Assure that deflateParams() will not switch functions mid-block.

This alters the specification in zlib.h, so that deflateParams()
will not change any parameters if there is not enough output space
in the event that a block is emitted in order to allow switching
the compression function.

1 files changed, 6 insertions, 5 deletions

diff --git a/deflate.c b/deflate.c
index 3d24cbc..0a78b5a 100644
--- a/deflate.c
+++ b/deflate.c
@@ -517,7 +517,6 @@ int ZEXPORT deflateParams(strm, level, strategy)
 {
     deflate_state *s;
     compress_func func;
-    int err = Z_OK;
 
     if (deflateStateCheck(strm)) return Z_STREAM_ERROR;
     s = strm->state;
@@ -534,9 +533,11 @@ int ZEXPORT deflateParams(strm, level, strategy)
 
     if ((strategy != s->strategy || func != configuration_table[level].func)) {
         /* Flush the last buffer: */
-        err = deflate(strm, Z_BLOCK);
-        if (err == Z_BUF_ERROR && s->pending == 0)
-            err = Z_OK;
+        int err = deflate(strm, Z_BLOCK);
+        if (err == Z_STREAM_ERROR)
+            return err;
+        if (strm->avail_out == 0)
+            return Z_BUF_ERROR;
     }
     if (s->level != level) {
         s->level = level;
@@ -546,7 +547,7 @@ int ZEXPORT deflateParams(strm, level, strategy)
         s->max_chain_length = configuration_table[level].max_chain;
     }
     s->strategy = strategy;
-    return err;
+    return Z_OK;
 }
 
 /* ========================================================================= */