1 files changed, 52 insertions, 0 deletions
diff --git a/llvm/lib/DebugInfo/PDB/Raw/MappedBlockStream.cpp b/llvm/lib/DebugInfo/PDB/Raw/MappedBlockStream.cpp
new file mode 100644
index 00000000000..ed954bbed28
--- /dev/null
+++ b/llvm/lib/DebugInfo/PDB/Raw/MappedBlockStream.cpp
@@ -0,0 +1,52 @@
+//===- MappedBlockStream.cpp - Reads stream data from a PDBFile -----------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/PDB/Raw/MappedBlockStream.h"
+#include "llvm/DebugInfo/PDB/Raw/PDBFile.h"
+
+using namespace llvm;
+
+MappedBlockStream::MappedBlockStream(uint32_t StreamIdx, const PDBFile &File) : Pdb(File) {
+  StreamLength = Pdb.getStreamByteSize(StreamIdx);
+  BlockList = Pdb.getStreamBlockList(StreamIdx);
+}
+
+std::error_code
+MappedBlockStream::readBytes(uint32_t Offset,
+                             MutableArrayRef<uint8_t> Buffer) const {
+  uint32_t BlockNum = Offset / Pdb.getBlockSize();
+  uint32_t OffsetInBlock = Offset % Pdb.getBlockSize();
+
+  // Make sure we aren't trying to read beyond the end of the stream.
+  if (Buffer.size() > StreamLength)
+    return std::make_error_code(std::errc::bad_address);
+  if (Offset > StreamLength - Buffer.size())
+    return std::make_error_code(std::errc::bad_address);
+
+  uint32_t BytesLeft = Buffer.size();
+  uint32_t BytesWritten = 0;
+  uint8_t *WriteBuffer = Buffer.data();
+  while (BytesLeft > 0) {
+    uint32_t StreamBlockAddr = BlockList[BlockNum];
+
+    StringRef Data = Pdb.getBlockData(StreamBlockAddr, Pdb.getBlockSize());
+
+    const char *ChunkStart = Data.data() + OffsetInBlock;
+    uint32_t BytesInChunk =
+        std::min(BytesLeft, Pdb.getBlockSize() - OffsetInBlock);
+    ::memcpy(WriteBuffer + BytesWritten, ChunkStart, BytesInChunk);
+
+    BytesWritten += BytesInChunk;
+    BytesLeft -= BytesInChunk;
+    ++BlockNum;
+    OffsetInBlock = 0;
+  }
+
+  return std::error_code();
+}