wordwrap.go

Documentation: github.com/mitchellh/go-wordwrap

     1  package wordwrap
     2  
     3  import (
     4  	"bytes"
     5  	"unicode"
     6  )
     7  
     8  const nbsp = 0xA0
     9  
    10  // WrapString wraps the given string within lim width in characters.
    11  //
    12  // Wrapping is currently naive and only happens at white-space. A future
    13  // version of the library will implement smarter wrapping. This means that
    14  // pathological cases can dramatically reach past the limit, such as a very
    15  // long word.
    16  func WrapString(s string, lim uint) string {
    17  	// Initialize a buffer with a slightly larger size to account for breaks
    18  	init := make([]byte, 0, len(s))
    19  	buf := bytes.NewBuffer(init)
    20  
    21  	var current uint
    22  	var wordBuf, spaceBuf bytes.Buffer
    23  	var wordBufLen, spaceBufLen uint
    24  
    25  	for _, char := range s {
    26  		if char == '\n' {
    27  			if wordBuf.Len() == 0 {
    28  				if current+spaceBufLen > lim {
    29  					current = 0
    30  				} else {
    31  					current += spaceBufLen
    32  					spaceBuf.WriteTo(buf)
    33  				}
    34  				spaceBuf.Reset()
    35  				spaceBufLen = 0
    36  			} else {
    37  				current += spaceBufLen + wordBufLen
    38  				spaceBuf.WriteTo(buf)
    39  				spaceBuf.Reset()
    40  				spaceBufLen = 0
    41  				wordBuf.WriteTo(buf)
    42  				wordBuf.Reset()
    43  				wordBufLen = 0
    44  			}
    45  			buf.WriteRune(char)
    46  			current = 0
    47  		} else if unicode.IsSpace(char) && char != nbsp {
    48  			if spaceBuf.Len() == 0 || wordBuf.Len() > 0 {
    49  				current += spaceBufLen + wordBufLen
    50  				spaceBuf.WriteTo(buf)
    51  				spaceBuf.Reset()
    52  				spaceBufLen = 0
    53  				wordBuf.WriteTo(buf)
    54  				wordBuf.Reset()
    55  				wordBufLen = 0
    56  			}
    57  
    58  			spaceBuf.WriteRune(char)
    59  			spaceBufLen++
    60  		} else {
    61  			wordBuf.WriteRune(char)
    62  			wordBufLen++
    63  
    64  			if current+wordBufLen+spaceBufLen > lim && wordBufLen < lim {
    65  				buf.WriteRune('\n')
    66  				current = 0
    67  				spaceBuf.Reset()
    68  				spaceBufLen = 0
    69  			}
    70  		}
    71  	}
    72  
    73  	if wordBuf.Len() == 0 {
    74  		if current+spaceBufLen <= lim {
    75  			spaceBuf.WriteTo(buf)
    76  		}
    77  	} else {
    78  		spaceBuf.WriteTo(buf)
    79  		wordBuf.WriteTo(buf)
    80  	}
    81  
    82  	return buf.String()
    83  }
    84
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