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_READERWRITER_H 15 #define LLVM_BITCODE_READERWRITER_H 16 17 #include "llvm/Support/ErrorOr.h" 18 #include <string> 19 20 namespace llvm { 21 class BitstreamWriter; 22 class MemoryBuffer; 23 class DataStreamer; 24 class LLVMContext; 25 class Module; 26 class ModulePass; 27 class raw_ostream; 28 29 /// Read the header of the specified bitcode buffer and prepare for lazy 30 /// deserialization of function bodies. If successful, this takes ownership 31 /// of 'buffer. On error, this *does not* take ownership of Buffer. 32 ErrorOr<Module *> getLazyBitcodeModule(MemoryBuffer *Buffer, 33 LLVMContext &Context); 34 35 /// getStreamedBitcodeModule - Read the header of the specified stream 36 /// and prepare for lazy deserialization and streaming of function bodies. 37 /// On error, this returns null, and fills in *ErrMsg with an error 38 /// description if ErrMsg is non-null. 39 Module *getStreamedBitcodeModule(const std::string &name, 40 DataStreamer *streamer, 41 LLVMContext &Context, 42 std::string *ErrMsg = nullptr); 43 44 /// Read the header of the specified bitcode buffer and extract just the 45 /// triple information. If successful, this returns a string and *does not* 46 /// take ownership of 'buffer'. On error, this returns "". 47 std::string getBitcodeTargetTriple(MemoryBuffer *Buffer, 48 LLVMContext &Context); 49 50 /// Read the specified bitcode file, returning the module. 51 /// This method *never* takes ownership of Buffer. 52 ErrorOr<Module *> parseBitcodeFile(MemoryBuffer *Buffer, 53 LLVMContext &Context); 54 55 /// WriteBitcodeToFile - Write the specified module to the specified 56 /// raw output stream. For streams where it matters, the given stream 57 /// should be in "binary" mode. 58 void WriteBitcodeToFile(const Module *M, raw_ostream &Out); 59 60 61 /// isBitcodeWrapper - Return true if the given bytes are the magic bytes 62 /// for an LLVM IR bitcode wrapper. 63 /// 64 inline bool isBitcodeWrapper(const unsigned char *BufPtr, 65 const unsigned char *BufEnd) { 66 // See if you can find the hidden message in the magic bytes :-). 67 // (Hint: it's a little-endian encoding.) 68 return BufPtr != BufEnd && 69 BufPtr[0] == 0xDE && 70 BufPtr[1] == 0xC0 && 71 BufPtr[2] == 0x17 && 72 BufPtr[3] == 0x0B; 73 } 74 75 /// isRawBitcode - Return true if the given bytes are the magic bytes for 76 /// raw LLVM IR bitcode (without a wrapper). 77 /// 78 inline bool isRawBitcode(const unsigned char *BufPtr, 79 const unsigned char *BufEnd) { 80 // These bytes sort of have a hidden message, but it's not in 81 // little-endian this time, and it's a little redundant. 82 return BufPtr != BufEnd && 83 BufPtr[0] == 'B' && 84 BufPtr[1] == 'C' && 85 BufPtr[2] == 0xc0 && 86 BufPtr[3] == 0xde; 87 } 88 89 /// isBitcode - Return true if the given bytes are the magic bytes for 90 /// LLVM IR bitcode, either with or without a wrapper. 91 /// 92 inline bool isBitcode(const unsigned char *BufPtr, 93 const unsigned char *BufEnd) { 94 return isBitcodeWrapper(BufPtr, BufEnd) || 95 isRawBitcode(BufPtr, BufEnd); 96 } 97 98 /// SkipBitcodeWrapperHeader - Some systems wrap bc files with a special 99 /// header for padding or other reasons. The format of this header is: 100 /// 101 /// struct bc_header { 102 /// uint32_t Magic; // 0x0B17C0DE 103 /// uint32_t Version; // Version, currently always 0. 104 /// uint32_t BitcodeOffset; // Offset to traditional bitcode file. 105 /// uint32_t BitcodeSize; // Size of traditional bitcode file. 106 /// ... potentially other gunk ... 107 /// }; 108 /// 109 /// This function is called when we find a file with a matching magic number. 110 /// In this case, skip down to the subsection of the file that is actually a 111 /// BC file. 112 /// If 'VerifyBufferSize' is true, check that the buffer is large enough to 113 /// contain the whole bitcode file. 114 inline bool SkipBitcodeWrapperHeader(const unsigned char *&BufPtr, 115 const unsigned char *&BufEnd, 116 bool VerifyBufferSize) { 117 enum { 118 KnownHeaderSize = 4*4, // Size of header we read. 119 OffsetField = 2*4, // Offset in bytes to Offset field. 120 SizeField = 3*4 // Offset in bytes to Size field. 121 }; 122 123 // Must contain the header! 124 if (BufEnd-BufPtr < KnownHeaderSize) return true; 125 126 unsigned Offset = ( BufPtr[OffsetField ] | 127 (BufPtr[OffsetField+1] << 8) | 128 (BufPtr[OffsetField+2] << 16) | 129 (BufPtr[OffsetField+3] << 24)); 130 unsigned Size = ( BufPtr[SizeField ] | 131 (BufPtr[SizeField +1] << 8) | 132 (BufPtr[SizeField +2] << 16) | 133 (BufPtr[SizeField +3] << 24)); 134 135 // Verify that Offset+Size fits in the file. 136 if (VerifyBufferSize && Offset+Size > unsigned(BufEnd-BufPtr)) 137 return true; 138 BufPtr += Offset; 139 BufEnd = BufPtr+Size; 140 return false; 141 } 142 } // End llvm namespace 143 144 #endif 145
