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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
//go:build unix
package mmap
import (
"fmt"
"io/fs"
"os"
"syscall"
)
func mmapFile(f *os.File) (Data, error) {
st, err := f.Stat()
if err != nil {
return Data{}, err
}
size := st.Size()
pagesize := int64(os.Getpagesize())
if int64(int(size+(pagesize-1))) != size+(pagesize-1) {
return Data{}, fmt.Errorf("%s: too large for mmap", f.Name())
}
n := int(size)
if n == 0 {
return Data{f, nil}, nil
}
mmapLength := int(((size + pagesize - 1) / pagesize) * pagesize) // round up to page size
data, err := syscall.Mmap(int(f.Fd()), 0, mmapLength, syscall.PROT_READ, syscall.MAP_SHARED)
if err != nil {
return Data{}, &fs.PathError{Op: "mmap", Path: f.Name(), Err: err}
}
return Data{f, data[:n]}, nil
}
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