mirror of https://github.com/perkeep/perkeep.git
88 lines
2.0 KiB
Go
88 lines
2.0 KiB
Go
/*
|
|
Copyright 2011 The Perkeep Authors
|
|
|
|
Licensed under the Apache License, Version 2.0 (the "License");
|
|
you may not use this file except in compliance with the License.
|
|
You may obtain 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 blob
|
|
|
|
// ChanPeeker wraps a channel receiving SizedRefs and adds a 1 element
|
|
// buffer on it, with Peek and Take methods.
|
|
type ChanPeeker struct {
|
|
Ch <-chan SizedRef
|
|
|
|
// Invariant after a call to Peek: either peekok or closed.
|
|
closed bool
|
|
peekok bool // whether peek is valid
|
|
peek SizedRef
|
|
}
|
|
|
|
// MustPeek returns the next SizedRef or panics if none is available.
|
|
func (cp *ChanPeeker) MustPeek() SizedRef {
|
|
sr, ok := cp.Peek()
|
|
if !ok {
|
|
panic("No Peek value available")
|
|
}
|
|
return sr
|
|
}
|
|
|
|
// Peek returns the next SizedRef and whether one was available.
|
|
func (cp *ChanPeeker) Peek() (sr SizedRef, ok bool) {
|
|
if cp.closed {
|
|
return
|
|
}
|
|
if cp.peekok {
|
|
return cp.peek, true
|
|
}
|
|
v, ok := <-cp.Ch
|
|
if !ok {
|
|
cp.closed = true
|
|
return
|
|
}
|
|
cp.peek = v
|
|
cp.peekok = true
|
|
return cp.peek, true
|
|
}
|
|
|
|
// Closed reports true if no more SizedRef values are available.
|
|
func (cp *ChanPeeker) Closed() bool {
|
|
cp.Peek()
|
|
return cp.closed
|
|
}
|
|
|
|
// MustTake returns the next SizedRef, else panics if none is available.
|
|
func (cp *ChanPeeker) MustTake() SizedRef {
|
|
sr, ok := cp.Take()
|
|
if !ok {
|
|
panic("MustTake called on empty channel")
|
|
}
|
|
return sr
|
|
}
|
|
|
|
// Take returns the next SizedRef and whether one was available for the taking.
|
|
func (cp *ChanPeeker) Take() (sr SizedRef, ok bool) {
|
|
v, ok := cp.Peek()
|
|
if !ok {
|
|
return
|
|
}
|
|
cp.peekok = false
|
|
return v, true
|
|
}
|
|
|
|
// ConsumeAll drains the channel of all items.
|
|
func (cp *ChanPeeker) ConsumeAll() {
|
|
for !cp.Closed() {
|
|
cp.Take()
|
|
}
|
|
}
|