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inv.go
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inv.go
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// Copyright © 2011-12 Qtrac Ltd.
//
// This program or package and any associated files are licensed under the
// Apache License, Version 2.0 (the "License"); you may not use these files
// except in compliance with the License. You can get a copy of the License
// at: http://www.apache.org/licenses/LICENSE-2.0.
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package main
import (
"encoding/binary"
"errors"
"fmt"
"io"
"strconv"
"time"
)
type InvMarshaler struct{}
const invDateFormat = "20060102" // This date must always be used.
var byteOrder = binary.LittleEndian
func (InvMarshaler) MarshalInvoices(writer io.Writer,
invoices []*Invoice) error {
var write invWriterFunc = func(x interface{}) error {
return binary.Write(writer, byteOrder, x)
}
if err := write(uint32(magicNumber)); err != nil {
return err
}
if err := write(uint16(fileVersion)); err != nil {
return err
}
if err := write(int32(len(invoices))); err != nil {
return err
}
for _, invoice := range invoices {
if err := write.writeInvoice(invoice); err != nil {
return err
}
}
return nil
}
type invWriterFunc func(interface{}) error
func (write invWriterFunc) writeInvoice(invoice *Invoice) error {
for _, i := range []int{invoice.Id, invoice.CustomerId} {
if err := write(int32(i)); err != nil {
return err
}
}
for _, date := range []time.Time{invoice.Raised, invoice.Due} {
if err := write.writeDate(date); err != nil {
return err
}
}
if err := write.writeBool(invoice.Paid); err != nil {
return err
}
if err := write.writeString(invoice.Note); err != nil {
return err
}
if err := write(int32(len(invoice.Items))); err != nil {
return err
}
for _, item := range invoice.Items {
if err := write.writeItem(item); err != nil {
return err
}
}
return nil
}
func (write invWriterFunc) writeDate(date time.Time) error {
i, err := strconv.Atoi(date.Format(invDateFormat))
if err != nil {
return err
}
return write(int32(i))
}
func (write invWriterFunc) writeBool(b bool) error {
var v int8
if b {
v = 1
}
return write(v)
}
func (write invWriterFunc) writeString(s string) error {
if err := write(int32(len(s))); err != nil {
return err
}
return write([]byte(s))
}
func (write invWriterFunc) writeItem(item *Item) error {
if err := write.writeString(item.Id); err != nil {
return err
}
if err := write(item.Price); err != nil {
return err
}
if err := write(int16(item.Quantity)); err != nil {
return err
}
return write.writeString(item.Note)
}
func (InvMarshaler) UnmarshalInvoices(reader io.Reader) ([]*Invoice,
error) {
if err := checkInvVersion(reader); err != nil {
return nil, err
}
count, err := readIntFromInt32(reader)
if err != nil {
return nil, err
}
invoices := make([]*Invoice, 0, count)
for i := 0; i < count; i++ {
invoice, err := readInvInvoice(reader)
if err != nil {
return nil, err
}
invoices = append(invoices, invoice)
}
return invoices, nil
}
func readIntFromInt32(reader io.Reader) (int, error) {
var i32 int32
err := binary.Read(reader, byteOrder, &i32)
return int(i32), err
}
func readIntFromInt16(reader io.Reader) (int, error) {
var i16 int16
err := binary.Read(reader, byteOrder, &i16)
return int(i16), err
}
func readBoolFromInt8(reader io.Reader) (bool, error) {
var i8 int8
err := binary.Read(reader, byteOrder, &i8)
return i8 == 1, err
}
func checkInvVersion(reader io.Reader) error {
var magic uint32
if err := binary.Read(reader, byteOrder, &magic); err != nil {
return err
}
if magic != magicNumber {
return errors.New("cannot read non-invoices inv file")
}
var version uint16
if err := binary.Read(reader, byteOrder, &version); err != nil {
return err
}
if version > fileVersion {
return fmt.Errorf("version %d is too new to read", version)
}
return nil
}
func readInvInvoice(reader io.Reader) (invoice *Invoice, err error) {
invoice = &Invoice{}
for _, pId := range []*int{&invoice.Id, &invoice.CustomerId} {
if *pId, err = readIntFromInt32(reader); err != nil {
return nil, err
}
}
for _, pDate := range []*time.Time{&invoice.Raised, &invoice.Due} {
if *pDate, err = readInvDate(reader); err != nil {
return nil, err
}
}
if invoice.Paid, err = readBoolFromInt8(reader); err != nil {
return nil, err
}
if invoice.Note, err = readInvString(reader); err != nil {
return nil, err
}
var count int
if count, err = readIntFromInt32(reader); err != nil {
return nil, err
}
invoice.Items, err = readInvItems(reader, count)
return invoice, err
}
func readInvItems(reader io.Reader, count int) ([]*Item, error) {
items := make([]*Item, 0, count)
for i := 0; i < count; i++ {
item, err := readInvItem(reader)
if err != nil {
return nil, err
}
items = append(items, item)
}
return items, nil
}
func readInvDate(reader io.Reader) (time.Time, error) {
var n int32
if err := binary.Read(reader, byteOrder, &n); err != nil {
return time.Time{}, err
}
return time.Parse(invDateFormat, fmt.Sprint(n))
}
func readInvString(reader io.Reader) (string, error) {
var length int32
if err := binary.Read(reader, byteOrder, &length); err != nil {
return "", nil
}
raw := make([]byte, length)
if err := binary.Read(reader, byteOrder, &raw); err != nil {
return "", err
}
return string(raw), nil
}
func readInvItem(reader io.Reader) (item *Item, err error) {
item = &Item{}
if item.Id, err = readInvString(reader); err != nil {
return nil, err
}
if err = binary.Read(reader, byteOrder, &item.Price); err != nil {
return nil, err
}
if item.Quantity, err = readIntFromInt16(reader); err != nil {
return nil, err
}
item.Note, err = readInvString(reader)
return item, nil
}