43 lines
910 B
Go
43 lines
910 B
Go
package attachment
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import (
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"io"
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"github.com/pkg/errors"
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)
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type Open = func() (io.ReadCloser, error)
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// ReusableReader provides an API which allows a reader to be used multiple
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// times. It is NOT thread-safe to use.
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type ReusableReader struct {
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open func() (io.ReadCloser, error)
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src io.ReadCloser
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}
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var _ io.Reader = (*ReusableReader)(nil)
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// NewReusableReader creates a new reader that is reusable after a read failure
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// or a close. The given open() callback MUST be reproducible.
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func NewReusableReader(open Open) *ReusableReader {
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return &ReusableReader{open, nil}
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}
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func (r *ReusableReader) Read(b []byte) (int, error) {
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if r.src == nil {
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o, err := r.open()
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if err != nil {
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return 0, errors.Wrap(err, "Failed to open reader")
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}
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r.src = o
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}
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n, err := r.src.Read(b)
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if err != nil { // err could be EOF or anything unexpected
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r.src.Close()
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r.src = nil
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}
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return n, err
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}
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