libgo/go/patch/apply.go

   1 // Copyright 2009 The Go Authors.  All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 package patch
   6
   7 import "os"
   8
   9 // An Op is a single operation to execute to apply a patch.
  10 type Op struct {
  11         Verb Verb   // action
  12         Src  string // source file
  13         Dst  string // destination file
  14         Mode int    // mode for destination (if non-zero)
  15         Data []byte // data for destination (if non-nil)
  16 }
  17
  18 // Apply applies the patch set to the files named in the patch set,
  19 // constructing an in-memory copy of the new file state.
  20 // It is the client's job to write the changes to the file system
  21 // if desired.
  22 //
  23 // The function readFile should return the contents of the named file.
  24 // Typically this function will be io.ReadFile.
  25 //
  26 func (set *Set) Apply(readFile func(string) ([]byte, os.Error)) ([]Op, os.Error) {
  27         op := make([]Op, len(set.File))
  28
  29         for i, f := range set.File {
  30                 o := &op[i]
  31                 o.Verb = f.Verb
  32                 o.Src = f.Src
  33                 o.Dst = f.Dst
  34                 o.Mode = f.NewMode
  35                 if f.Diff != NoDiff || o.Verb != Edit {
  36                         // Clients assume o.Data == nil means no data diff.
  37                         // Start with a non-nil data.
  38                         var old []byte = make([]byte, 0) // not nil
  39                         var err os.Error
  40                         if f.Src != "" {
  41                                 old, err = readFile(f.Src)
  42                                 if err != nil {
  43                                         return nil, &os.PathError{string(f.Verb), f.Src, err}
  44                                 }
  45                         }
  46                         o.Data, err = f.Diff.Apply(old)
  47                         if err != nil {
  48                                 return nil, &os.PathError{string(f.Verb), f.Src, err}
  49                         }
  50                 }
  51         }
  52
  53         return op, nil
  54 }