9c88801a12
Back in the before time, the best practices surrounding usage of Context weren't quite worked out. We defined our own type to make usage easier. As this packaged was used elsewhere, it make it more and more challenging to integrate with the forked `Context` type. Now that it is available in the standard library, we can just use that one directly. To make usage more consistent, we now use `dcontext` when referring to the distribution context package. Signed-off-by: Stephen J Day <stephen.day@docker.com>
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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"io/ioutil"
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"github.com/docker/distribution/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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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 ioutil.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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