replaced regex with faster impl for float parsing (quickfixgo#143)

* replaced regex with faster impl for float parsing

* added test cases for fix_float

Author: pdaures

fix_float.go

@@ -2,7 +2,6 @@ package quickfix
 
 import (
 	"fmt"
-	"regexp"
 	"strconv"
 )
 
@@ -22,8 +21,10 @@ func (f *FIXFloat) Read(bytes []byte) error {
 	}
 
 	//strconv allows values like "+100.00", which is not allowed for FIX float types
-	if valid, _ := regexp.MatchString("^[0-9.-]+$", string(bytes)); !valid {
-		return fmt.Errorf("invalid value %v", string(bytes))
+	for _, b := range bytes {
+		if b != '.' && b != '-' && !isDecimal(b) {
+			return fmt.Errorf("invalid value %v", string(bytes))
+		}
 	}
 
 	*f = FIXFloat(val)
@@ -34,3 +35,7 @@ func (f *FIXFloat) Read(bytes []byte) error {
 func (f FIXFloat) Write() []byte {
 	return []byte(strconv.FormatFloat(float64(f), 'f', -1, 64))
 }
+
+func isDecimal(b byte) bool {
+	return '0' <= b && b <= '9'
+}

fix_float_test.go

@@ -29,7 +29,12 @@ func TestFloatRead(t *testing.T) {
 		expectError bool
 	}{
 		{[]byte("15"), 15.0, false},
+		{[]byte("99.9"), 99.9, false},
+		{[]byte("0.00"), 0.0, false},
+		{[]byte("-99.9"), -99.9, false},
+		{[]byte("-99.9.9"), 0.0, true},
 		{[]byte("blah"), 0.0, true},
+		{[]byte("1.a1"), 0.0, true},
 		{[]byte("+200.00"), 0.0, true},
 	}
 
@@ -46,3 +51,11 @@ func TestFloatRead(t *testing.T) {
 		}
 	}
 }
+
+func BenchmarkFloatRead(b *testing.B) {
+	val := []byte("15.1234")
+	for i := 0; i < b.N; i++ {
+		var field FIXFloat
+		field.Read(val)
+	}
+}