github.com/outcaste-io/ristretto@v0.2.3/z/mmap_darwin.go (about)

     1  /*
     2   * Copyright 2019 Dgraph Labs, Inc. and Contributors
     3   *
     4   * Licensed under the Apache License, Version 2.0 (the "License");
     5   * you may not use this file except in compliance with the License.
     6   * You may obtain a copy of the License at
     7   *
     8   *     http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13   * See the License for the specific language governing permissions and
    14   * limitations under the License.
    15   */
    16  
    17  package z
    18  
    19  import (
    20  	"os"
    21  	"syscall"
    22  	"unsafe"
    23  
    24  	"golang.org/x/sys/unix"
    25  )
    26  
    27  // Mmap uses the mmap system call to memory-map a file. If writable is true,
    28  // memory protection of the pages is set so that they may be written to as well.
    29  func mmap(fd *os.File, writable bool, size int64) ([]byte, error) {
    30  	mtype := unix.PROT_READ
    31  	if writable {
    32  		mtype |= unix.PROT_WRITE
    33  	}
    34  	return unix.Mmap(int(fd.Fd()), 0, int(size), mtype, unix.MAP_SHARED)
    35  }
    36  
    37  // Munmap unmaps a previously mapped slice.
    38  func munmap(b []byte) error {
    39  	return unix.Munmap(b)
    40  }
    41  
    42  // This is required because the unix package does not support the madvise system call on OS X.
    43  func madvise(b []byte, readahead bool) error {
    44  	advice := unix.MADV_NORMAL
    45  	if !readahead {
    46  		advice = unix.MADV_RANDOM
    47  	}
    48  
    49  	_, _, e1 := syscall.Syscall(syscall.SYS_MADVISE, uintptr(unsafe.Pointer(&b[0])),
    50  		uintptr(len(b)), uintptr(advice))
    51  	if e1 != 0 {
    52  		return e1
    53  	}
    54  	return nil
    55  }
    56  
    57  func msync(b []byte) error {
    58  	return unix.Msync(b, unix.MS_SYNC)
    59  }