mmap_unix.go raw

   1  //go:build !windows && !darwin && !plan9 && !linux && !wasip1 && !js
   2  // +build !windows,!darwin,!plan9,!linux,!wasip1,!js
   3  
   4  /*
   5   * SPDX-FileCopyrightText: © Hypermode Inc. <hello@hypermode.com>
   6   * SPDX-License-Identifier: Apache-2.0
   7   */
   8  
   9  package z
  10  
  11  import (
  12  	"os"
  13  
  14  	"golang.org/x/sys/unix"
  15  )
  16  
  17  // Mmap uses the mmap system call to memory-map a file. If writable is true,
  18  // memory protection of the pages is set so that they may be written to as well.
  19  func mmap(fd *os.File, writable bool, size int64) ([]byte, error) {
  20  	mtype := unix.PROT_READ
  21  	if writable {
  22  		mtype |= unix.PROT_WRITE
  23  	}
  24  	return unix.Mmap(int(fd.Fd()), 0, int(size), mtype, unix.MAP_SHARED)
  25  }
  26  
  27  // Munmap unmaps a previously mapped slice.
  28  func munmap(b []byte) error {
  29  	return unix.Munmap(b)
  30  }
  31  
  32  // Madvise uses the madvise system call to give advise about the use of memory
  33  // when using a slice that is memory-mapped to a file. Set the readahead flag to
  34  // false if page references are expected in random order.
  35  func madvise(b []byte, readahead bool) error {
  36  	flags := unix.MADV_NORMAL
  37  	if !readahead {
  38  		flags = unix.MADV_RANDOM
  39  	}
  40  	return unix.Madvise(b, flags)
  41  }
  42  
  43  func msync(b []byte) error {
  44  	return unix.Msync(b, unix.MS_SYNC)
  45  }
  46