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//===- StreamingMemoryObject.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 LLVM_SUPPORT_STREAMINGMEMORYOBJECT_H
#define LLVM_SUPPORT_STREAMINGMEMORYOBJECT_H
#include "llvm/Support/Compiler.h"
#include "llvm/Support/DataStream.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MemoryObject.h"
#include <cassert>
#include <memory>
#include <vector>
namespace llvm {
/// 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 MemoryObject {
public:
StreamingMemoryObject(DataStreamer *streamer);
uint64_t getExtent() const override;
uint64_t readBytes(uint8_t *Buf, uint64_t Size,
uint64_t Address) const override;
const uint8_t *getPointer(uint64_t address, uint64_t size) const override {
// 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.
llvm_unreachable("getPointer in streaming memory objects not allowed");
return nullptr;
}
bool isValidAddress(uint64_t address) const override;
/// 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;
mutable std::vector<unsigned char> Bytes;
std::unique_ptr<DataStreamer> Streamer;
mutable size_t BytesRead; // Bytes read from stream
size_t BytesSkipped;// Bytes skipped at start of stream (e.g. wrapper/header)
mutable size_t ObjectSize; // 0 if unknown, set if wrapper seen or EOF reached
mutable 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) const {
if (EOFReached)
return Pos < ObjectSize;
while (Pos >= BytesRead) {
Bytes.resize(BytesRead + BytesSkipped + kChunkSize);
size_t bytes = Streamer->GetBytes(&Bytes[BytesRead + BytesSkipped],
kChunkSize);
BytesRead += bytes;
if (bytes != kChunkSize) { // reached EOF/ran out of bytes
ObjectSize = BytesRead;
EOFReached = true;
break;
}
}
return Pos < BytesRead;
}
StreamingMemoryObject(const StreamingMemoryObject&) = delete;
void operator=(const StreamingMemoryObject&) = delete;
};
MemoryObject *getNonStreamedMemoryObject(
const unsigned char *Start, const unsigned char *End);
}
#endif // STREAMINGMEMORYOBJECT_H_
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