github.com/sberex/go-sberex@v1.8.2-0.20181113200658-ed96ac38f7d7/common/math/integer.go (about)

     1  // This file is part of the go-sberex library. The go-sberex library is 
     2  // free software: you can redistribute it and/or modify it under the terms 
     3  // of the GNU Lesser General Public License as published by the Free 
     4  // Software Foundation, either version 3 of the License, or (at your option)
     5  // any later version.
     6  //
     7  // The go-sberex library is distributed in the hope that it will be useful, 
     8  // but WITHOUT ANY WARRANTY; without even the implied warranty of
     9  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser 
    10  // General Public License <http://www.gnu.org/licenses/> for more details.
    11  
    12  package math
    13  
    14  import (
    15  	"fmt"
    16  	"strconv"
    17  )
    18  
    19  const (
    20  	// Integer limit values.
    21  	MaxInt8   = 1<<7 - 1
    22  	MinInt8   = -1 << 7
    23  	MaxInt16  = 1<<15 - 1
    24  	MinInt16  = -1 << 15
    25  	MaxInt32  = 1<<31 - 1
    26  	MinInt32  = -1 << 31
    27  	MaxInt64  = 1<<63 - 1
    28  	MinInt64  = -1 << 63
    29  	MaxUint8  = 1<<8 - 1
    30  	MaxUint16 = 1<<16 - 1
    31  	MaxUint32 = 1<<32 - 1
    32  	MaxUint64 = 1<<64 - 1
    33  )
    34  
    35  // HexOrDecimal64 marshals uint64 as hex or decimal.
    36  type HexOrDecimal64 uint64
    37  
    38  // UnmarshalText implements encoding.TextUnmarshaler.
    39  func (i *HexOrDecimal64) UnmarshalText(input []byte) error {
    40  	int, ok := ParseUint64(string(input))
    41  	if !ok {
    42  		return fmt.Errorf("invalid hex or decimal integer %q", input)
    43  	}
    44  	*i = HexOrDecimal64(int)
    45  	return nil
    46  }
    47  
    48  // MarshalText implements encoding.TextMarshaler.
    49  func (i HexOrDecimal64) MarshalText() ([]byte, error) {
    50  	return []byte(fmt.Sprintf("%#x", uint64(i))), nil
    51  }
    52  
    53  // ParseUint64 parses s as an integer in decimal or hexadecimal syntax.
    54  // Leading zeros are accepted. The empty string parses as zero.
    55  func ParseUint64(s string) (uint64, bool) {
    56  	if s == "" {
    57  		return 0, true
    58  	}
    59  	if len(s) >= 2 && (s[:2] == "0x" || s[:2] == "0X") {
    60  		v, err := strconv.ParseUint(s[2:], 16, 64)
    61  		return v, err == nil
    62  	}
    63  	v, err := strconv.ParseUint(s, 10, 64)
    64  	return v, err == nil
    65  }
    66  
    67  // MustParseUint64 parses s as an integer and panics if the string is invalid.
    68  func MustParseUint64(s string) uint64 {
    69  	v, ok := ParseUint64(s)
    70  	if !ok {
    71  		panic("invalid unsigned 64 bit integer: " + s)
    72  	}
    73  	return v
    74  }
    75  
    76  // NOTE: The following methods need to be optimised using either bit checking or asm
    77  
    78  // SafeSub returns subtraction result and whether overflow occurred.
    79  func SafeSub(x, y uint64) (uint64, bool) {
    80  	return x - y, x < y
    81  }
    82  
    83  // SafeAdd returns the result and whether overflow occurred.
    84  func SafeAdd(x, y uint64) (uint64, bool) {
    85  	return x + y, y > MaxUint64-x
    86  }
    87  
    88  // SafeMul returns multiplication result and whether overflow occurred.
    89  func SafeMul(x, y uint64) (uint64, bool) {
    90  	if x == 0 || y == 0 {
    91  		return 0, false
    92  	}
    93  	return x * y, y > MaxUint64/x
    94  }