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// Copyright 2020 The gVisor 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 buffer provides the implementation of a buffer view.
//
// A view is an flexible buffer, supporting the safecopy operations natively as
// well as the ability to grow via either prepend or append, as well as shrink.
package buffer
// buffer encapsulates a queueable byte buffer.
//
// +stateify savable
type buffer struct {
data []byte
read int
write int
bufferEntry
}
// init performs in-place initialization for zero value.
func (b *buffer) init(size int) {
b.data = make([]byte, size)
}
// initWithData initializes b with data, taking ownership.
func (b *buffer) initWithData(data []byte) {
b.data = data
b.read = 0
b.write = len(data)
}
// Reset resets read and write locations, effectively emptying the buffer.
func (b *buffer) Reset() {
b.read = 0
b.write = 0
}
// Remove removes r from the unread portion. It returns false if r does not
// fully reside in b.
func (b *buffer) Remove(r Range) bool {
sz := b.ReadSize()
switch {
case r.Len() != r.Intersect(Range{end: sz}).Len():
return false
case r.Len() == 0:
// Noop
case r.begin == 0:
b.read += r.end
case r.end == sz:
b.write -= r.Len()
default:
// Remove from the middle of b.data.
copy(b.data[b.read+r.begin:], b.data[b.read+r.end:b.write])
b.write -= r.Len()
}
return true
}
// Full indicates the buffer is full.
//
// This indicates there is no capacity left to write.
func (b *buffer) Full() bool {
return b.write == len(b.data)
}
// ReadSize returns the number of bytes available for reading.
func (b *buffer) ReadSize() int {
return b.write - b.read
}
// ReadMove advances the read index by the given amount.
func (b *buffer) ReadMove(n int) {
b.read += n
}
// ReadSlice returns the read slice for this buffer.
func (b *buffer) ReadSlice() []byte {
return b.data[b.read:b.write]
}
// WriteSize returns the number of bytes available for writing.
func (b *buffer) WriteSize() int {
return len(b.data) - b.write
}
// WriteMove advances the write index by the given amount.
func (b *buffer) WriteMove(n int) {
b.write += n
}
// WriteSlice returns the write slice for this buffer.
func (b *buffer) WriteSlice() []byte {
return b.data[b.write:]
}
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