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