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49 lines
787 B
49 lines
787 B
package pdf
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import (
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"io"
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)
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type alphaReader struct {
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reader io.Reader
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}
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func newAlphaReader(reader io.Reader) *alphaReader {
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return &alphaReader{reader: reader}
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}
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func checkASCII85(r byte) byte {
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if r >= '!' && r <= 'u' { // 33 <= ascii85 <=117
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return r
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}
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if r == '~' {
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return 1 // for marking possible end of data
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}
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return 0 // if non-ascii85
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}
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func (a *alphaReader) Read(p []byte) (int, error) {
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n, err := a.reader.Read(p)
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if err == io.EOF {
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}
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if err != nil {
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return n, err
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}
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buf := make([]byte, n)
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tilda := false
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for i := 0; i < n; i++ {
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char := checkASCII85(p[i])
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if char == '>' && tilda { // end of data
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break
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}
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if char > 1 {
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buf[i] = char
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}
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if char == 1 {
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tilda = true // possible end of data
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}
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}
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copy(p, buf)
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return n, nil
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}
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