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-rw-r--r--erts/emulator/nifs/common/zlib_nif.c25
1 files changed, 21 insertions, 4 deletions
diff --git a/erts/emulator/nifs/common/zlib_nif.c b/erts/emulator/nifs/common/zlib_nif.c
index 104e52754a..b709ed5a6f 100644
--- a/erts/emulator/nifs/common/zlib_nif.c
+++ b/erts/emulator/nifs/common/zlib_nif.c
@@ -717,7 +717,9 @@ static ERL_NIF_TERM zlib_deflateEnd(ErlNifEnv *env, int argc, const ERL_NIF_TERM
static ERL_NIF_TERM zlib_deflateParams(ErlNifEnv *env, int argc, const ERL_NIF_TERM argv[]) {
zlib_data_t *d;
+
int res, level, strategy;
+ Bytef dummy_buffer;
if(argc != 3 || !get_zlib_data(env, argv[0], &d)
|| !enif_get_int(env, argv[1], &level)
@@ -729,12 +731,27 @@ static ERL_NIF_TERM zlib_deflateParams(ErlNifEnv *env, int argc, const ERL_NIF_T
return enif_raise_exception(env, am_not_initialized);
}
- /* deflateParams will flush everything currently in the stream, corrupting
- * the heap unless it's empty. We therefore pretend to have a full output
- * buffer, forcing a Z_BUF_ERROR if there's anything left to be flushed. */
- d->s.avail_out = 0;
+ /* This is a bit of a hack; deflateParams flushes with Z_BLOCK which won't
+ * stop at a byte boundary, so we can't split this operation up, and we
+ * can't allocate a buffer large enough to fit it in one go since we have
+ * to support zlib versions that lack deflatePending.
+ *
+ * We therefore flush everything prior to this call to ensure that we are
+ * stopped on a byte boundary and have no pending data. We then hand it a
+ * dummy buffer to detect when this assumption doesn't hold (Hopefully
+ * never), and to smooth over an issue with zlib 1.2.11 which always
+ * returns Z_BUF_ERROR when d->s.avail_out is 0, regardless of whether
+ * there's any pending data or not. */
+
+ d->s.next_out = &dummy_buffer;
+ d->s.avail_out = 1;
+
res = deflateParams(&d->s, level, strategy);
+ if(d->s.avail_out == 0) {
+ return zlib_return(env, Z_STREAM_ERROR);
+ }
+
return zlib_return(env, res);
}