golang zip

zip.go

package packaging

import (
	"archive/zip"
	"io"
)

type PackageContents struct {
	Data     io.Reader
	FileName string
}

// Writes a zip file to the writer with the package contents
func Zip(contents []PackageContents, output io.Writer) error {
	zipWriter := zip.NewWriter(output)

	for _, file := range contents {
		zipEntry, err := zipWriter.CreateHeader(&zip.FileHeader{
			Name: file.FileName,
		})

		if err != nil {
			return err
		}

		_, err = io.Copy(zipEntry, file.Data)
		if err != nil {
			return err
		}
	}

	err := zipWriter.Close()
	if err != nil {
		return err
	}

	return nil
}

// Given a zip file reader stream gets a writer for each file
// and allows you to dump the contents of the zip file to the writer
// zips require random access so we need to know the content size
// and have a reader that supports random reads
func Unzip(zipFile io.ReaderAt, contentsSize int, writerProvider func(fileName string) io.Writer) error {
	zipReader, err := zip.NewReader(zipFile, int64(contentsSize))
	if err != nil {
		return err
	}

	for _, file := range zipReader.File {
		fileWriter := writerProvider(file.Name)

		fileReaderCloser, err := file.Open()
		if err != nil {
			return err
		}

		_, err = io.Copy(fileWriter, fileReaderCloser)
		if err != nil {
			return err
		}
	}

	return nil
}

zip_test.go

package packaging

import (
	"bytes"
	"io"
	"io/ioutil"
	"testing"

	"github.com/stretchr/testify/assert"
)

func TestZipUnzip(t *testing.T) {
	testFileData := "data"

	buffer := bytes.NewBuffer([]byte{})

	testFile := PackageContents{
		FileName: "test.txt",
		Data:     bytes.NewReader([]byte(testFileData)),
	}

	_ = Zip([]PackageContents{testFile}, buffer)

	zippedBytes, _ := ioutil.ReadAll(buffer)

	assert.True(t, len(zippedBytes) > 0)

	resultBuffer := bytes.NewBuffer([]byte{})

	_ = Unzip(bytes.NewReader(zippedBytes), len(zippedBytes), func(fileName string) io.Writer {
		// verify the filename is properly called back
		t.Helper()
		assert.Equal(t, testFile.FileName, fileName)

		return resultBuffer
	})

	unzippedTestFileData, _ := ioutil.ReadAll(resultBuffer)

	// assert we were able to unzip the data and that the resulting file is equal to the
	// original
	assert.Equal(t, []byte(testFileData), unzippedTestFileData)
}