forked from jpillora/cloud-torrent
/
groupby.go
81 lines (71 loc) · 1.36 KB
/
groupby.go
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package itertools
type groupBy struct {
curKey interface{}
curKeyOk bool
curValue interface{}
keyFunc func(interface{}) interface{}
input Iterator
groupKey interface{}
groupKeyOk bool
}
type Group interface {
Iterator
Key() interface{}
}
type group struct {
gb *groupBy
key interface{}
first bool
}
func (me *group) Next() (ok bool) {
if me.first {
me.first = false
return true
}
me.gb.advance()
if !me.gb.curKeyOk || me.gb.curKey != me.key {
return
}
ok = true
return
}
func (me group) Value() (ret interface{}) {
ret = me.gb.curValue
return
}
func (me group) Key() interface{} {
return me.key
}
func (me *groupBy) advance() {
me.curKeyOk = me.input.Next()
if me.curKeyOk {
me.curValue = me.input.Value()
me.curKey = me.keyFunc(me.curValue)
}
}
func (me *groupBy) Next() (ok bool) {
for me.curKey == me.groupKey {
ok = me.input.Next()
if !ok {
return
}
me.curValue = me.input.Value()
me.curKey = me.keyFunc(me.curValue)
me.curKeyOk = true
}
me.groupKey = me.curKey
me.groupKeyOk = true
return true
}
func (me *groupBy) Value() (ret interface{}) {
return &group{me, me.groupKey, true}
}
func GroupBy(input Iterator, keyFunc func(interface{}) interface{}) Iterator {
if keyFunc == nil {
keyFunc = func(a interface{}) interface{} { return a }
}
return &groupBy{
input: input,
keyFunc: keyFunc,
}
}