README.md (7415B)
1 # Unicode Text Segmentation for Go 2 3 [](https://pkg.go.dev/github.com/rivo/uniseg) 4 [](https://goreportcard.com/report/github.com/rivo/uniseg) 5 6 This Go package implements Unicode Text Segmentation according to [Unicode Standard Annex #29](https://unicode.org/reports/tr29/), Unicode Line Breaking according to [Unicode Standard Annex #14](https://unicode.org/reports/tr14/) (Unicode version 15.0.0), and monospace font string width calculation similar to [wcwidth](https://man7.org/linux/man-pages/man3/wcwidth.3.html). 7 8 ## Background 9 10 ### Grapheme Clusters 11 12 In Go, [strings are read-only slices of bytes](https://go.dev/blog/strings). They can be turned into Unicode code points using the `for` loop or by casting: `[]rune(str)`. However, multiple code points may be combined into one user-perceived character or what the Unicode specification calls "grapheme cluster". Here are some examples: 13 14 |String|Bytes (UTF-8)|Code points (runes)|Grapheme clusters| 15 |-|-|-|-| 16 |Käse|6 bytes: `4b 61 cc 88 73 65`|5 code points: `4b 61 308 73 65`|4 clusters: `[4b],[61 308],[73],[65]`| 17 |🏳️🌈|14 bytes: `f0 9f 8f b3 ef b8 8f e2 80 8d f0 9f 8c 88`|4 code points: `1f3f3 fe0f 200d 1f308`|1 cluster: `[1f3f3 fe0f 200d 1f308]`| 18 |🇩🇪|8 bytes: `f0 9f 87 a9 f0 9f 87 aa`|2 code points: `1f1e9 1f1ea`|1 cluster: `[1f1e9 1f1ea]`| 19 20 This package provides tools to iterate over these grapheme clusters. This may be used to determine the number of user-perceived characters, to split strings in their intended places, or to extract individual characters which form a unit. 21 22 ### Word Boundaries 23 24 Word boundaries are used in a number of different contexts. The most familiar ones are selection (double-click mouse selection), cursor movement ("move to next word" control-arrow keys), and the dialog option "Whole Word Search" for search and replace. They are also used in database queries, to determine whether elements are within a certain number of words of one another. Searching may also use word boundaries in determining matching items. This package provides tools to determine word boundaries within strings. 25 26 ### Sentence Boundaries 27 28 Sentence boundaries are often used for triple-click or some other method of selecting or iterating through blocks of text that are larger than single words. They are also used to determine whether words occur within the same sentence in database queries. This package provides tools to determine sentence boundaries within strings. 29 30 ### Line Breaking 31 32 Line breaking, also known as word wrapping, is the process of breaking a section of text into lines such that it will fit in the available width of a page, window or other display area. This package provides tools to determine where a string may or may not be broken and where it must be broken (for example after newline characters). 33 34 ### Monospace Width 35 36 Most terminals or text displays / text editors using a monospace font (for example source code editors) use a fixed width for each character. Some characters such as emojis or characters found in Asian and other languages may take up more than one character cell. This package provides tools to determine the number of cells a string will take up when displayed in a monospace font. See [here](https://pkg.go.dev/github.com/rivo/uniseg#hdr-Monospace_Width) for more information. 37 38 ## Installation 39 40 ```bash 41 go get github.com/rivo/uniseg 42 ``` 43 44 ## Examples 45 46 ### Counting Characters in a String 47 48 ```go 49 n := uniseg.GraphemeClusterCount("🇩🇪🏳️🌈") 50 fmt.Println(n) 51 // 2 52 ``` 53 54 ### Calculating the Monospace String Width 55 56 ```go 57 width := uniseg.StringWidth("🇩🇪🏳️🌈!") 58 fmt.Println(width) 59 // 5 60 ``` 61 62 ### Using the [`Graphemes`](https://pkg.go.dev/github.com/rivo/uniseg#Graphemes) Class 63 64 This is the most convenient method of iterating over grapheme clusters: 65 66 ```go 67 gr := uniseg.NewGraphemes("👍🏼!") 68 for gr.Next() { 69 fmt.Printf("%x ", gr.Runes()) 70 } 71 // [1f44d 1f3fc] [21] 72 ``` 73 74 ### Using the [`Step`](https://pkg.go.dev/github.com/rivo/uniseg#Step) or [`StepString`](https://pkg.go.dev/github.com/rivo/uniseg#StepString) Function 75 76 This avoids allocating a new `Graphemes` object but it requires the handling of states and boundaries: 77 78 ```go 79 str := "🇩🇪🏳️🌈" 80 state := -1 81 var c string 82 for len(str) > 0 { 83 c, str, _, state = uniseg.StepString(str, state) 84 fmt.Printf("%x ", []rune(c)) 85 } 86 // [1f1e9 1f1ea] [1f3f3 fe0f 200d 1f308] 87 ``` 88 89 ### Advanced Examples 90 91 The [`Graphemes`](https://pkg.go.dev/github.com/rivo/uniseg#Graphemes) class offers the most convenient way to access all functionality of this package. But in some cases, it may be better to use the specialized functions directly. For example, if you're only interested in word segmentation, use [`FirstWord`](https://pkg.go.dev/github.com/rivo/uniseg#FirstWord) or [`FirstWordInString`](https://pkg.go.dev/github.com/rivo/uniseg#FirstWordInString): 92 93 ```go 94 str := "Hello, world!" 95 state := -1 96 var c string 97 for len(str) > 0 { 98 c, str, state = uniseg.FirstWordInString(str, state) 99 fmt.Printf("(%s)\n", c) 100 } 101 // (Hello) 102 // (,) 103 // ( ) 104 // (world) 105 // (!) 106 ``` 107 108 Similarly, use 109 110 - [`FirstGraphemeCluster`](https://pkg.go.dev/github.com/rivo/uniseg#FirstGraphemeCluster) or [`FirstGraphemeClusterInString`](https://pkg.go.dev/github.com/rivo/uniseg#FirstGraphemeClusterInString) for grapheme cluster determination only, 111 - [`FirstSentence`](https://pkg.go.dev/github.com/rivo/uniseg#FirstSentence) or [`FirstSentenceInString`](https://pkg.go.dev/github.com/rivo/uniseg#FirstSentenceInString) for sentence segmentation only, and 112 - [`FirstLineSegment`](https://pkg.go.dev/github.com/rivo/uniseg#FirstLineSegment) or [`FirstLineSegmentInString`](https://pkg.go.dev/github.com/rivo/uniseg#FirstLineSegmentInString) for line breaking / word wrapping (although using [`Step`](https://pkg.go.dev/github.com/rivo/uniseg#Step) or [`StepString`](https://pkg.go.dev/github.com/rivo/uniseg#StepString) is preferred as it will observe grapheme cluster boundaries). 113 114 If you're only interested in the width of characters, use [`FirstGraphemeCluster`](https://pkg.go.dev/github.com/rivo/uniseg#FirstGraphemeCluster) or [`FirstGraphemeClusterInString`](https://pkg.go.dev/github.com/rivo/uniseg#FirstGraphemeClusterInString). It is much faster than using [`Step`](https://pkg.go.dev/github.com/rivo/uniseg#Step), [`StepString`](https://pkg.go.dev/github.com/rivo/uniseg#StepString), or the [`Graphemes`](https://pkg.go.dev/github.com/rivo/uniseg#Graphemes) class because it does not include the logic for word / sentence / line boundaries. 115 116 Finally, if you need to reverse a string while preserving grapheme clusters, use [`ReverseString`](https://pkg.go.dev/github.com/rivo/uniseg#ReverseString): 117 118 ```go 119 fmt.Println(uniseg.ReverseString("🇩🇪🏳️🌈")) 120 // 🏳️🌈🇩🇪 121 ``` 122 123 ## Documentation 124 125 Refer to https://pkg.go.dev/github.com/rivo/uniseg for the package's documentation. 126 127 ## Dependencies 128 129 This package does not depend on any packages outside the standard library. 130 131 ## Sponsor this Project 132 133 [Become a Sponsor on GitHub](https://github.com/sponsors/rivo?metadata_source=uniseg_readme) to support this project! 134 135 ## Your Feedback 136 137 Add your issue here on GitHub, preferably before submitting any PR's. Feel free to get in touch if you have any questions.