tread.c - plan9port - [fork] Plan 9 from user space
HTML git clone git://src.adamsgaard.dk/plan9port
DIR Log
DIR Files
DIR Refs
DIR README
DIR LICENSE
---
tread.c (2160B)
---
1 #include <u.h>
2 #include <libc.h>
3 #include <draw.h>
4 #include <memdraw.h>
5
6 Memimage*
7 readmemimage(int fd)
8 {
9 char hdr[5*12+1];
10 int dy;
11 u32int chan;
12 uint l, n;
13 int m, j;
14 int new, miny, maxy;
15 Rectangle r;
16 uchar *tmp;
17 int ldepth, chunk;
18 Memimage *i;
19
20 if(readn(fd, hdr, 11) != 11){
21 werrstr("readimage: short header");
22 return nil;
23 }
24 if(memcmp(hdr, "compressed\n", 11) == 0)
25 return creadmemimage(fd);
26 if(readn(fd, hdr+11, 5*12-11) != 5*12-11){
27 werrstr("readimage: short header (2)");
28 return nil;
29 }
30
31 /*
32 * distinguish new channel descriptor from old ldepth.
33 * channel descriptors have letters as well as numbers,
34 * while ldepths are a single digit formatted as %-11d.
35 */
36 new = 0;
37 for(m=0; m<10; m++){
38 if(hdr[m] != ' '){
39 new = 1;
40 break;
41 }
42 }
43 if(hdr[11] != ' '){
44 werrstr("readimage: bad format");
45 return nil;
46 }
47 if(new){
48 hdr[11] = '\0';
49 if((chan = strtochan(hdr)) == 0){
50 werrstr("readimage: bad channel string %s", hdr);
51 return nil;
52 }
53 }else{
54 ldepth = ((int)hdr[10])-'0';
55 if(ldepth<0 || ldepth>3){
56 werrstr("readimage: bad ldepth %d", ldepth);
57 return nil;
58 }
59 chan = drawld2chan[ldepth];
60 }
61
62 r.min.x = atoi(hdr+1*12);
63 r.min.y = atoi(hdr+2*12);
64 r.max.x = atoi(hdr+3*12);
65 r.max.y = atoi(hdr+4*12);
66 if(r.min.x>r.max.x || r.min.y>r.max.y){
67 werrstr("readimage: bad rectangle");
68 return nil;
69 }
70
71 miny = r.min.y;
72 maxy = r.max.y;
73
74 l = bytesperline(r, chantodepth(chan));
75 i = allocmemimage(r, chan);
76 if(i == nil)
77 return nil;
78 chunk = 32*1024;
79 if(chunk < l)
80 chunk = l;
81 tmp = malloc(chunk);
82 if(tmp == nil)
83 goto Err;
84 while(maxy > miny){
85 dy = maxy - miny;
86 if(dy*l > chunk)
87 dy = chunk/l;
88 if(dy <= 0){
89 werrstr("readmemimage: image too wide for buffer");
90 goto Err;
91 }
92 n = dy*l;
93 m = readn(fd, tmp, n);
94 if(m != n){
95 werrstr("readmemimage: read count %d not %d: %r", m, n);
96 Err:
97 freememimage(i);
98 free(tmp);
99 return nil;
100 }
101 if(!new) /* an old image: must flip all the bits */
102 for(j=0; j<chunk; j++)
103 tmp[j] ^= 0xFF;
104
105 if(loadmemimage(i, Rect(r.min.x, miny, r.max.x, miny+dy), tmp, chunk) <= 0)
106 goto Err;
107 miny += dy;
108 }
109 free(tmp);
110 return i;
111 }