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example_test.go
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example_test.go
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/*
* zipindex, (C)2021 MinIO, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package zipindex_test
import (
"bytes"
"errors"
"fmt"
"io"
"log"
"os"
"github.com/minio/zipindex"
)
func ExampleReadDir() {
b, err := os.ReadFile("testdata/big.zip")
if err != nil {
panic(err)
}
// We only need the end of the file to parse the directory.
// Usually this should be at least 64K on initial try.
sz := 10 << 10
var files zipindex.Files
for {
files, err = zipindex.ReadDir(b[len(b)-sz:], int64(len(b)), nil)
if err == nil {
fmt.Printf("Got %d files\n", len(files))
break
}
var terr zipindex.ErrNeedMoreData
if errors.As(err, &terr) {
if terr.FromEnd > 1<<20 {
panic("we will only provide max 1MB data")
}
sz = int(terr.FromEnd)
fmt.Printf("Retrying with %d bytes at the end of file\n", sz)
} else {
// Unable to parse...
panic(err)
}
}
fmt.Printf("First file: %+v", files[0])
// Output:
// Retrying with 57912 bytes at the end of file
// Got 1000 files
// First file: {Name:file-0.txt CompressedSize64:1 UncompressedSize64:1 Offset:0 CRC32:4108050209 Method:0 Flags:0 Custom:map[]}
}
// ExampleReadFile demonstrates how to read the index of a file on disk.
func ExampleReadFile() {
files, err := zipindex.ReadFile("testdata/go-with-datadesc-sig.zip", nil)
if err != nil {
panic(err)
}
fmt.Printf("Got %d files\n", len(files))
fmt.Printf("First file: %+v", files[0])
// Output:
// Got 2 files
// First file: {Name:foo.txt CompressedSize64:4 UncompressedSize64:4 Offset:0 CRC32:2117232040 Method:0 Flags:8 Custom:map[]}
}
// ExampleReadFile demonstrates how to read the index of a file on disk.
func ExampleReaderAt() {
f, err := os.Open("testdata/big.zip")
if err != nil {
panic(err)
}
fi, err := f.Stat()
if err != nil {
panic(err)
}
// Read and allow up to 10MB index.
files, err := zipindex.ReaderAt(f, fi.Size(), 10<<20, nil)
if err != nil {
panic(err)
}
fmt.Printf("Got %d files\n", len(files))
fmt.Printf("First file: %+v", files[0])
// Output:
// Got 1000 files
// First file: {Name:file-0.txt CompressedSize64:1 UncompressedSize64:1 Offset:0 CRC32:4108050209 Method:0 Flags:0 Custom:map[]}
}
// ExampleFileFilter demonstrates how to filter incoming files.
func ExampleFileFilter() {
files, err := zipindex.ReadFile("testdata/unix.zip",
func(dst *zipindex.File, entry *zipindex.ZipDirEntry) *zipindex.File {
if dst.Name == "hello" {
// Filter out on specific properties.
return nil
}
// Add custom data.
if dst.Custom == nil {
dst.Custom = make(map[string]string, 3)
}
dst.Custom["modified"] = entry.Modified.String()
dst.Custom["perm"] = fmt.Sprintf("0%o", entry.Mode().Perm())
if len(entry.Comment) > 0 {
dst.Custom["comment"] = entry.Comment
}
return dst
})
if err != nil {
panic(err)
}
fmt.Printf("Got %d files\n", len(files))
for i, file := range files {
fmt.Printf("%d: %+v\n", i, file)
}
// Output:
// Got 3 files
// 0: {Name:dir/bar CompressedSize64:6 UncompressedSize64:6 Offset:71 CRC32:2055117726 Method:0 Flags:0 Custom:map[modified:2011-12-08 10:04:50 +0000 +0000 perm:0666]}
// 1: {Name:dir/empty/ CompressedSize64:0 UncompressedSize64:0 Offset:142 CRC32:0 Method:0 Flags:0 Custom:map[modified:2011-12-08 10:08:06 +0000 +0000 perm:0777]}
// 2: {Name:readonly CompressedSize64:12 UncompressedSize64:12 Offset:210 CRC32:3127775578 Method:0 Flags:0 Custom:map[modified:2011-12-08 10:06:08 +0000 +0000 perm:0444]}
}
// ExampleReadFile demonstrates how to read the index of a file on disk.
func ExampleFindSerialized() {
files, err := zipindex.ReadFile("testdata/go-with-datadesc-sig.zip", nil)
if err != nil {
panic(err)
}
files.OptimizeSize()
serialized, err := files.Serialize()
if err != nil {
panic(err)
}
file, err := zipindex.FindSerialized(serialized, "bar.txt")
if err != nil {
panic(err)
}
fmt.Printf("bar.txt: %+v", *file)
// Output:
// bar.txt: {Name:bar.txt CompressedSize64:4 UncompressedSize64:4 Offset:57 CRC32:0 Method:0 Flags:8 Custom:map[]}
}
func ExampleDeserializeFiles() {
exitOnErr := func(err error) {
if err != nil {
log.Fatalln(err)
}
}
b, err := os.ReadFile("testdata/big.zip")
exitOnErr(err)
// We only need the end of the file to parse the directory.
// Usually this should be at least 64K on initial try.
sz := 64 << 10
var files zipindex.Files
files, err = zipindex.ReadDir(b[len(b)-sz:], int64(len(b)), nil)
// Omitted: Check if ErrNeedMoreData and retry with more data
exitOnErr(err)
// OptimizeSize files will make the size as efficient as possible
// without loosing data.
files.OptimizeSize()
// Serialize files to binary.
serialized, err := files.Serialize()
exitOnErr(err)
// This output may change if compression is improved.
// Output is rounded up.
fmt.Printf("Size of serialized data: %dKB\n", (len(serialized)+1023)/1024)
// StripCRC(true) will strip CRC, even if there is no file descriptor.
files.StripCRC(true)
// StripFlags(1<<3) will strip all flags that aren't a file descriptor flag (bit 3).
files.StripFlags(1 << 3)
noCRC, err := files.Serialize()
exitOnErr(err)
// This output may change if compression is improved.
// Output is rounded up.
fmt.Printf("Size of serialized data without CRC: %dKB\n", (len(noCRC)+1023)/1024)
// Deserialize the content (with CRC).
files, err = zipindex.DeserializeFiles(serialized)
exitOnErr(err)
file := files.Find("file-10.txt")
fmt.Printf("Reading file: %+v\n", *file)
// Create a reader with entire zip file...
rs := bytes.NewReader(b)
// Seek to the file offset.
_, err = rs.Seek(file.Offset, io.SeekStart)
exitOnErr(err)
// Provide the forwarded reader..
rc, err := file.Open(rs)
exitOnErr(err)
defer rc.Close()
// Read the zip file content.
content, err := io.ReadAll(rc)
exitOnErr(err)
fmt.Printf("File content is '%s'\n", string(content))
// Output:
// Size of serialized data: 6KB
// Size of serialized data without CRC: 1KB
// Reading file: {Name:file-10.txt CompressedSize64:2 UncompressedSize64:2 Offset:410 CRC32:2707236321 Method:0 Flags:0 Custom:map[]}
// File content is '10'
}