dos2unix - dos2unix.go

     1  // Package dos2unix provides functions to convert between dos and unix line
     2  // termination styles
     3  package dos2unix // import "vimagination.zapto.org/dos2unix"
     4  
     5  import (
     6  	"io"
     7  	"slices"
     8  )
     9  
    10  type byteReader struct {
    11  	io.Reader
    12  	buf [1]byte
    13  }
    14  
    15  func (b *byteReader) ReadByte() (byte, error) {
    16  	_, err := io.ReadFull(b.Reader, b.buf[:])
    17  	return b.buf[0], err
    18  }
    19  
    20  type dos2unix struct {
    21  	r    io.Reader
    22  	b    bool
    23  	char [1]byte
    24  }
    25  
    26  func (d *dos2unix) Read(b []byte) (int, error) {
    27  	if len(b) == 0 {
    28  		return 0, nil
    29  	}
    30  
    31  	var n int
    32  
    33  	s := b
    34  
    35  	if d.b {
    36  		b[0] = d.char[0]
    37  		s = b[1:]
    38  		n = 1
    39  
    40  		if d.b = len(s) == 0 && b[0] == '\r'; d.b {
    41  			_, err := d.r.Read(d.char[:])
    42  			if d.char[0] == '\n' {
    43  				b[0] = '\n'
    44  				d.b = false
    45  			}
    46  
    47  			return n, err
    48  		}
    49  	}
    50  
    51  	m, err := d.r.Read(s)
    52  	n += m
    53  
    54  	lastIsCR := false
    55  
    56  	for i := 0; i < n; i++ {
    57  		c := b[i]
    58  		if lastIsCR && c == '\n' {
    59  			b = slices.Delete(b, i-1, i)
    60  			n--
    61  			i--
    62  		}
    63  
    64  		lastIsCR = c == '\r'
    65  	}
    66  
    67  	if lastIsCR && err == nil {
    68  		n--
    69  		d.char[0] = '\r'
    70  	}
    71  
    72  	d.b = lastIsCR
    73  
    74  	return n, err
    75  }
    76  
    77  // DOS2Unix wraps a byte reader with a reader that replaces all instances of
    78  // \r\n with \n
    79  func DOS2Unix(r io.Reader) io.Reader {
    80  	return &dos2unix{r: r}
    81  }
    82  
    83  type unix2dos struct {
    84  	r  io.ByteReader
    85  	lf bool
    86  }
    87  
    88  func (u *unix2dos) Read(b []byte) (int, error) {
    89  	var n int
    90  	for len(b) > 0 {
    91  		if u.lf {
    92  			b[0] = '\n'
    93  			u.lf = false
    94  			b = b[1:]
    95  			n++
    96  			continue
    97  		}
    98  		c, err := u.r.ReadByte()
    99  		if err != nil {
   100  			return n, err
   101  		}
   102  		if c == '\n' {
   103  			u.lf = true
   104  			c = '\r'
   105  		}
   106  		b[0] = c
   107  		b = b[1:]
   108  		n++
   109  	}
   110  	return n, nil
   111  }
   112  
   113  // Unix2DOS wraps a byte reader with a reader that replaces all instances of \n
   114  // with \r\n.
   115  //
   116  // When reading from a non-buffered input, it is recommended to wrap the Reader
   117  // with a bufio.Reader.
   118  func Unix2DOS(r io.Reader) io.Reader {
   119  	br, ok := r.(io.ByteReader)
   120  	if !ok {
   121  		br = &byteReader{Reader: r}
   122  	}
   123  	return &unix2dos{r: br}
   124  }
   125