v1.4.7/internal/ipaddr/parse.go

// Copyright 2009 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// Simple file i/o and string manipulation, to avoid
// depending on strconv and bufio and strings.

package ipaddr

// Bigger than we need, not too big to worry about overflow
const big = 0xFFFFFF

// Decimal to integer.
// Returns number, characters consumed, success.
func dtoi(s string) (n int, i int, ok bool) {
	n = 0
	for i = 0; i < len(s) && '0' <= s[i] && s[i] <= '9'; i++ {
		n = n*10 + int(s[i]-'0')
		if n >= big {
			return big, i, false
		}
	}
	if i == 0 {
		return 0, 0, false
	}
	return n, i, true
}

// Hexadecimal to integer.
// Returns number, characters consumed, success.
func xtoi(s string) (n int, i int, ok bool) {
	n = 0
	for i = 0; i < len(s); i++ {
		if '0' <= s[i] && s[i] <= '9' {
			n *= 16
			n += int(s[i] - '0')
		} else if 'a' <= s[i] && s[i] <= 'f' {
			n *= 16
			n += int(s[i]-'a') + 10
		} else if 'A' <= s[i] && s[i] <= 'F' {
			n *= 16
			n += int(s[i]-'A') + 10
		} else {
			break
		}
		if n >= big {
			return 0, i, false
		}
	}
	if i == 0 {
		return 0, i, false
	}
	return n, i, true
}