[GitHub] ivankelly commented on a change in pull request #3159: Added support for ZSTD compression

[GitBox <gi...@apache.org>]

ivankelly commented on a change in pull request #3159: Added support for ZSTD compression
URL: https://github.com/apache/pulsar/pull/3159#discussion_r240634794
 
 

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 File path: pulsar-client-cpp/lib/CompressionCodecZstd.cc
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+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+#include "CompressionCodecZstd.h"
+
+#if HAS_ZSTD
+#include <zstd.h>
+
+namespace pulsar {
+
+SharedBuffer CompressionCodecZstd::encode(const SharedBuffer& raw) {
+    // Get the max size of the compressed data and allocate a buffer to hold it
+    size_t maxCompressedSize = ZSTD_compressBound(raw.readableBytes());
+    SharedBuffer compressed = SharedBuffer::allocate(maxCompressedSize);
+
+    int compressedSize = ZSTD_compress(compressed.mutableData(), maxCompressedSize, raw.data(), raw.readableBytes(),
+                                       ZSTD_CLEVEL_DEFAULT);
+    compressed.bytesWritten(compressedSize);
+
+    return compressed;
+}
+
+bool CompressionCodecZstd::decode(const SharedBuffer& encoded, uint32_t uncompressedSize,
+                                 SharedBuffer& decoded) {
+    SharedBuffer decompressed = SharedBuffer::allocate(uncompressedSize);
+
+    size_t result = ZSTD_decompress(decompressed.mutableData(), uncompressedSize, encoded.data(), encoded.readableBytes());
+    if (result == uncompressedSize) {
+        decompressed.bytesWritten(uncompressedSize);
+        decoded = decompressed;
 
 Review comment:
   This looks weird. I guess it's copy constructing onto the instance passed in, but this would look weird in any language. Out of scope for this patch, but it should be possible to do something like 
   ```
   decoded.reallocate(uncompressedSize);
   ```
   And then use that buffer directly.

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