mangle.go

Documentation: github.com/sassoftware/relic/lib/zipslicer

     1  //
     2  // Copyright (c) SAS Institute Inc.
     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 zipslicer
    18  
    19  import (
    20  	"bytes"
    21  	"time"
    22  
    23  	"github.com/sassoftware/relic/lib/binpatch"
    24  )
    25  
    26  type Mangler struct {
    27  	outz          *Directory
    28  	patch         *binpatch.PatchSet
    29  	newcontents   bytes.Buffer
    30  	indir, insize int64
    31  }
    32  
    33  type MangleFunc func(*MangleFile) error
    34  
    35  // Walk all the files in the directory in-order, invoking a callback that can
    36  // decide whether to keep or discard each one. Returns a Mangler that can be
    37  // used to add more files and eventually produce a binary patch against the
    38  // original zip.
    39  func (d *Directory) Mangle(callback MangleFunc) (*Mangler, error) {
    40  	m := &Mangler{
    41  		outz:   new(Directory),
    42  		patch:  binpatch.New(),
    43  		indir:  d.DirLoc,
    44  		insize: d.Size,
    45  	}
    46  	for _, f := range d.File {
    47  		mf := &MangleFile{File: *f, m: m}
    48  		if err := callback(mf); err != nil {
    49  			return nil, err
    50  		}
    51  		if mf.deleted {
    52  			size, err := mf.GetTotalSize()
    53  			if err != nil {
    54  				return nil, err
    55  			}
    56  			m.patch.Add(int64(mf.Offset), size, nil)
    57  		} else {
    58  			if _, err := m.outz.AddFile(&mf.File); err != nil {
    59  				return nil, err
    60  			}
    61  		}
    62  	}
    63  	return m, nil
    64  }
    65  
    66  // Add a new file to a zip mangler
    67  func (m *Mangler) NewFile(name string, contents []byte) error {
    68  	deflate := len(contents) != 0
    69  	_, err := m.outz.NewFile(name, nil, contents, &m.newcontents, time.Now(), deflate, true)
    70  	return err
    71  }
    72  
    73  // Create a binary patchset out of the operations performed in this mangler
    74  func (m *Mangler) MakePatch(forceZip64 bool) (*binpatch.PatchSet, error) {
    75  	w := &m.newcontents
    76  	if err := m.outz.WriteDirectory(w, w, forceZip64); err != nil {
    77  		return nil, err
    78  	}
    79  	m.patch.Add(m.indir, m.insize-m.indir, m.newcontents.Bytes())
    80  	return m.patch, nil
    81  }
    82  
    83  type MangleFile struct {
    84  	File
    85  	m       *Mangler
    86  	deleted bool
    87  }
    88  
    89  // Mark this file for deletion
    90  func (f *MangleFile) Delete() {
    91  	f.deleted = true
    92  }
    93
View as plain text