Support: Implement StreamingMemoryObject::getPointer

The implementation is fairly obvious.  This is preparation for using
some blobs in bitcode.

For clarity (and perhaps future-proofing?), I moved the call to
JumpToBit in BitstreamCursor::readRecord ahead of calling
MemoryObject::getPointer, since JumpToBit can theoretically (a) read
bytes, which (b) invalidates the blob pointer.

This isn't strictly necessary the two memory objects we have:

  - The return of RawMemoryObject::getPointer is valid until the memory
    object is destroyed.

  - StreamingMemoryObject::getPointer is valid until the next chunk is
    read from the stream.  Since the JumpToBit call is only going ahead
    to a word boundary, we'll never load another chunk.

However, reordering makes it clear by inspection that the blob returned
by BitstreamCursor::readRecord will be valid.

I added some tests for StreamingMemoryObject::getPointer and
BitstreamCursor::readRecord.

llvm-svn: 264549

llvm/unittests/Bitcode/BitstreamReaderTest.cpp

@@ -7,13 +7,31 @@
 //
 //===----------------------------------------------------------------------===//
 
+#include "llvm/ADT/STLExtras.h"
 #include "llvm/Bitcode/BitstreamReader.h"
+#include "llvm/Bitcode/BitstreamWriter.h"
+#include "llvm/Support/StreamingMemoryObject.h"
 #include "gtest/gtest.h"
 
 using namespace llvm;
 
 namespace {
 
+class BufferStreamer : public DataStreamer {
+  StringRef Buffer;
+
+public:
+  BufferStreamer(StringRef Buffer) : Buffer(Buffer) {}
+  size_t GetBytes(unsigned char *OutBuffer, size_t Length) override {
+    if (Length >= Buffer.size())
+      Length = Buffer.size();
+
+    std::copy(Buffer.begin(), Buffer.begin() + Length, OutBuffer);
+    Buffer = Buffer.drop_front(Length);
+    return Length;
+  }
+};
+
 TEST(BitstreamReaderTest, AtEndOfStream) {
   uint8_t Bytes[4] = {
     0x00, 0x01, 0x02, 0x03
@@ -165,4 +183,65 @@ TEST(BitstreamReaderTest, setArtificialByteLimitPastTheEndKnown) {
   EXPECT_TRUE(Cursor.AtEndOfStream());
 }
 
+TEST(BitstreamReaderTest, readRecordWithBlobWhileStreaming) {
+  SmallVector<uint8_t, 1> BlobData;
+  for (unsigned I = 0, E = 1024; I != E; ++I)
+    BlobData.push_back(I);
+
+  // Try a bunch of different sizes.
+  const unsigned Magic = 0x12345678;
+  const unsigned BlockID = bitc::FIRST_APPLICATION_BLOCKID;
+  const unsigned RecordID = 1;
+  for (unsigned I = 0, BlobSize = 0, E = BlobData.size(); BlobSize < E;
+       BlobSize += ++I) {
+    StringRef BlobIn((const char *)BlobData.begin(), BlobSize);
+
+    // Write the bitcode.
+    SmallVector<char, 1> Buffer;
+    unsigned AbbrevID;
+    {
+      BitstreamWriter Stream(Buffer);
+      Stream.Emit(Magic, 32);
+      Stream.EnterSubblock(BlockID, 3);
+
+      BitCodeAbbrev *Abbrev = new BitCodeAbbrev();
+      Abbrev->Add(BitCodeAbbrevOp(RecordID));
+      Abbrev->Add(BitCodeAbbrevOp(BitCodeAbbrevOp::Blob));
+      AbbrevID = Stream.EmitAbbrev(Abbrev);
+      unsigned Record[] = {RecordID};
+      Stream.EmitRecordWithBlob(AbbrevID, makeArrayRef(Record), BlobIn);
+
+      Stream.ExitBlock();
+    }
+
+    // Stream the buffer into the reader.
+    BitstreamReader R(make_unique<StreamingMemoryObject>(
+        make_unique<BufferStreamer>(StringRef(Buffer.begin(), Buffer.size()))));
+    BitstreamCursor Stream(R);
+
+    // Header.  Included in test so that we can run llvm-bcanalyzer to debug
+    // when there are problems.
+    ASSERT_EQ(Magic, Stream.Read(32));
+
+    // Block.
+    BitstreamEntry Entry =
+        Stream.advance(BitstreamCursor::AF_DontAutoprocessAbbrevs);
+    ASSERT_EQ(BitstreamEntry::SubBlock, Entry.Kind);
+    ASSERT_EQ(BlockID, Entry.ID);
+    ASSERT_FALSE(Stream.EnterSubBlock(BlockID));
+
+    // Abbreviation.
+    Entry = Stream.advance();
+    ASSERT_EQ(BitstreamEntry::Record, Entry.Kind);
+    ASSERT_EQ(AbbrevID, Entry.ID);
+
+    // Record.
+    StringRef BlobOut;
+    SmallVector<uint64_t, 1> Record;
+    ASSERT_EQ(RecordID, Stream.readRecord(Entry.ID, Record, &BlobOut));
+    EXPECT_TRUE(Record.empty());
+    EXPECT_EQ(BlobIn, BlobOut);
+  }
+}
+
 } // end anonymous namespace