github.com/matrixorigin/matrixone@v1.2.0/pkg/common/buffer/chunk.go (about)

     1  // Copyright 2021 - 2023 Matrix Origin
     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
    16  
    17  import (
    18  	"unsafe"
    19  
    20  	"golang.org/x/sys/unix"
    21  )
    22  
    23  func init() {
    24  	var c chunk
    25  
    26  	ChunkSize = int(unsafe.Sizeof(c))
    27  }
    28  
    29  func (c *chunk) alloc(sz int) []byte {
    30  	c.Lock()
    31  	defer c.Unlock()
    32  	if int(c.off)+sz+int(PointerSize) >= len(c.data) {
    33  		c.flag |= FULL
    34  		return nil
    35  	}
    36  	data := c.data[c.off : int(c.off)+sz+int(PointerSize)]
    37  	*((*unsafe.Pointer)(unsafe.Pointer(unsafe.SliceData(data)))) = unsafe.Pointer(c)
    38  	c.off += uint32(sz + int(PointerSize))
    39  	c.numAlloc++
    40  	return data[PointerSize:]
    41  }
    42  
    43  func (c *chunk) free() {
    44  	c.Lock()
    45  	if c.numFree = c.numFree + 1; c.numFree == c.numAlloc &&
    46  		c.flag&FULL == FULL { // this chunk is no longer needed
    47  		unix.Munmap(c.data)
    48  		return
    49  	}
    50  	c.Unlock()
    51  }