Blob.go

gistfile1.txt

// SPDX-License-Identifier: Apache-2.0

package gitinterface

import (
	"bytes"
	"errors"
	"io"
	"os/exec"

	"github.com/gittuf/gittuf/internal/third_party/go-git"
	"github.com/gittuf/gittuf/internal/third_party/go-git/plumbing"
	"github.com/gittuf/gittuf/internal/third_party/go-git/plumbing/object"
	"github.com/gittuf/gittuf/internal/third_party/go-git/storage/memory"
)

type Blob interface {
	GetBlob(repo *git.Repository, blobID plumbing.Hash) (*object.Blob, error)
	WriteBlob(repo *git.Repository, contents []byte) (plumbing.Hash, error)
	ReadBlob(repo *git.Repository, blobID plumbing.Hash) ([]byte, error)
	EmptyBlob() plumbing.Hash
}

type blob struct{}

type BlobType int

const (
	GoGitBlob     BlobType = iota
	GitBinaryBlob          // Use git binary to get blob

)

func NewBlob(gitType BlobType) Blob {
	switch gitType {
	case GoGitBlob:
		return &blob{}
	case GitBinaryBlob:
		return &blob{}
	}

}

var ErrWrittenBlobLengthMismatch = errors.New("length of blob written does not match length of contents")

// ReadBlob returns the contents of a the blob referenced by blobID.
func (b *blob) ReadBlob(repo *git.Repository, blobID plumbing.Hash) ([]byte, error) {
	blob1, err := b.GetBlob(repo, blobID)
	if err != nil {
		return nil, err
	}

	reader, err := blob1.Reader()
	if err != nil {
		return nil, err
	}

	return io.ReadAll(reader)
}

// WriteBlob creates a blob object with the specified contents and returns the
// ID of the resultant blob.
func (b *blob) WriteBlob(repo *git.Repository, contents []byte) (plumbing.Hash, error) {
	obj := repo.Storer.NewEncodedObject()
	obj.SetType(plumbing.BlobObject)

	writer, err := obj.Writer()
	if err != nil {
		return plumbing.ZeroHash, err
	}

	length, err := writer.Write(contents)
	if err != nil {
		return plumbing.ZeroHash, err
	}

	if length != len(contents) {
		return plumbing.ZeroHash, ErrWrittenBlobLengthMismatch
	}

	return repo.Storer.SetEncodedObject(obj)
}

// GetBlob returns the requested blob object.
func (b *blob) GetBlob(repo *git.Repository, blobID plumbing.Hash) (*object.Blob, error) {
	
	return repo.BlobObject(blobID)
}

// EmptyBlob returns the hash of an empty blob in a Git repository.
// Note: it is generated on the fly rather than stored as a constant to support
// SHA-256 repositories in future.
func (b *blob) EmptyBlob() plumbing.Hash {
	obj := memory.NewStorage().NewEncodedObject()
	obj.SetType(plumbing.BlobObject)

	return obj.Hash()
}