1 package uniseg 2 3 import "unicode/utf8" 4 5 // FirstWord returns the first word found in the given byte slice according to 6 // the rules of [Unicode Standard Annex #29, Word Boundaries]. This function can 7 // be called continuously to extract all words from a byte slice, as illustrated 8 // in the example below. 9 // 10 // If you don't know the current state, for example when calling the function 11 // for the first time, you must pass -1. For consecutive calls, pass the state 12 // and rest slice returned by the previous call. 13 // 14 // The "rest" slice is the sub-slice of the original byte slice "b" starting 15 // after the last byte of the identified word. If the length of the "rest" slice 16 // is 0, the entire byte slice "b" has been processed. The "word" byte slice is 17 // the sub-slice of the input slice containing the identified word. 18 // 19 // Given an empty byte slice "b", the function returns nil values. 20 // 21 // [Unicode Standard Annex #29, Word Boundaries]: http://unicode.org/reports/tr29/#Word_Boundaries 22 func FirstWord(b []byte, state int) (word, rest []byte, newState int) { 23 // An empty byte slice returns nothing. 24 if len(b) == 0 { 25 return 26 } 27 28 // Extract the first rune. 29 r, length := utf8.DecodeRune(b) 30 if len(b) <= length { // If we're already past the end, there is nothing else to parse. 31 return b, nil, wbAny 32 } 33 34 // If we don't know the state, determine it now. 35 if state < 0 { 36 state, _ = transitionWordBreakState(state, r, b[length:], "") 37 } 38 39 // Transition until we find a boundary. 40 var boundary bool 41 for { 42 r, l := utf8.DecodeRune(b[length:]) 43 state, boundary = transitionWordBreakState(state, r, b[length+l:], "") 44 45 if boundary { 46 return b[:length], b[length:], state 47 } 48 49 length += l 50 if len(b) <= length { 51 return b, nil, wbAny 52 } 53 } 54 } 55 56 // FirstWordInString is like [FirstWord] but its input and outputs are strings. 57 func FirstWordInString(str string, state int) (word, rest string, newState int) { 58 // An empty byte slice returns nothing. 59 if len(str) == 0 { 60 return 61 } 62 63 // Extract the first rune. 64 r, length := utf8.DecodeRuneInString(str) 65 if len(str) <= length { // If we're already past the end, there is nothing else to parse. 66 return str, "", wbAny 67 } 68 69 // If we don't know the state, determine it now. 70 if state < 0 { 71 state, _ = transitionWordBreakState(state, r, nil, str[length:]) 72 } 73 74 // Transition until we find a boundary. 75 var boundary bool 76 for { 77 r, l := utf8.DecodeRuneInString(str[length:]) 78 state, boundary = transitionWordBreakState(state, r, nil, str[length+l:]) 79 80 if boundary { 81 return str[:length], str[length:], state 82 } 83 84 length += l 85 if len(str) <= length { 86 return str, "", wbAny 87 } 88 } 89 } 90