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509156a4ab
The reading of 64 bit values could still be optimized, but at least this cuts down on the number of virtual calls to fetch more data. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@221865 91177308-0d34-0410-b5e6-96231b3b80d8
92 lines
3.7 KiB
C++
92 lines
3.7 KiB
C++
//===- StreamingMemoryObject.h - Streamable data interface -----*- C++ -*-===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#ifndef LLVM_SUPPORT_STREAMINGMEMORYOBJECT_H
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#define LLVM_SUPPORT_STREAMINGMEMORYOBJECT_H
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#include "llvm/Support/Compiler.h"
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#include "llvm/Support/DataStream.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/MemoryObject.h"
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#include <cassert>
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#include <memory>
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#include <vector>
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namespace llvm {
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/// Interface to data which is actually streamed from a DataStreamer. In
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/// addition to inherited members, it has the dropLeadingBytes and
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/// setKnownObjectSize methods which are not applicable to non-streamed objects.
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class StreamingMemoryObject : public MemoryObject {
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public:
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StreamingMemoryObject(DataStreamer *streamer);
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uint64_t getExtent() const override;
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uint64_t readBytes(uint8_t *Buf, uint64_t Size,
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uint64_t Address) const override;
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const uint8_t *getPointer(uint64_t address, uint64_t size) const override {
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// This could be fixed by ensuring the bytes are fetched and making a copy,
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// requiring that the bitcode size be known, or otherwise ensuring that
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// the memory doesn't go away/get reallocated, but it's
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// not currently necessary. Users that need the pointer don't stream.
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llvm_unreachable("getPointer in streaming memory objects not allowed");
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return nullptr;
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}
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bool isValidAddress(uint64_t address) const override;
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/// Drop s bytes from the front of the stream, pushing the positions of the
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/// remaining bytes down by s. This is used to skip past the bitcode header,
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/// since we don't know a priori if it's present, and we can't put bytes
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/// back into the stream once we've read them.
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bool dropLeadingBytes(size_t s);
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/// If the data object size is known in advance, many of the operations can
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/// be made more efficient, so this method should be called before reading
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/// starts (although it can be called anytime).
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void setKnownObjectSize(size_t size);
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private:
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const static uint32_t kChunkSize = 4096 * 4;
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mutable std::vector<unsigned char> Bytes;
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std::unique_ptr<DataStreamer> Streamer;
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mutable size_t BytesRead; // Bytes read from stream
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size_t BytesSkipped;// Bytes skipped at start of stream (e.g. wrapper/header)
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mutable size_t ObjectSize; // 0 if unknown, set if wrapper seen or EOF reached
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mutable bool EOFReached;
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// Fetch enough bytes such that Pos can be read or EOF is reached
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// (i.e. BytesRead > Pos). Return true if Pos can be read.
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// Unlike most of the functions in BitcodeReader, returns true on success.
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// Most of the requests will be small, but we fetch at kChunkSize bytes
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// at a time to avoid making too many potentially expensive GetBytes calls
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bool fetchToPos(size_t Pos) const {
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if (EOFReached) return Pos < ObjectSize;
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while (Pos >= BytesRead) {
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Bytes.resize(BytesRead + BytesSkipped + kChunkSize);
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size_t bytes = Streamer->GetBytes(&Bytes[BytesRead + BytesSkipped],
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kChunkSize);
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BytesRead += bytes;
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if (BytesRead <= Pos) { // reached EOF/ran out of bytes
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ObjectSize = BytesRead;
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EOFReached = true;
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return false;
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}
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}
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return true;
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}
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StreamingMemoryObject(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION;
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void operator=(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION;
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};
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MemoryObject *getNonStreamedMemoryObject(
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const unsigned char *Start, const unsigned char *End);
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}
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#endif // STREAMINGMEMORYOBJECT_H_
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