github.com/ledgerwatch/erigon-lib@v1.0.0/mmap/mmap_windows.go (about)

     1  /*
     2     Copyright 2021 Erigon 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 mmap
    18  
    19  import (
    20  	"os"
    21  	"unsafe"
    22  
    23  	"golang.org/x/sys/windows"
    24  )
    25  
    26  const MaxMapSize = 0xFFFFFFFFFFFF
    27  
    28  func Mmap(f *os.File, size int) ([]byte, *[MaxMapSize]byte, error) {
    29  	// Open a file mapping handle.
    30  	sizelo := uint32(size >> 32)
    31  	sizehi := uint32(size) & 0xffffffff
    32  	h, errno := windows.CreateFileMapping(windows.Handle(f.Fd()), nil, windows.PAGE_READONLY, sizelo, sizehi, nil)
    33  	if h == 0 {
    34  		return nil, nil, os.NewSyscallError("CreateFileMapping", errno)
    35  	}
    36  
    37  	// Create the memory map.
    38  	addr, errno := windows.MapViewOfFile(h, windows.FILE_MAP_READ, 0, 0, uintptr(size))
    39  	if addr == 0 {
    40  		return nil, nil, os.NewSyscallError("MapViewOfFile", errno)
    41  	}
    42  
    43  	// Close mapping handle.
    44  	if err := windows.CloseHandle(windows.Handle(h)); err != nil {
    45  		return nil, nil, os.NewSyscallError("CloseHandle", err)
    46  	}
    47  
    48  	// Convert to a byte array.
    49  	mmapHandle2 := ((*[MaxMapSize]byte)(unsafe.Pointer(addr)))
    50  	return mmapHandle2[:size], mmapHandle2, nil
    51  }
    52  
    53  func MadviseSequential(mmapHandle1 []byte) error { return nil }
    54  func MadviseNormal(mmapHandle1 []byte) error     { return nil }
    55  func MadviseWillNeed(mmapHandle1 []byte) error   { return nil }
    56  func MadviseRandom(mmapHandle1 []byte) error     { return nil }
    57  
    58  func Munmap(_ []byte, mmapHandle2 *[MaxMapSize]byte) error {
    59  	if mmapHandle2 == nil {
    60  		return nil
    61  	}
    62  
    63  	addr := (uintptr)(unsafe.Pointer(&mmapHandle2[0]))
    64  	if err := windows.UnmapViewOfFile(addr); err != nil {
    65  		return os.NewSyscallError("UnmapViewOfFile", err)
    66  	}
    67  	return nil
    68  }