added bounding to compression level change

diff --git a/contrib/adaptive-compression/adapt.c b/contrib/adaptive-compression/adapt.c
index 758bf558999b400b3329d5faabb8eecf47c49837..c542c9a3db051863ed2a086c8c83ca318350b358 100644 (file)
--- a/contrib/adaptive-compression/adapt.c
+++ b/contrib/adaptive-compression/adapt.c
@@ -323,20 +323,23 @@ static void adaptCompressionLevel(adaptCCtx* ctx)
     if (1 - createCompletion > threshold) {
         /* job creation was not finished, compression thread waited */
         unsigned const change = MAX_COMPRESSION_LEVEL_CHANGE - createCompletion * MAX_COMPRESSION_LEVEL_CHANGE;
+        unsigned const boundChange = MIN(change, ZSTD_maxCLevel() - ctx->compressionLevel);
         DEBUG(2, "increasing compression level %u by %u\n", ctx->compressionLevel, change);
-        ctx->compressionLevel += change;
+        ctx->compressionLevel += boundChange;
     }
     else if (1 - writeCompletion > threshold) {
         /* write thread was not finished, compression thread waited */
         unsigned const change = MAX_COMPRESSION_LEVEL_CHANGE - writeCompletion * MAX_COMPRESSION_LEVEL_CHANGE;
+        unsigned const boundChange = MIN(change, ZSTD_maxCLevel() - ctx->compressionLevel);
         DEBUG(2, "increasing compression level %u by %u\n", ctx->compressionLevel, change);
-        ctx->compressionLevel += change;
+        ctx->compressionLevel += boundChange;
     }
     else if (1 - compressionCompletion > threshold) {
         /* compression thread was not finished, one of the other two threads waited */
         unsigned const change = MAX_COMPRESSION_LEVEL_CHANGE - compressionCompletion * MAX_COMPRESSION_LEVEL_CHANGE;
+        unsigned const boundChange = MIN(change, ctx->compressionLevel - 1);
         DEBUG(2, "decreasing compression level %u by %u\n", ctx->compressionLevel, change);
-        ctx->compressionLevel -= change;
+        ctx->compressionLevel -= boundChange;
     }
     /* reset */
     pthread_mutex_lock(&ctx->completion_mutex.pMutex);