BitcodeWriter: Expose less implementation details -- make BackpatchWord private

and remove getBuffer().

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@151748 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/Bitcode/BitstreamWriter.h

@@ -59,6 +59,15 @@ class BitstreamWriter {
   };
   std::vector<BlockInfo> BlockInfoRecords;
 
+  // BackpatchWord - Backpatch a 32-bit word in the output with the specified
+  // value.
+  void BackpatchWord(unsigned ByteNo, unsigned NewWord) {
+    Out[ByteNo++] = (unsigned char)(NewWord >>  0);
+    Out[ByteNo++] = (unsigned char)(NewWord >>  8);
+    Out[ByteNo++] = (unsigned char)(NewWord >> 16);
+    Out[ByteNo  ] = (unsigned char)(NewWord >> 24);
+  }
+
 public:
   explicit BitstreamWriter(std::vector<unsigned char> &O)
     : Out(O), CurBit(0), CurValue(0), CurCodeSize(2) {}
@@ -78,8 +87,6 @@ public:
     }
   }
 
-  std::vector<unsigned char> &getBuffer() { return Out; }
-
   /// \brief Retrieve the current position in the stream, in bits.
   uint64_t GetCurrentBitNo() const { return Out.size() * 8 + CurBit; }
 
@@ -164,15 +171,6 @@ public:
     Emit(Val, CurCodeSize);
   }
 
-  // BackpatchWord - Backpatch a 32-bit word in the output with the specified
-  // value.
-  void BackpatchWord(unsigned ByteNo, unsigned NewWord) {
-    Out[ByteNo++] = (unsigned char)(NewWord >>  0);
-    Out[ByteNo++] = (unsigned char)(NewWord >>  8);
-    Out[ByteNo++] = (unsigned char)(NewWord >> 16);
-    Out[ByteNo  ] = (unsigned char)(NewWord >> 24);
-  }
-
   //===--------------------------------------------------------------------===//
   // Block Manipulation
   //===--------------------------------------------------------------------===//

lib/Bitcode/Writer/BitcodeWriter.cpp

@@ -1774,7 +1774,18 @@ enum {
   DarwinBCHeaderSize = 5*4
 };
 
-static void EmitDarwinBCHeader(BitstreamWriter &Stream, const Triple &TT) {
+static void WriteInt32ToBuffer(uint32_t Value,
+                               std::vector<unsigned char> &Buffer,
+                               uint32_t &Position) {
+  Buffer[Position + 0] = (unsigned char) (Value >>  0);
+  Buffer[Position + 1] = (unsigned char) (Value >>  8);
+  Buffer[Position + 2] = (unsigned char) (Value >> 16);
+  Buffer[Position + 3] = (unsigned char) (Value >> 24);
+  Position += 4;
+}
+
+static void EmitDarwinBCHeaderAndTrailer(std::vector<unsigned char> &Buffer,
+                                         const Triple &TT) {
   unsigned CPUType = ~0U;
 
   // Match x86_64-*, i[3-9]86-*, powerpc-*, powerpc64-*, arm-*, thumb-*,
@@ -1801,50 +1812,39 @@ static void EmitDarwinBCHeader(BitstreamWriter &Stream, const Triple &TT) {
     CPUType = DARWIN_CPU_TYPE_ARM;
 
   // Traditional Bitcode starts after header.
+  assert(Buffer.size() >= DarwinBCHeaderSize &&
+         "Expected header size to be reserved");
   unsigned BCOffset = DarwinBCHeaderSize;
+  unsigned BCSize = Buffer.size()-DarwinBCHeaderSize;
 
-  Stream.Emit(0x0B17C0DE, 32);
+  // Write the magic and version.
-  Stream.Emit(0         , 32);  // Version.
+  unsigned Position = 0;
-  Stream.Emit(BCOffset  , 32);
+  WriteInt32ToBuffer(0x0B17C0DE , Buffer, Position);
-  Stream.Emit(0         , 32);  // Filled in later.
+  WriteInt32ToBuffer(0          , Buffer, Position); // Version.
-  Stream.Emit(CPUType   , 32);
+  WriteInt32ToBuffer(BCOffset   , Buffer, Position);
-}
+  WriteInt32ToBuffer(BCSize     , Buffer, Position);
-
+  WriteInt32ToBuffer(CPUType    , Buffer, Position);
-/// EmitDarwinBCTrailer - Emit the darwin epilog after the bitcode file and
-/// finalize the header.
-static void EmitDarwinBCTrailer(BitstreamWriter &Stream, unsigned BufferSize) {
-  // Update the size field in the header.
-  Stream.BackpatchWord(DarwinBCSizeFieldOffset, BufferSize-DarwinBCHeaderSize);
 
   // If the file is not a multiple of 16 bytes, insert dummy padding.
-  while (BufferSize & 15) {
+  while (Buffer.size() & 15)
-    Stream.Emit(0, 8);
+    Buffer.push_back(0);
-    ++BufferSize;
-  }
 }
 
-static void WriteBitcodeToStream(const Module *M, BitstreamWriter &Stream);
-
 /// WriteBitcodeToFile - Write the specified module to the specified output
 /// stream.
 void llvm::WriteBitcodeToFile(const Module *M, raw_ostream &Out) {
   std::vector<unsigned char> Buffer;
-  BitstreamWriter Stream(Buffer);
-
   Buffer.reserve(256*1024);
 
-  WriteBitcodeToStream( M, Stream );
+  // If this is darwin or another generic macho target, reserve space for the
-
+  // header.
-  // Write the generated bitstream to "Out".
-  Out.write((char*)&Buffer.front(), Buffer.size());
-}
-
-static void WriteBitcodeToStream(const Module *M, BitstreamWriter &Stream) {
-  // If this is darwin or another generic macho target, emit a file header and
-  // trailer if needed.
   Triple TT(M->getTargetTriple());
   if (TT.isOSDarwin())
-    EmitDarwinBCHeader(Stream, TT);
+    Buffer.insert(Buffer.begin(), DarwinBCHeaderSize, 0);
+
+  // Emit the module into the buffer.
+  {
+    BitstreamWriter Stream(Buffer);
 
     // Emit the file header.
     Stream.Emit((unsigned)'B', 8);
@@ -1856,7 +1856,11 @@ static void WriteBitcodeToStream(const Module *M, BitstreamWriter &Stream) {
 
     // Emit the module.
     WriteModule(M, Stream);
+  }
 
   if (TT.isOSDarwin())
-    EmitDarwinBCTrailer(Stream, Stream.getBuffer().size());
+    EmitDarwinBCHeaderAndTrailer(Buffer, TT);
+
+  // Write the generated bitstream to "Out".
+  Out.write((char*)&Buffer.front(), Buffer.size());
 }