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//===- BinaryItemStream.h ---------------------------------------*- 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_BINARYITEMSTREAM_H
#define LLVM_SUPPORT_BINARYITEMSTREAM_H
#include "llvm/ADT/ArrayRef.h"
#include "llvm/Support/BinaryStream.h"
#include "llvm/Support/BinaryStreamError.h"
#include "llvm/Support/Error.h"
#include <cstddef>
#include <cstdint>
namespace llvm {
template <typename T> struct BinaryItemTraits {
static size_t length(const T &Item) = delete;
static ArrayRef<uint8_t> bytes(const T &Item) = delete;
};
/// BinaryItemStream represents a sequence of objects stored in some kind of
/// external container but for which it is useful to view as a stream of
/// contiguous bytes. An example of this might be if you have a collection of
/// records and you serialize each one into a buffer, and store these serialized
/// records in a container. The pointers themselves are not laid out
/// contiguously in memory, but we may wish to read from or write to these
/// records as if they were.
template <typename T, typename Traits = BinaryItemTraits<T>>
class BinaryItemStream : public BinaryStream {
public:
explicit BinaryItemStream(llvm::support::endianness Endian)
: Endian(Endian) {}
llvm::support::endianness getEndian() const override { return Endian; }
Error readBytes(uint32_t Offset, uint32_t Size,
ArrayRef<uint8_t> &Buffer) override {
auto ExpectedIndex = translateOffsetIndex(Offset);
if (!ExpectedIndex)
return ExpectedIndex.takeError();
const auto &Item = Items[*ExpectedIndex];
if (auto EC = checkOffset(Offset, Size))
return EC;
if (Size > Traits::length(Item))
return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
Buffer = Traits::bytes(Item).take_front(Size);
return Error::success();
}
Error readLongestContiguousChunk(uint32_t Offset,
ArrayRef<uint8_t> &Buffer) override {
auto ExpectedIndex = translateOffsetIndex(Offset);
if (!ExpectedIndex)
return ExpectedIndex.takeError();
Buffer = Traits::bytes(Items[*ExpectedIndex]);
return Error::success();
}
void setItems(ArrayRef<T> ItemArray) { Items = ItemArray; }
uint32_t getLength() override {
uint32_t Size = 0;
for (const auto &Item : Items)
Size += Traits::length(Item);
return Size;
}
private:
Expected<uint32_t> translateOffsetIndex(uint32_t Offset) const {
uint32_t CurrentOffset = 0;
uint32_t CurrentIndex = 0;
for (const auto &Item : Items) {
if (CurrentOffset >= Offset)
break;
CurrentOffset += Traits::length(Item);
++CurrentIndex;
}
if (CurrentOffset != Offset)
return make_error<BinaryStreamError>(stream_error_code::stream_too_short);
return CurrentIndex;
}
llvm::support::endianness Endian;
ArrayRef<T> Items;
};
} // end namespace llvm
#endif // LLVM_SUPPORT_BINARYITEMSTREAM_H
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