//===--- TranslationUnit.cpp - Abstraction for Translation Units ----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
// FIXME: This should eventually be moved out of the driver, or replaced
//        with its eventual successor.
//
//===----------------------------------------------------------------------===//

#include "clang/AST/TranslationUnit.h"

#include "clang/Basic/TargetInfo.h"
#include "clang/Basic/SourceManager.h"
#include "clang/AST/AST.h"

#include "llvm/Bitcode/Serialize.h"
#include "llvm/Bitcode/Deserialize.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/System/Path.h"
#include "llvm/ADT/OwningPtr.h"

#include <stdio.h>

using namespace clang;

enum { BasicMetadataBlock = 1,
       ASTContextBlock = 2,
       DeclsBlock = 3 };


bool clang::EmitASTBitcodeFile(const TranslationUnit& TU, 
                               const llvm::sys::Path& Filename) {  

  // Reserve 256K for bitstream buffer.
  std::vector<unsigned char> Buffer;
  Buffer.reserve(256*1024);
  
  // Create bitstream.
  llvm::BitstreamWriter Stream(Buffer);
  
  // Emit the preamble.
  Stream.Emit((unsigned)'B', 8);
  Stream.Emit((unsigned)'C', 8);
  Stream.Emit(0xC, 4);
  Stream.Emit(0xF, 4);
  Stream.Emit(0xE, 4);
  Stream.Emit(0x0, 4);
  
  { 
    // Create serializer.  Placing it in its own scope assures any necessary
    // finalization of bits to the buffer in the serializer's dstor.    
    llvm::Serializer Sezr(Stream);  
    
    // Emit the translation unit.
    TU.Emit(Sezr);
  }
  
  // Write the bits to disk. 
  if (FILE* fp = fopen(Filename.c_str(),"wb")) {
    fwrite((char*)&Buffer.front(), sizeof(char), Buffer.size(), fp);
    fclose(fp);
    return true;
  }

  return false;  
}

void TranslationUnit::Emit(llvm::Serializer& Sezr) const {

  // ===---------------------------------------------------===/
  //      Serialize the top-level decls.
  // ===---------------------------------------------------===/  
  
  Sezr.EnterBlock(DeclsBlock);

  // Only serialize the head of a decl chain.  The ASTConsumer interfaces
  // provides us with each top-level decl, including those nested in
  // a decl chain, so we may be passed decls that are already serialized.  
  for (const_iterator I=begin(), E=end(); I!=E; ++I) 
      if (!Sezr.isRegistered(*I))
        Sezr.EmitOwnedPtr(*I);
  
  Sezr.ExitBlock();
  
  // ===---------------------------------------------------===/
  //      Serialize the "Translation Unit" metadata.
  // ===---------------------------------------------------===/

  // Emit ASTContext.
  Sezr.EnterBlock(ASTContextBlock);  
  Sezr.EmitOwnedPtr(Context);  
  Sezr.ExitBlock();    
  
  Sezr.EnterBlock(BasicMetadataBlock);
  
  // Block for SourceManager, LangOptions, and Target.  Allows easy skipping
  // around to the block for the Selectors during deserialization.
  Sezr.EnterBlock();
    
  // Emit the SourceManager.
  Sezr.Emit(Context->getSourceManager());
  
  // Emit the LangOptions.
  Sezr.Emit(LangOpts);
  
  // Emit the Target.
  Sezr.EmitPtr(&Context->Target);
  Sezr.EmitCStr(Context->Target.getTargetTriple());
  
  Sezr.ExitBlock(); // exit "BasicMetadataBlock"
  
  // Emit the Selectors.
  Sezr.Emit(Context->Selectors);
  
  // Emit the Identifier Table.
  Sezr.Emit(Context->Idents);
  
  Sezr.ExitBlock();  // exit "ASTContextBlock"
}

TranslationUnit*
clang::ReadASTBitcodeFile(const llvm::sys::Path& Filename, FileManager& FMgr) {
  
  // Create the memory buffer that contains the contents of the file.  
  llvm::OwningPtr<llvm::MemoryBuffer> 
    MBuffer(llvm::MemoryBuffer::getFile(Filename.c_str(),
                                        strlen(Filename.c_str())));
  
  if (!MBuffer) {
    // FIXME: Provide diagnostic.
    return NULL;
  }
  
  // Check if the file is of the proper length.
  if (MBuffer->getBufferSize() & 0x3) {
    // FIXME: Provide diagnostic: "Length should be a multiple of 4 bytes."
    return NULL;
  }
  
  // Create the bitstream reader.
  unsigned char *BufPtr = (unsigned char *) MBuffer->getBufferStart();
  llvm::BitstreamReader Stream(BufPtr,BufPtr+MBuffer->getBufferSize());
  
  if (Stream.Read(8) != 'B' ||
      Stream.Read(8) != 'C' ||
      Stream.Read(4) != 0xC ||
      Stream.Read(4) != 0xF ||
      Stream.Read(4) != 0xE ||
      Stream.Read(4) != 0x0) {
    // FIXME: Provide diagnostic.
    return NULL;
  }
  
  // Create the deserializer.
  llvm::Deserializer Dezr(Stream);
  
  return TranslationUnit::Create(Dezr,FMgr);
}

TranslationUnit* TranslationUnit::Create(llvm::Deserializer& Dezr,
                                         FileManager& FMgr) {
  
  // Create the translation unit object.
  TranslationUnit* TU = new TranslationUnit();
  
  // ===---------------------------------------------------===/
  //      Deserialize the "Translation Unit" metadata.
  // ===---------------------------------------------------===/
  
  // Skip to the BasicMetaDataBlock.  First jump to ASTContextBlock
  // (which will appear earlier) and record its location.
  
  bool FoundBlock = Dezr.SkipToBlock(ASTContextBlock);
  assert (FoundBlock);
  
  llvm::Deserializer::Location ASTContextBlockLoc =
  Dezr.getCurrentBlockLocation();
  
  FoundBlock = Dezr.SkipToBlock(BasicMetadataBlock);
  assert (FoundBlock);
  
  // Read the SourceManager.
  SourceManager::CreateAndRegister(Dezr,FMgr);
  
  // Read the LangOptions.
  TU->LangOpts.Read(Dezr);
  
  { // Read the TargetInfo.
    llvm::SerializedPtrID PtrID = Dezr.ReadPtrID();
    char* triple = Dezr.ReadCStr(NULL,0,true);
    std::string Triple(triple);
    Dezr.RegisterPtr(PtrID,TargetInfo::CreateTargetInfo(&Triple,
                                                        &Triple+1));
    delete [] triple;
  }
  
  // For Selectors, we must read the identifier table first because the
  //  SelectorTable depends on the identifiers being already deserialized.
  llvm::Deserializer::Location SelectorBlkLoc = Dezr.getCurrentBlockLocation();  
  Dezr.SkipBlock();
  
  // Read the identifier table.
  IdentifierTable::CreateAndRegister(Dezr);
  
  // Now jump back and read the selectors.
  Dezr.JumpTo(SelectorBlkLoc);
  SelectorTable::CreateAndRegister(Dezr);
  
  // Now jump back to ASTContextBlock and read the ASTContext.
  Dezr.JumpTo(ASTContextBlockLoc);
  TU->Context = Dezr.ReadOwnedPtr<ASTContext>();
  
  // "Rewind" the stream.  Find the block with the serialized top-level decls.
  Dezr.Rewind();
  FoundBlock = Dezr.SkipToBlock(DeclsBlock);
  assert (FoundBlock);
  llvm::Deserializer::Location DeclBlockLoc = Dezr.getCurrentBlockLocation();
  
  while (!Dezr.FinishedBlock(DeclBlockLoc))
    TU->AddTopLevelDecl(Dezr.ReadOwnedPtr<Decl>());

  return TU;
}

