90 lines
2.6 KiB
Go
90 lines
2.6 KiB
Go
package uniseg
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import "unicode/utf8"
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// FirstWord returns the first word found in the given byte slice according to
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// the rules of [Unicode Standard Annex #29, Word Boundaries]. This function can
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// be called continuously to extract all words from a byte slice, as illustrated
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// in the example below.
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//
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// If you don't know the current state, for example when calling the function
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// for the first time, you must pass -1. For consecutive calls, pass the state
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// and rest slice returned by the previous call.
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//
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// The "rest" slice is the sub-slice of the original byte slice "b" starting
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// after the last byte of the identified word. If the length of the "rest" slice
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// is 0, the entire byte slice "b" has been processed. The "word" byte slice is
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// the sub-slice of the input slice containing the identified word.
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//
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// Given an empty byte slice "b", the function returns nil values.
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//
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// [Unicode Standard Annex #29, Word Boundaries]: http://unicode.org/reports/tr29/#Word_Boundaries
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func FirstWord(b []byte, state int) (word, rest []byte, newState int) {
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// An empty byte slice returns nothing.
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if len(b) == 0 {
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return
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}
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// Extract the first rune.
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r, length := utf8.DecodeRune(b)
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if len(b) <= length { // If we're already past the end, there is nothing else to parse.
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return b, nil, wbAny
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}
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// If we don't know the state, determine it now.
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if state < 0 {
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state, _ = transitionWordBreakState(state, r, b[length:], "")
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}
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// Transition until we find a boundary.
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var boundary bool
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for {
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r, l := utf8.DecodeRune(b[length:])
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state, boundary = transitionWordBreakState(state, r, b[length+l:], "")
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if boundary {
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return b[:length], b[length:], state
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}
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length += l
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if len(b) <= length {
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return b, nil, wbAny
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}
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}
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}
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// FirstWordInString is like [FirstWord] but its input and outputs are strings.
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func FirstWordInString(str string, state int) (word, rest string, newState int) {
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// An empty byte slice returns nothing.
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if len(str) == 0 {
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return
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}
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// Extract the first rune.
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r, length := utf8.DecodeRuneInString(str)
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if len(str) <= length { // If we're already past the end, there is nothing else to parse.
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return str, "", wbAny
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}
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// If we don't know the state, determine it now.
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if state < 0 {
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state, _ = transitionWordBreakState(state, r, nil, str[length:])
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}
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// Transition until we find a boundary.
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var boundary bool
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for {
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r, l := utf8.DecodeRuneInString(str[length:])
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state, boundary = transitionWordBreakState(state, r, nil, str[length+l:])
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if boundary {
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return str[:length], str[length:], state
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}
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length += l
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if len(str) <= length {
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return str, "", wbAny
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}
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}
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}
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