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// 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_test
import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
"testing"
)
func pow2(i int) float64 {
switch {
case i < 0:
return 1 / pow2(-i)
case i == 0:
return 1
case i == 1:
return 2
}
return pow2(i/2) * pow2(i-i/2)
}
// Wrapper around strconv.ParseFloat(x, 64). Handles dddddp+ddd (binary exponent)
// itself, passes the rest on to strconv.ParseFloat.
func myatof64(s string) (f float64, ok bool) {
if mant, exp, ok := strings.Cut(s, "p"); ok {
n, err := strconv.ParseInt(mant, 10, 64)
if err != nil {
return 0, false
}
e, err1 := strconv.Atoi(exp)
if err1 != nil {
println("bad e", exp)
return 0, false
}
v := float64(n)
// We expect that v*pow2(e) fits in a float64,
// but pow2(e) by itself may not. Be careful.
if e <= -1000 {
v *= pow2(-1000)
e += 1000
for e < 0 {
v /= 2
e++
}
return v, true
}
if e >= 1000 {
v *= pow2(1000)
e -= 1000
for e > 0 {
v *= 2
e--
}
return v, true
}
return v * pow2(e), true
}
f1, err := strconv.ParseFloat(s, 64)
if err != nil {
return 0, false
}
return f1, true
}
// Wrapper around strconv.ParseFloat(x, 32). Handles dddddp+ddd (binary exponent)
// itself, passes the rest on to strconv.ParseFloat.
func myatof32(s string) (f float32, ok bool) {
if mant, exp, ok := strings.Cut(s, "p"); ok {
n, err := strconv.Atoi(mant)
if err != nil {
println("bad n", mant)
return 0, false
}
e, err1 := strconv.Atoi(exp)
if err1 != nil {
println("bad p", exp)
return 0, false
}
return float32(float64(n) * pow2(e)), true
}
f64, err1 := strconv.ParseFloat(s, 32)
f1 := float32(f64)
if err1 != nil {
return 0, false
}
return f1, true
}
func TestFp(t *testing.T) {
f, err := os.Open("testdata/testfp.txt")
if err != nil {
t.Fatal("testfp: open testdata/testfp.txt:", err)
}
defer f.Close()
s := bufio.NewScanner(f)
for lineno := 1; s.Scan(); lineno++ {
line := s.Text()
if len(line) == 0 || line[0] == '#' {
continue
}
a := strings.Split(line, " ")
if len(a) != 4 {
t.Error("testdata/testfp.txt:", lineno, ": wrong field count")
continue
}
var s string
var v float64
switch a[0] {
case "float64":
var ok bool
v, ok = myatof64(a[2])
if !ok {
t.Error("testdata/testfp.txt:", lineno, ": cannot atof64 ", a[2])
continue
}
s = fmt.Sprintf(a[1], v)
case "float32":
v1, ok := myatof32(a[2])
if !ok {
t.Error("testdata/testfp.txt:", lineno, ": cannot atof32 ", a[2])
continue
}
s = fmt.Sprintf(a[1], v1)
v = float64(v1)
}
if s != a[3] {
t.Error("testdata/testfp.txt:", lineno, ": ", a[0], " ", a[1], " ", a[2], " (", v, ") ",
"want ", a[3], " got ", s)
}
}
if s.Err() != nil {
t.Fatal("testfp: read testdata/testfp.txt: ", s.Err())
}
}
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