// ScanEnum is a helper function to simplify the implementation of fmt.Scanner
// methods for "enum-like" types, that is, user-defined types where the set of
// values and string representations is fixed.
// ScanEnum allows multiple string representations for the same value.
//
// State is the state passed to the implementation of the fmt.Scanner method.
// Values holds as map values the values of the type, with their string
// representations as keys.
// If fold is true, comparison of the string representation uses
// strings.EqualFold, otherwise the equal operator for strings.
//
// On a match, ScanEnum stops after reading the last rune of the matched string,
// and returns the corresponding value together with a nil error.
// On no match, ScanEnum attempts to unread the last rune (the first rune that
// could not potentially match any of the values), and returns a non-nil error,
// together with a nil value for interface{}.
// On I/O error, ScanEnum returns the I/O error, together with a nil value for
// interface{}.
//
func scanEnum(state fmt.ScanState, values map[string]interface{}, fold bool) (
interface{}, error) {
//
rd := make([]rune, 0, scanEnumBufferHint)
keys := make(map[string]struct{}, len(values)) // potential keys
for s, _ := range values {
keys[s] = struct{}{}
}
for {
r, _, err := state.ReadRune()
if err != nil {
return nil, err
}
rd = append(rd, r)
srd := string(rd)
lrd := len(srd)
for s, _ := range keys {
if strEq(srd, s, fold) {
return values[s], nil
}
if len(rd) < len(s) && !strEq(srd, s[:lrd], fold) {
delete(keys, s)
}
}
if len(keys) == 0 {
state.UnreadRune()
return nil, fmt.Errorf("unsupported value %q", srd)
}
}
panic("never reached")
}
// Scan is a support routine for fmt.Scanner; it sets z to the value of
// the scanned number. It accepts the formats 'b' (binary), 'o' (octal),
// 'd' (decimal), 'x' (lowercase hexadecimal), and 'X' (uppercase hexadecimal).
func (z *Int) Scan(s fmt.ScanState, ch rune) error {
s.SkipSpace() // skip leading space characters
base := 0
switch ch {
case 'b':
base = 2
case 'o':
base = 8
case 'd':
base = 10
case 'x', 'X':
base = 16
case 's', 'v':
// let scan determine the base
case 'z':
base = 60
default:
return errors.New("Int.Scan: invalid verb")
}
charset := "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz."
if base != 0 {
charset = charset[:base]
}
// Read the number into in
in := make([]byte, 0, 16)
var err error
var n int
for {
ch, n, err = s.ReadRune()
if err == io.EOF {
break
}
if err != nil {
return err
}
if n > 1 {
// Wide character - must be the end
s.UnreadRune()
break
}
if len(in) == 0 {
if ch == '+' {
// Skip leading + as gmp doesn't understand them
continue
}
if ch == '-' {
goto ok
}
}
if len(in) == 1 && base == 0 {
if ch == 'b' || ch == 'x' {
goto ok
}
}
if !strings.ContainsRune(charset, ch) {
// Bad character - end
s.UnreadRune()
break
}
ok:
in = append(in, byte(ch))
}
// Use GMP to convert it as it is very efficient for large numbers
z.doinit()
// null terminate for C
in = append(in, 0)
if C.mpz_set_str(&z.i[0], (*C.char)(unsafe.Pointer(&in[0])), C.int(base)) < 0 {
return errors.New("Int.Scan: failed")
}
return nil
}