/
map.go
216 lines (180 loc) · 4.39 KB
/
map.go
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package vm
import (
"bytes"
"errors"
"log"
)
type Map []byte
func CreateMap() Map {
return []byte{0x01, 0x00, 0x00}
}
func MapFromByteArray(m []byte) (Map, error) {
if len(m) <= 0 {
return Map{}, errors.New("empty map")
}
if m[0] != 0x01 {
return Map{}, errors.New("invalid datatype supplied")
}
return Map(m), nil
}
func (m *Map) getSize() (uint16, error) {
value, err := ByteArrayToUI16((*m)[1:3])
if err != nil {
return 0, errors.New("cannot get size of map")
}
return value, nil
}
func (m *Map) setSize(ba []byte) {
(*m)[1] = ba[0]
(*m)[2] = ba[1]
}
func (m *Map) IncrementSize() {
s, err := m.getSize()
if err != nil {
log.Fatal("could not increment size")
}
s++
m.setSize(UInt16ToByteArray(s))
}
func (m *Map) DecrementSize() error {
s, err := m.getSize()
if err != nil {
log.Fatal("could not decrement size")
}
if s <= 0 {
return errors.New("Map size already 0")
}
s--
m.setSize(UInt16ToByteArray(s))
return nil
}
func (m *Map) MapContainsKey(key []byte) (bool, error) {
offset := 3
l := len(*m)
for index := offset; index < l; {
if l == 3 {
return false, nil
}
k, keyEndsBefore, err := getElement(m, index)
sizeOfValue, err := getElementSize(m, keyEndsBefore)
if err != nil {
return false, err
}
valueStartsAt := keyEndsBefore //Just for better readability
if bytes.Equal(key, k) {
return true, err
}
valueEndsBefore := nextElementStartsAt(valueStartsAt, sizeOfValue)
if index == valueEndsBefore {
return false, errors.New("element sizes are 0")
}
index = valueEndsBefore
}
return false, nil
}
func (m *Map) Append(key []byte, value []byte) error {
sk := len(key)
sv := len(value)
if sk > int(UINT16_MAX) || sv > int(UINT16_MAX) {
return errors.New("key or value size overflows uint16")
}
tmp := append(*m, UInt16ToByteArray(uint16(sk))...)
tmp = append(tmp, key...)
tmp = append(tmp, UInt16ToByteArray(uint16(sv))...)
tmp = append(tmp, value...)
*m = tmp
m.IncrementSize()
return nil
}
func (m *Map) SetVal(key []byte, value []byte) error {
err := m.Remove(key)
m.Append(key, value)
if err != nil {
return err
}
return nil
}
func (m *Map) GetVal(key []byte) ([]byte, error) {
offset := 3
l := len(*m)
for index := offset; index < l; {
if l == 3 {
return []byte{}, errors.New("no elements in map")
}
k, valueStartsAt, err := getElement(m, index)
if err != nil {
return []byte{}, err
}
v, nextElementStartsAt, err := getElement(m, valueStartsAt)
if err != nil {
return []byte{}, err
}
if bytes.Equal(key, k) {
return v, nil
}
if index == nextElementStartsAt {
return []byte{}, errors.New("element sizes are 0")
}
index = nextElementStartsAt
}
return []byte{}, errors.New("key not found")
}
func (m *Map) Remove(key []byte) error {
offset := 3
l := len(*m)
for index := offset; index < l; {
if l == 3 {
return errors.New("no elements in map")
}
k, keyEndsBefore, err := getElement(m, index)
if err != nil {
return err
}
sizeOfValue, err := getElementSize(m, keyEndsBefore)
if err != nil {
return err
}
valueStartsAt := keyEndsBefore //Just for better readability
valueEndsBefore := nextElementStartsAt(valueStartsAt, sizeOfValue)
if bytes.Equal(key, k) {
tmp := append([]byte{}, (*m)[:index]...)
*m = append(tmp, (*m)[valueEndsBefore:]...)
m.DecrementSize()
return nil
}
if index == valueEndsBefore {
return errors.New("element sizes are 0")
}
index = valueEndsBefore
}
return errors.New("key not found")
}
func getElement(m *Map, startsAt int) (element []byte, endsBefore int, err error) {
size, err := getElementSize(m, startsAt)
if err != nil {
return []byte{}, 0, err
}
endsBefore = nextElementStartsAt(startsAt, size)
element, err = getBytesOfElement(m, startsAt, endsBefore)
if err != nil {
return []byte{}, 0, err
}
return element, endsBefore, err
}
func getBytesOfElement(m *Map, startsAt int, endsBefore int) ([]byte, error) {
if startsAt >= endsBefore {
return []byte{}, errors.New("can't retrieve element")
}
length := len(*m)
if length < startsAt+2 || length < endsBefore {
return []byte{}, errors.New("map internals error")
}
return (*m)[startsAt+2 : endsBefore], nil
}
func nextElementStartsAt(index int, elementSize uint16) int {
return index + 2 + int(elementSize)
}
func getElementSize(m *Map, index int) (uint16, error) {
elementSize, err := ByteArrayToUI16((*m)[index : index+2])
return elementSize, err
}