44 lines
852 B
Go
44 lines
852 B
Go
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package media
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import (
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"bytes"
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"io"
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)
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// ModuloReader reads from a reader in block sizes that are exactly modulo
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// modSize, with any remainder buffered until the next read.
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type ModuloReader struct {
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io.ReadCloser
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buf bytes.Buffer
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modSize int
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}
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func NewModuloReader(r io.ReadCloser, modSize int) *ModuloReader {
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return &ModuloReader{ReadCloser: r, modSize: modSize}
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}
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func (r *ModuloReader) Read(p []byte) (int, error) {
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// err is always io.EOF or nil
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nr1, _ := r.buf.Read(p)
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nr2, err := r.ReadCloser.Read(p[nr1:])
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nr := nr1 + nr2
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rem := nr % r.modSize
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// if there was an error, return immediately.
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if err == io.EOF {
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return nr, err
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} else if err != nil {
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return nr - rem, err
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}
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// write any remainder to the buffer
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if rem != 0 {
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// err is always nil
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_, _ = r.buf.Write(p[nr-rem : nr])
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}
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return nr - rem, err
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}
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