commit fd762e496aab787a20c0c48a42eb8a8e065be1ea
Author: Martin Schanzenbach <schanzen@gnunet.org>
Date: Sat, 16 Jul 2022 19:44:53 +0200
initial commit
Diffstat:
4 files changed, 179 insertions(+), 0 deletions(-)
diff --git a/go.mod b/go.mod
@@ -0,0 +1,3 @@
+module taler.net/taler-util
+
+go 1.18
diff --git a/main.go b/main.go
@@ -0,0 +1,9 @@
+package main
+
+import(
+ "fmt"
+)
+
+func main() {
+ fmt.Println(ParseAmount("EUR:1.5"))
+}
diff --git a/pkg/taler/amount.go b/pkg/taler/amount.go
@@ -0,0 +1,117 @@
+package taler
+
+import(
+ "errors"
+ "regexp"
+ "strconv"
+ "fmt"
+ "math"
+ "strings"
+)
+
+// The GNU Taler Amount ob
+type Amount struct {
+
+ // The type of currency, e.g. EUR
+ Currency string
+
+ // The value (before the ".")
+ Value uint64
+
+ // The fraction (after the ".", optional)
+ Fraction uint64
+}
+
+const FractionalLength = 8
+
+const FractionalBase = 1e8
+
+const MaxAmountValue = 2^52
+
+func NewAmount(currency string, value uint64, fraction uint64) Amount {
+ return Amount{
+ Currency: currency,
+ Value: value,
+ Fraction: fraction,
+ }
+}
+
+func (a *Amount) Sub(b Amount) (*Amount,error) {
+ if a.Currency != b.Currency {
+ return nil, errors.New("Currency mismatch!")
+ }
+ v := a.Value
+ f := a.Fraction
+ if a.Fraction < b.Fraction {
+ v -= 1
+ f += FractionalBase
+ }
+ f -= b.Fraction
+ if v < b.Value {
+ return nil, errors.New("Amount Overflow!")
+ }
+ v -= b.Value
+ r := Amount{
+ Currency: a.Currency,
+ Value: v,
+ Fraction: f,
+ }
+ return &r, nil
+}
+
+func (a *Amount) Add(b Amount) (*Amount,error) {
+ if a.Currency != b.Currency {
+ return nil, errors.New("Currency mismatch!")
+ }
+ v := a.Value +
+ b.Value +
+ uint64(math.Floor((float64(a.Fraction) + float64(b.Fraction)) / FractionalBase))
+
+ if v >= MaxAmountValue {
+ return nil, errors.New("Amount Overflow!")
+ }
+ f := uint64((a.Fraction + b.Fraction) % FractionalBase)
+ r := Amount{
+ Currency: a.Currency,
+ Value: v,
+ Fraction: f,
+ }
+ return &r, nil
+}
+func ParseAmount(s string) (*Amount,error) {
+ re, err := regexp.Compile(`^\s*([-_*A-Za-z0-9]+):([0-9]+)\.?([0-9]+)?\s*$`)
+ parsed := re.FindStringSubmatch(s)
+
+ if nil != err {
+ return nil, errors.New(fmt.Sprintf("invalid amount: %s", s))
+ }
+ tail := "0.0"
+ if len(parsed) >= 4 {
+ tail = "0." + parsed[3]
+ }
+ if len(tail) > FractionalLength + 1 {
+ return nil, errors.New("fraction too long")
+ }
+ value, err := strconv.ParseUint(parsed[2], 10, 64)
+ if nil != err {
+ return nil, errors.New(fmt.Sprintf("Unable to parse value %s", parsed[2]))
+ }
+ fractionF, err := strconv.ParseFloat(tail, 64)
+ if nil != err {
+ return nil, errors.New(fmt.Sprintf("Unable to parse fraction %s", tail))
+ }
+ fraction := uint64(math.Round(fractionF * FractionalBase))
+ currency := parsed[1]
+ a := NewAmount(currency, value, fraction)
+ return &a, nil
+}
+
+func (a *Amount) String() string {
+ v := strconv.FormatUint(a.Value, 10)
+ if a.Fraction != 0 {
+ f := strconv.FormatUint(a.Fraction, 10)
+ f = strings.TrimRight(f, "0")
+ v = fmt.Sprintf("%s.%s", v, f)
+ }
+ return fmt.Sprintf("%s:%s", a.Currency, v)
+}
diff --git a/pkg/taler/amount_test.go b/pkg/taler/amount_test.go
@@ -0,0 +1,50 @@
+package taler
+
+import (
+ "testing"
+)
+
+var a = Amount{
+ Currency: "EUR",
+ Value: 1,
+ Fraction: 50000000,
+}
+var b = Amount{
+ Currency: "EUR",
+ Value: 23,
+ Fraction: 70007000,
+}
+var c = Amount{
+ Currency: "EUR",
+ Value: 25,
+ Fraction: 20007000,
+}
+
+
+
+
+func TestAmountAdd(t *testing.T) {
+ d, err := a.Add(b)
+ if err != nil {
+ t.Errorf("Failed adding amount")
+ }
+ if c.String() != d.String() {
+ t.Errorf("Failed to add to correct amount")
+ }
+}
+
+func TestAmountSub(t *testing.T) {
+ d, err := c.Sub(b)
+ if err != nil {
+ t.Errorf("Failed substracting amount")
+ }
+ if a.String() != d.String() {
+ t.Errorf("Failed to substract to correct amount")
+ }
+}
+
+func TestAmountString(t *testing.T) {
+ if c.String() != "EUR:25.20007" {
+ t.Errorf("Failed to generate correct string")
+ }
+}
