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Refactored the grapheme walker to a proper state machine.
This commit is contained in:
Ate Eskola
parent
57fe5b80e5
commit
6550747c72
1 changed files with 174 additions and 137 deletions
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@ -712,6 +712,8 @@ import std.traits : isConvertibleToString, isIntegral, isSomeChar,
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isSomeString, Unqual, isDynamicArray;
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// debug = std_uni;
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import std.internal.unicode_tables; // generated file
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debug(std_uni) import std.stdio; // writefln, writeln
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private:
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@ -6963,7 +6965,6 @@ private:
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enum EMPTY_CASE_TRIE = ushort.max;// from what gen_uni uses internally
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// TODO: redo the most of hangul stuff algorithmically in case of Graphemes too
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// kill unrolled switches
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// Use combined trie instead of checking for '\r' | '\n' | ccTrie,
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// or extend | '\u200D' separately
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@ -6972,14 +6973,156 @@ private static bool isRegionalIndicator(dchar ch) @safe pure @nogc nothrow
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return ch >= '\U0001F1E6' && ch <= '\U0001F1FF';
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}
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// Our grapheme decoder is a state machine, this is list of all possible
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// states before each code point.
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private enum GraphemeState {
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Start,
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CR,
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RI,
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L,
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V,
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LVT,
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Emoji,
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EmojiZWJ,
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Prepend,
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End
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}
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// Message values whether end of grapheme is reached
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private enum TransformRes {
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goOn, // No, unless the source range ends here
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redo, // Run last character again with new state
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retInclude, // Yes, after the just iterated character
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retExclude // Yes, before the just iterated character
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}
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// The logic of the grapheme decoding is all here
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private enum TransformRes
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function(ref GraphemeState, dchar) @safe pure nothrow @nogc [] graphemeTransforms =
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[
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GraphemeState.Start: (ref state, ch)
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{
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if (graphemeControlTrie[ch] || ch == '\n')
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return TransformRes.retInclude;
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with (GraphemeState) state =
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ch == '\r' ? CR :
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isRegionalIndicator(ch) ? RI :
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isHangL(ch) ? L :
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hangLV[ch] || isHangV(ch) ? V :
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hangLVT[ch] || isHangT(ch) ? LVT :
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prependTrie[ch] ? Prepend :
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xpictoTrie[ch] ? Emoji :
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End;
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// No matter what we encountered, we always include the
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// first code point in the grapheme.
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return TransformRes.goOn;
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},
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GraphemeState.CR: (ref state, ch) => ch == '\n' ?
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TransformRes.retInclude :
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TransformRes.retExclude,
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GraphemeState.RI: (ref state, ch)
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{
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state = GraphemeState.End;
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return isRegionalIndicator(ch) ?
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TransformRes.goOn :
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TransformRes.redo;
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},
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GraphemeState.L: (ref state, ch)
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{
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if (isHangL(ch))
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return TransformRes.goOn;
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else if (isHangV(ch) || hangLV[ch])
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{
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state = GraphemeState.V;
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return TransformRes.goOn;
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}
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else if (hangLVT[ch])
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{
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state = GraphemeState.LVT;
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return TransformRes.goOn;
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}
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state = GraphemeState.End;
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return TransformRes.redo;
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},
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GraphemeState.V: (ref state, ch)
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{
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if (isHangV(ch))
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return TransformRes.goOn;
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else if (isHangT(ch))
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{
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state = GraphemeState.LVT;
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return TransformRes.goOn;
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}
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state = GraphemeState.End;
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return TransformRes.redo;
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},
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GraphemeState.LVT: (ref state, ch)
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{
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if (isHangT(ch))
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return TransformRes.goOn;
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state = GraphemeState.End;
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return TransformRes.redo;
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},
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GraphemeState.Emoji: (ref state, ch)
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{
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if (graphemeExtendTrie[ch])
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return TransformRes.goOn;
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static assert(!graphemeExtendTrie['\u200D']);
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if (ch == '\u200D')
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{
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state = GraphemeState.EmojiZWJ;
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return TransformRes.goOn;
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}
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state = GraphemeState.End;
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// There might still be spacing marks are
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// at the end, which are not allowed in
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// middle of emoji sequences
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return TransformRes.redo;
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},
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GraphemeState.EmojiZWJ: (ref state, ch)
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{
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state = GraphemeState.Emoji;
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if (xpictoTrie[ch])
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return TransformRes.goOn;
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return TransformRes.redo;
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},
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GraphemeState.Prepend: (ref state, ch)
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{
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// Control characters need to be special cased
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// because the starting state would include them in
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// the current grapheme.
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if (graphemeControlTrie[ch] || ch == '\r' || ch == '\n')
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return TransformRes.retExclude;
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state = GraphemeState.Start;
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return TransformRes.redo;
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},
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GraphemeState.End: (ref state, ch)
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=> !graphemeExtendTrie[ch] && !spacingMarkTrie[ch] && ch != '\u200D' ?
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TransformRes.retExclude :
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TransformRes.goOn
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];
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template genericDecodeGrapheme(bool getValue)
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{
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alias graphemeExtend = graphemeExtendTrie;
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alias spacingMark = spacingMarkTrie;
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alias prepend = prependTrie;
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alias ccTrie = graphemeControlTrie;
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alias xpicto = xpictoTrie;
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static if (getValue)
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alias Value = Grapheme;
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else
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@ -6987,150 +7130,44 @@ template genericDecodeGrapheme(bool getValue)
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Value genericDecodeGrapheme(Input)(ref Input range)
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{
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import std.internal.unicode_tables : isHangL, isHangT, isHangV; // generated file
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enum GraphemeState {
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Start,
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CR,
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RI,
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L,
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V,
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LVT,
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Emoji,
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EmojiZWJ,
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Prepend
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}
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static if (getValue)
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Grapheme grapheme;
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auto state = GraphemeState.Start;
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dchar ch;
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void popCodePoint() {
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static if (getValue)
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grapheme ~= ch;
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range.popFront();
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}
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assert(!range.empty, "Attempting to decode grapheme from an empty " ~ Input.stringof);
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outer:
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while (!range.empty)
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{
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ch = range.front;
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final switch (state) with(GraphemeState)
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{
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case Start:
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popCodePoint();
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if (ch == '\r')
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state = CR;
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else if (ccTrie[ch] || ch == '\n')
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goto L_End;
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else if (isRegionalIndicator(ch))
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state = RI;
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else if (isHangL(ch))
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state = L;
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else if (hangLV[ch] || isHangV(ch))
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state = V;
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else if (hangLVT[ch])
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state = LVT;
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else if (isHangT(ch))
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state = LVT;
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else if (prepend[ch])
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state = Prepend;
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else if (xpicto[ch])
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state = Emoji;
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else
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goto L_End_Extend;
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break;
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case CR:
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if (ch == '\n')
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popCodePoint();
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goto L_End;
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case Emoji:
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if (!graphemeExtend[ch])
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{
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static assert(!graphemeExtend['\u200D']);
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if (ch == '\u200D')
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state = EmojiZWJ;
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else
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{
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// We will recheck for extensions since spacing
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// marks are allowed at the end, but not at middle of
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// emoji sequences, unlike extend code points.
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goto L_End_Extend;
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}
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}
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popCodePoint();
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break;
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case EmojiZWJ:
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state = Emoji;
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if (xpicto[ch])
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{
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popCodePoint();
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break;
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}
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goto case Emoji;
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case RI:
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if (isRegionalIndicator(ch))
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popCodePoint();
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goto L_End_Extend;
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case L:
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if (isHangL(ch))
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popCodePoint();
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else if (isHangV(ch) || hangLV[ch])
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{
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state = V;
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popCodePoint();
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}
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else if (hangLVT[ch])
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{
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state = LVT;
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popCodePoint();
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}
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else
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goto L_End_Extend;
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break;
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case V:
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if (isHangV(ch))
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popCodePoint();
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else if (isHangT(ch))
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{
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state = LVT;
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popCodePoint();
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}
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else
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goto L_End_Extend;
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break;
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case LVT:
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if (isHangT(ch))
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{
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popCodePoint();
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}
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else
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goto L_End_Extend;
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break;
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case Prepend:
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// Unlike the starting state, we must not pop control
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// characters here.
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if (ccTrie[ch] || ch == '\r' || ch == '\n')
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goto L_End;
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else
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goto case Start;
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rerun:
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final switch (graphemeTransforms[state](state, ch))
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with(TransformRes)
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{
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case goOn:
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static if (getValue)
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grapheme ~= ch;
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range.popFront();
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continue;
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case redo:
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goto rerun;
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case retInclude:
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static if (getValue)
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grapheme ~= ch;
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range.popFront();
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break outer;
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case retExclude:
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break outer;
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}
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}
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L_End_Extend:
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while (!range.empty)
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{
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ch = range.front;
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// extend & spacing marks
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if (!graphemeExtend[ch] && !spacingMark[ch] && ch != '\u200D')
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break;
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popCodePoint();
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}
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L_End:
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static if (getValue)
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return grapheme;
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}
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}
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public: // Public API continues
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@ -7179,6 +7216,8 @@ if (is(C : dchar))
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static assert(c2 == 3); // \u0301 has 2 UTF-8 code units
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}
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// TODO: make this @nogc. Probably no big deal since the state machine is
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// already GC-free.
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@safe pure nothrow unittest
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{
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// grinning face ~ emoji modifier fitzpatrick type-5 ~ grinning face
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@ -10596,8 +10635,6 @@ private:
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@safe pure nothrow @nogc @property
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{
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import std.internal.unicode_tables; // generated file
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// It's important to use auto return here, so that the compiler
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// only runs semantic on the return type if the function gets
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// used. Also these are functions rather than templates to not
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