1 //===- StreamableMemoryObject.h - Streamable data interface -----*- 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 11 #ifndef LLVM_SUPPORT_STREAMABLEMEMORYOBJECT_H 12 #define LLVM_SUPPORT_STREAMABLEMEMORYOBJECT_H 13 14 #include "llvm/ADT/OwningPtr.h" 15 #include "llvm/Support/Compiler.h" 16 #include "llvm/Support/DataStream.h" 17 #include "llvm/Support/MemoryObject.h" 18 #include <vector> 19 20 namespace llvm { 21 22 /// StreamableMemoryObject - Interface to data which might be streamed. 23 /// Streamability has 2 important implications/restrictions. First, the data 24 /// might not yet exist in memory when the request is made. This just means 25 /// that readByte/readBytes might have to block or do some work to get it. 26 /// More significantly, the exact size of the object might not be known until 27 /// it has all been fetched. This means that to return the right result, 28 /// getExtent must also wait for all the data to arrive; therefore it should 29 /// not be called on objects which are actually streamed (this would defeat 30 /// the purpose of streaming). Instead, isValidAddress and isObjectEnd can be 31 /// used to test addresses without knowing the exact size of the stream. 32 /// Finally, getPointer can be used instead of readBytes to avoid extra copying. 33 class StreamableMemoryObject : public MemoryObject { 34 public: 35 /// Destructor - Override as necessary. 36 virtual ~StreamableMemoryObject(); 37 38 /// getBase - Returns the lowest valid address in the region. 39 /// 40 /// @result - The lowest valid address. 41 virtual uint64_t getBase() const LLVM_OVERRIDE = 0; 42 43 /// getExtent - Returns the size of the region in bytes. (The region is 44 /// contiguous, so the highest valid address of the region 45 /// is getBase() + getExtent() - 1). 46 /// May block until all bytes in the stream have been read 47 /// 48 /// @result - The size of the region. 49 virtual uint64_t getExtent() const LLVM_OVERRIDE = 0; 50 51 /// readByte - Tries to read a single byte from the region. 52 /// May block until (address - base) bytes have been read 53 /// @param address - The address of the byte, in the same space as getBase(). 54 /// @param ptr - A pointer to a byte to be filled in. Must be non-NULL. 55 /// @result - 0 if successful; -1 if not. Failure may be due to a 56 /// bounds violation or an implementation-specific error. 57 virtual int readByte(uint64_t address, uint8_t *ptr) const LLVM_OVERRIDE = 0; 58 59 /// readBytes - Tries to read a contiguous range of bytes from the 60 /// region, up to the end of the region. 61 /// May block until (address - base + size) bytes have 62 /// been read. Additionally, StreamableMemoryObjects will 63 /// not do partial reads - if size bytes cannot be read, 64 /// readBytes will fail. 65 /// 66 /// @param address - The address of the first byte, in the same space as 67 /// getBase(). 68 /// @param size - The number of bytes to copy. 69 /// @param buf - A pointer to a buffer to be filled in. Must be non-NULL 70 /// and large enough to hold size bytes. 71 /// @result - 0 if successful; -1 if not. Failure may be due to a 72 /// bounds violation or an implementation-specific error. 73 virtual int readBytes(uint64_t address, 74 uint64_t size, 75 uint8_t *buf) const LLVM_OVERRIDE = 0; 76 77 /// getPointer - Ensures that the requested data is in memory, and returns 78 /// A pointer to it. More efficient than using readBytes if the 79 /// data is already in memory. 80 /// May block until (address - base + size) bytes have been read 81 /// @param address - address of the byte, in the same space as getBase() 82 /// @param size - amount of data that must be available on return 83 /// @result - valid pointer to the requested data 84 virtual const uint8_t *getPointer(uint64_t address, uint64_t size) const = 0; 85 86 /// isValidAddress - Returns true if the address is within the object 87 /// (i.e. between base and base + extent - 1 inclusive) 88 /// May block until (address - base) bytes have been read 89 /// @param address - address of the byte, in the same space as getBase() 90 /// @result - true if the address may be read with readByte() 91 virtual bool isValidAddress(uint64_t address) const = 0; 92 93 /// isObjectEnd - Returns true if the address is one past the end of the 94 /// object (i.e. if it is equal to base + extent) 95 /// May block until (address - base) bytes have been read 96 /// @param address - address of the byte, in the same space as getBase() 97 /// @result - true if the address is equal to base + extent 98 virtual bool isObjectEnd(uint64_t address) const = 0; 99 }; 100 101 /// StreamingMemoryObject - interface to data which is actually streamed from 102 /// a DataStreamer. In addition to inherited members, it has the 103 /// dropLeadingBytes and setKnownObjectSize methods which are not applicable 104 /// to non-streamed objects. 105 class StreamingMemoryObject : public StreamableMemoryObject { 106 public: 107 StreamingMemoryObject(DataStreamer *streamer); 108 virtual uint64_t getBase() const LLVM_OVERRIDE { return 0; } 109 virtual uint64_t getExtent() const LLVM_OVERRIDE; 110 virtual int readByte(uint64_t address, uint8_t *ptr) const LLVM_OVERRIDE; 111 virtual int readBytes(uint64_t address, 112 uint64_t size, 113 uint8_t *buf) const LLVM_OVERRIDE; 114 virtual const uint8_t *getPointer(uint64_t address, 115 uint64_t size) const LLVM_OVERRIDE { 116 // This could be fixed by ensuring the bytes are fetched and making a copy, 117 // requiring that the bitcode size be known, or otherwise ensuring that 118 // the memory doesn't go away/get reallocated, but it's 119 // not currently necessary. Users that need the pointer don't stream. 120 assert(0 && "getPointer in streaming memory objects not allowed"); 121 return NULL; 122 } 123 virtual bool isValidAddress(uint64_t address) const LLVM_OVERRIDE; 124 virtual bool isObjectEnd(uint64_t address) const LLVM_OVERRIDE; 125 126 /// Drop s bytes from the front of the stream, pushing the positions of the 127 /// remaining bytes down by s. This is used to skip past the bitcode header, 128 /// since we don't know a priori if it's present, and we can't put bytes 129 /// back into the stream once we've read them. 130 bool dropLeadingBytes(size_t s); 131 132 /// If the data object size is known in advance, many of the operations can 133 /// be made more efficient, so this method should be called before reading 134 /// starts (although it can be called anytime). 135 void setKnownObjectSize(size_t size); 136 137 private: 138 const static uint32_t kChunkSize = 4096 * 4; 139 mutable std::vector<unsigned char> Bytes; 140 OwningPtr<DataStreamer> Streamer; 141 mutable size_t BytesRead; // Bytes read from stream 142 size_t BytesSkipped;// Bytes skipped at start of stream (e.g. wrapper/header) 143 mutable size_t ObjectSize; // 0 if unknown, set if wrapper seen or EOF reached 144 mutable bool EOFReached; 145 146 // Fetch enough bytes such that Pos can be read or EOF is reached 147 // (i.e. BytesRead > Pos). Return true if Pos can be read. 148 // Unlike most of the functions in BitcodeReader, returns true on success. 149 // Most of the requests will be small, but we fetch at kChunkSize bytes 150 // at a time to avoid making too many potentially expensive GetBytes calls 151 bool fetchToPos(size_t Pos) const { 152 if (EOFReached) return Pos < ObjectSize; 153 while (Pos >= BytesRead) { 154 Bytes.resize(BytesRead + BytesSkipped + kChunkSize); 155 size_t bytes = Streamer->GetBytes(&Bytes[BytesRead + BytesSkipped], 156 kChunkSize); 157 BytesRead += bytes; 158 if (bytes < kChunkSize) { 159 if (ObjectSize && BytesRead < Pos) 160 assert(0 && "Unexpected short read fetching bitcode"); 161 if (BytesRead <= Pos) { // reached EOF/ran out of bytes 162 ObjectSize = BytesRead; 163 EOFReached = true; 164 return false; 165 } 166 } 167 } 168 return true; 169 } 170 171 StreamingMemoryObject(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION; 172 void operator=(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION; 173 }; 174 175 StreamableMemoryObject *getNonStreamedMemoryObject( 176 const unsigned char *Start, const unsigned char *End); 177 178 } 179 #endif // STREAMABLEMEMORYOBJECT_H_ 180
