// Copyright (c) the JPEG XL Project Authors. All rights reserved.

//

// Use of this source code is governed by a BSD-style

// license that can be found in the LICENSE file.

#ifndef LIB_JXL_PACK_H_

#define LIB_JXL_PACK_H_

// Pack/UnpackSigned utilities.

#include <cstddef>

#include <cstdint>

#include "lib/jxl/base/compiler_specific.h"

namespace jxl {

// Encodes non-negative (X) into (2 * X), negative (-X) into (2 * X - 1)

constexpr uint32_t PackSigned(int32_t value)

    JXL_NO_SANITIZE("unsigned-integer-overflow") {

  return (static_cast<uint32_t>(value) << 1) ^

         ((static_cast<uint32_t>(~value) >> 31) - 1);

}

// Reverse to PackSigned, i.e. UnpackSigned(PackSigned(X)) == X.

// (((~value) & 1) - 1) is either 0 or 0xFF...FF and it will have an expected

// unsigned-integer-overflow.

// NB: semantically `value` should have type `uint32_t`, but for efficiency and

// convenience its type is `size_t` (i.e. `uint32_t` or `uint64_t`).

constexpr int32_t UnpackSigned(size_t value)

    JXL_NO_SANITIZE("unsigned-integer-overflow") {

  // TODO(Ivan): fails in C++11 mode, restore with a guard?

  // JXL_DASSERT((value & 0xFFFFFFFF) == value);  // no-op in 32-bit build

  return static_cast<int32_t>((value >> 1) ^ (((~value) & 1) - 1));

}

}  // namespace jxl

#endif  // LIB_JXL_PACK_H_