Compress empty strings with underlying compressor

[folly.git] / folly / io / compression / Zlib.cpp

diff --git a/folly/io/compression/Zlib.cpp b/folly/io/compression/Zlib.cpp
index 5cb5dcbf3597b7fe72d85adf3457ae2803d8cba0..38cfa1adb2f00a925f47b1321ac3acc5177d2c0e 100644 (file)
--- a/folly/io/compression/Zlib.cpp
+++ b/folly/io/compression/Zlib.cpp
@@ -176,7 +176,10 @@ bool ZlibStreamCodec::canUncompress(const IOBuf* data, Optional<uint64_t>)
 
 uint64_t ZlibStreamCodec::doMaxCompressedLength(
     uint64_t uncompressedLength) const {
-  return deflateBound(nullptr, uncompressedLength);
+  // When passed a nullptr, deflateBound() adds 6 bytes for a zlib wrapper. A
+  // gzip wrapper is 18 bytes, so we add the 12 byte difference.
+  return deflateBound(nullptr, uncompressedLength) +
+      (options_.format == Options::Format::GZIP ? 12 : 0);
 }
 
 std::unique_ptr<Codec> ZlibStreamCodec::createCodec(