include/llvm/Bitcode/ReaderWriter.h

//===-- llvm/Bitcode/ReaderWriter.h - Bitcode reader/writers ----*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This header defines interfaces to read and write LLVM bitcode files/streams.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_BITCODE_H
#define LLVM_BITCODE_H

#include <iosfwd>
#include <string>

namespace llvm {
  class Module;
  class ModuleProvider;
  class MemoryBuffer;
  class ModulePass;
  class BitstreamWriter;
  class LLVMContext;
  class raw_ostream;
  
  /// getBitcodeModuleProvider - Read the header of the specified bitcode buffer
  /// and prepare for lazy deserialization of function bodies.  If successful,
  /// this takes ownership of 'buffer' and returns a non-null pointer.  On
  /// error, this returns null, *does not* take ownership of Buffer, and fills
  /// in *ErrMsg with an error description if ErrMsg is non-null.
  ModuleProvider *getBitcodeModuleProvider(MemoryBuffer *Buffer,
                                           LLVMContext& Context,
                                           std::string *ErrMsg = 0);

  /// ParseBitcodeFile - Read the specified bitcode file, returning the module.
  /// If an error occurs, this returns null and fills in *ErrMsg if it is
  /// non-null.  This method *never* takes ownership of Buffer.
  Module *ParseBitcodeFile(MemoryBuffer *Buffer, LLVMContext& Context,
                           std::string *ErrMsg = 0);

  /// WriteBitcodeToFile - Write the specified module to the specified output
  /// stream.
  void WriteBitcodeToFile(const Module *M, std::ostream &Out);

  /// WriteBitcodeToFile - Write the specified module to the specified
  /// raw output stream.
  void WriteBitcodeToFile(const Module *M, raw_ostream &Out);

  /// WriteBitcodeToStream - Write the specified module to the specified
  /// raw output stream.
  void WriteBitcodeToStream(const Module *M, BitstreamWriter &Stream);

  /// CreateBitcodeWriterPass - Create and return a pass that writes the module
  /// to the specified ostream.
  ModulePass *CreateBitcodeWriterPass(std::ostream &Str);

  /// createBitcodeWriterPass - Create and return a pass that writes the module
  /// to the specified ostream.
  ModulePass *createBitcodeWriterPass(raw_ostream &Str);
  
  
  /// isBitcodeWrapper - Return true fi this is a wrapper for LLVM IR bitcode
  /// files.
  static bool inline isBitcodeWrapper(unsigned char *BufPtr,
                                      unsigned char *BufEnd) {
    return (BufPtr != BufEnd && BufPtr[0] == 0xDE && BufPtr[1] == 0xC0 && 
            BufPtr[2] == 0x17 && BufPtr[3] == 0x0B);
  }
  
  /// SkipBitcodeWrapperHeader - Some systems wrap bc files with a special
  /// header for padding or other reasons.  The format of this header is:
  ///
  /// struct bc_header {
  ///   uint32_t Magic;         // 0x0B17C0DE
  ///   uint32_t Version;       // Version, currently always 0.
  ///   uint32_t BitcodeOffset; // Offset to traditional bitcode file.
  ///   uint32_t BitcodeSize;   // Size of traditional bitcode file.
  ///   ... potentially other gunk ...
  /// };
  /// 
  /// This function is called when we find a file with a matching magic number.
  /// In this case, skip down to the subsection of the file that is actually a
  /// BC file.
  static inline bool SkipBitcodeWrapperHeader(unsigned char *&BufPtr,
                                              unsigned char *&BufEnd) {
    enum {
      KnownHeaderSize = 4*4,  // Size of header we read.
      OffsetField = 2*4,      // Offset in bytes to Offset field.
      SizeField = 3*4         // Offset in bytes to Size field.
    };
    
    // Must contain the header!
    if (BufEnd-BufPtr < KnownHeaderSize) return true;
    
    unsigned Offset = ( BufPtr[OffsetField  ]        |
                       (BufPtr[OffsetField+1] << 8)  |
                       (BufPtr[OffsetField+2] << 16) |
                       (BufPtr[OffsetField+3] << 24));
    unsigned Size   = ( BufPtr[SizeField    ]        |
                       (BufPtr[SizeField  +1] << 8)  |
                       (BufPtr[SizeField  +2] << 16) |
                       (BufPtr[SizeField  +3] << 24));
    
    // Verify that Offset+Size fits in the file.
    if (Offset+Size > unsigned(BufEnd-BufPtr))
      return true;
    BufPtr += Offset;
    BufEnd = BufPtr+Size;
    return false;
  }
} // End llvm namespace

#endif