From 498f21f63fb89a39c17702a5bae230123a33ca34 Mon Sep 17 00:00:00 2001
From: Daviw Williams <david@volumesoffun.com>
Date: Wed, 2 Oct 2013 16:48:30 +0200
Subject: [PATCH] Replaced arrays with std::vector.

---
 .../PolyVoxCore/MinizBlockCompressor.h        |  5 +++
 .../PolyVoxCore/MinizBlockCompressor.inl      | 31 ++++++++++++-------
 2 files changed, 25 insertions(+), 11 deletions(-)

diff --git a/library/PolyVoxCore/include/PolyVoxCore/MinizBlockCompressor.h b/library/PolyVoxCore/include/PolyVoxCore/MinizBlockCompressor.h
index 577cf782..04a7438f 100644
--- a/library/PolyVoxCore/include/PolyVoxCore/MinizBlockCompressor.h
+++ b/library/PolyVoxCore/include/PolyVoxCore/MinizBlockCompressor.h
@@ -44,12 +44,17 @@ namespace PolyVox
 		void decompress(CompressedBlock<VoxelType>* pSrcBlock, UncompressedBlock<VoxelType>* pDstBlock);
 
 	private:
+		uint32_t getExpectedCompressedSize(uint32_t uUncompressedInputSize);
 		uint32_t getMaxCompressedSize(uint32_t uUncompressedInputSize);
 		uint32_t compressWithMiniz(const void* pSrcData, uint32_t uSrcLength, void* pDstData, uint32_t uDstLength);
 		uint32_t decompressWithMiniz(const void* pSrcData, uint32_t uSrcLength, void* pDstData, uint32_t uDstLength);
 
 		unsigned int m_uCompressionFlags;
 
+		// Data gets compressed into this, then we check how big the result
+		// is and copy the required number of bytes to the destination block.
+		std::vector<uint8_t> m_vecTempBuffer;
+
 		// tdefl_compressor contains all the state needed by the low-level compressor so it's a pretty big struct (~300k).
 		tdefl_compressor* m_pDeflator;
 	};
diff --git a/library/PolyVoxCore/include/PolyVoxCore/MinizBlockCompressor.inl b/library/PolyVoxCore/include/PolyVoxCore/MinizBlockCompressor.inl
index fbba8856..c820ec34 100644
--- a/library/PolyVoxCore/include/PolyVoxCore/MinizBlockCompressor.inl
+++ b/library/PolyVoxCore/include/PolyVoxCore/MinizBlockCompressor.inl
@@ -62,9 +62,11 @@ namespace PolyVox
 		void* pSrcData = reinterpret_cast<void*>(pSrcBlock->getData());
 		size_t uSrcLength = pSrcBlock->getDataSizeInBytes();
 
-		uint8_t tempBuffer[1000];
-		uint8_t* pDstData = reinterpret_cast<uint8_t*>( tempBuffer );				
-		size_t uDstLength = 1000;
+		// This compressor is expected to be used many times to compress a large number of blocks, but they are all
+		// expected to have the same size. Therefore the resize() function below will only perform allocation once.
+		m_vecTempBuffer.resize(getExpectedCompressedSize(uSrcLength));
+		uint8_t* pDstData = &(m_vecTempBuffer[0]);
+		size_t uDstLength = m_vecTempBuffer.size();
 
 		uint32_t uCompressedLength = 0;
 
@@ -82,12 +84,13 @@ namespace PolyVox
 			// buffer is not big enough. So now we try again using a buffer that is definitely big enough.
 			// Note that ideally we will choose our earlier buffer size so that this almost never happens.
 			logWarning() << "The compressor failed to compress the block, probabaly due to the buffer being too small.";
-			logWarning() << "The compression will be tried again with a larger buffer";
-			uint32_t uMaxCompressedSize = getMaxCompressedSize(uSrcLength);
-			uint8_t* buffer = new uint8_t[ uMaxCompressedSize ];
+			logWarning() << "The compression will be tried again with a larger buffer.";
 
-			pDstData = reinterpret_cast<uint8_t*>( buffer );				
-			uDstLength = uMaxCompressedSize;
+			std::vector<uint8_t> vecExtraBigBuffer;
+			vecExtraBigBuffer.resize(getMaxCompressedSize(uSrcLength));
+
+			uint8_t* pDstData = &(vecExtraBigBuffer[0]);
+			size_t uDstLength = vecExtraBigBuffer.size();
 
 			try
 			{		
@@ -101,11 +104,8 @@ namespace PolyVox
 			{
 				// At this point it didn't work even with a bigger buffer.
 				// Not much more we can do so just rethrow the exception.
-				delete[] buffer;
 				POLYVOX_THROW(std::runtime_error, "Failed to compress block data");
 			}
-
-			delete[] buffer;
 		}
 	}
 
@@ -125,6 +125,15 @@ namespace PolyVox
 		POLYVOX_THROW_IF(uUncompressedLength != pDstBlock->getDataSizeInBytes(), std::runtime_error, "Decompressed data does not have the expected length");
 	}
 
+	template <typename VoxelType>
+	uint32_t MinizBlockCompressor<VoxelType>::getExpectedCompressedSize(uint32_t uUncompressedInputSize)
+	{
+		// We expect this block compressor will be used for smoothly changing volume data such as density fields and so
+		// the compression rate might not be great. The value beloew is basically a guess based on previous experience.
+		uint32_t uExpectedCompressionRate = 4;
+		return uUncompressedInputSize / uExpectedCompressionRate;
+	}
+
 	template <typename VoxelType>
 	uint32_t MinizBlockCompressor<VoxelType>::getMaxCompressedSize(uint32_t uUncompressedInputSize)
 	{