[llvm-pdbdump] Correctly read data larger than a block

A bug was introduced when the code was refactored which resulted in a
bad memory access.

This fixes PR27565.

llvm-svn: 267953

llvm/lib/DebugInfo/PDB/Raw/PDBStream.cpp

@@ -13,9 +13,9 @@
 using namespace llvm;
 
 PDBStream::PDBStream(uint32_t StreamIdx, const PDBFile &File) : Pdb(File) {
-  this->StreamLength = Pdb.getStreamByteSize(StreamIdx);
-  this->BlockList = Pdb.getStreamBlockList(StreamIdx);
-  this->Offset = 0;
+  StreamLength = Pdb.getStreamByteSize(StreamIdx);
+  BlockList = Pdb.getStreamBlockList(StreamIdx);
+  Offset = 0;
 }
 
 std::error_code PDBStream::readInteger(uint32_t &Dest) {
@@ -41,34 +41,20 @@ std::error_code PDBStream::readBytes(void *Dest, uint32_t Length) {
   uint32_t OffsetInBlock = Offset % Pdb.getBlockSize();
 
   // Make sure we aren't trying to read beyond the end of the stream.
-  if (this->Offset + Length > this->StreamLength)
+  if (Length > StreamLength)
+    return std::make_error_code(std::errc::bad_address);
+  if (Offset > StreamLength - Length)
     return std::make_error_code(std::errc::bad_address);
 
-  // Modify the passed in offset to point to the data after the object.
-  Offset += Length;
-
-  // Handle the contiguous case: the offset + size stays within a block.
-  if (OffsetInBlock + Length <= Pdb.getBlockSize()) {
-    uint32_t StreamBlockAddr = this->BlockList[BlockNum];
-
-    StringRef Data = Pdb.getBlockData(StreamBlockAddr, Pdb.getBlockSize());
-    ::memcpy(Dest, Data.data() + OffsetInBlock, Length);
-    return std::error_code();
-  }
-
-  // The non-contiguous case: we will stitch together non-contiguous chunks
   uint32_t BytesLeft = Length;
   uint32_t BytesWritten = 0;
   char *WriteBuffer = static_cast<char *>(Dest);
   while (BytesLeft > 0) {
-    uint32_t StreamBlockAddr = this->BlockList[BlockNum];
-    uint64_t StreamBlockOffset =
-        PDBFile::blockToOffset(StreamBlockAddr, Pdb.getBlockSize()) +
-        OffsetInBlock;
+    uint32_t StreamBlockAddr = BlockList[BlockNum];
 
     StringRef Data = Pdb.getBlockData(StreamBlockAddr, Pdb.getBlockSize());
 
-    const char *ChunkStart = Data.data() + StreamBlockOffset;
+    const char *ChunkStart = Data.data() + OffsetInBlock;
     uint32_t BytesInChunk =
         std::min(BytesLeft, Pdb.getBlockSize() - OffsetInBlock);
     ::memcpy(WriteBuffer + BytesWritten, ChunkStart, BytesInChunk);
@@ -78,11 +64,15 @@ std::error_code PDBStream::readBytes(void *Dest, uint32_t Length) {
     ++BlockNum;
     OffsetInBlock = 0;
   }
+
+  // Modify the offset to point to the data after the object.
+  Offset += Length;
+
   return std::error_code();
 }
 
-void PDBStream::setOffset(uint32_t O) { this->Offset = O; }
+void PDBStream::setOffset(uint32_t O) { Offset = O; }
 
-uint32_t PDBStream::getOffset() const { return this->Offset; }
+uint32_t PDBStream::getOffset() const { return Offset; }
 
-uint32_t PDBStream::getLength() const { return this->StreamLength; }
+uint32_t PDBStream::getLength() const { return StreamLength; }