forked from TrueCloudLab/distribution
71 lines
1.5 KiB
Go
71 lines
1.5 KiB
Go
package storage
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import (
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"context"
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"errors"
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"io"
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"github.com/distribution/distribution/v3/registry/storage/driver"
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)
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const (
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maxBlobGetSize = 4 << 20
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)
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func getContent(ctx context.Context, driver driver.StorageDriver, p string) ([]byte, error) {
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r, err := driver.Reader(ctx, p, 0)
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if err != nil {
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return nil, err
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}
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defer r.Close()
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return readAllLimited(r, maxBlobGetSize)
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}
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func readAllLimited(r io.Reader, limit int64) ([]byte, error) {
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r = limitReader(r, limit)
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return io.ReadAll(r)
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}
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// limitReader returns a new reader limited to n bytes. Unlike io.LimitReader,
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// this returns an error when the limit reached.
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func limitReader(r io.Reader, n int64) io.Reader {
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return &limitedReader{r: r, n: n}
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}
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// limitedReader implements a reader that errors when the limit is reached.
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//
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// Partially cribbed from net/http.MaxBytesReader.
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type limitedReader struct {
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r io.Reader // underlying reader
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n int64 // max bytes remaining
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err error // sticky error
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}
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func (l *limitedReader) Read(p []byte) (n int, err error) {
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if l.err != nil {
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return 0, l.err
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}
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if len(p) == 0 {
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return 0, nil
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}
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// If they asked for a 32KB byte read but only 5 bytes are
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// remaining, no need to read 32KB. 6 bytes will answer the
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// question of the whether we hit the limit or go past it.
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if int64(len(p)) > l.n+1 {
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p = p[:l.n+1]
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}
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n, err = l.r.Read(p)
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if int64(n) <= l.n {
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l.n -= int64(n)
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l.err = err
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return n, err
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}
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n = int(l.n)
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l.n = 0
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l.err = errors.New("storage: read exceeds limit")
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return n, l.err
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}
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