inet.af/netstack@v0.0.0-20220214151720-7585b01ddccf/buffer/buffer.go (about)

     1  // Copyright 2020 The gVisor Authors.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  // Package buffer provides the implementation of a buffer view.
    16  //
    17  // A view is an flexible buffer, supporting the safecopy operations natively as
    18  // well as the ability to grow via either prepend or append, as well as shrink.
    19  package buffer
    20  
    21  // buffer encapsulates a queueable byte buffer.
    22  //
    23  // +stateify savable
    24  type buffer struct {
    25  	data  []byte
    26  	read  int
    27  	write int
    28  	bufferEntry
    29  }
    30  
    31  // init performs in-place initialization for zero value.
    32  func (b *buffer) init(size int) {
    33  	b.data = make([]byte, size)
    34  }
    35  
    36  // initWithData initializes b with data, taking ownership.
    37  func (b *buffer) initWithData(data []byte) {
    38  	b.data = data
    39  	b.read = 0
    40  	b.write = len(data)
    41  }
    42  
    43  // Reset resets read and write locations, effectively emptying the buffer.
    44  func (b *buffer) Reset() {
    45  	b.read = 0
    46  	b.write = 0
    47  }
    48  
    49  // Remove removes r from the unread portion. It returns false if r does not
    50  // fully reside in b.
    51  func (b *buffer) Remove(r Range) bool {
    52  	sz := b.ReadSize()
    53  	switch {
    54  	case r.Len() != r.Intersect(Range{end: sz}).Len():
    55  		return false
    56  	case r.Len() == 0:
    57  		// Noop
    58  	case r.begin == 0:
    59  		b.read += r.end
    60  	case r.end == sz:
    61  		b.write -= r.Len()
    62  	default:
    63  		// Remove from the middle of b.data.
    64  		copy(b.data[b.read+r.begin:], b.data[b.read+r.end:b.write])
    65  		b.write -= r.Len()
    66  	}
    67  	return true
    68  }
    69  
    70  // Full indicates the buffer is full.
    71  //
    72  // This indicates there is no capacity left to write.
    73  func (b *buffer) Full() bool {
    74  	return b.write == len(b.data)
    75  }
    76  
    77  // ReadSize returns the number of bytes available for reading.
    78  func (b *buffer) ReadSize() int {
    79  	return b.write - b.read
    80  }
    81  
    82  // ReadMove advances the read index by the given amount.
    83  func (b *buffer) ReadMove(n int) {
    84  	b.read += n
    85  }
    86  
    87  // ReadSlice returns the read slice for this buffer.
    88  func (b *buffer) ReadSlice() []byte {
    89  	return b.data[b.read:b.write]
    90  }
    91  
    92  // WriteSize returns the number of bytes available for writing.
    93  func (b *buffer) WriteSize() int {
    94  	return len(b.data) - b.write
    95  }
    96  
    97  // WriteMove advances the write index by the given amount.
    98  func (b *buffer) WriteMove(n int) {
    99  	b.write += n
   100  }
   101  
   102  // WriteSlice returns the write slice for this buffer.
   103  func (b *buffer) WriteSlice() []byte {
   104  	return b.data[b.write:]
   105  }