ref: 39fb26df70b6d8878953ff18046cdc12817a2e42
dir: /sys/src/libmemdraw/read.c/
#include <u.h> #include <libc.h> #include <draw.h> #include <memdraw.h> Memimage* readmemimage(int fd) { char hdr[5*12+1]; int dy; ulong chan; uint l, n; int m, j; int new, miny, maxy; Rectangle r; uchar *tmp; int ldepth, chunk; Memimage *i; if(readn(fd, hdr, 11) != 11){ werrstr("readimage: short header"); return nil; } if(memcmp(hdr, "compressed\n", 11) == 0) return creadmemimage(fd); if(readn(fd, hdr+11, 5*12-11) != 5*12-11){ werrstr("readimage: short header (2)"); return nil; } /* * distinguish new channel descriptor from old ldepth. * channel descriptors have letters as well as numbers, * while ldepths are a single digit formatted as %-11d. */ new = 0; for(m=0; m<10; m++){ if(hdr[m] != ' '){ new = 1; break; } } if(hdr[11] != ' '){ werrstr("readimage: bad format"); return nil; } if(new){ hdr[11] = '\0'; if((chan = strtochan(hdr)) == 0){ werrstr("readimage: bad channel string %s", hdr); return nil; } }else{ ldepth = ((int)hdr[10])-'0'; if(ldepth<0 || ldepth>3){ werrstr("readimage: bad ldepth %d", ldepth); return nil; } chan = drawld2chan[ldepth]; } r.min.x = atoi(hdr+1*12); r.min.y = atoi(hdr+2*12); r.max.x = atoi(hdr+3*12); r.max.y = atoi(hdr+4*12); if(r.min.x>r.max.x || r.min.y>r.max.y){ werrstr("readimage: bad rectangle"); return nil; } miny = r.min.y; maxy = r.max.y; l = bytesperline(r, chantodepth(chan)); i = allocmemimage(r, chan); if(i == nil) return nil; chunk = 32*1024; if(chunk < l) chunk = l; tmp = malloc(chunk); if(tmp == nil) goto Err; while(maxy > miny){ dy = maxy - miny; if(dy*l > chunk) dy = chunk/l; n = dy*l; m = readn(fd, tmp, n); if(m != n){ werrstr("readmemimage: read count %d not %d: %r", m, n); Err: freememimage(i); free(tmp); return nil; } if(!new) /* an old image: must flip all the bits */ for(j=0; j<chunk; j++) tmp[j] ^= 0xFF; if(loadmemimage(i, Rect(r.min.x, miny, r.max.x, miny+dy), tmp, chunk) <= 0) goto Err; miny += dy; } free(tmp); return i; }