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package oci
import (
"context"
"fmt"
"io"
"os"
ocispec "github.com/opencontainers/image-spec/specs-go/v1"
oras "oras.land/oras-go/v2"
"oras.land/oras-go/v2/registry/remote"
)
func FetchImageBlob(r, reference, dst string, statusReader func(ocispec.Descriptor) io.Writer) error {
// 0. Create a file store for the output
fs, err := os.Create(dst)
if err != nil {
return err
}
defer fs.Close()
// 1. Connect to a remote repository
ctx := context.Background()
repo, err := remote.NewRepository(r)
if err != nil {
return fmt.Errorf("failed to create repository: %v", err)
}
repo.SkipReferrersGC = true
// https://github.com/oras-project/oras/blob/main/cmd/oras/internal/option/remote.go#L364
// https://github.com/oras-project/oras/blob/main/cmd/oras/root/blob/fetch.go#L136
desc, reader, err := oras.Fetch(ctx, repo.Blobs(), reference, oras.DefaultFetchOptions)
if err != nil {
return fmt.Errorf("failed to fetch image: %v", err)
}
if statusReader != nil {
// 3. Write the file to the file store
_, err = io.Copy(io.MultiWriter(fs, statusReader(desc)), reader)
if err != nil {
return err
}
} else {
_, err = io.Copy(fs, reader)
if err != nil {
return err
}
}
return nil
}
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