big: make Int and Rat implement fmt.Scanner

R=gri
CC=golang-dev
https://golang.org/cl/4552056

src/pkg/big/int.go

@@ -10,6 +10,7 @@ import (
 	"fmt"
 	"os"
 	"rand"
+	"strings"
 )
 
 // An Int represents a signed multi-precision integer.
@@ -325,7 +326,7 @@ func charset(ch int) string {
 		return lowercaseDigits[0:2]
 	case 'o':
 		return lowercaseDigits[0:8]
-	case 'd', 'v':
+	case 'd', 's', 'v':
 		return lowercaseDigits[0:10]
 	case 'x':
 		return lowercaseDigits[0:16]
@@ -374,6 +375,49 @@ func (x *Int) Format(s fmt.State, ch int) {
 }
 
 
+// Scan is a support routine for fmt.Scanner. It accepts the formats
+// 'b' (binary), 'o' (octal), 'd' (decimal), 'x' (lowercase hexadecimal),
+// and 'X' (uppercase hexadecimal).
+func (x *Int) Scan(s fmt.ScanState, ch int) os.Error {
+	var base int
+	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
+	default:
+		return os.ErrorString("Int.Scan: invalid verb")
+	}
+
+	ch, _, err := s.ReadRune()
+	if err != nil {
+		return err
+	}
+	neg := false
+	switch ch {
+	case '-':
+		neg = true
+	case '+': // nothing to do
+	default:
+		s.UnreadRune()
+	}
+
+	x.abs, _, err = x.abs.scan(s, base)
+	if err != nil {
+		return err
+	}
+	x.neg = len(x.abs) > 0 && neg // 0 has no sign
+
+	return nil
+}
+
+
 // Int64 returns the int64 representation of z.
 // If z cannot be represented in an int64, the result is undefined.
 func (x *Int) Int64() int64 {
@@ -401,26 +445,27 @@ func (x *Int) Int64() int64 {
 // base 2. Otherwise the selected base is 10.
 //
 func (z *Int) SetString(s string, base int) (*Int, bool) {
-	if len(s) == 0 || base < 0 || base == 1 || 16 < base {
-		return z, false
-	}
-
-	neg := s[0] == '-'
-	if neg || s[0] == '+' {
+	neg := false
+	if len(s) > 0 {
+		switch s[0] {
+		case '-':
+			neg = true
+			fallthrough
+		case '+':
 			s = s[1:]
-		if len(s) == 0 {
-			return z, false
 		}
 	}
 
-	var scanned int
-	z.abs, _, scanned = z.abs.scan(s, base)
-	if scanned != len(s) {
+	r := strings.NewReader(s)
+	abs, _, err := z.abs.scan(r, base)
+	if err != nil {
 		return z, false
 	}
-	z.neg = len(z.abs) > 0 && neg // 0 has no sign
+	_, _, err = r.ReadRune()
 
-	return z, true
+	z.abs = abs
+	z.neg = len(abs) > 0 && neg // 0 has no sign
+	return z, err == os.EOF     // err == os.EOF => scan consumed all of s
 }
 
 
@@ -784,11 +829,11 @@ func (z *Int) GobEncode() ([]byte, os.Error) {
 // GobDecode implements the gob.GobDecoder interface.
 func (z *Int) GobDecode(buf []byte) os.Error {
 	if len(buf) == 0 {
-		return os.NewError("Int.GobDecode: no data")
+		return os.ErrorString("Int.GobDecode: no data")
 	}
 	b := buf[0]
 	if b>>1 != version {
-		return os.NewError(fmt.Sprintf("Int.GobDecode: encoding version %d not supported", b>>1))
+		return os.ErrorString(fmt.Sprintf("Int.GobDecode: encoding version %d not supported", b>>1))
 	}
 	z.neg = b&1 != 0
 	z.abs = z.abs.setBytes(buf[1:])

src/pkg/big/int_test.go

@@ -397,6 +397,49 @@ func TestFormat(t *testing.T) {
 }
 
 
+var scanTests = []struct {
+	input     string
+	format    string
+	output    string
+	remaining int
+}{
+	{"1010", "%b", "10", 0},
+	{"0b1010", "%v", "10", 0},
+	{"12", "%o", "10", 0},
+	{"012", "%v", "10", 0},
+	{"10", "%d", "10", 0},
+	{"10", "%v", "10", 0},
+	{"a", "%x", "10", 0},
+	{"0xa", "%v", "10", 0},
+	{"A", "%X", "10", 0},
+	{"-A", "%X", "-10", 0},
+	{"+0b1011001", "%v", "89", 0},
+	{"0xA", "%v", "10", 0},
+	{"0 ", "%v", "0", 1},
+	{"2+3", "%v", "2", 2},
+	{"0XABC 12", "%v", "2748", 3},
+}
+
+
+func TestScan(t *testing.T) {
+	var buf bytes.Buffer
+	for i, test := range scanTests {
+		x := new(Int)
+		buf.Reset()
+		buf.WriteString(test.input)
+		if _, err := fmt.Fscanf(&buf, test.format, x); err != nil {
+			t.Errorf("#%d error: %s", i, err.String())
+		}
+		if x.String() != test.output {
+			t.Errorf("#%d got %s; want %s", i, x.String(), test.output)
+		}
+		if buf.Len() != test.remaining {
+			t.Errorf("#%d got %d bytes remaining; want %d", i, buf.Len(), test.remaining)
+		}
+	}
+}
+
+
 // Examples from the Go Language Spec, section "Arithmetic operators"
 var divisionSignsTests = []struct {
 	x, y int64

src/pkg/big/nat.go

@@ -18,7 +18,11 @@ package big
 // These are the building blocks for the operations on signed integers
 // and rationals.
 
-import "rand"
+import (
+	"io"
+	"os"
+	"rand"
+)
 
 
 // An unsigned integer x of the form
@@ -604,68 +608,95 @@ func (x nat) bitLen() int {
 }
 
 
-func hexValue(ch byte) int {
-	var d byte
+func hexValue(ch int) int {
+	var d int
 	switch {
 	case '0' <= ch && ch <= '9':
 		d = ch - '0'
-	case 'a' <= ch && ch <= 'f':
+	case 'a' <= ch && ch <= 'z':
 		d = ch - 'a' + 10
-	case 'A' <= ch && ch <= 'F':
+	case 'A' <= ch && ch <= 'Z':
 		d = ch - 'A' + 10
 	default:
 		return -1
 	}
-	return int(d)
+	return d
 }
 
 
-// scan returns the natural number corresponding to the
-// longest possible prefix of s representing a natural number in a
-// given conversion base, the actual conversion base used, and the
-// prefix length. The syntax of natural numbers follows the syntax
-// of unsigned integer literals in Go.
+// scan returns the natural number corresponding to the longest
+// possible prefix read from r representing a natural number in a
+// given conversion base, the actual conversion base used, and an
+// error, if any. The syntax of natural numbers follows the syntax of
+// unsigned integer literals in Go.
 //
 // If the base argument is 0, the string prefix determines the actual
 // conversion base. A prefix of ``0x'' or ``0X'' selects base 16; the
 // ``0'' prefix selects base 8, and a ``0b'' or ``0B'' prefix selects
 // base 2. Otherwise the selected base is 10.
 //
-func (z nat) scan(s string, base int) (nat, int, int) {
+func (z nat) scan(r io.RuneScanner, base int) (nat, int, os.Error) {
+	n := 0
+	ch, _, err := r.ReadRune()
+	if err != nil {
+		return z, 0, err
+	}
 	// determine base if necessary
-	i, n := 0, len(s)
 	if base == 0 {
 		base = 10
-		if n > 0 && s[0] == '0' {
-			base, i = 8, 1
-			if n > 1 {
-				switch s[1] {
+		if ch == '0' {
+			n++
+			switch ch, _, err = r.ReadRune(); err {
+			case nil:
+				base = 8
+				switch ch {
 				case 'x', 'X':
-					base, i = 16, 2
+					base = 16
 				case 'b', 'B':
-					base, i = 2, 2
+					base = 2
 				}
+				if base == 2 || base == 16 {
+					n--
+					if ch, _, err = r.ReadRune(); err != nil {
+						return z, 0, os.ErrorString("syntax error scanning binary or hexadecimal number")
+					}
+				}
+			case os.EOF:
+				return z, 10, nil
+			default:
+				return z, 0, err
 			}
 		}
 	}
 
-	// reject illegal bases or strings consisting only of prefix
-	if base < 2 || 16 < base || (base != 8 && i >= n) {
-		return z, 0, 0
+	// reject illegal bases
+	if base < 2 || 'z'-'a'+10 < base {
+		return z, 0, os.ErrorString("illegal number base")
 	}
 
 	// convert string
 	z = z.make(0)
-	for ; i < n; i++ {
-		d := hexValue(s[i])
+	for {
+		d := hexValue(ch)
 		if 0 <= d && d < base {
 			z = z.mulAddWW(z, Word(base), Word(d))
 		} else {
+			r.UnreadRune()
+			if n > 0 {
+				break
+			}
+			return z, 0, os.ErrorString("syntax error scanning number")
+		}
+		n++
+		if ch, _, err = r.ReadRune(); err != nil {
+			if err == os.EOF {
 				break
 			}
+			return z, 0, err
+		}
 	}
 
-	return z.norm(), base, i
+	return z.norm(), base, nil
 }
 
 

src/pkg/big/nat_test.go

@@ -4,7 +4,10 @@
 
 package big
 
-import "testing"
+import (
+	"strings"
+	"testing"
+)
 
 var cmpTests = []struct {
 	x, y nat
@@ -180,6 +183,8 @@ var strTests = []struct {
 	{nat{1234567890}, uppercaseDigits[0:10], "1234567890"},
 	{nat{0xdeadbeef}, lowercaseDigits[0:16], "deadbeef"},
 	{nat{0xdeadbeef}, uppercaseDigits[0:16], "DEADBEEF"},
+	{nat{0x229be7}, lowercaseDigits[0:17], "1a2b3c"},
+	{nat{0x309663e6}, uppercaseDigits[0:32], "O9COV6"},
 }
 
 
@@ -190,15 +195,58 @@ func TestString(t *testing.T) {
 			t.Errorf("string%+v\n\tgot s = %s; want %s", a, s, a.s)
 		}
 
-		x, b, n := nat(nil).scan(a.s, len(a.c))
+		x, b, err := nat(nil).scan(strings.NewReader(a.s), len(a.c))
 		if x.cmp(a.x) != 0 {
 			t.Errorf("scan%+v\n\tgot z = %v; want %v", a, x, a.x)
 		}
 		if b != len(a.c) {
 			t.Errorf("scan%+v\n\tgot b = %d; want %d", a, b, len(a.c))
 		}
-		if n != len(a.s) {
-			t.Errorf("scan%+v\n\tgot n = %d; want %d", a, n, len(a.s))
+		if err != nil {
+			t.Errorf("scan%+v\n\tgot error = %s", a, err)
+		}
+	}
+}
+
+
+var natScanTests = []struct {
+	s    string // string to be scanned
+	x    nat    // expected nat
+	base int    // expected base
+	ok   bool   // expected success
+}{
+	{s: ""},
+	{"0", nil, 10, true},
+	{"0 ", nil, 8, true},
+	{s: "0x"},
+	{"08", nil, 8, true},
+	{"0b1", nat{1}, 2, true},
+	{"0b11000101", nat{0xc5}, 2, true},
+	{"03271", nat{03271}, 8, true},
+	{"10ab", nat{10}, 10, true},
+	{"1234567890", nat{1234567890}, 10, true},
+	{"0xdeadbeef", nat{0xdeadbeef}, 16, true},
+	{"0XDEADBEEF", nat{0xdeadbeef}, 16, true},
+}
+
+
+func TestScanBase0(t *testing.T) {
+	for _, a := range natScanTests {
+		x, b, err := nat(nil).scan(strings.NewReader(a.s), 0)
+		if err == nil && !a.ok {
+			t.Errorf("scan%+v\n\texpected error", a)
+		}
+		if err != nil {
+			if a.ok {
+				t.Errorf("scan%+v\n\tgot error = %s", a, err)
+			}
+			continue
+		}
+		if x.cmp(a.x) != 0 {
+			t.Errorf("scan%+v\n\tgot z = %v; want %v", a, x, a.x)
+		}
+		if b != a.base {
+			t.Errorf("scan%+v\n\tgot b = %d; want %d", a, b, a.base)
 		}
 	}
 }
@@ -344,14 +392,14 @@ var expNNTests = []struct {
 
 func TestExpNN(t *testing.T) {
 	for i, test := range expNNTests {
-		x, _, _ := nat(nil).scan(test.x, 0)
-		y, _, _ := nat(nil).scan(test.y, 0)
-		out, _, _ := nat(nil).scan(test.out, 0)
+		x, _, _ := nat(nil).scan(strings.NewReader(test.x), 0)
+		y, _, _ := nat(nil).scan(strings.NewReader(test.y), 0)
+		out, _, _ := nat(nil).scan(strings.NewReader(test.out), 0)
 
 		var m nat
 
 		if len(test.m) > 0 {
-			m, _, _ = nat(nil).scan(test.m, 0)
+			m, _, _ = nat(nil).scan(strings.NewReader(test.m), 0)
 		}
 
 		z := nat(nil).expNN(x, y, m)

src/pkg/big/rat.go

@@ -6,7 +6,11 @@
 
 package big
 
-import "strings"
+import (
+	"fmt"
+	"os"
+	"strings"
+)
 
 // A Rat represents a quotient a/b of arbitrary precision. The zero value for
 // a Rat, 0/0, is not a legal Rat.
@@ -209,6 +213,28 @@ func (z *Rat) Set(x *Rat) *Rat {
 }
 
 
+func ratTok(ch int) bool {
+	return strings.IndexRune("+-/0123456789.eE", ch) >= 0
+}
+
+
+// Scan is a support routine for fmt.Scanner. It accepts the formats
+// 'e', 'E', 'f', 'F', 'g', 'G', and 'v'. All formats are equivalent.
+func (z *Rat) Scan(s fmt.ScanState, ch int) os.Error {
+	tok, err := s.Token(true, ratTok)
+	if err != nil {
+		return err
+	}
+	if strings.IndexRune("efgEFGv", ch) < 0 {
+		return os.ErrorString("Rat.Scan: invalid verb")
+	}
+	if _, ok := z.SetString(string(tok)); !ok {
+		return os.ErrorString("Rat.Scan: invalid syntax")
+	}
+	return nil
+}
+
+
 // SetString sets z to the value of s and returns z and a boolean indicating
 // success. s can be given as a fraction "a/b" or as a floating-point number
 // optionally followed by an exponent. If the operation failed, the value of z
@@ -225,8 +251,8 @@ func (z *Rat) SetString(s string) (*Rat, bool) {
 			return z, false
 		}
 		s = s[sep+1:]
-		var n int
-		if z.b, _, n = z.b.scan(s, 10); n != len(s) {
+		var err os.Error
+		if z.b, _, err = z.b.scan(strings.NewReader(s), 10); err != nil {
 			return z, false
 		}
 		return z.norm(), true

src/pkg/big/rat_test.go

@@ -4,7 +4,11 @@
 
 package big
 
-import "testing"
+import (
+	"bytes"
+	"fmt"
+	"testing"
+)
 
 
 var setStringTests = []struct {
@@ -53,6 +57,29 @@ func TestRatSetString(t *testing.T) {
 }
 
 
+func TestRatScan(t *testing.T) {
+	var buf bytes.Buffer
+	for i, test := range setStringTests {
+		x := new(Rat)
+		buf.Reset()
+		buf.WriteString(test.in)
+
+		_, err := fmt.Fscanf(&buf, "%v", x)
+		if err == nil != test.ok {
+			if test.ok {
+				t.Errorf("#%d error: %s", i, err.String())
+			} else {
+				t.Errorf("#%d expected error", i)
+			}
+			continue
+		}
+		if err == nil && x.RatString() != test.out {
+			t.Errorf("#%d got %s want %s", i, x.RatString(), test.out)
+		}
+	}
+}
+
+
 var floatStringTests = []struct {
 	in   string
 	prec int