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|
package zip
import (
"errors"
"io"
)
type httpReadAt struct {
URL string
Size int64
cached bool
cachedReader *httpReader
}
func (h *httpReadAt) cachedRead(p []byte, off int64) (n int, err error) {
if off < 0 || off > h.Size {
return 0, errors.New("outside of bounds")
}
if h.cachedReader != nil && (h.cachedReader.Off != off || h.cachedReader.N < int64(len(p))) {
h.cachedReader.Close()
h.cachedReader = nil
}
if h.cachedReader == nil {
h.cachedReader = &httpReader{URL: h.URL, Off: off, N: h.Size - off}
}
return io.ReadFull(h.cachedReader, p)
}
func (h *httpReadAt) ephemeralRead(p []byte, off int64) (n int, err error) {
r := httpReader{URL: h.URL, Off: off, N: int64(len(p))}
defer r.Close()
return io.ReadFull(&r, p)
}
func (h *httpReadAt) ReadAt(p []byte, off int64) (n int, err error) {
if h.cached {
return h.cachedRead(p, off)
}
return h.ephemeralRead(p, off)
}
func (h *httpReadAt) withCachedReader(fn func()) {
h.cached = true
defer func() {
if h.cachedReader != nil {
h.cachedReader.Close()
}
h.cached = false
}()
fn()
}
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