BinaryBuffer.h

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//===-- BinaryBuffer.h - Little-endian binary buffer ------------*- C++ -*-===//
//
// Part of the LLZK Project, under the Apache License v2.0.
// See LICENSE.txt for license information.
// Copyright 2026 Project LLZK
// SPDX-License-Identifier: Apache-2.0
//
//===----------------------------------------------------------------------===//
 
#pragma once
 
#include "llzk/Util/DynamicAPIntHelper.h"
 
#include <llvm/ADT/ArrayRef.h>
#include <llvm/ADT/SmallVector.h>
#include <llvm/Support/Endian.h>
 
#include <climits>
#include <cstdint>
 
namespace llzk {

class BinaryBuffer {
public:
  void writeU32(uint32_t value) { writeInteger(value); }
  void writeU64(uint64_t value) { writeInteger(value); }
 
  void writeBytes(llvm::ArrayRef<char> bytes) { buffer_.append(bytes.begin(), bytes.end()); }
 
  void writeFieldElement(uint32_t size, const llvm::DynamicAPInt &value) {
    llvm::APInt exact = toExactWidthAPInt(value, size * CHAR_BIT);
    for (uint32_t i = 0; i < size; ++i) {
      buffer_.push_back(static_cast<char>(exact.extractBitsAsZExtValue(8, i * 8)));
    }
  }
 
  uint64_t size() const { return static_cast<uint64_t>(buffer_.size()); }
  llvm::ArrayRef<char> bytes() const { return buffer_; }
 
private:
  template <typename T> void writeInteger(T value) {
    char bytes[sizeof(T)];
    llvm::support::endian::write<T, llvm::endianness::little>(bytes, value);
    writeBytes(bytes);
  }
 
  llvm::SmallVector<char> buffer_;
};
 
} // namespace llzk