image.go

Documentation: github.com/google/go-containerregistry/pkg/v1/random

     1  // Copyright 2018 Google LLC All Rights Reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //    http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package random
    16  
    17  import (
    18  	"archive/tar"
    19  	"bytes"
    20  	"crypto"
    21  	"encoding/hex"
    22  	"fmt"
    23  	"io"
    24  	"math/rand"
    25  
    26  	v1 "github.com/google/go-containerregistry/pkg/v1"
    27  	"github.com/google/go-containerregistry/pkg/v1/empty"
    28  	"github.com/google/go-containerregistry/pkg/v1/mutate"
    29  	"github.com/google/go-containerregistry/pkg/v1/partial"
    30  	"github.com/google/go-containerregistry/pkg/v1/types"
    31  )
    32  
    33  // uncompressedLayer implements partial.UncompressedLayer from raw bytes.
    34  type uncompressedLayer struct {
    35  	diffID    v1.Hash
    36  	mediaType types.MediaType
    37  	content   []byte
    38  }
    39  
    40  // DiffID implements partial.UncompressedLayer
    41  func (ul *uncompressedLayer) DiffID() (v1.Hash, error) {
    42  	return ul.diffID, nil
    43  }
    44  
    45  // Uncompressed implements partial.UncompressedLayer
    46  func (ul *uncompressedLayer) Uncompressed() (io.ReadCloser, error) {
    47  	return io.NopCloser(bytes.NewBuffer(ul.content)), nil
    48  }
    49  
    50  // MediaType returns the media type of the layer
    51  func (ul *uncompressedLayer) MediaType() (types.MediaType, error) {
    52  	return ul.mediaType, nil
    53  }
    54  
    55  var _ partial.UncompressedLayer = (*uncompressedLayer)(nil)
    56  
    57  // Image returns a pseudo-randomly generated Image.
    58  func Image(byteSize, layers int64, options ...Option) (v1.Image, error) {
    59  	adds := make([]mutate.Addendum, 0, 5)
    60  	for i := int64(0); i < layers; i++ {
    61  		layer, err := Layer(byteSize, types.DockerLayer, options...)
    62  		if err != nil {
    63  			return nil, err
    64  		}
    65  		adds = append(adds, mutate.Addendum{
    66  			Layer: layer,
    67  			History: v1.History{
    68  				Author:    "random.Image",
    69  				Comment:   fmt.Sprintf("this is a random history %d of %d", i, layers),
    70  				CreatedBy: "random",
    71  			},
    72  		})
    73  	}
    74  
    75  	return mutate.Append(empty.Image, adds...)
    76  }
    77  
    78  // Layer returns a layer with pseudo-randomly generated content.
    79  func Layer(byteSize int64, mt types.MediaType, options ...Option) (v1.Layer, error) {
    80  	o := getOptions(options)
    81  	rng := rand.New(o.source) //nolint:gosec
    82  
    83  	fileName := fmt.Sprintf("random_file_%d.txt", rng.Int())
    84  
    85  	// Hash the contents as we write it out to the buffer.
    86  	var b bytes.Buffer
    87  	hasher := crypto.SHA256.New()
    88  	mw := io.MultiWriter(&b, hasher)
    89  
    90  	// Write a single file with a random name and random contents.
    91  	tw := tar.NewWriter(mw)
    92  	if err := tw.WriteHeader(&tar.Header{
    93  		Name:     fileName,
    94  		Size:     byteSize,
    95  		Typeflag: tar.TypeReg,
    96  	}); err != nil {
    97  		return nil, err
    98  	}
    99  	if _, err := io.CopyN(tw, rng, byteSize); err != nil {
   100  		return nil, err
   101  	}
   102  	if err := tw.Close(); err != nil {
   103  		return nil, err
   104  	}
   105  
   106  	h := v1.Hash{
   107  		Algorithm: "sha256",
   108  		Hex:       hex.EncodeToString(hasher.Sum(make([]byte, 0, hasher.Size()))),
   109  	}
   110  
   111  	return partial.UncompressedToLayer(&uncompressedLayer{
   112  		diffID:    h,
   113  		mediaType: mt,
   114  		content:   b.Bytes(),
   115  	})
   116  }
   117
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