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Diffstat (limited to 'include/llvm/Support/StreamableMemoryObject.h')
| -rw-r--r-- | include/llvm/Support/StreamableMemoryObject.h | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/include/llvm/Support/StreamableMemoryObject.h b/include/llvm/Support/StreamableMemoryObject.h new file mode 100644 index 0000000000..b0e202cbf7 --- /dev/null +++ b/include/llvm/Support/StreamableMemoryObject.h @@ -0,0 +1,181 @@ +//===- StreamableMemoryObject.h - Streamable data interface - -*- C++ -*-===// +// +// The LLVM Compiler Infrastructure +// +// This file is distributed under the University of Illinois Open Source +// License. See LICENSE.TXT for details. +// +//===----------------------------------------------------------------------===// + + +#ifndef STREAMABLEMEMORYOBJECT_H_ +#define STREAMABLEMEMORYOBJECT_H_ + +#include "llvm/ADT/OwningPtr.h" +#include "llvm/Support/MemoryObject.h" +#include "llvm/Support/DataStream.h" +#include <vector> + +namespace llvm { + +/// StreamableMemoryObject - Interface to data which might be streamed. +/// Streamability has 2 important implications/restrictions. First, the data +/// might not yet exist in memory when the request is made. This just means +/// that readByte/readBytes might have to block or do some work to get it. +/// More significantly, the exact size of the object might not be known until +/// it has all been fetched. This means that to return the right result, +/// getExtent must also wait for all the data to arrive; therefore it should +/// not be called on objects which are actually streamed (this would defeat +/// the purpose of streaming). Instead, isValidAddress and isObjectEnd can be +/// used to test addresses without knowing the exact size of the stream. +/// Finally, getPointer can be used instead of readBytes to avoid extra copying. +class StreamableMemoryObject : public MemoryObject { + public: + /// Destructor - Override as necessary. + virtual ~StreamableMemoryObject(); + + /// getBase - Returns the lowest valid address in the region. + /// + /// @result - The lowest valid address. + virtual uint64_t getBase() const = 0; + + /// getExtent - Returns the size of the region in bytes. (The region is + /// contiguous, so the highest valid address of the region + /// is getBase() + getExtent() - 1). + /// May block until all bytes in the stream have been read + /// + /// @result - The size of the region. + virtual uint64_t getExtent() = 0; + + /// readByte - Tries to read a single byte from the region. + /// May block until (address - base) bytes have been read + /// @param address - The address of the byte, in the same space as getBase(). + /// @param ptr - A pointer to a byte to be filled in. Must be non-NULL. + /// @result - 0 if successful; -1 if not. Failure may be due to a + /// bounds violation or an implementation-specific error. + virtual int readByte(uint64_t address, uint8_t* ptr) = 0; + + /// readBytes - Tries to read a contiguous range of bytes from the + /// region, up to the end of the region. + /// May block until (address - base + size) bytes have + /// been read. Additionally, StreamableMemoryObjects will + /// not do partial reads - if size bytes cannot be read, + /// readBytes will fail. + /// + /// @param address - The address of the first byte, in the same space as + /// getBase(). + /// @param size - The maximum number of bytes to copy. + /// @param buf - A pointer to a buffer to be filled in. Must be non-NULL + /// and large enough to hold size bytes. + /// @param copied - A pointer to a nunber that is filled in with the number + /// of bytes actually read. May be NULL. + /// @result - 0 if successful; -1 if not. Failure may be due to a + /// bounds violation or an implementation-specific error. + virtual int readBytes(uint64_t address, + uint64_t size, + uint8_t* buf, + uint64_t* copied) = 0; + + /// getPointer - Ensures that the requested data is in memory, and returns + /// A pointer to it. More efficient than using readBytes if the + /// data is already in memory. + /// May block until (address - base + size) bytes have been read + /// @param address - address of the byte, in the same space as getBase() + /// @param size - amount of data that must be available on return + /// @result - valid pointer to the requested data + virtual const uint8_t *getPointer(uint64_t address, uint64_t size) = 0; + + /// isValidAddress - Returns true if the address is within the object + /// (i.e. between base and base + extent - 1 inclusive) + /// May block until (address - base) bytes have been read + /// @param address - address of the byte, in the same space as getBase() + /// @result - true if the address may be read with readByte() + virtual bool isValidAddress(uint64_t address) = 0; + + /// isObjectEnd - Returns true if the address is one past the end of the + /// object (i.e. if it is equal to base + extent) + /// May block until (address - base) bytes have been read + /// @param address - address of the byte, in the same space as getBase() + /// @result - true if the address is equal to base + extent + virtual bool isObjectEnd(uint64_t address) = 0; +}; + +/// StreamingMemoryObject - interface to data which is actually streamed from +/// a DataStreamer. In addition to inherited members, it has the +/// dropLeadingBytes and setKnownObjectSize methods which are not applicable +/// to non-streamed objects. +class StreamingMemoryObject : public StreamableMemoryObject { +public: + StreamingMemoryObject(DataStreamer *streamer); + virtual uint64_t getBase() const { return 0; } + virtual uint64_t getExtent(); + virtual int readByte(uint64_t address, uint8_t* ptr); + virtual int readBytes(uint64_t address, + uint64_t size, + uint8_t* buf, + uint64_t* copied); + virtual const uint8_t *getPointer(uint64_t address, uint64_t size) { + // This could be fixed by ensuring the bytes are fetched and making a copy, + // requiring that the bitcode size be known, or otherwise ensuring that + // the memory doesn't go away/get reallocated, but it's + // not currently necessary. Users that need the pointer don't stream. + assert(0 && "getPointer in streaming memory objects not allowed"); + return NULL; + } + virtual bool isValidAddress(uint64_t address); + virtual bool isObjectEnd(uint64_t address); + + /// Drop s bytes from the front of the stream, pushing the positions of the + /// remaining bytes down by s. This is used to skip past the bitcode header, + /// since we don't know a priori if it's present, and we can't put bytes + /// back into the stream once we've read them. + bool dropLeadingBytes(size_t s); + + /// If the data object size is known in advance, many of the operations can + /// be made more efficient, so this method should be called before reading + /// starts (although it can be called anytime). + void setKnownObjectSize(size_t size); + +private: + const static uint32_t kChunkSize = 4096 * 4; + std::vector<unsigned char> Bytes; + OwningPtr<DataStreamer> Streamer; + size_t BytesRead; // Bytes read from stream + size_t BytesSkipped;// Bytes skipped at start of stream (e.g. wrapper/header) + size_t ObjectSize; // 0 if unknown, set if wrapper was seen or EOF reached + bool EOFReached; + + // Fetch enough bytes such that Pos can be read or EOF is reached + // (i.e. BytesRead > Pos). Return true if Pos can be read. + // Unlike most of the functions in BitcodeReader, returns true on success. + // Most of the requests will be small, but we fetch at kChunkSize bytes + // at a time to avoid making too many potentially expensive GetBytes calls + bool fetchToPos(size_t Pos) { + if (EOFReached) return Pos < ObjectSize; + while (Pos >= BytesRead) { + Bytes.resize(BytesRead + kChunkSize); + size_t bytes = Streamer->GetBytes(&Bytes[BytesRead + BytesSkipped], + kChunkSize); + BytesRead += bytes; + if (bytes < kChunkSize) { + if (ObjectSize && BytesRead < Pos) + assert(0 && "Unexpected short read fetching bitcode"); + if (BytesRead <= Pos) { // reached EOF/ran out of bytes + ObjectSize = BytesRead; + EOFReached = true; + return false; + } + } + } + return true; + } + + StreamingMemoryObject(const StreamingMemoryObject&); // DO NOT IMPLEMENT + void operator=(const StreamingMemoryObject&); // DO NOT IMPLEMENT +}; + +StreamableMemoryObject *getNonStreamedMemoryObject( + const unsigned char *Start, const unsigned char *End); + +} +#endif // STREAMABLEMEMORYOBJECT_H_ |