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 = 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 = 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 = 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 maximum 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 /// @param copied - A pointer to a nunber that is filled in with the number 72 /// of bytes actually read. May be NULL. 73 /// @result - 0 if successful; -1 if not. Failure may be due to a 74 /// bounds violation or an implementation-specific error. 75 virtual int readBytes(uint64_t address, 76 uint64_t size, 77 uint8_t* buf, 78 uint64_t* copied) const = 0; 79 80 /// getPointer - Ensures that the requested data is in memory, and returns 81 /// A pointer to it. More efficient than using readBytes if the 82 /// data is already in memory. 83 /// May block until (address - base + size) bytes have been read 84 /// @param address - address of the byte, in the same space as getBase() 85 /// @param size - amount of data that must be available on return 86 /// @result - valid pointer to the requested data 87 virtual const uint8_t *getPointer(uint64_t address, uint64_t size) const = 0; 88 89 /// isValidAddress - Returns true if the address is within the object 90 /// (i.e. between base and base + extent - 1 inclusive) 91 /// May block until (address - base) bytes have been read 92 /// @param address - address of the byte, in the same space as getBase() 93 /// @result - true if the address may be read with readByte() 94 virtual bool isValidAddress(uint64_t address) const = 0; 95 96 /// isObjectEnd - Returns true if the address is one past the end of the 97 /// object (i.e. if it is equal to base + extent) 98 /// May block until (address - base) bytes have been read 99 /// @param address - address of the byte, in the same space as getBase() 100 /// @result - true if the address is equal to base + extent 101 virtual bool isObjectEnd(uint64_t address) const = 0; 102 }; 103 104 /// StreamingMemoryObject - interface to data which is actually streamed from 105 /// a DataStreamer. In addition to inherited members, it has the 106 /// dropLeadingBytes and setKnownObjectSize methods which are not applicable 107 /// to non-streamed objects. 108 class StreamingMemoryObject : public StreamableMemoryObject { 109 public: 110 StreamingMemoryObject(DataStreamer *streamer); 111 virtual uint64_t getBase() const LLVM_OVERRIDE { return 0; } 112 virtual uint64_t getExtent() const LLVM_OVERRIDE; 113 virtual int readByte(uint64_t address, uint8_t* ptr) const LLVM_OVERRIDE; 114 virtual int readBytes(uint64_t address, 115 uint64_t size, 116 uint8_t* buf, 117 uint64_t* copied) const LLVM_OVERRIDE; 118 virtual const uint8_t *getPointer(uint64_t address, 119 uint64_t size) const LLVM_OVERRIDE { 120 // This could be fixed by ensuring the bytes are fetched and making a copy, 121 // requiring that the bitcode size be known, or otherwise ensuring that 122 // the memory doesn't go away/get reallocated, but it's 123 // not currently necessary. Users that need the pointer don't stream. 124 assert(0 && "getPointer in streaming memory objects not allowed"); 125 return NULL; 126 } 127 virtual bool isValidAddress(uint64_t address) const LLVM_OVERRIDE; 128 virtual bool isObjectEnd(uint64_t address) const LLVM_OVERRIDE; 129 130 /// Drop s bytes from the front of the stream, pushing the positions of the 131 /// remaining bytes down by s. This is used to skip past the bitcode header, 132 /// since we don't know a priori if it's present, and we can't put bytes 133 /// back into the stream once we've read them. 134 bool dropLeadingBytes(size_t s); 135 136 /// If the data object size is known in advance, many of the operations can 137 /// be made more efficient, so this method should be called before reading 138 /// starts (although it can be called anytime). 139 void setKnownObjectSize(size_t size); 140 141 private: 142 const static uint32_t kChunkSize = 4096 * 4; 143 mutable std::vector<unsigned char> Bytes; 144 OwningPtr<DataStreamer> Streamer; 145 mutable size_t BytesRead; // Bytes read from stream 146 size_t BytesSkipped;// Bytes skipped at start of stream (e.g. wrapper/header) 147 mutable size_t ObjectSize; // 0 if unknown, set if wrapper seen or EOF reached 148 mutable bool EOFReached; 149 150 // Fetch enough bytes such that Pos can be read or EOF is reached 151 // (i.e. BytesRead > Pos). Return true if Pos can be read. 152 // Unlike most of the functions in BitcodeReader, returns true on success. 153 // Most of the requests will be small, but we fetch at kChunkSize bytes 154 // at a time to avoid making too many potentially expensive GetBytes calls 155 bool fetchToPos(size_t Pos) const { 156 if (EOFReached) return Pos < ObjectSize; 157 while (Pos >= BytesRead) { 158 Bytes.resize(BytesRead + BytesSkipped + kChunkSize); 159 size_t bytes = Streamer->GetBytes(&Bytes[BytesRead + BytesSkipped], 160 kChunkSize); 161 BytesRead += bytes; 162 if (bytes < kChunkSize) { 163 if (ObjectSize && BytesRead < Pos) 164 assert(0 && "Unexpected short read fetching bitcode"); 165 if (BytesRead <= Pos) { // reached EOF/ran out of bytes 166 ObjectSize = BytesRead; 167 EOFReached = true; 168 return false; 169 } 170 } 171 } 172 return true; 173 } 174 175 StreamingMemoryObject(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION; 176 void operator=(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION; 177 }; 178 179 StreamableMemoryObject *getNonStreamedMemoryObject( 180 const unsigned char *Start, const unsigned char *End); 181 182 } 183 #endif // STREAMABLEMEMORYOBJECT_H_ 184
