64 lines
1.1 KiB
Go
64 lines
1.1 KiB
Go
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package ctxio
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import (
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"context"
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"errors"
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"io"
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"sync"
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)
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type CacheReader struct {
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m sync.Mutex
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fo int64
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fr *FileBuffer
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to int64
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tr Reader
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}
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var _ FileReader = (*CacheReader)(nil)
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func NewCacheReader(r Reader) (FileReader, error) {
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fr := NewFileBuffer(nil)
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tr := TeeReader(r, fr)
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return &CacheReader{fr: fr, tr: tr}, nil
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}
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func (dtr *CacheReader) ReadAt(ctx context.Context, p []byte, off int64) (int, error) {
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dtr.m.Lock()
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defer dtr.m.Unlock()
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tb := off + int64(len(p))
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if tb > dtr.fo {
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w, err := CopyN(ctx, Discard, dtr.tr, tb-dtr.fo)
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dtr.to += w
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if err != nil && err != io.EOF {
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return 0, err
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}
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}
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n, err := dtr.fr.ReadAt(ctx, p, off)
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dtr.fo += int64(n)
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return n, err
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}
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func (dtr *CacheReader) Read(ctx context.Context, p []byte) (n int, err error) {
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dtr.m.Lock()
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defer dtr.m.Unlock()
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// use directly tee reader here
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n, err = dtr.tr.Read(ctx, p)
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dtr.to += int64(n)
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return
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}
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func (dtr *CacheReader) Close(ctx context.Context) error {
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frcloser := dtr.fr.Close(ctx)
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var closeerr error
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if rc, ok := dtr.tr.(ReadCloser); ok {
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closeerr = rc.Close(ctx)
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}
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return errors.Join(frcloser, closeerr)
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}
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