On Mon, 12 Jul 2021, o...@eigenstate.org wrote:
Why not make getchunk allocate? Somethign like:
---
//.git/fs/object/e8259861da3a55c03491904e4d11c5c15b7577c5/tree/sys/src/cmd/jpg/readpng.c
+++ sys/src/cmd/jpg/readpng.c
@@ -94,7 +94,7 @@
}
static int
-getchunk(Biobuf *b, char *type, uchar *d, int m)
+getchunk(Biobuf *b, char *type, uchar **d)
{
uchar buf[8];
ulong crc = 0, crc2;
@@ -103,11 +103,10 @@
if(Bread(b, buf, 8) != 8)
return -1;
n = get4(buf);
+ *d = pngmalloc(n, 0);
memmove(type, buf+4, 4);
type[4] = 0;
- if(n > m)
- sysfatal("getchunk needed %d, had %d", n, m);
- nr = Bread(b, d, n);
+ nr = Bread(b, *d, n);
if(nr != n)
sysfatal("getchunk read %d, expected %d", nr, n);
crc = blockcrc(crctab, crc, type, 4);
@@ -131,7 +130,7 @@
Again:
z->p = z->buf;
z->e = z->p;
- n = getchunk(z->io, type, z->p, IDATSIZE);
+ n = getchunk(z->io, type, &z->p);
if(n < 0 || strcmp(type, "IEND") == 0)
return -1;
z->e = z->p + n;
Hi Ori,
I thought that it would be a good idea to have a separate function
to just get the size without squeezing the fs through all the chunk,
it could be useful in the future. getchunk() could call it, but I
didn't see the point. I imagine that this is not a complete patch
but a suggestion, but anyway remember that you don't need z->buf
any more, and don't forget to free z->p for the next iteration.
By the way after revisiting readpng.c I noticed that I checked for
a negative value of the IHDR chunk length, better do like in the
original code:
[...]
n = chunklen(b);
if(n < 13)
sysfatal("missing IHDR chunk");
[...]
Regards,
adr.
------------------------------------------
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