Factorized funtions to read the eof offset dictionary of serialized trimeshes

include/mitsuba/render/trimesh.h

@@ -310,6 +310,23 @@ protected:
 	/// Load a Mitsuba compressed triangle mesh substream
 	void loadCompressed(Stream *stream, int idx = 0);
 
+	/**
+	 * \brief Read the idx-th entry from the offset diccionary at the end of
+	 * the stream, which has to be open already, given the file version tag.
+	 * This function modifies the position of the stream.
+	 */
+	size_t readOffset(ref<Stream>& stream, short version, int idx) const;
+
+	/**
+	 * \brief Read the entirety of the end-of-file offset dictionary from the
+	 * already open stream, replacing the contents of the input vector.
+	 * If the file is not large enough the function returns -1
+	 * and does not modify the vector.
+	 * This function modifies the position of the stream.
+	 */
+	 int readOffsetDictionary(ref<Stream>& stream, short version,
+		 std::vector<size_t>& outOffsets) const;
+
 	/// Prepare internal tables for sampling uniformly wrt. area
 	void prepareSamplingTable();
 protected:

src/librender/trimesh.cpp

@@ -171,7 +171,6 @@ static void readHelper(Stream *stream, bool fileDoublePrecision,
 	}
 }
 
-
 void TriMesh::loadCompressed(Stream *_stream, int index) {
 	ref<Stream> stream = _stream;
 
@@ -194,28 +193,9 @@ void TriMesh::loadCompressed(Stream *_stream, int index) {
 		Log(EError, "Encountered an incompatible file version!");
 
 	if (index != 0) {
-		size_t streamSize = stream->getSize();
-
-		/* Determine the position of the requested substream. This
-		   is stored at the end of the file */
-		stream->seek(streamSize - sizeof(uint32_t));
-		uint32_t count = stream->readUInt();
-		if (index < 0 || index > (int) count) {
-			Log(EError, "Unable to unserialize mesh, "
-				"shape index is out of range! (requested %i out of 0..%i)",
-				index, count-1);
-		}
-
-		// Seek to the correct position
-		if (version == MTS_FILEFORMAT_VERSION_V4) {
-			stream->seek(stream->getSize() - sizeof(uint64_t) * (count-index) - sizeof(uint32_t));
-			stream->seek(stream->readSize());
-		} else {
-			stream->seek(stream->getSize() - sizeof(uint32_t) * (count-index + 1));
-			stream->seek(stream->readUInt());
-		}
-
-		stream->skip(sizeof(short) * 2);
+		const size_t offset = readOffset(stream, version, index);
+		stream->seek(offset);
+		stream->skip(sizeof(short) * 2); // Skip the header
 	}
 
 	stream = new ZStream(stream);
@@ -282,6 +262,74 @@ void TriMesh::loadCompressed(Stream *_stream, int index) {
 	m_flipNormals = false;
 }
 
+size_t TriMesh::readOffset(ref<Stream>& stream, short version, int idx) const {
+	const size_t streamSize = stream->getSize();
+
+	/* Determine the position of the requested substream. This is stored
+	   at the end of the file */
+	stream->seek(streamSize - sizeof(uint32_t));
+	uint32_t count = stream->readUInt();
+	if (idx < 0 || idx > (int) count) {
+		Log(EError, "Unable to unserialize mesh, "
+			"shape index is out of range! (requested %i out of 0..%i)",
+			idx, count-1);
+	}
+
+	// Seek to the correct position
+	if (version == MTS_FILEFORMAT_VERSION_V4) {
+		stream->seek(stream->getSize() - sizeof(uint64_t) * (count-idx) - sizeof(uint32_t));
+		return stream->readSize();
+	} else {
+		Assert(version == MTS_FILEFORMAT_VERSION_V3);
+		stream->seek(stream->getSize() - sizeof(uint32_t) * (count-idx + 1));
+		return stream->readUInt();
+	}
+}
+
+int TriMesh::readOffsetDictionary(ref<Stream>& stream, short version,
+		 std::vector<size_t>& outOffsets) const {
+	const size_t streamSize = stream->getSize();
+	stream->seek(streamSize - sizeof(uint32_t));
+	const uint32_t count = stream->readUInt();
+
+	// Check if the stream is large enough to contain that number of meshes
+	const size_t minSize = sizeof(uint32_t) + count *
+		( 2*sizeof(uint16_t)   // Header
+		+   sizeof(uint32_t)   // Flags
+		+   sizeof(char)       // Name
+		+ 2*sizeof(uint64_t)   // Number of vertices and triangles
+		+ 3*sizeof(float)      // One vertex
+		+ 3*sizeof(uint32_t)); // One triange
+
+	if (streamSize >= minSize) {
+		outOffsets.resize(count);
+		if (version == MTS_FILEFORMAT_VERSION_V4) {
+			stream->seek(stream->getSize() - sizeof(uint64_t) * count - sizeof(uint32_t));
+			if (typeid(size_t) == typeid(uint64_t)) {
+				stream->readArray(&outOffsets[0], count);
+			} else {
+				for (size_t i = 0; i < count; ++i) {
+					outOffsets[i] = static_cast<size_t>(stream->readSize());
+				}
+			}
+		} else {
+			stream->seek(stream->getSize() - sizeof(uint32_t) * (count + 1));
+			Assert(version == MTS_FILEFORMAT_VERSION_V3);
+			if (typeid(size_t) == typeid(uint32_t)) {
+				stream->readArray(&outOffsets[0], count);
+			} else {
+				for (size_t i = 0; i < count; ++i) {
+					outOffsets[i] = stream->readUInt();
+				}
+			}
+		}
+		return count;
+	} else {
+		Log(EDebug, "The serialized mesh does not contain a valid dictionary");
+		return -1;
+	}
+}
+
 TriMesh::~TriMesh() {
 	if (m_positions)
 		delete[] m_positions;