Merge pull request #951 from facebook/lastBlock

saves 3-bytes on small input with streaming API

lib/compress/zstd_compress.c

@@ -2535,7 +2535,8 @@ static size_t ZSTD_resetCStream_internal(ZSTD_CStream* zcs,
 
     zcs->inToCompress = 0;
     zcs->inBuffPos = 0;
-    zcs->inBuffTarget = zcs->blockSize;
+    zcs->inBuffTarget = zcs->blockSize
+                      + (zcs->blockSize == pledgedSrcSize);   /* for small input: avoid automatic flush on reaching end of block, since it would require to add a 3-bytes null block to end frame */
     zcs->outBuffContentSize = zcs->outBuffFlushedSize = 0;
     zcs->streamStage = zcss_load;
     zcs->frameEnded = 0;

tests/playTests.sh

@@ -126,6 +126,10 @@ $ZSTD -d > $INTOVOID && die "should have refused : compressed data from terminal
 fi
 $ECHO "test : null-length file roundtrip"
 $ECHO -n '' | $ZSTD - --stdout | $ZSTD -d --stdout
+$ECHO "test : ensure small file doesn't add 3-bytes null block"
+./datagen -g1 > tmp1
+$ZSTD tmp1 -c | wc -c | grep "14"
+$ZSTD < tmp1  | wc -c | grep "14"
 $ECHO "test : decompress file with wrong suffix (must fail)"
 $ZSTD -d tmpCompressed && die "wrong suffix error not detected!"
 $ZSTD -df tmp && die "should have refused : wrong extension"