[pdb] Use MappedBlockStream to parse the PDB directory.

In order to efficiently write PDBs, we need to be able to make a
StreamWriter class similar to a StreamReader, which can transparently deal
with writing to discontiguous streams, and we need to use this for all
writing, similar to how we use StreamReader for all reading.

Most discontiguous streams are the typical numbered streams that appear in
a PDB file and are described by the directory, but the exception to this,
that until now has been parsed by hand, is the directory itself.
MappedBlockStream works by querying the directory to find out which blocks
a stream occupies and various other things, so naturally the same logic
could not possibly work to describe the blocks that the directory itself
resided on.

To solve this, I've introduced an abstraction IPDBStreamData, which allows
the client to query for the list of blocks occupied by the stream, as well
as the stream length. I provide two implementations of this: one which
queries the directory (for indexed streams), and one which queries the
super block (for the directory stream).

This has the side benefit of vastly simplifying the code to parse the
directory. Whereas before a mini state machine was rolled by hand, now we
simply use FixedStreamArray to read out the stream sizes, then build a
vector of FixedStreamArrays for the stream map, all in just a few lines of
code.

Reviewed By: ruiu
Differential Revision: http://reviews.llvm.org/D21046

llvm-svn: 271982

1 files changed, 55 insertions, 100 deletions

diff --git a/llvm/lib/DebugInfo/PDB/Raw/PDBFile.cpp b/llvm/lib/DebugInfo/PDB/Raw/PDBFile.cpp
index 73d8eef..81762e7 100644
--- a/llvm/lib/DebugInfo/PDB/Raw/PDBFile.cpp
+++ b/llvm/lib/DebugInfo/PDB/Raw/PDBFile.cpp
@@ -8,8 +8,12 @@
 //===----------------------------------------------------------------------===//
 
 #include "llvm/DebugInfo/PDB/Raw/PDBFile.h"
+
 #include "llvm/ADT/ArrayRef.h"
+#include "llvm/DebugInfo/CodeView/StreamArray.h"
+#include "llvm/DebugInfo/CodeView/StreamReader.h"
 #include "llvm/DebugInfo/PDB/Raw/DbiStream.h"
+#include "llvm/DebugInfo/PDB/Raw/IndexedStreamData.h"
 #include "llvm/DebugInfo/PDB/Raw/InfoStream.h"
 #include "llvm/DebugInfo/PDB/Raw/NameHashTable.h"
 #include "llvm/DebugInfo/PDB/Raw/PublicsStream.h"
@@ -49,13 +53,28 @@ struct SuperBlock {
   // This contains the block # of the block map.
   support::ulittle32_t BlockMapAddr;
 };
+
+class DirectoryStreamData : public IPDBStreamData {
+public:
+  DirectoryStreamData(const PDBFile &File) : File(File) {}
+
+  virtual uint32_t getLength() { return File.getNumDirectoryBytes(); }
+  virtual llvm::ArrayRef<llvm::support::ulittle32_t> getStreamBlocks() {
+    return File.getDirectoryBlockArray();
+  }
+
+private:
+  const PDBFile &File;
+};
+
+typedef codeview::FixedStreamArray<support::ulittle32_t> ulittle_array;
 }
 
 struct llvm::pdb::PDBFileContext {
   std::unique_ptr<MemoryBuffer> Buffer;
   const SuperBlock *SB;
-  std::vector<uint32_t> StreamSizes;
-  DenseMap<uint32_t, std::vector<uint32_t>> StreamMap;
+  ArrayRef<support::ulittle32_t> StreamSizes;
+  std::vector<ulittle_array> StreamMap;
 };
 
 static Error checkOffset(MemoryBufferRef M, uintptr_t Addr,
@@ -109,10 +128,14 @@ uint32_t PDBFile::getStreamByteSize(uint32_t StreamIndex) const {
   return Context->StreamSizes[StreamIndex];
 }
 
-llvm::ArrayRef<uint32_t>
+ArrayRef<support::ulittle32_t>
 PDBFile::getStreamBlockList(uint32_t StreamIndex) const {
-  auto &Data = Context->StreamMap[StreamIndex];
-  return llvm::ArrayRef<uint32_t>(Data);
+  auto Result = Context->StreamMap[StreamIndex];
+  codeview::StreamReader Reader(Result.getUnderlyingStream());
+  ArrayRef<support::ulittle32_t> Array;
+  if (auto EC = Reader.readArray(Array, Result.size()))
+    return ArrayRef<support::ulittle32_t>();
+  return Array;
 }
 
 StringRef PDBFile::getBlockData(uint32_t BlockIndex, uint32_t NumBytes) const {
@@ -184,113 +207,44 @@ Error PDBFile::parseFileHeaders() {
 
 Error PDBFile::parseStreamData() {
   assert(Context && Context->SB);
+  if (DirectoryStream)
+    return Error::success();
 
-  bool SeenNumStreams = false;
+  // bool SeenNumStreams = false;
   uint32_t NumStreams = 0;
-  uint32_t StreamIdx = 0;
-  uint64_t DirectoryBytesRead = 0;
+  // uint32_t StreamIdx = 0;
+  // uint64_t DirectoryBytesRead = 0;
 
-  MemoryBufferRef M = *Context->Buffer;
   const SuperBlock *SB = Context->SB;
 
-  auto DirectoryBlocks = getDirectoryBlockArray();
-
-  // The structure of the directory is as follows:
-  //    struct PDBDirectory {
-  //      uint32_t NumStreams;
-  //      uint32_t StreamSizes[NumStreams];
-  //      uint32_t StreamMap[NumStreams][];
-  //    };
-  //
-  //  Empty streams don't consume entries in the StreamMap.
-  for (uint32_t DirectoryBlockAddr : DirectoryBlocks) {
-    uint64_t DirectoryBlockOffset =
-        blockToOffset(DirectoryBlockAddr, SB->BlockSize);
-    auto DirectoryBlock =
-        makeArrayRef(reinterpret_cast<const support::ulittle32_t *>(
-                         M.getBufferStart() + DirectoryBlockOffset),
-                     SB->BlockSize / sizeof(support::ulittle32_t));
-    if (auto EC = checkOffset(M, DirectoryBlock))
-      return EC;
-
-    // We read data out of the directory four bytes at a time.  Depending on
-    // where we are in the directory, the contents may be: the number of streams
-    // in the directory, a stream's size, or a block in the stream map.
-    for (uint32_t Data : DirectoryBlock) {
-      // Don't read beyond the end of the directory.
-      if (DirectoryBytesRead == SB->NumDirectoryBytes)
-        break;
-
-      DirectoryBytesRead += sizeof(Data);
-
-      // This data must be the number of streams if we haven't seen it yet.
-      if (!SeenNumStreams) {
-        NumStreams = Data;
-        SeenNumStreams = true;
-        continue;
-      }
-      // This data must be a stream size if we have not seen them all yet.
-      if (Context->StreamSizes.size() < NumStreams) {
-        // It seems like some streams have their set to -1 when their contents
-        // are not present.  Treat them like empty streams for now.
-        if (Data == UINT32_MAX)
-          Context->StreamSizes.push_back(0);
-        else
-          Context->StreamSizes.push_back(Data);
-        continue;
-      }
-
-      // This data must be a stream block number if we have seen all of the
-      // stream sizes.
-      std::vector<uint32_t> *StreamBlocks = nullptr;
-      // Figure out which stream this block number belongs to.
-      while (StreamIdx < NumStreams) {
-        uint64_t NumExpectedStreamBlocks =
-            bytesToBlocks(Context->StreamSizes[StreamIdx], SB->BlockSize);
-        StreamBlocks = &Context->StreamMap[StreamIdx];
-        if (NumExpectedStreamBlocks > StreamBlocks->size())
-          break;
-        ++StreamIdx;
-      }
-      // It seems this block doesn't belong to any stream?  The stream is either
-      // corrupt or something more mysterious is going on.
-      if (StreamIdx == NumStreams)
-        return make_error<RawError>(raw_error_code::corrupt_file,
-                                    "Orphaned block found?");
-
-      uint64_t BlockOffset = blockToOffset(Data, getBlockSize());
-      if (BlockOffset + getBlockSize() < BlockOffset)
-        return make_error<RawError>(raw_error_code::corrupt_file,
-                                    "Bogus stream block number");
-      if (BlockOffset + getBlockSize() > M.getBufferSize())
-        return make_error<RawError>(raw_error_code::corrupt_file,
-                                    "Stream block number is out of bounds");
-
-      StreamBlocks->push_back(Data);
-    }
-  }
-
-  if (Context->StreamSizes.size() != NumStreams)
-    return make_error<RawError>(
-        raw_error_code::corrupt_file,
-        "The directory has fewer streams then expected");
+  // Normally you can't use a MappedBlockStream without having fully parsed the
+  // PDB file, because it accesses the directory and various other things, which
+  // is exactly what we are attempting to parse.  By specifying a custom
+  // subclass of IPDBStreamData which only accesses the fields that have already
+  // been parsed, we can avoid this and reuse MappedBlockStream.
+  auto SD = llvm::make_unique<DirectoryStreamData>(*this);
+  DirectoryStream = llvm::make_unique<MappedBlockStream>(std::move(SD), *this);
+  codeview::StreamReader Reader(*DirectoryStream);
+  if (auto EC = Reader.readInteger(NumStreams))
+    return EC;
 
-  for (uint32_t I = 0; I != NumStreams; ++I) {
+  if (auto EC = Reader.readArray(Context->StreamSizes, NumStreams))
+    return EC;
+  for (uint32_t I = 0; I < NumStreams; ++I) {
     uint64_t NumExpectedStreamBlocks =
-        bytesToBlocks(getStreamByteSize(I), getBlockSize());
-    size_t NumStreamBlocks = getStreamBlockList(I).size();
-    if (NumExpectedStreamBlocks != NumStreamBlocks)
-      return make_error<RawError>(raw_error_code::corrupt_file,
-                                  "The number of stream blocks is not "
-                                  "sufficient for the size of this stream");
+        bytesToBlocks(getStreamByteSize(I), SB->BlockSize);
+    ulittle_array Blocks;
+    if (auto EC = Reader.readArray(Blocks, NumExpectedStreamBlocks))
+      return EC;
+    Context->StreamMap.push_back(Blocks);
   }
 
   // We should have read exactly SB->NumDirectoryBytes bytes.
-  assert(DirectoryBytesRead == SB->NumDirectoryBytes);
+  assert(Reader.bytesRemaining() == 0);
   return Error::success();
 }
 
-llvm::ArrayRef<support::ulittle32_t> PDBFile::getDirectoryBlockArray() {
+llvm::ArrayRef<support::ulittle32_t> PDBFile::getDirectoryBlockArray() const {
   return makeArrayRef(
       reinterpret_cast<const support::ulittle32_t *>(
           Context->Buffer->getBufferStart() + getBlockMapOffset()),
@@ -371,7 +325,8 @@ Expected<NameHashTable &> PDBFile::getStringTable() {
 
     if (NameStreamIndex == 0)
       return make_error<RawError>(raw_error_code::no_stream);
-    auto S = llvm::make_unique<MappedBlockStream>(NameStreamIndex, *this);
+    auto SD = llvm::make_unique<IndexedStreamData>(NameStreamIndex, *this);
+    auto S = llvm::make_unique<MappedBlockStream>(std::move(SD), *this);
     codeview::StreamReader Reader(*S);
     auto N = llvm::make_unique<NameHashTable>();
     if (auto EC = N->load(Reader))