1 /* $Id: pushback.c,v 1.1 2000/12/09 03:08:23 apbianco Exp $
4 Revision 1.1 2000/12/09 03:08:23 apbianco
5 2000-12-08 Alexandre Petit-Bianco <apbianco@cygnus.com>
9 Revision 1.2 2000/08/23 19:42:17 cory
10 Added support for more Unix platforms. The following code has been hacked
11 to work on AIX, Solaris, True 64, and HP-UX.
12 Added bigendian check. Probably works on most big and little endian platforms
15 Revision 1.1.1.1 1999/12/06 03:09:13 toast
20 Revision 1.1 1999/05/10 08:32:37 burnsbr
26 pushback.c - code for a pushback buffer to handle file I/O
27 Copyright (C) 1999 Bryan Burns
29 This program is free software; you can redistribute it and/or
30 modify it under the terms of the GNU General Public License
31 as published by the Free Software Foundation; either version 2
32 of the License, or (at your option) any later version.
34 This program is distributed in the hope that it will be useful,
35 but WITHOUT ANY WARRANTY; without even the implied warranty of
36 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
37 GNU General Public License for more details.
39 You should have received a copy of the GNU General Public License
40 along with this program; if not, write to the Free Software
41 Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
51 void pb_init(pb_file *pbf, int fd){
53 pbf->next = pbf->pb_buff;
57 int pb_push(pb_file *pbf, void *buff, int amt){
62 printf("%d bytes being pushed back to the buffer\n", amt);
65 /* determine how much we can take */
66 if((RDSZ - pbf->buff_amt) < amt)
67 in_amt = RDSZ - pbf->buff_amt;
74 /* figure out if we need to wrap around, and if so, by how much */
75 if(((pbf->pb_buff + RDSZ) - pbf->next) < in_amt)
76 wrap = in_amt - ((pbf->pb_buff + RDSZ) - pbf->next);
78 /* write everything up til the end of the buffer */
79 memcpy(pbf->next, buff, (in_amt - wrap));
81 /* finish writing what's wrapped around */
82 memcpy(pbf->pb_buff, ((char *)buff + (in_amt - wrap)), wrap);
84 /* update the buff_amt field */
85 pbf->buff_amt += in_amt;
88 printf("%d bytes we can't accept\n", (amt - in_amt));
95 int pb_read(pb_file *pbf, void *buff, int amt){
102 printf("%d bytes requested from us\n", amt);
104 while(out_amt < amt){
105 /* if our push-back buffer contains some data */
106 if(pbf->buff_amt > 0){
109 printf("giving data from buffer\n");
112 /* calculate how much we can actually give the caller */
113 if( (amt - out_amt) < pbf->buff_amt )
114 tmp = (amt - out_amt);
118 /* Determine if we're going to need to wrap around the buffer */
119 if(tmp > ((pbf->pb_buff + RDSZ) - pbf->next))
120 wrap = tmp - ((pbf->pb_buff + RDSZ) - pbf->next);
122 memcpy(bp, pbf->next, (tmp - wrap));
123 bp = &(((char *)bp)[tmp - wrap]);
125 /* If we need to wrap, read from the start of the buffer */
127 memcpy(bp, pbf->pb_buff, wrap);
128 bp = &(((char *)bp)[wrap]);
131 /* update the buff_amt field */
132 pbf->buff_amt -= tmp;
136 printf("%d bytes remaining in buffer\n", pbf->buff_amt);
139 /* if the buffer is empty, reset the next header to the front of the
140 buffer so subsequent pushbacks/reads won't have to wrap */
141 if(pbf->buff_amt == 0)
142 pbf->next = pbf->pb_buff;
148 printf("Reading from file..\n");
151 /* The pushback buffer was empty, so we just need to read from the file */
152 tmp = read(pbf->fd, bp, (amt - out_amt));
158 bp = &(((char *)bp)[tmp]);
163 printf("managed to read %d bytes\n", out_amt);