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mmap_unix.go (1113B)

      1 // Copyright 2011 The Go Authors.  All rights reserved.
      2 // Use of this source code is governed by a BSD-style
      3 // license that can be found in the LICENSE file.
      4 
      5 //go:build unix
      6 
      7 package mmap
      8 
      9 import (
     10 	"fmt"
     11 	"io/fs"
     12 	"os"
     13 	"syscall"
     14 )
     15 
     16 func mmapFile(f *os.File) (*Data, error) {
     17 	st, err := f.Stat()
     18 	if err != nil {
     19 		return nil, err
     20 	}
     21 	size := st.Size()
     22 	pagesize := int64(os.Getpagesize())
     23 	if int64(int(size+(pagesize-1))) != size+(pagesize-1) {
     24 		return nil, fmt.Errorf("%s: too large for mmap", f.Name())
     25 	}
     26 	n := int(size)
     27 	if n == 0 {
     28 		return &Data{f, nil, nil}, nil
     29 	}
     30 	mmapLength := int(((size + pagesize - 1) / pagesize) * pagesize) // round up to page size
     31 	data, err := syscall.Mmap(int(f.Fd()), 0, mmapLength, syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED)
     32 	if err != nil {
     33 		return nil, &fs.PathError{Op: "mmap", Path: f.Name(), Err: err}
     34 	}
     35 	return &Data{f, data[:n], nil}, nil
     36 }
     37 
     38 func munmapFile(d *Data) error {
     39 	if len(d.Data) == 0 {
     40 		return nil
     41 	}
     42 	err := syscall.Munmap(d.Data)
     43 	if err != nil {
     44 		return &fs.PathError{Op: "munmap", Path: d.f.Name(), Err: err}
     45 	}
     46 	return nil
     47 }