/
mmap.go
75 lines (61 loc) · 1.16 KB
/
mmap.go
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//go:build linux || darwin
package store
import (
"io"
"golang.org/x/exp/mmap"
)
var (
_ DataInput = &MmapDataInput{}
)
type MmapDataInput struct {
*BaseDataInput
pos int64
reader *mmap.ReaderAt
isEOF bool
}
func NewMmapDataInput(file string) (*MmapDataInput, error) {
reader, err := mmap.Open(file)
if err != nil {
return nil, err
}
input := &MmapDataInput{
pos: 0,
reader: reader,
isEOF: false,
}
input.BaseDataInput = NewBaseDataInput(input)
return input, nil
}
func (m *MmapDataInput) Read(p []byte) (n int, err error) {
if m.isEOF {
return 0, io.EOF
}
less := m.reader.Len() - int(m.pos)
if len(p) > less {
size, err := m.reader.ReadAt(p[:less], m.pos)
if err != nil {
return 0, err
}
m.pos += int64(size)
m.isEOF = true
return size, nil
}
size, err := m.reader.ReadAt(p, m.pos)
if err != nil {
return 0, err
}
m.pos += int64(size)
return size, nil
}
func (m *MmapDataInput) Clone() CloneReader {
input := &MmapDataInput{
pos: m.pos,
reader: m.reader,
isEOF: m.isEOF,
}
input.BaseDataInput = NewBaseDataInput(input)
return input
}
func (m *MmapDataInput) Close() error {
return m.reader.Close()
}