github.com/pdfcpu/pdfcpu@v0.11.1/pkg/filter/asciiHexDecode.go (about)

     1  /*
     2  Copyright 2018 The pdfcpu Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8  	http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package filter
    18  
    19  import (
    20  	"bytes"
    21  	"encoding/hex"
    22  	"io"
    23  )
    24  
    25  type asciiHexDecode struct {
    26  	baseFilter
    27  }
    28  
    29  const eodHexDecode = '>'
    30  
    31  // Encode implements encoding for an ASCIIHexDecode filter.
    32  func (f asciiHexDecode) Encode(r io.Reader) (io.Reader, error) {
    33  
    34  	bb, err := getReaderBytes(r)
    35  	if err != nil {
    36  		return nil, err
    37  	}
    38  
    39  	dst := make([]byte, hex.EncodedLen(len(bb)))
    40  	hex.Encode(dst, bb)
    41  
    42  	// eod marker
    43  	dst = append(dst, eodHexDecode)
    44  
    45  	return bytes.NewBuffer(dst), nil
    46  }
    47  
    48  // Decode implements decoding for an ASCIIHexDecode filter.
    49  func (f asciiHexDecode) Decode(r io.Reader) (io.Reader, error) {
    50  	return f.DecodeLength(r, -1)
    51  }
    52  
    53  func (f asciiHexDecode) DecodeLength(r io.Reader, maxLen int64) (io.Reader, error) {
    54  	bb, err := getReaderBytes(r)
    55  	if err != nil {
    56  		return nil, err
    57  	}
    58  
    59  	var p []byte
    60  
    61  	// Remove any white space and cut off on eod
    62  	for i := 0; i < len(bb); i++ {
    63  		if bb[i] == eodHexDecode {
    64  			break
    65  		}
    66  		if !bytes.ContainsRune([]byte{0x09, 0x0A, 0x0C, 0x0D, 0x20}, rune(bb[i])) {
    67  			p = append(p, bb[i])
    68  		}
    69  	}
    70  
    71  	// if len == odd add "0"
    72  	if len(p)%2 == 1 {
    73  		p = append(p, '0')
    74  	}
    75  
    76  	if maxLen < 0 {
    77  		maxLen = int64(hex.DecodedLen(len(p)))
    78  	}
    79  	dst := make([]byte, maxLen)
    80  
    81  	if _, err := hex.Decode(dst, p[:maxLen*2]); err != nil {
    82  		return nil, err
    83  	}
    84  
    85  	return bytes.NewBuffer(dst), nil
    86  }