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int.go
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int.go
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// Copyright (c) 2015 Taco de Wolff
//
// Permission is hereby granted, free of charge, to any person
// obtaining a copy of this software and associated documentation
// files (the "Software"), to deal in the Software without
// restriction, including without limitation the rights to use,
// copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following
// conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
// OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
// HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
// WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
// OTHER DEALINGS IN THE SOFTWARE.
package byteconv
import (
"math"
"strconv"
)
// ParseInt parses a byte-slice and returns the integer it represents. If an
// invalid character is encountered, it returns a syntax error.
func ParseInt(b []byte) (v int64, ok bool, err error) {
if len(b) == 0 {
return
}
if UseStdLib {
v, err = strconv.ParseInt(string(b), 10, 64)
ok = err == nil
return
}
i := 0
neg := false
if len(b) > 0 && (b[0] == '+' || b[0] == '-') {
neg = b[0] == '-'
i++
}
n := uint64(0)
for i < len(b) {
c := b[i]
if n > math.MaxUint64/10 {
return 0, false, rangeError("ParseInt", string(b))
} else if c >= '0' && c <= '9' {
n *= 10
n += uint64(c - '0')
} else {
break
}
i++
}
if !neg && n > uint64(math.MaxInt64) || n > uint64(math.MaxInt64)+1 {
return 0, false, rangeError("ParseInt", string(b))
} else if neg {
return -int64(n), true, nil
}
if len(b) != i {
return 0, false, syntaxError("ParseInt", string(b))
}
return int64(n), true, nil
}
func LenInt(i int64) int {
if i < 0 {
i = -i
}
switch {
case i < 10:
return 1
case i < 100:
return 2
case i < 1000:
return 3
case i < 10000:
return 4
case i < 100000:
return 5
case i < 1000000:
return 6
case i < 10000000:
return 7
case i < 100000000:
return 8
case i < 1000000000:
return 9
case i < 10000000000:
return 10
case i < 100000000000:
return 11
case i < 1000000000000:
return 12
case i < 10000000000000:
return 13
case i < 100000000000000:
return 14
case i < 1000000000000000:
return 15
case i < 10000000000000000:
return 16
case i < 100000000000000000:
return 17
case i < 1000000000000000000:
return 18
}
return 19
}