| // 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:] |
| } |