Second thoughts on TOAST decompression.
On detecting a corrupted match tag, pglz_decompress() should just
summarily return -1.  Breaking out of the loop, as I did in
doesn't quite guarantee that will happen.  Also, we can use
unlikely() on that check, just in case it helps.
Backpatch to v13, like the previous patch.
@@ -680,9 +680,12 @@ pglz_compress(const char *source, int32 slen, char *dest,
* pglz_decompress -
*
* Decompresses source into dest. Returns the number of bytes
- * decompressed in the destination buffer, and *optionally*
- * checks that both the source and dest buffers have been
- * fully read and written to, respectively.
+ * decompressed into the destination buffer, or -1 if the
+ * compressed data is corrupted.
+ *
+ * If check_complete is true, the data is considered corrupted
+ * if we don't exactly fill the destination buffer. Callers that
+ * are extracting a slice typically can't apply this check.
* ----------
*/
int32
@@ -736,8 +739,8 @@ pglz_decompress(const char *source, int32 slen, char *dest,
* must check this, else we risk an infinite loop below in the
* face of corrupt data.)
*/
- if (sp > srcend || off == 0)
- break;
+ if (unlikely(sp > srcend || off == 0))
+ return -1;
/*
* Don't emit more data than requested.
@@ -809,9 +812,7 @@ pglz_decompress(const char *source, int32 slen, char *dest,
}
/*
- * Check we decompressed the right amount. If we are slicing, then we
- * won't necessarily be at the end of the source or dest buffers when we
- * hit a stop, so we don't test them.
+ * If requested, check we decompressed the right amount.
*/
if (check_complete && (dp != destend || sp != srcend))
return -1;
