github.com/flower-corp/rosedb@v1.1.2-0.20230117132829-21dc4f7b319a/mmap/mmap_unix.go (about)

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