ReaderWriter.h revision f0356fe140af1a30587b9a86bcfb1b2c51b8ce20 
1//===-- llvm/Bitcode/ReaderWriter.h - Bitcode reader/writers ----*- C++ -*-===//
2//
3//                     The LLVM Compiler Infrastructure
4//
5// This file is distributed under the University of Illinois Open Source
6// License. See LICENSE.TXT for details.
7//
8//===----------------------------------------------------------------------===//
9//
10// This header defines interfaces to read and write LLVM bitcode files/streams.
11//
12//===----------------------------------------------------------------------===//
13
14#ifndef LLVM_BITCODE_H
15#define LLVM_BITCODE_H
16
17#include <string>
18
19namespace llvm {
20  class Module;
21  class MemoryBuffer;
22  class ModulePass;
23  class BitstreamWriter;
24  class LLVMContext;
25  class raw_ostream;
26
27  /// getLazyBitcodeModule - Read the header of the specified bitcode buffer
28  /// and prepare for lazy deserialization of function bodies.  If successful,
29  /// this takes ownership of 'buffer' and returns a non-null pointer.  On
30  /// error, this returns null, *does not* take ownership of Buffer, and fills
31  /// in *ErrMsg with an error description if ErrMsg is non-null.
32  Module *getLazyBitcodeModule(MemoryBuffer *Buffer,
33                               LLVMContext& Context,
34                               std::string *ErrMsg = 0);
35
36  /// ParseBitcodeFile - Read the specified bitcode file, returning the module.
37  /// If an error occurs, this returns null and fills in *ErrMsg if it is
38  /// non-null.  This method *never* takes ownership of Buffer.
39  Module *ParseBitcodeFile(MemoryBuffer *Buffer, LLVMContext& Context,
40                           std::string *ErrMsg = 0);
41
42  /// WriteBitcodeToFile - Write the specified module to the specified
43  /// raw output stream.
44  void WriteBitcodeToFile(const Module *M, raw_ostream &Out);
45
46  /// WriteBitcodeToStream - Write the specified module to the specified
47  /// raw output stream.
48  void WriteBitcodeToStream(const Module *M, BitstreamWriter &Stream);
49
50  /// createBitcodeWriterPass - Create and return a pass that writes the module
51  /// to the specified ostream.
52  ModulePass *createBitcodeWriterPass(raw_ostream &Str);
53
54
55  /// isBitcodeWrapper - Return true if the given bytes are the magic bytes
56  /// for an LLVM IR bitcode wrapper.
57  ///
58  static inline bool isBitcodeWrapper(const unsigned char *BufPtr,
59                                      const unsigned char *BufEnd) {
60    // See if you can find the hidden message in the magic bytes :-).
61    // (Hint: it's a little-endian encoding.)
62    return BufPtr != BufEnd &&
63           BufPtr[0] == 0xDE &&
64           BufPtr[1] == 0xC0 &&
65           BufPtr[2] == 0x17 &&
66           BufPtr[3] == 0x0B;
67  }
68
69  /// isRawBitcode - Return true if the given bytes are the magic bytes for
70  /// raw LLVM IR bitcode (without a wrapper).
71  ///
72  static inline bool isRawBitcode(const unsigned char *BufPtr,
73                                  const unsigned char *BufEnd) {
74    // These bytes sort of have a hidden message, but it's not in
75    // little-endian this time, and it's a little redundant.
76    return BufPtr != BufEnd &&
77           BufPtr[0] == 'B' &&
78           BufPtr[1] == 'C' &&
79           BufPtr[2] == 0xc0 &&
80           BufPtr[3] == 0xde;
81  }
82
83  /// isBitcode - Return true if the given bytes are the magic bytes for
84  /// LLVM IR bitcode, either with or without a wrapper.
85  ///
86  static bool inline isBitcode(const unsigned char *BufPtr,
87                               const unsigned char *BufEnd) {
88    return isBitcodeWrapper(BufPtr, BufEnd) ||
89           isRawBitcode(BufPtr, BufEnd);
90  }
91
92  /// SkipBitcodeWrapperHeader - Some systems wrap bc files with a special
93  /// header for padding or other reasons.  The format of this header is:
94  ///
95  /// struct bc_header {
96  ///   uint32_t Magic;         // 0x0B17C0DE
97  ///   uint32_t Version;       // Version, currently always 0.
98  ///   uint32_t BitcodeOffset; // Offset to traditional bitcode file.
99  ///   uint32_t BitcodeSize;   // Size of traditional bitcode file.
100  ///   ... potentially other gunk ...
101  /// };
102  ///
103  /// This function is called when we find a file with a matching magic number.
104  /// In this case, skip down to the subsection of the file that is actually a
105  /// BC file.
106  static inline bool SkipBitcodeWrapperHeader(unsigned char *&BufPtr,
107                                              unsigned char *&BufEnd) {
108    enum {
109      KnownHeaderSize = 4*4,  // Size of header we read.
110      OffsetField = 2*4,      // Offset in bytes to Offset field.
111      SizeField = 3*4         // Offset in bytes to Size field.
112    };
113
114    // Must contain the header!
115    if (BufEnd-BufPtr < KnownHeaderSize) return true;
116
117    unsigned Offset = ( BufPtr[OffsetField  ]        |
118                       (BufPtr[OffsetField+1] << 8)  |
119                       (BufPtr[OffsetField+2] << 16) |
120                       (BufPtr[OffsetField+3] << 24));
121    unsigned Size   = ( BufPtr[SizeField    ]        |
122                       (BufPtr[SizeField  +1] << 8)  |
123                       (BufPtr[SizeField  +2] << 16) |
124                       (BufPtr[SizeField  +3] << 24));
125
126    // Verify that Offset+Size fits in the file.
127    if (Offset+Size > unsigned(BufEnd-BufPtr))
128      return true;
129    BufPtr += Offset;
130    BufEnd = BufPtr+Size;
131    return false;
132  }
133} // End llvm namespace
134
135#endif
136