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 19 namespace 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. For streams where it matters, the given stream 44 /// should be in "binary" mode. 45 void WriteBitcodeToFile(const Module *M, raw_ostream &Out); 46 47 /// WriteBitcodeToStream - Write the specified module to the specified 48 /// raw output stream. 49 void WriteBitcodeToStream(const Module *M, BitstreamWriter &Stream); 50 51 /// createBitcodeWriterPass - Create and return a pass that writes the module 52 /// to the specified ostream. 53 ModulePass *createBitcodeWriterPass(raw_ostream &Str); 54 55 56 /// isBitcodeWrapper - Return true if the given bytes are the magic bytes 57 /// for an LLVM IR bitcode wrapper. 58 /// isBitcodeWrapper(const unsigned char * BufPtr,const unsigned char * BufEnd)59 static inline bool isBitcodeWrapper(const unsigned char *BufPtr, 60 const unsigned char *BufEnd) { 61 // See if you can find the hidden message in the magic bytes :-). 62 // (Hint: it's a little-endian encoding.) 63 return BufPtr != BufEnd && 64 BufPtr[0] == 0xDE && 65 BufPtr[1] == 0xC0 && 66 BufPtr[2] == 0x17 && 67 BufPtr[3] == 0x0B; 68 } 69 70 /// isRawBitcode - Return true if the given bytes are the magic bytes for 71 /// raw LLVM IR bitcode (without a wrapper). 72 /// isRawBitcode(const unsigned char * BufPtr,const unsigned char * BufEnd)73 static inline bool isRawBitcode(const unsigned char *BufPtr, 74 const unsigned char *BufEnd) { 75 // These bytes sort of have a hidden message, but it's not in 76 // little-endian this time, and it's a little redundant. 77 return BufPtr != BufEnd && 78 BufPtr[0] == 'B' && 79 BufPtr[1] == 'C' && 80 BufPtr[2] == 0xc0 && 81 BufPtr[3] == 0xde; 82 } 83 84 /// isBitcode - Return true if the given bytes are the magic bytes for 85 /// LLVM IR bitcode, either with or without a wrapper. 86 /// isBitcode(const unsigned char * BufPtr,const unsigned char * BufEnd)87 static bool inline isBitcode(const unsigned char *BufPtr, 88 const unsigned char *BufEnd) { 89 return isBitcodeWrapper(BufPtr, BufEnd) || 90 isRawBitcode(BufPtr, BufEnd); 91 } 92 93 /// SkipBitcodeWrapperHeader - Some systems wrap bc files with a special 94 /// header for padding or other reasons. The format of this header is: 95 /// 96 /// struct bc_header { 97 /// uint32_t Magic; // 0x0B17C0DE 98 /// uint32_t Version; // Version, currently always 0. 99 /// uint32_t BitcodeOffset; // Offset to traditional bitcode file. 100 /// uint32_t BitcodeSize; // Size of traditional bitcode file. 101 /// ... potentially other gunk ... 102 /// }; 103 /// 104 /// This function is called when we find a file with a matching magic number. 105 /// In this case, skip down to the subsection of the file that is actually a 106 /// BC file. SkipBitcodeWrapperHeader(unsigned char * & BufPtr,unsigned char * & BufEnd)107 static inline bool SkipBitcodeWrapperHeader(unsigned char *&BufPtr, 108 unsigned char *&BufEnd) { 109 enum { 110 KnownHeaderSize = 4*4, // Size of header we read. 111 OffsetField = 2*4, // Offset in bytes to Offset field. 112 SizeField = 3*4 // Offset in bytes to Size field. 113 }; 114 115 // Must contain the header! 116 if (BufEnd-BufPtr < KnownHeaderSize) return true; 117 118 unsigned Offset = ( BufPtr[OffsetField ] | 119 (BufPtr[OffsetField+1] << 8) | 120 (BufPtr[OffsetField+2] << 16) | 121 (BufPtr[OffsetField+3] << 24)); 122 unsigned Size = ( BufPtr[SizeField ] | 123 (BufPtr[SizeField +1] << 8) | 124 (BufPtr[SizeField +2] << 16) | 125 (BufPtr[SizeField +3] << 24)); 126 127 // Verify that Offset+Size fits in the file. 128 if (Offset+Size > unsigned(BufEnd-BufPtr)) 129 return true; 130 BufPtr += Offset; 131 BufEnd = BufPtr+Size; 132 return false; 133 } 134 } // End llvm namespace 135 136 #endif 137