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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package tiff
import (
"bufio"
"io"
)
type byteReader interface {
io.Reader
io.ByteReader
}
// unpackBits decodes the PackBits-compressed data in src and returns the
// uncompressed data.
//
// The PackBits compression format is described in section 9 (p. 42)
// of the TIFF spec.
func unpackBits(r io.Reader) ([]byte, error) {
buf := make([]byte, 128)
dst := make([]byte, 0, 1024)
br, ok := r.(byteReader)
if !ok {
br = bufio.NewReader(r)
}
for {
b, err := br.ReadByte()
if err != nil {
if err == io.EOF {
return dst, nil
}
return nil, err
}
code := int(int8(b))
switch {
case code >= 0:
n, err := io.ReadFull(br, buf[:code+1])
if err != nil {
return nil, err
}
dst = append(dst, buf[:n]...)
case code == -128:
// No-op.
default:
if b, err = br.ReadByte(); err != nil {
return nil, err
}
for j := 0; j < 1-code; j++ {
buf[j] = b
}
dst = append(dst, buf[:1-code]...)
}
}
}
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