1 files changed, 198 insertions, 0 deletions
diff --git a/src/strconv/atoi.go b/src/strconv/atoi.go
new file mode 100644
index 000000000..9ecec5a58
--- /dev/null
+++ b/src/strconv/atoi.go
@@ -0,0 +1,198 @@
+// 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.
+
+package strconv
+
+import "errors"
+
+// ErrRange indicates that a value is out of range for the target type.
+var ErrRange = errors.New("value out of range")
+
+// ErrSyntax indicates that a value does not have the right syntax for the target type.
+var ErrSyntax = errors.New("invalid syntax")
+
+// A NumError records a failed conversion.
+type NumError struct {
+	Func string // the failing function (ParseBool, ParseInt, ParseUint, ParseFloat)
+	Num  string // the input
+	Err  error  // the reason the conversion failed (ErrRange, ErrSyntax)
+}
+
+func (e *NumError) Error() string {
+	return "strconv." + e.Func + ": " + "parsing " + Quote(e.Num) + ": " + e.Err.Error()
+}
+
+func syntaxError(fn, str string) *NumError {
+	return &NumError{fn, str, ErrSyntax}
+}
+
+func rangeError(fn, str string) *NumError {
+	return &NumError{fn, str, ErrRange}
+}
+
+const intSize = 32 << (^uint(0) >> 63)
+
+// IntSize is the size in bits of an int or uint value.
+const IntSize = intSize
+
+// Return the first number n such that n*base >= 1<<64.
+func cutoff64(base int) uint64 {
+	if base < 2 {
+		return 0
+	}
+	return (1<<64-1)/uint64(base) + 1
+}
+
+// ParseUint is like ParseInt but for unsigned numbers.
+func ParseUint(s string, base int, bitSize int) (n uint64, err error) {
+	var cutoff, maxVal uint64
+
+	if bitSize == 0 {
+		bitSize = int(IntSize)
+	}
+
+	s0 := s
+	switch {
+	case len(s) < 1:
+		err = ErrSyntax
+		goto Error
+
+	case 2 <= base && base <= 36:
+		// valid base; nothing to do
+
+	case base == 0:
+		// Look for octal, hex prefix.
+		switch {
+		case s[0] == '0' && len(s) > 1 && (s[1] == 'x' || s[1] == 'X'):
+			base = 16
+			s = s[2:]
+			if len(s) < 1 {
+				err = ErrSyntax
+				goto Error
+			}
+		case s[0] == '0':
+			base = 8
+		default:
+			base = 10
+		}
+
+	default:
+		err = errors.New("invalid base " + Itoa(base))
+		goto Error
+	}
+
+	n = 0
+	cutoff = cutoff64(base)
+	maxVal = 1<<uint(bitSize) - 1
+
+	for i := 0; i < len(s); i++ {
+		var v byte
+		d := s[i]
+		switch {
+		case '0' <= d && d <= '9':
+			v = d - '0'
+		case 'a' <= d && d <= 'z':
+			v = d - 'a' + 10
+		case 'A' <= d && d <= 'Z':
+			v = d - 'A' + 10
+		default:
+			n = 0
+			err = ErrSyntax
+			goto Error
+		}
+		if int(v) >= base {
+			n = 0
+			err = ErrSyntax
+			goto Error
+		}
+
+		if n >= cutoff {
+			// n*base overflows
+			n = 1<<64 - 1
+			err = ErrRange
+			goto Error
+		}
+		n *= uint64(base)
+
+		n1 := n + uint64(v)
+		if n1 < n || n1 > maxVal {
+			// n+v overflows
+			n = 1<<64 - 1
+			err = ErrRange
+			goto Error
+		}
+		n = n1
+	}
+
+	return n, nil
+
+Error:
+	return n, &NumError{"ParseUint", s0, err}
+}
+
+// ParseInt interprets a string s in the given base (2 to 36) and
+// returns the corresponding value i.  If base == 0, the base is
+// implied by the string's prefix: base 16 for "0x", base 8 for
+// "0", and base 10 otherwise.
+//
+// The bitSize argument specifies the integer type
+// that the result must fit into.  Bit sizes 0, 8, 16, 32, and 64
+// correspond to int, int8, int16, int32, and int64.
+//
+// The errors that ParseInt returns have concrete type *NumError
+// and include err.Num = s.  If s is empty or contains invalid
+// digits, err.Err = ErrSyntax and the returned value is 0;
+// if the value corresponding to s cannot be represented by a
+// signed integer of the given size, err.Err = ErrRange and the
+// returned value is the maximum magnitude integer of the
+// appropriate bitSize and sign.
+func ParseInt(s string, base int, bitSize int) (i int64, err error) {
+	const fnParseInt = "ParseInt"
+
+	if bitSize == 0 {
+		bitSize = int(IntSize)
+	}
+
+	// Empty string bad.
+	if len(s) == 0 {
+		return 0, syntaxError(fnParseInt, s)
+	}
+
+	// Pick off leading sign.
+	s0 := s
+	neg := false
+	if s[0] == '+' {
+		s = s[1:]
+	} else if s[0] == '-' {
+		neg = true
+		s = s[1:]
+	}
+
+	// Convert unsigned and check range.
+	var un uint64
+	un, err = ParseUint(s, base, bitSize)
+	if err != nil && err.(*NumError).Err != ErrRange {
+		err.(*NumError).Func = fnParseInt
+		err.(*NumError).Num = s0
+		return 0, err
+	}
+	cutoff := uint64(1 << uint(bitSize-1))
+	if !neg && un >= cutoff {
+		return int64(cutoff - 1), rangeError(fnParseInt, s0)
+	}
+	if neg && un > cutoff {
+		return -int64(cutoff), rangeError(fnParseInt, s0)
+	}
+	n := int64(un)
+	if neg {
+		n = -n
+	}
+	return n, nil
+}
+
+// Atoi is shorthand for ParseInt(s, 10, 0).
+func Atoi(s string) (i int, err error) {
+	i64, err := ParseInt(s, 10, 0)
+	return int(i64), err
+}