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io_reader.go
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/
io_reader.go
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package contextaware
import (
"context"
"io"
"time"
)
// A Reader is an io.Reader that also supports cancellation via a context.Context.
type Reader interface {
io.Reader
ReadContext(ctx context.Context, p []byte) (n int, err error)
}
// NewReader creates a new contextaware.Reader from an existing io.Reader.
func NewReader(r io.Reader) Reader {
return WrapIO(r).(Reader)
}
func wrapReader(r io.Reader) Reader {
if cr, ok := r.(Reader); ok {
return cr
}
if obj, ok := supportsSetReadDeadline(r); ok {
return readerViaSetDeadline{r, obj.SetReadDeadline}
}
if obj, ok := supportsSetDeadline(r); ok {
return readerViaSetDeadline{r, obj.SetDeadline}
}
return readerViaRead{r}
}
type readerViaRead struct {
io.Reader
}
func (r readerViaRead) ReadContext(ctx context.Context, p []byte) (n int, err error) {
select {
case <-ctx.Done():
return 0, ctx.Err()
default:
}
return r.Read(p)
}
type readerViaSetDeadline struct {
io.Reader
setDeadline func(time.Time) error
}
func (r readerViaSetDeadline) ReadContext(ctx context.Context, p []byte) (n int, err error) {
return withCancelViaDeadline(ctx, r.setDeadline, func() (int, error) {
return r.Read(p)
})
}