;
123 			if (size != iosize)
124 			{
125 				size = iosize;
126 				buf = sm_malloc(size);
127 			}
128 		}
129 		if (buf == NULL)
130 		{
131 			/* No luck; switch to unbuffered I/O. */
132 nbf:
133 			fp->f_flags = flags | SMNBF;
134 			fp->f_w = 0;
135 			fp->f_bf.smb_base = fp->f_p = fp->f_nbuf;
136 			fp->f_bf.smb_size = 1;
137 			return ret;
138 		}
139 		flags |= SMMBF;
140 	}
141 
142 	/*
143 	**  Kill any seek optimization if the buffer is not the
144 	**  right size.
145 	**
146 	**  SHOULD WE ALLOW MULTIPLES HERE (i.e., ok iff (size % iosize) == 0)?
147 	*/
148 
149 	if (size != iosize)
150 		flags |= SMNPT;
151 
152 	/*
153 	**  Fix up the SM_FILE_T fields, and set sm_cleanup for output flush on
154 	**  exit (since we are buffered in some way).
155 	*/
156 
157 	if (mode == SM_IO_LBF)
158 		flags |= SMLBF;
159 	else if (mode == SM_IO_NOW)
160 		flags |= SMNOW;
161 	else if (mode == SM_IO_FBF)
162 		flags |= SMFBF;
163 	fp->f_flags = flags;
164 	fp->f_bf.smb_base = fp->f_p = (unsigned char *)buf;
165 	fp->f_bf.smb_size = size;
166 	/* fp->f_lbfsize is still 0 */
167 	if (flags & SMWR)
168 	{
169 		/*
170 		**  Begin or continue writing: see sm_wsetup().  Note
171 		**  that SMNBF is impossible (it was handled earlier).
172 		*/
173 
174 		if (flags & SMLBF)
175 		{
176 			fp->f_w = 0;
177 			fp->f_lbfsize = -fp->f_bf.smb_size;
178 		}
179 		else
180 			fp->f_w = size;
181 	}
182 	else
183 	{
184 		/* begin/continue reading, or stay in intermediate state */
185 		fp->f_w = 0;
186 	}
187 
188 	atexit(sm_cleanup);
189 	return ret;
190 }
191