github.com/kovansky/hugo@v0.92.3-0.20220224232819-63076e4ff19f/hugofs/hashing_fs.go (about) 1 // Copyright 2019 The Hugo Authors. 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 // http://www.apache.org/licenses/LICENSE-2.0 7 // 8 // Unless required by applicable law or agreed to in writing, software 9 // distributed under the License is distributed on an "AS IS" BASIS, 10 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 11 // See the License for the specific language governing permissions and 12 // limitations under the License. 13 14 package hugofs 15 16 import ( 17 "crypto/md5" 18 "encoding/hex" 19 "hash" 20 "os" 21 22 "github.com/spf13/afero" 23 ) 24 25 var _ afero.Fs = (*md5HashingFs)(nil) 26 27 // FileHashReceiver will receive the filename an the content's MD5 sum on file close. 28 type FileHashReceiver interface { 29 OnFileClose(name, md5sum string) 30 } 31 32 type md5HashingFs struct { 33 afero.Fs 34 hashReceiver FileHashReceiver 35 } 36 37 // NewHashingFs creates a new filesystem that will receive MD5 checksums of 38 // any written file content on Close. Note that this is probably not a good 39 // idea for "full build" situations, but when doing fast render mode, the amount 40 // of files published is low, and it would be really nice to know exactly which 41 // of these files where actually changed. 42 // Note that this will only work for file operations that use the io.Writer 43 // to write content to file, but that is fine for the "publish content" use case. 44 func NewHashingFs(delegate afero.Fs, hashReceiver FileHashReceiver) afero.Fs { 45 return &md5HashingFs{Fs: delegate, hashReceiver: hashReceiver} 46 } 47 48 func (fs *md5HashingFs) Create(name string) (afero.File, error) { 49 f, err := fs.Fs.Create(name) 50 if err == nil { 51 f = fs.wrapFile(f) 52 } 53 return f, err 54 } 55 56 func (fs *md5HashingFs) OpenFile(name string, flag int, perm os.FileMode) (afero.File, error) { 57 f, err := fs.Fs.OpenFile(name, flag, perm) 58 if err == nil && isWrite(flag) { 59 f = fs.wrapFile(f) 60 } 61 return f, err 62 } 63 64 func (fs *md5HashingFs) wrapFile(f afero.File) afero.File { 65 return &hashingFile{File: f, h: md5.New(), hashReceiver: fs.hashReceiver} 66 } 67 68 func (fs *md5HashingFs) Name() string { 69 return "md5HashingFs" 70 } 71 72 type hashingFile struct { 73 hashReceiver FileHashReceiver 74 h hash.Hash 75 afero.File 76 } 77 78 func (h *hashingFile) Write(p []byte) (n int, err error) { 79 n, err = h.File.Write(p) 80 if err != nil { 81 return 82 } 83 return h.h.Write(p) 84 } 85 86 func (h *hashingFile) Close() error { 87 sum := hex.EncodeToString(h.h.Sum(nil)) 88 h.hashReceiver.OnFileClose(h.Name(), sum) 89 return h.File.Close() 90 }