github.com/zuoyebang/bitalostable@v1.0.1-0.20240229032404-e3b99a834294/internal/cache/value.go (about)

     1  // Copyright 2020 The LevelDB-Go and Pebble Authors. All rights reserved. Use
     2  // of this source code is governed by a BSD-style license that can be found in
     3  // the LICENSE file.
     4  
     5  package cache
     6  
     7  // Value holds a reference counted immutable value.
     8  type Value struct {
     9  	buf []byte
    10  	// Reference count for the value. The value is freed when the reference count
    11  	// drops to zero.
    12  	ref refcnt
    13  }
    14  
    15  // Buf returns the buffer associated with the value. The contents of the buffer
    16  // should not be changed once the value has been added to the cache. Instead, a
    17  // new Value should be created and added to the cache to replace the existing
    18  // value.
    19  func (v *Value) Buf() []byte {
    20  	if v == nil {
    21  		return nil
    22  	}
    23  	return v.buf
    24  }
    25  
    26  // Truncate the buffer to the specified length. The buffer length should not be
    27  // changed once the value has been added to the cache as there may be
    28  // concurrent readers of the Value. Instead, a new Value should be created and
    29  // added to the cache to replace the existing value.
    30  func (v *Value) Truncate(n int) {
    31  	v.buf = v.buf[:n]
    32  }
    33  
    34  func (v *Value) refs() int32 {
    35  	return v.ref.refs()
    36  }
    37  
    38  func (v *Value) acquire() {
    39  	v.ref.acquire()
    40  }
    41  
    42  func (v *Value) release() {
    43  	if v.ref.release() {
    44  		v.free()
    45  	}
    46  }