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// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// https://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#ifndef ASTC_CODEC_BASE_UINT128_H_
#define ASTC_CODEC_BASE_UINT128_H_
#include <cassert>
#include <cstdint>
namespace astc_codec {
namespace base {
class UInt128 {
public:
UInt128() = default;
UInt128(uint64_t low) : low_(low) { }
UInt128(uint64_t high, uint64_t low) : low_(low), high_(high) { }
UInt128(const UInt128& other) : low_(other.low_), high_(other.high_) { }
uint64_t LowBits() const { return low_; }
uint64_t HighBits() const { return high_; }
// Allow explicit casts to uint64_t.
explicit operator uint64_t() const { return low_; }
// Copy operators.
UInt128& operator=(const UInt128& other) {
high_ = other.high_;
low_ = other.low_;
return *this;
}
// Equality operators.
bool operator==(const UInt128& other) const {
return high_ == other.high_ && low_ == other.low_;
}
bool operator!=(const UInt128& other) const {
return high_ != other.high_ || low_ != other.low_;
}
// Shifting.
UInt128& operator<<=(int shift) {
high_ = shift >= 64 ? (shift >= 128 ? 0 : low_ << (shift - 64))
: high_ << shift;
if (shift > 0 && shift < 64) {
const uint64_t overlappingBits = low_ >> (64 - shift);
high_ |= overlappingBits;
}
low_ = shift >= 64 ? 0 : low_ << shift;
return *this;
}
UInt128 operator<<(int shift) const {
UInt128 result = *this;
result <<= shift;
return result;
}
UInt128& operator>>=(int shift) {
low_ = shift >= 64 ? (shift >= 128 ? 0 : high_ >> (shift - 64))
: low_ >> shift;
if (shift > 0 && shift < 64) {
const uint64_t overlappingBits = high_ << (64 - shift);
low_ |= overlappingBits;
}
high_ = shift >= 64 ? 0 : high_ >> shift;
return *this;
}
UInt128 operator>>(int shift) const {
UInt128 result = *this;
result >>= shift;
return result;
}
// Binary operations.
UInt128& operator|=(const UInt128& other) {
high_ |= other.high_;
low_ |= other.low_;
return *this;
}
UInt128 operator|(const UInt128& other) const {
UInt128 result = *this;
result |= other;
return result;
}
UInt128& operator&=(const UInt128& other) {
high_ &= other.high_;
low_ &= other.low_;
return *this;
}
UInt128 operator&(const UInt128& other) const {
UInt128 result = *this;
result &= other;
return result;
}
UInt128& operator^=(const UInt128& other) {
high_ ^= other.high_;
low_ ^= other.low_;
return *this;
}
UInt128 operator^(const UInt128& other) const {
UInt128 result = *this;
result ^= other;
return result;
}
UInt128 operator~() const {
UInt128 result = *this;
result.high_ = ~high_;
result.low_ = ~low_;
return result;
}
// Addition/subtraction.
UInt128& operator+=(const UInt128& other) {
const uint64_t carry =
(((low_ & other.low_) & 1) + (low_ >> 1) + (other.low_ >> 1)) >> 63;
high_ += other.high_ + carry;
low_ += other.low_;
return *this;
}
UInt128 operator+(const UInt128& other) const {
UInt128 result = *this;
result += other;
return result;
}
UInt128& operator-=(const UInt128& other) {
low_ -= other.low_;
const uint64_t carry =
(((low_ & other.low_) & 1) + (low_ >> 1) + (other.low_ >> 1)) >> 63;
high_ -= other.high_ + carry;
return *this;
}
UInt128 operator-(const UInt128& other) const {
UInt128 result = *this;
result -= other;
return result;
}
private:
// TODO(google): Different order for little endian.
uint64_t low_ = 0;
uint64_t high_ = 0;
};
} // namespace base
} // namespace astc_codec
#endif // ASTC_CODEC_BASE_UINT128_H_
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