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jpg: be more tolerant with corrupted files, and dont crash

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This commit is contained in:
cinap_lenrek 2012-06-15 08:24:05 +02:00
parent 9b29d5be82
commit 9cb66f310b
1 changed files with 30 additions and 41 deletions
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71
sys/src/cmd/jpg/readjpg.c
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@ -397,12 +397,15 @@ marker(Header *h)
{
int c;
Again:
while((c=readbyte(h)) == 0)
fprint(2, "ReadJPG: skipping zero byte at offset %lld\n", Boffset(h->fd));
;
if(c != 0xFF)
jpgerror(h, "ReadJPG: expecting marker; found 0x%x at offset %lld\n", c, Boffset(h->fd));
goto Again;
while(c == 0xFF)
c = readbyte(h);
if(c == 0)
goto Again;
return c;
}
@ -440,13 +443,9 @@ readsegment(Header *h, int *markerp)
int m, n;
uchar tmp[2];
m = marker(h);
switch(m){
case EOI:
if((m = marker(h)) == EOI){
*markerp = m;
return 0;
case 0:
jpgerror(h, "ReadJPG: expecting marker; saw %.2x at offset %lld", m, Boffset(h->fd));
}
if(Breadn(h->fd, tmp, 2) != 2)
Readerr:
@ -473,7 +472,7 @@ int
huffmantable(Header *h, uchar *b)
{
Huffman *t;
int Tc, th, n, nsize, i, j, k, v, cnt, code, si, sr, m;
int Tc, th, n, nsize, i, j, k, v, cnt, code, si, sr;
int *maxcode;
nibbles(b[0], &Tc, &th);
@ -547,24 +546,21 @@ outF25:
maxcode = t->maxcode;
/* stupid startup algorithm: just run machine for each byte value */
for(v=0; v<256; ){
cnt = 7;
m = 1<<7;
code = 0;
cnt = 8;
sr = v;
i = 1;
for(;;i++){
if(sr & m)
for(i=1;;i++){
cnt--;
if(sr & (1<<cnt))
code |= 1;
if(code <= maxcode[i])
break;
code <<= 1;
m >>= 1;
if(m == 0){
if(cnt == 0){
t->shift[v] = 0;
t->value[v] = -1;
goto continueBytes;
}
cnt--;
}
t->shift[v] = 8-cnt;
t->value[v] = t->val[t->valptr[i]+(code-t->mincode[i])];
@ -707,22 +703,22 @@ baselinescan(Header *h, int colorspace)
memset(zz, 0, 8*8*sizeof(int));
zz[0] = qt[0]*DC[comp];
k = 1;
for(;;){
do{
t = decode(h, acht);
assert(t >= 0);
if((t&0x0F) == 0){
if((t&0xF0) != 0xF0)
break;
k += 16;
}else{
k += t>>4;
z = receive(h, t&0xF);
zz[zig[k]] = z*qt[k];
if(k == 63)
k += t>>4;
if(k >= 64)
break;
zz[zig[k]] = z*qt[k];
k++;
}
}
} while(k < 64);
idct(zz);
}
@ -1006,7 +1002,7 @@ progressiveac(Header *h, int comp, int Al)
blockno = tmcu*H*V + H*(y%V) + x%H;
acc = h->accoeff[comp][blockno];
k = Ss;
for(;;){
do {
rs = decode(h, acht);
/* XXX remove rrrr ssss as in baselinescan */
nibbles(rs, &rrrr, &ssss);
@ -1019,14 +1015,14 @@ progressiveac(Header *h, int comp, int Al)
}
k += 16;
}else{
k += rrrr;
z = receive(h, ssss);
acc[k] = z*qt[k]<<Al;
if(k == Se)
k += rrrr;
if(k > Se)
break;
acc[k] = z*qt[k]<<Al;
k++;
}
}
} while(k <= Se);
}
/* process restart marker, if present */
@ -1358,9 +1354,8 @@ static
int
decode(Header *h, Huffman *t)
{
int code, v, cnt, m, sr, i;
int code, v, cnt, sr, i;
int *maxcode;
static int badcode;
maxcode = t->maxcode;
if(h->cnt < 8)
@ -1376,30 +1371,24 @@ decode(Header *h, Huffman *t)
h->cnt -= 8;
if(h->cnt == 0)
nextbyte(h, 0);
h->cnt--;
cnt = h->cnt;
m = 1<<cnt;
sr = h->sr;
code <<= 1;
i = 9;
for(;;i++){
if(sr & m)
for(i = 9; i<17; i++){
cnt--;
if(sr & (1<<cnt))
code |= 1;
if(code <= maxcode[i])
break;
code <<= 1;
m >>= 1;
if(m == 0){
if(cnt == 0){
sr = nextbyte(h, 0);
m = 0x80;
cnt = 8;
}
cnt--;
}
if(i >= 17){
if(badcode == 0)
fprint(2, "badly encoded %dx%d JPEG file; ignoring bad value\n", h->X, h->Y);
badcode = 1;
/* bad code */
code = 0;
i = 0;
}
h->cnt = cnt;