90 lines
2.7 KiB
Go
90 lines
2.7 KiB
Go
package uniseg
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import "unicode/utf8"
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// FirstSentence returns the first sentence found in the given byte slice
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// according to the rules of [Unicode Standard Annex #29, Sentence Boundaries].
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// This function can be called continuously to extract all sentences from a byte
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// slice, as illustrated 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 sentence. If the length of the "rest"
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// slice is 0, the entire byte slice "b" has been processed. The "sentence" byte
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// slice is the sub-slice of the input slice containing the identified sentence.
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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, Sentence Boundaries]: http://unicode.org/reports/tr29/#Sentence_Boundaries
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func FirstSentence(b []byte, state int) (sentence, 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, sbAny
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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, _ = transitionSentenceBreakState(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 = transitionSentenceBreakState(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, sbAny
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}
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}
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}
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// FirstSentenceInString is like [FirstSentence] but its input and outputs are
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// strings.
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func FirstSentenceInString(str string, state int) (sentence, 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, "", sbAny
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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, _ = transitionSentenceBreakState(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 = transitionSentenceBreakState(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, "", sbAny
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}
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}
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}
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