github.com/angenalZZZ/gofunc@v0.0.0-20210507121333-48ff1be3917b/data/shm/shm.go (about)

     1  package shm
     2  
     3  import (
     4  	"fmt"
     5  	"io"
     6  )
     7  
     8  // SharedMemory is shared memory struct
     9  type SharedMemory struct {
    10  	m   *sharedMemory
    11  	pos int64
    12  }
    13  
    14  // Create is create shared memory
    15  func Create(name string, size int32) (*SharedMemory, error) {
    16  	m, err := create(name, size)
    17  	if err != nil {
    18  		return nil, err
    19  	}
    20  	return &SharedMemory{m, 0}, nil
    21  }
    22  
    23  // Open is open exist shared memory
    24  func Open(name string, size int32) (*SharedMemory, error) {
    25  	m, err := open(name, size)
    26  	if err != nil {
    27  		return nil, err
    28  	}
    29  	return &SharedMemory{m, 0}, nil
    30  }
    31  
    32  // Close is close & discard shared memory
    33  func (o *SharedMemory) Close() (err error) {
    34  	if o.m != nil {
    35  		err = o.m.close()
    36  		if err == nil {
    37  			o.m = nil
    38  		}
    39  	}
    40  	return err
    41  }
    42  
    43  // Read is read shared memory (current position)
    44  func (o *SharedMemory) Read(p []byte) (n int, err error) {
    45  	n, err = o.ReadAt(p, o.pos)
    46  	if err != nil {
    47  		return 0, err
    48  	}
    49  	o.pos += int64(n)
    50  	return n, nil
    51  }
    52  
    53  // ReadAt is read shared memory (offset)
    54  func (o *SharedMemory) ReadAt(p []byte, off int64) (n int, err error) {
    55  	return o.m.readAt(p, off)
    56  }
    57  
    58  // Seek is move read/write position at shared memory
    59  func (o *SharedMemory) Seek(offset int64, whence int) (int64, error) {
    60  	switch whence {
    61  	case io.SeekStart:
    62  		offset += int64(0)
    63  	case io.SeekCurrent:
    64  		offset += o.pos
    65  	case io.SeekEnd:
    66  		offset += int64(o.m.size)
    67  	}
    68  	if offset < 0 || offset >= int64(o.m.size) {
    69  		return 0, fmt.Errorf("invalid offset")
    70  	}
    71  	o.pos = offset
    72  	return offset, nil
    73  }
    74  
    75  // Write is write shared memory (current position)
    76  func (o *SharedMemory) Write(p []byte) (n int, err error) {
    77  	n, err = o.WriteAt(p, o.pos)
    78  	if err != nil {
    79  		return 0, err
    80  	}
    81  	o.pos += int64(n)
    82  	return n, nil
    83  }
    84  
    85  // WriteAt is write shared memory (offset)
    86  func (o *SharedMemory) WriteAt(p []byte, off int64) (n int, err error) {
    87  	return o.m.writeAt(p, off)
    88  }