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//===- 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 LLVM_SUPPORT_STREAMABLEMEMORYOBJECT_H
#define LLVM_SUPPORT_STREAMABLEMEMORYOBJECT_H
#include "llvm/ADT/OwningPtr.h"
#include "llvm/Support/Compiler.h"
#include "llvm/Support/DataStream.h"
#include "llvm/Support/MemoryObject.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 override = 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() const override = 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) const override = 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 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.
/// @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) const override = 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) const = 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) const = 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) const = 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 override { return 0; }
virtual uint64_t getExtent() const override;
virtual int readByte(uint64_t address, uint8_t *ptr) const override;
virtual int readBytes(uint64_t address,
uint64_t size,
uint8_t *buf) const override;
virtual 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.
assert(0 && "getPointer in streaming memory objects not allowed");
return NULL;
}
virtual bool isValidAddress(uint64_t address) const override;
virtual bool isObjectEnd(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;
OwningPtr<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) {
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&) LLVM_DELETED_FUNCTION;
void operator=(const StreamingMemoryObject&) LLVM_DELETED_FUNCTION;
};
StreamableMemoryObject *getNonStreamedMemoryObject(
const unsigned char *Start, const unsigned char *End);
}
#endif // STREAMABLEMEMORYOBJECT_H_
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