fork of https://github.com/sourcegraph/zoekt
1// Copyright 2016 Google Inc. All rights reserved.
2//
3// Licensed under the Apache License, Version 2.0 (the "License");
4// you may not use this file except in compliance with the License.
5// You may obtain a copy of the License at
6//
7// http://www.apache.org/licenses/LICENSE-2.0
8//
9// Unless required by applicable law or agreed to in writing, software
10// distributed under the License is distributed on an "AS IS" BASIS,
11// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12// See the License for the specific language governing permissions and
13// limitations under the License.
14
15//go:build linux || darwin
16
17package zoekt
18
19import (
20 "fmt"
21 "log"
22 "os"
23
24 "golang.org/x/sys/unix"
25)
26
27type mmapedIndexFile struct {
28 name string
29 size uint32
30 data []byte
31}
32
33func (f *mmapedIndexFile) Read(off, sz uint32) ([]byte, error) {
34 if off > off+sz || off+sz > uint32(len(f.data)) {
35 return nil, fmt.Errorf("out of bounds: %d, len %d, name %s", off+sz, len(f.data), f.name)
36 }
37 return f.data[off : off+sz], nil
38}
39
40func (f *mmapedIndexFile) Name() string {
41 return f.name
42}
43
44func (f *mmapedIndexFile) Size() (uint32, error) {
45 return f.size, nil
46}
47
48func (f *mmapedIndexFile) Close() {
49 if err := unix.Munmap(f.data); err != nil {
50 log.Printf("WARN failed to Munmap %s: %v", f.name, err)
51 }
52}
53
54// NewIndexFile returns a new index file. The index file takes
55// ownership of the passed in file, and may close it.
56func NewIndexFile(f *os.File) (IndexFile, error) {
57 defer f.Close()
58
59 fi, err := f.Stat()
60 if err != nil {
61 return nil, err
62 }
63
64 sz := fi.Size()
65 if sz >= maxUInt32 {
66 return nil, fmt.Errorf("file %s too large: %d", f.Name(), sz)
67 }
68 r := &mmapedIndexFile{
69 name: f.Name(),
70 size: uint32(sz),
71 }
72
73 rounded := (r.size + 4095) &^ 4095
74 r.data, err = unix.Mmap(int(f.Fd()), 0, int(rounded), unix.PROT_READ, unix.MAP_SHARED)
75 if err != nil {
76 return nil, err
77 }
78
79 return r, err
80}