| // Licensed to the Apache Software Foundation (ASF) under one |
| // or more contributor license agreements. See the NOTICE file |
| // distributed with this work for additional information |
| // regarding copyright ownership. The ASF licenses this file |
| // to you 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 |
| // |
| // http://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. |
| |
| package decimal128 // import "github.com/apache/arrow/go/arrow/decimal128" |
| |
| var ( |
| MaxDecimal128 = New(542101086242752217, 687399551400673280-1) |
| ) |
| |
| // Num represents a signed 128-bit integer in two's complement. |
| // Calculations wrap around and overflow is ignored. |
| // |
| // For a discussion of the algorithms, look at Knuth's volume 2, |
| // Semi-numerical Algorithms section 4.3.1. |
| // |
| // Adapted from the Apache ORC C++ implementation |
| type Num struct { |
| lo uint64 // low bits |
| hi int64 // high bits |
| } |
| |
| // New returns a new signed 128-bit integer value. |
| func New(hi int64, lo uint64) Num { |
| return Num{lo: lo, hi: hi} |
| } |
| |
| // FromU64 returns a new signed 128-bit integer value from the provided uint64 one. |
| func FromU64(v uint64) Num { |
| return New(0, v) |
| } |
| |
| // FromI64 returns a new signed 128-bit integer value from the provided int64 one. |
| func FromI64(v int64) Num { |
| switch { |
| case v > 0: |
| return New(0, uint64(v)) |
| case v < 0: |
| return New(-1, uint64(v)) |
| default: |
| return Num{} |
| } |
| } |
| |
| // LowBits returns the low bits of the two's complement representation of the number. |
| func (n Num) LowBits() uint64 { return n.lo } |
| |
| // HighBits returns the high bits of the two's complement representation of the number. |
| func (n Num) HighBits() int64 { return n.hi } |
| |
| // Sign returns: |
| // |
| // -1 if x < 0 |
| // 0 if x == 0 |
| // +1 if x > 0 |
| func (n Num) Sign() int { |
| if n == (Num{}) { |
| return 0 |
| } |
| return int(1 | (n.hi >> 63)) |
| } |