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373
LICENSE
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Mozilla Public License Version 2.0
==================================
1. Definitions
--------------
1.1. "Contributor"
means each individual or legal entity that creates, contributes to
the creation of, or owns Covered Software.
1.2. "Contributor Version"
means the combination of the Contributions of others (if any) used
by a Contributor and that particular Contributor's Contribution.
1.3. "Contribution"
means Covered Software of a particular Contributor.
1.4. "Covered Software"
means Source Code Form to which the initial Contributor has attached
the notice in Exhibit A, the Executable Form of such Source Code
Form, and Modifications of such Source Code Form, in each case
including portions thereof.
1.5. "Incompatible With Secondary Licenses"
means
(a) that the initial Contributor has attached the notice described
in Exhibit B to the Covered Software; or
(b) that the Covered Software was made available under the terms of
version 1.1 or earlier of the License, but not also under the
terms of a Secondary License.
1.6. "Executable Form"
means any form of the work other than Source Code Form.
1.7. "Larger Work"
means a work that combines Covered Software with other material, in
a separate file or files, that is not Covered Software.
1.8. "License"
means this document.
1.9. "Licensable"
means having the right to grant, to the maximum extent possible,
whether at the time of the initial grant or subsequently, any and
all of the rights conveyed by this License.
1.10. "Modifications"
means any of the following:
(a) any file in Source Code Form that results from an addition to,
deletion from, or modification of the contents of Covered
Software; or
(b) any new file in Source Code Form that contains any Covered
Software.
1.11. "Patent Claims" of a Contributor
means any patent claim(s), including without limitation, method,
process, and apparatus claims, in any patent Licensable by such
Contributor that would be infringed, but for the grant of the
License, by the making, using, selling, offering for sale, having
made, import, or transfer of either its Contributions or its
Contributor Version.
1.12. "Secondary License"
means either the GNU General Public License, Version 2.0, the GNU
Lesser General Public License, Version 2.1, the GNU Affero General
Public License, Version 3.0, or any later versions of those
licenses.
1.13. "Source Code Form"
means the form of the work preferred for making modifications.
1.14. "You" (or "Your")
means an individual or a legal entity exercising rights under this
License. For legal entities, "You" includes any entity that
controls, is controlled by, or is under common control with You. For
purposes of this definition, "control" means (a) the power, direct
or indirect, to cause the direction or management of such entity,
whether by contract or otherwise, or (b) ownership of more than
fifty percent (50%) of the outstanding shares or beneficial
ownership of such entity.
2. License Grants and Conditions
--------------------------------
2.1. Grants
Each Contributor hereby grants You a world-wide, royalty-free,
non-exclusive license:
(a) under intellectual property rights (other than patent or trademark)
Licensable by such Contributor to use, reproduce, make available,
modify, display, perform, distribute, and otherwise exploit its
Contributions, either on an unmodified basis, with Modifications, or
as part of a Larger Work; and
(b) under Patent Claims of such Contributor to make, use, sell, offer
for sale, have made, import, and otherwise transfer either its
Contributions or its Contributor Version.
2.2. Effective Date
The licenses granted in Section 2.1 with respect to any Contribution
become effective for each Contribution on the date the Contributor first
distributes such Contribution.
2.3. Limitations on Grant Scope
The licenses granted in this Section 2 are the only rights granted under
this License. No additional rights or licenses will be implied from the
distribution or licensing of Covered Software under this License.
Notwithstanding Section 2.1(b) above, no patent license is granted by a
Contributor:
(a) for any code that a Contributor has removed from Covered Software;
or
(b) for infringements caused by: (i) Your and any other third party's
modifications of Covered Software, or (ii) the combination of its
Contributions with other software (except as part of its Contributor
Version); or
(c) under Patent Claims infringed by Covered Software in the absence of
its Contributions.
This License does not grant any rights in the trademarks, service marks,
or logos of any Contributor (except as may be necessary to comply with
the notice requirements in Section 3.4).
2.4. Subsequent Licenses
No Contributor makes additional grants as a result of Your choice to
distribute the Covered Software under a subsequent version of this
License (see Section 10.2) or under the terms of a Secondary License (if
permitted under the terms of Section 3.3).
2.5. Representation
Each Contributor represents that the Contributor believes its
Contributions are its original creation(s) or it has sufficient rights
to grant the rights to its Contributions conveyed by this License.
2.6. Fair Use
This License is not intended to limit any rights You have under
applicable copyright doctrines of fair use, fair dealing, or other
equivalents.
2.7. Conditions
Sections 3.1, 3.2, 3.3, and 3.4 are conditions of the licenses granted
in Section 2.1.
3. Responsibilities
-------------------
3.1. Distribution of Source Form
All distribution of Covered Software in Source Code Form, including any
Modifications that You create or to which You contribute, must be under
the terms of this License. You must inform recipients that the Source
Code Form of the Covered Software is governed by the terms of this
License, and how they can obtain a copy of this License. You may not
attempt to alter or restrict the recipients' rights in the Source Code
Form.
3.2. Distribution of Executable Form
If You distribute Covered Software in Executable Form then:
(a) such Covered Software must also be made available in Source Code
Form, as described in Section 3.1, and You must inform recipients of
the Executable Form how they can obtain a copy of such Source Code
Form by reasonable means in a timely manner, at a charge no more
than the cost of distribution to the recipient; and
(b) You may distribute such Executable Form under the terms of this
License, or sublicense it under different terms, provided that the
license for the Executable Form does not attempt to limit or alter
the recipients' rights in the Source Code Form under this License.
3.3. Distribution of a Larger Work
You may create and distribute a Larger Work under terms of Your choice,
provided that You also comply with the requirements of this License for
the Covered Software. If the Larger Work is a combination of Covered
Software with a work governed by one or more Secondary Licenses, and the
Covered Software is not Incompatible With Secondary Licenses, this
License permits You to additionally distribute such Covered Software
under the terms of such Secondary License(s), so that the recipient of
the Larger Work may, at their option, further distribute the Covered
Software under the terms of either this License or such Secondary
License(s).
3.4. Notices
You may not remove or alter the substance of any license notices
(including copyright notices, patent notices, disclaimers of warranty,
or limitations of liability) contained within the Source Code Form of
the Covered Software, except that You may alter any license notices to
the extent required to remedy known factual inaccuracies.
3.5. Application of Additional Terms
You may choose to offer, and to charge a fee for, warranty, support,
indemnity or liability obligations to one or more recipients of Covered
Software. However, You may do so only on Your own behalf, and not on
behalf of any Contributor. You must make it absolutely clear that any
such warranty, support, indemnity, or liability obligation is offered by
You alone, and You hereby agree to indemnify every Contributor for any
liability incurred by such Contributor as a result of warranty, support,
indemnity or liability terms You offer. You may include additional
disclaimers of warranty and limitations of liability specific to any
jurisdiction.
4. Inability to Comply Due to Statute or Regulation
---------------------------------------------------
If it is impossible for You to comply with any of the terms of this
License with respect to some or all of the Covered Software due to
statute, judicial order, or regulation then You must: (a) comply with
the terms of this License to the maximum extent possible; and (b)
describe the limitations and the code they affect. Such description must
be placed in a text file included with all distributions of the Covered
Software under this License. Except to the extent prohibited by statute
or regulation, such description must be sufficiently detailed for a
recipient of ordinary skill to be able to understand it.
5. Termination
--------------
5.1. The rights granted under this License will terminate automatically
if You fail to comply with any of its terms. However, if You become
compliant, then the rights granted under this License from a particular
Contributor are reinstated (a) provisionally, unless and until such
Contributor explicitly and finally terminates Your grants, and (b) on an
ongoing basis, if such Contributor fails to notify You of the
non-compliance by some reasonable means prior to 60 days after You have
come back into compliance. Moreover, Your grants from a particular
Contributor are reinstated on an ongoing basis if such Contributor
notifies You of the non-compliance by some reasonable means, this is the
first time You have received notice of non-compliance with this License
from such Contributor, and You become compliant prior to 30 days after
Your receipt of the notice.
5.2. If You initiate litigation against any entity by asserting a patent
infringement claim (excluding declaratory judgment actions,
counter-claims, and cross-claims) alleging that a Contributor Version
directly or indirectly infringes any patent, then the rights granted to
You by any and all Contributors for the Covered Software under Section
2.1 of this License shall terminate.
5.3. In the event of termination under Sections 5.1 or 5.2 above, all
end user license agreements (excluding distributors and resellers) which
have been validly granted by You or Your distributors under this License
prior to termination shall survive termination.
************************************************************************
* *
* 6. Disclaimer of Warranty *
* ------------------------- *
* *
* Covered Software is provided under this License on an "as is" *
* basis, without warranty of any kind, either expressed, implied, or *
* statutory, including, without limitation, warranties that the *
* Covered Software is free of defects, merchantable, fit for a *
* particular purpose or non-infringing. The entire risk as to the *
* quality and performance of the Covered Software is with You. *
* Should any Covered Software prove defective in any respect, You *
* (not any Contributor) assume the cost of any necessary servicing, *
* repair, or correction. This disclaimer of warranty constitutes an *
* essential part of this License. No use of any Covered Software is *
* authorized under this License except under this disclaimer. *
* *
************************************************************************
************************************************************************
* *
* 7. Limitation of Liability *
* -------------------------- *
* *
* Under no circumstances and under no legal theory, whether tort *
* (including negligence), contract, or otherwise, shall any *
* Contributor, or anyone who distributes Covered Software as *
* permitted above, be liable to You for any direct, indirect, *
* special, incidental, or consequential damages of any character *
* including, without limitation, damages for lost profits, loss of *
* goodwill, work stoppage, computer failure or malfunction, or any *
* and all other commercial damages or losses, even if such party *
* shall have been informed of the possibility of such damages. This *
* limitation of liability shall not apply to liability for death or *
* personal injury resulting from such party's negligence to the *
* extent applicable law prohibits such limitation. Some *
* jurisdictions do not allow the exclusion or limitation of *
* incidental or consequential damages, so this exclusion and *
* limitation may not apply to You. *
* *
************************************************************************
8. Litigation
-------------
Any litigation relating to this License may be brought only in the
courts of a jurisdiction where the defendant maintains its principal
place of business and such litigation shall be governed by laws of that
jurisdiction, without reference to its conflict-of-law provisions.
Nothing in this Section shall prevent a party's ability to bring
cross-claims or counter-claims.
9. Miscellaneous
----------------
This License represents the complete agreement concerning the subject
matter hereof. If any provision of this License is held to be
unenforceable, such provision shall be reformed only to the extent
necessary to make it enforceable. Any law or regulation which provides
that the language of a contract shall be construed against the drafter
shall not be used to construe this License against a Contributor.
10. Versions of the License
---------------------------
10.1. New Versions
Mozilla Foundation is the license steward. Except as provided in Section
10.3, no one other than the license steward has the right to modify or
publish new versions of this License. Each version will be given a
distinguishing version number.
10.2. Effect of New Versions
You may distribute the Covered Software under the terms of the version
of the License under which You originally received the Covered Software,
or under the terms of any subsequent version published by the license
steward.
10.3. Modified Versions
If you create software not governed by this License, and you want to
create a new license for such software, you may create and use a
modified version of this License if you rename the license and remove
any references to the name of the license steward (except to note that
such modified license differs from this License).
10.4. Distributing Source Code Form that is Incompatible With Secondary
Licenses
If You choose to distribute Source Code Form that is Incompatible With
Secondary Licenses under the terms of this version of the License, the
notice described in Exhibit B of this License must be attached.
Exhibit A - Source Code Form License Notice
-------------------------------------------
This Source Code Form is subject to the terms of the Mozilla Public
License, v. 2.0. If a copy of the MPL was not distributed with this
file, You can obtain one at http://mozilla.org/MPL/2.0/.
If it is not possible or desirable to put the notice in a particular
file, then You may include the notice in a location (such as a LICENSE
file in a relevant directory) where a recipient would be likely to look
for such a notice.
You may add additional accurate notices of copyright ownership.
Exhibit B - "Incompatible With Secondary Licenses" Notice
---------------------------------------------------------
This Source Code Form is "Incompatible With Secondary Licenses", as
defined by the Mozilla Public License, v. 2.0.

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README.md
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# asar [![GoDoc](https://godoc.org/layeh.com/asar?status.svg)](https://godoc.org/layeh.com/asar)
Package asar reads and writes ASAR (Atom-Shell Archive) archives
import (
"os"
"layeh.com/asar"
)
f, err := os.Open("sample.asar")
if err != nil {
panic(err)
}
defer f.Close()
archive, err := asar.Decode(f)
if err != nil {
panic(err)
}
test := archive.Find("test", "file.txt")
if test == nil {
panic("file not found")
}
// print contents of test/file.txt in sample.asar
fmt.Println(test.String())
## License
MPL 2.0
## Author
Tim Cooper (tim.cooper@layeh.com)

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builder.go
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package asar // import "b612.me/asar"
import (
"io"
"strings"
)
// Builder helps construct an Entry.
//
// A builder keeps track of the root Entry and the active Entry. When entries
// are added using the Add* methods, they are added as children to the active
// Entry.
type Builder struct {
root, current *Entry
}
// Root returns the root Entry.
func (b *Builder) Root() *Entry {
return b.root
}
func (b *Builder) init() {
if b.root == nil {
b.root = &Entry{
Flags: FlagDir,
}
b.current = b.root
}
}
// Parent sets the active entry to the parent of the active Entry (i.e. moves up
// a level).
//
// The function panics if called on the root Entry.
func (b *Builder) Parent() *Builder {
if b.current == b.root {
panic("root has no parent")
}
b.current = b.current.Parent
return b
}
// AddString adds a new file Entry whose contents are the given string.
func (b *Builder) AddString(name, contents string, flags Flag) *Builder {
return b.Add(name, strings.NewReader(contents), int64(len(contents)), flags)
}
// Add adds a new file Entry.
func (b *Builder) Add(name string, ra io.ReaderAt, size int64, flags Flag) *Builder {
b.init()
child := &Entry{
Name: name,
Size: size,
Flags: flags,
Parent: b.current,
r: ra,
}
b.current.Children = append(b.current.Children, child)
return b
}
// AddDir adds a new directory Entry. The active Entry is switched to this newly
// added Entry.
func (b *Builder) AddDir(name string, flags Flag) *Builder {
b.init()
child := &Entry{
Name: name,
Flags: flags | FlagDir,
Parent: b.current,
}
b.current.Children = append(b.current.Children, child)
b.current = child
return b
}

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cmd/asar/main.go
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package main // import "b612.me/cmd/asar"
import (
"flag"
"fmt"
"os"
"path/filepath"
"b612.me/asar"
)
func main() {
flag.Usage = func() {
fmt.Fprintf(os.Stderr, "usage: %s [options] [command]\n", os.Args[0])
fmt.Fprintf(os.Stderr, "Commands:\n")
fmt.Fprintf(os.Stderr, "\n")
fmt.Fprintf(os.Stderr, " l|list <archive>\n")
fmt.Fprintf(os.Stderr, " list contents of asar archive\n")
fmt.Fprintf(os.Stderr, " x|extract <archive> <dir>\n")
fmt.Fprintf(os.Stderr, " extract contents of asar archive to directory\n")
fmt.Fprintf(os.Stderr, "\n")
flag.PrintDefaults()
}
flag.Parse()
if flag.NArg() < 2 {
flag.Usage()
os.Exit(3)
}
file, err := os.Open(flag.Arg(1))
if err != nil {
fmt.Fprintf(os.Stderr, "asar: %s\n", err)
os.Exit(1)
}
defer file.Close()
root, err := asar.Decode(file)
if err != nil {
fmt.Fprintf(os.Stderr, "asar: %s\n", err)
os.Exit(1)
}
switch command := flag.Arg(0); command {
case "l", "list":
root.Walk(func(path string, _ os.FileInfo, _ error) error {
fmt.Println("/" + path)
return nil
})
case "x", "extract":
if flag.NArg() < 3 {
flag.Usage()
os.Exit(1)
}
target := flag.Arg(2)
err := root.Walk(func(path string, info os.FileInfo, _ error) error {
entry := info.Sys().(*asar.Entry)
realPath := filepath.Join(target, path)
if entry.Flags&asar.FlagDir != 0 {
return os.MkdirAll(realPath, 0755)
}
if entry.Flags&asar.FlagUnpacked != 0 {
return nil
}
perm := os.FileMode(0644)
if entry.Flags&asar.FlagExecutable != 0 {
perm |= 0111
}
f, err := os.OpenFile(realPath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, perm)
if err != nil {
return err
}
_, err = entry.WriteTo(f)
if err != nil {
f.Close()
return err
}
if err := f.Close(); err != nil {
return err
}
return nil
})
if err != nil {
fmt.Fprintf(os.Stderr, "asar: %s\n", err)
os.Exit(1)
}
}
}

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decoder.go
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package asar // import "b612.me/asar"
import (
"encoding/binary"
"errors"
"io"
)
var (
errMalformed = errors.New("asar: malformed archive")
)
// Decode decodes the ASAR archive in ra.
//
// Returns the root element and nil on success. nil and an error is returned on
// failure.
func Decode(ra io.ReaderAt) (*Entry, error) {
headerSize := uint32(0)
headerStringSize := uint32(0)
// [pickle object header (4 bytes) == 4]
// [pickle uint32 = $header_object_size]
{
var buff [8]byte
if n, _ := ra.ReadAt(buff[:], 0); n != 8 {
return nil, errMalformed
}
dataSize := binary.LittleEndian.Uint32(buff[:4])
if dataSize != 4 {
return nil, errMalformed
}
headerSize = binary.LittleEndian.Uint32(buff[4:8])
}
// [pickle object header (4 bytes)]
// [pickle data header (4 bytes) == $string_size]
// [pickle string ($string_size bytes)]
{
var buff [8]byte
if n, _ := ra.ReadAt(buff[:], 8); n != 8 {
return nil, errMalformed
}
headerObjectSize := binary.LittleEndian.Uint32(buff[:4])
if headerObjectSize != headerSize-4 {
return nil, errMalformed
}
headerStringSize = binary.LittleEndian.Uint32(buff[4:8])
}
// read header string
headerSection := io.NewSectionReader(ra, 8+8, int64(headerStringSize))
baseOffset := 8 + int64(headerSize)
baseOffset += baseOffset % 4 // pickle objects are uint32 aligned
root, err := decodeHeader(ra, headerSection, baseOffset)
if err != nil {
return nil, err
}
return root, nil
}

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decoder_test.go
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package asar // import "b612.me/asar"
import (
"bytes"
"io/ioutil"
"os"
"path/filepath"
"testing"
)
func TestExtractThis(t *testing.T) {
f, err := os.Open("testdata/extractthis.asar")
if err != nil {
t.Fatal(err)
}
defer f.Close()
root, err := Decode(f)
if err != nil {
t.Fatal(err)
}
if root.Flags&FlagDir == 0 {
t.Fatal("expecting root directory to have FlagDir")
}
{
f1 := root.Find("dir1", "file1.txt")
if f1 == nil {
t.Fatal("could not find dir1/file1.txt")
}
if f1.Path() != "dir1/file1.txt" {
t.Fatal("unexpected path")
}
body, err := ioutil.ReadAll(f1.Open())
if err != nil {
t.Fatal(err)
}
if !bytes.Equal(body, []byte(`file one.`)) {
t.Fatalf("dir1/file1.txt body is incorrect (got %s)", body)
}
}
{
f2 := root.Find("dir2").Find("file3.txt")
if f2 == nil {
t.Fatal("could not find dir2/file3.txt")
}
s := f2.String()
if s != `123` {
t.Fatalf("dir2/file3.txt body is incorrect (got %s)", s)
}
}
{
empty := root.Find("emptyfile.txt")
if empty == nil {
t.Fatal("could not find emptyfile.txt")
}
if len(empty.Bytes()) != 0 {
t.Fatal("expecting emptyfile.txt to be empty")
}
}
{
var i int
root.Walk(func(_ string, _ os.FileInfo, _ error) error {
i++
return nil
})
if i != 7 {
t.Fatalf("expected to walk over 7 items, got %d", i)
}
}
{
var i int
root.Walk(func(_ string, fi os.FileInfo, _ error) error {
i++
if fi.IsDir() {
return filepath.SkipDir
}
return nil
})
if i != 4 {
t.Fatalf("expected to walk over 4 items, got %d", i)
}
}
}

2
doc.go
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// Package asar reads and writes ASAR (Atom-Shell Archive) archives.
package asar // import "b612.me/asar"

131
encoder.go
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package asar // import "b612.me/asar"
import (
"bytes"
"encoding/binary"
"encoding/json"
"io"
"strconv"
)
type entryEncoder struct {
Contents []io.Reader
CurrentOffset int64
Header bytes.Buffer
Encoder *json.Encoder
}
func (enc *entryEncoder) Write(v interface{}) {
enc.Encoder.Encode(v)
enc.Header.Truncate(enc.Header.Len() - 1) // cut off trailing new line
}
func (enc *entryEncoder) WriteField(key string, v interface{}) {
enc.Write(key)
enc.Header.WriteByte(':')
enc.Write(v)
}
func (enc *entryEncoder) Encode(e *Entry) error {
enc.Header.WriteByte('{')
if e.Flags&FlagDir != 0 {
if e.Flags&FlagUnpacked != 0 {
enc.WriteField("unpacked", true)
enc.Header.WriteByte(',')
}
enc.Write("files")
enc.Header.WriteString(":{")
for i, child := range e.Children {
if i > 0 {
enc.Header.WriteByte(',')
}
if !validFilename(child.Name) {
panic(errHeader)
}
enc.Write(child.Name)
enc.Header.WriteByte(':')
if err := enc.Encode(child); err != nil {
return err
}
}
enc.Header.WriteByte('}')
} else {
enc.Write("size")
enc.Header.WriteByte(':')
enc.Write(e.Size)
if e.Flags&FlagExecutable != 0 {
enc.Header.WriteByte(',')
enc.WriteField("executable", true)
}
enc.Header.WriteByte(',')
if e.Flags&FlagUnpacked == 0 {
enc.WriteField("offset", strconv.FormatInt(enc.CurrentOffset, 10))
enc.CurrentOffset += e.Size
enc.Contents = append(enc.Contents, io.NewSectionReader(e.r, e.Offset+e.baseOffset, e.Size))
} else {
enc.WriteField("unpacked", true)
}
}
enc.Header.WriteByte('}')
return nil
}
// EncodeTo writes an ASAR archive containing Entry's descendants. This function
// is usally called on the root entry.
func (e *Entry) EncodeTo(w io.Writer) (n int64, err error) {
defer func() {
if r := recover(); r != nil {
if e := r.(error); e != nil {
err = e
} else {
panic(r)
}
}
}()
encoder := entryEncoder{}
{
var reserve [16]byte
encoder.Header.Write(reserve[:])
}
encoder.Encoder = json.NewEncoder(&encoder.Header)
if err = encoder.Encode(e); err != nil {
return
}
length := encoder.Header.Len() - 16
var newLen int
{
var padding [3]byte
if mod := length % 4; mod != 0 {
encoder.Header.Write(padding[:4-mod])
}
newLen = encoder.Header.Len() - 16
}
header := encoder.Header.Bytes()
binary.LittleEndian.PutUint32(header[:4], 4)
binary.LittleEndian.PutUint32(header[4:8], 8+uint32(newLen))
binary.LittleEndian.PutUint32(header[8:12], 4+uint32(newLen))
binary.LittleEndian.PutUint32(header[12:16], uint32(length))
n, err = encoder.Header.WriteTo(w)
if err != nil {
return
}
for _, chunk := range encoder.Contents {
var written int64
written, err = io.Copy(w, chunk)
n += written
if err != nil {
return
}
}
return
}

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encoder_test.go
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package asar // import "b612.me/asar"
import (
"io/ioutil"
"strings"
"testing"
)
func TestEncodeInvalidName(t *testing.T) {
root := New(".", nil, 0, 0, FlagDir)
root.Children = append(
root.Children,
New(".", strings.NewReader("test"), 4, 0, FlagNone),
)
if _, err := root.EncodeTo(ioutil.Discard); err == nil {
t.Fatal("we should have had an error")
}
}
func TestEncodeUnpacked(t *testing.T) {
root := New(".", nil, 0, 0, FlagDir)
root.Children = append(
root.Children,
New("sample", nil, 0, 0, FlagUnpacked),
)
if _, err := root.EncodeTo(ioutil.Discard); err != nil {
t.Fatalf("err: %s", err)
}
}

231
entry.go
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package asar // import "b612.me/asar"
import (
"errors"
"io"
"io/ioutil"
"os"
"path/filepath"
"strings"
"time"
)
// Flag is a bit field of Entry flags.
type Flag uint32
const (
// FlagNone denotes an entry with no flags.
FlagNone Flag = 0
// FlagDir denotes a directory entry.
FlagDir Flag = 1 << iota
// FlagExecutable denotes a file with the executable bit set.
FlagExecutable
// FlagUnpacked denotes that the entry's contents are not included in
// the archive.
FlagUnpacked
)
// Entry is a file or a folder in an ASAR archive.
type Entry struct {
Name string
Size int64
Offset int64
Flags Flag
Parent *Entry
Children []*Entry
r io.ReaderAt
baseOffset int64
}
// New creates a new Entry.
func New(name string, ra io.ReaderAt, size, offset int64, flags Flag) *Entry {
return &Entry{
Name: name,
Size: size,
Offset: offset,
Flags: flags,
r: ra,
}
}
// FileInfo returns the os.FileInfo information about the entry.
func (e *Entry) FileInfo() os.FileInfo {
return fileInfo{e}
}
type fileInfo struct {
e *Entry
}
func (f fileInfo) Name() string {
return f.e.Name
}
func (f fileInfo) Size() int64 {
return f.e.Size
}
func (f fileInfo) Mode() os.FileMode {
if f.e.Flags&FlagDir != 0 {
return 0555 | os.ModeDir
}
if f.e.Flags&FlagExecutable != 0 {
return 0555
}
return 0444
}
func (f fileInfo) ModTime() time.Time {
return time.Time{}
}
func (f fileInfo) IsDir() bool {
return f.e.Flags&FlagDir != 0
}
func (f fileInfo) Sys() interface{} {
return f.e
}
// Path returns the file path to the entry.
//
// For example, given the following tree structure:
//
// root
// - sub1
// - sub2
// - file2.jpg
//
// file2.jpg's path would be:
//
// sub2/file2.jpg
func (e *Entry) Path() string {
if e.Parent == nil {
return ""
}
var p []string
for e != nil && e.Parent != nil {
p = append(p, e.Name)
e = e.Parent
}
l := len(p) / 2
for i := 0; i < l; i++ {
j := len(p) - i - 1
p[i], p[j] = p[j], p[i]
}
return strings.Join(p, "/")
}
// Open returns an *io.SectionReader of the entry's contents. nil is returned if
// the entry cannot be opened (e.g. because it is a directory).
func (e *Entry) Open() *io.SectionReader {
if e.Flags&FlagDir != 0 || e.Flags&FlagUnpacked != 0 {
return nil
}
return io.NewSectionReader(e.r, e.baseOffset+e.Offset, e.Size)
}
// WriteTo writes the entry's contents to the given writer. nil is returned if the entry cannot
// be opened (e.g. if the entry is a directory).
func (e *Entry) WriteTo(w io.Writer) (n int64, err error) {
r := e.Open()
if r == nil {
return 0, errors.New("asar: entry cannot be opened")
}
return io.Copy(w, r)
}
// Bytes returns the entry's contents as a byte slice. nil is returned if the
// entry cannot be read.
func (e *Entry) Bytes() []byte {
body := e.Open()
if body == nil {
return nil
}
b, err := ioutil.ReadAll(body)
if err != nil {
return nil
}
return b
}
// Bytes returns the entry's contents as a string. nil is returned if the entry
// cannot be read.
func (e *Entry) String() string {
body := e.Bytes()
if body == nil {
return ""
}
return string(body)
}
// Find searches for a sub-entry of the current entry. nil is returned if the
// requested sub-entry cannot be found.
//
// For example, given the following tree structure:
//
// root
// - sub1
// - sub2
// - sub2.1
// - file2.jpg
//
// The following expression would return the .jpg *Entry:
//
// root.Find("sub2", "sub2.1", "file2.jpg")
func (e *Entry) Find(path ...string) *Entry {
pathLoop:
for _, name := range path {
for _, child := range e.Children {
if child.Name == name {
e = child
continue pathLoop
}
}
return nil
}
return e
}
// Walk recursively walks over the entry's children. See filepath.Walk and
// filepath.WalkFunc for more information.
func (e *Entry) Walk(walkFn filepath.WalkFunc) error {
return walk(e, "", walkFn)
}
func walk(e *Entry, parentPath string, walkFn filepath.WalkFunc) error {
for i := 0; i < len(e.Children); i++ {
child := e.Children[i]
childPath := parentPath + child.Name
err := walkFn(childPath, child.FileInfo(), nil)
if err == filepath.SkipDir {
continue
}
if err != nil {
return err
}
if child.Flags&FlagDir == 0 {
continue
}
if err := walk(child, childPath+"/", walkFn); err != nil {
return err
}
}
return nil
}
func validFilename(filename string) bool {
if filename == "." || filename == ".." {
return false
}
return strings.IndexAny(filename, "\x00\\/") == -1
}

3
go.mod
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module b612.me/asar
go 1.17

212
header.go
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package asar // import "b612.me/asar"
import (
"encoding/json"
"errors"
"io"
)
var (
errHeader = errors.New("asar: invalid file header")
)
type jsonReader struct {
ASAR io.ReaderAt
BaseOffset int64
D *json.Decoder
Token json.Token
}
func (j *jsonReader) Peek() json.Token {
if j.Token != nil {
return j.Token
}
tkn, err := j.D.Token()
if err != nil {
if err == io.EOF {
return nil
}
panic(err)
}
j.Token = tkn
return tkn
}
func (j *jsonReader) HasDelimRune(r rune) bool {
peek := j.Peek()
ru, ok := peek.(json.Delim)
if !ok {
return false
}
if rune(ru) != r {
return false
}
return true
}
func (j *jsonReader) Next() json.Token {
if j.Token != nil {
t := j.Token
j.Token = nil
return t
}
tkn, err := j.D.Token()
if err != nil {
if err == io.EOF {
return nil
}
panic(err)
}
return tkn
}
func (j *jsonReader) NextDelimRune() rune {
tkn := j.Next()
r, ok := tkn.(json.Delim)
if !ok {
panic(errHeader)
}
return rune(r)
}
func (j *jsonReader) ExpectDelim(r rune) {
next := j.NextDelimRune()
if next != r {
panic(errHeader)
}
}
func (j *jsonReader) ExpectBool() bool {
tkn := j.Next()
b, ok := tkn.(bool)
if !ok {
panic(errHeader)
}
return b
}
func (j *jsonReader) ExpectString() string {
next := j.Next()
str, ok := next.(string)
if !ok {
panic(errHeader)
}
return str
}
func (j *jsonReader) ExpectStringVal(val string) {
str := j.ExpectString()
if str != val {
panic(errHeader)
}
}
func (j *jsonReader) ExpectInt64() int64 {
var number json.Number
switch j.Peek().(type) {
case string:
number = json.Number(j.ExpectString())
case json.Number:
number = j.Next().(json.Number)
default:
panic(errHeader)
}
val, err := number.Int64()
if err != nil {
panic(errHeader)
}
return val
}
func parseRoot(r *jsonReader) *Entry {
entry := &Entry{
Flags: FlagDir,
}
r.ExpectDelim('{')
r.ExpectStringVal("files")
parseFiles(r, entry)
r.ExpectDelim('}')
if r.Next() != nil {
panic(errHeader)
}
return entry
}
func parseFiles(r *jsonReader, parent *Entry) {
r.ExpectDelim('{')
for !r.HasDelimRune('}') {
parseEntry(r, parent)
}
r.ExpectDelim('}')
}
func parseEntry(r *jsonReader, parent *Entry) {
name := r.ExpectString()
if name == "" {
panic(errHeader)
}
if !validFilename(name) {
panic(errHeader)
}
r.ExpectDelim('{')
child := &Entry{
Name: name,
Parent: parent,
}
for !r.HasDelimRune('}') {
switch r.ExpectString() {
case "files":
child.Flags |= FlagDir
parseFiles(r, child)
case "size":
child.Size = r.ExpectInt64()
case "offset":
child.Offset = r.ExpectInt64()
case "unpacked":
if r.ExpectBool() {
child.Flags |= FlagUnpacked
}
case "executable":
if r.ExpectBool() {
child.Flags |= FlagExecutable
}
default:
panic(errHeader)
}
}
if child.Flags&FlagDir == 0 {
child.r = r.ASAR
child.baseOffset = r.BaseOffset
}
parent.Children = append(parent.Children, child)
r.ExpectDelim('}')
}
func decodeHeader(asar io.ReaderAt, header *io.SectionReader, offset int64) (entry *Entry, err error) {
decoder := json.NewDecoder(header)
decoder.UseNumber()
reader := jsonReader{
ASAR: asar,
BaseOffset: offset,
D: decoder,
}
defer func() {
if r := recover(); r != nil {
if e := r.(error); e != nil {
err = e
} else {
panic(r)
}
}
}()
entry = parseRoot(&reader)
return
}

20
testdata/LICENSE vendored
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Copyright (c) 2014 GitHub Inc.
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

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testdata/extractthis/dir1/file1.txt vendored
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file one.

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testdata/extractthis/dir2/file3.txt vendored
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testdata/extractthis/emptyfile.txt vendored
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testdata/extractthis/file0.txt vendored
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file0 content
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