1 /*
2 http://code.google.com/p/inferno-os/source/browse/libbio/bgetc.c
3
4 Copyright © 1994-1999 Lucent Technologies Inc. All rights reserved.
5 Revisions Copyright © 2000-2007 Vita Nuova Holdings Limited (www.vitanuova.com). All rights reserved.
6
7 Permission is hereby granted, free of charge, to any person obtaining a copy
8 of this software and associated documentation files (the "Software"), to deal
9 in the Software without restriction, including without limitation the rights
10 to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11 copies of the Software, and to permit persons to whom the Software is
12 furnished to do so, subject to the following conditions:
13
14 The above copyright notice and this permission notice shall be included in
15 all copies or substantial portions of the Software.
16
17 THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
20 AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22 OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
23 THE SOFTWARE.
24 */
25
26 #include <u.h>
27 #include <libc.h>
28 #include <bio.h>
29
30 int
31 Bgetc(Biobuf *bp)
32 {
33 int i;
34
35 loop:
36 i = bp->icount;
37 if(i != 0) {
38 bp->icount = i+1;
39 return bp->ebuf[i];
40 }
41 if(bp->state != Bractive) {
42 if(bp->state == Bracteof)
43 bp->state = Bractive;
44 return Beof;
45 }
46 /*
47 * get next buffer, try to keep Bungetsize
48 * characters pre-catenated from the previous
49 * buffer to allow that many ungets.
50 */
51 memmove(bp->bbuf-Bungetsize, bp->ebuf-Bungetsize, Bungetsize);
52 i = read(bp->fid, bp->bbuf, bp->bsize);
53 bp->gbuf = bp->bbuf;
54 if(i <= 0) {
55 bp->state = Bracteof;
56 if(i < 0)
57 bp->state = Binactive;
58 return Beof;
59 }
60 if(i < bp->bsize) {
61 memmove(bp->ebuf-i-Bungetsize, bp->bbuf-Bungetsize, i+Bungetsize);
62 bp->gbuf = bp->ebuf-i;
63 }
64 bp->icount = -i;
65 bp->offset += i;
66 goto loop;
67 }
68
69 int
70 Bungetc(Biobuf *bp)
71 {
72
73 if(bp->state == Bracteof)
74 bp->state = Bractive;
75 if(bp->state != Bractive)
76 return Beof;
77 bp->icount--;
78 return 1;
79 }