ASCII optimizations for isPrintableValidUTF8.
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Ferdinand Majerech
parent
1c0702f3cd
commit
7409f3bbd9
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@ -736,21 +736,111 @@ auto toUTF8(ubyte[] input, const UTFEncoding encoding) @safe pure nothrow
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return result;
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}
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/// Determine if all characters (code points, not bytes) in a string are printable,
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/// except for one or more trailing zeroes.
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///
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/// Params:
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///
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/// chars =
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bool isPrintableValidUTF8(const char[] chars) @safe pure nothrow @nogc
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/// Determine if all characters (code points, not bytes) in a string are printable.
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bool isPrintableValidUTF8(const char[] chars) @trusted pure nothrow @nogc
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{
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for(size_t b = 0; b < chars.length;)
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// This is oversized (only 128 entries are necessary) simply because having 256
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// entries improves performance... for some reason (alignment?)
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bool[256] printable = [false, false, false, false, false, false, false, false,
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false, true, true, false, false, true, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true,
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true, true, true, true, true, true, true, true,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false,
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false, false, false, false, false, false, false, false];
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for(size_t index = 0; index < chars.length;)
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{
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const dchar c = chars[b] < 0x80 ? chars[b++] : decodeValidUTF8NoGC(chars, b);
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if(!((c == 0x09 || c == 0x0A || c == 0x0D || c == 0x85) ||
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(c >= 0x20 && c <= 0x7E) ||
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(c >= 0xA0 && c <= '\uD7FF') ||
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(c >= '\uE000' && c <= '\uFFFD')))
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// Fast path for ASCII.
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// Both this while() block and the if() block below it are optimized, unrolled
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// versions of the for() block below them; the while()/if() block could be
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// removed without affecting logic, but both help increase performance.
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size_t asciiCount = countASCII(chars[index .. $]);
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// 8 ASCII iterations unrolled, looping while there are at most 8 ASCII chars.
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while(asciiCount > 8)
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{
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const dchar b0 = chars[index];
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const dchar b1 = chars[index + 1];
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const dchar b2 = chars[index + 2];
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const dchar b3 = chars[index + 3];
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const dchar b4 = chars[index + 4];
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const dchar b5 = chars[index + 5];
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const dchar b6 = chars[index + 6];
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const dchar b7 = chars[index + 7];
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index += 8;
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asciiCount -= 8;
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const all = printable[b0] & printable[b1] & printable[b2] & printable[b3] &
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printable[b4] & printable[b5] & printable[b6] & printable[b1];
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if(!all)
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{
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return false;
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}
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}
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// 4 ASCII iterations unrolled
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if(asciiCount > 4)
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{
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const char b0 = chars[index];
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const char b1 = chars[index + 1];
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const char b2 = chars[index + 2];
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const char b3 = chars[index + 3];
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index += 4;
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asciiCount -= 4;
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if(!printable[b0]) { return false; }
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if(!printable[b1]) { return false; }
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if(!printable[b2]) { return false; }
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if(!printable[b3]) { return false; }
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}
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// Any remaining ASCII chars. This is really the only code needed to handle
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// ASCII, the above if() and while() blocks are just an optimization.
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for(; asciiCount > 0; --asciiCount)
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{
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const char b = chars[index];
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++index;
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if(b >= 0x20) { continue; }
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if(printable[b]) { continue; }
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return false;
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}
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if(index == chars.length) { break; }
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// Not ASCII, need to decode.
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const dchar c = decodeValidUTF8NoGC(chars, index);
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// We now c is not ASCII, so only check for printable non-ASCII chars.
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if(!(c == 0x85 || (c >= 0xA0 && c <= '\uD7FF') ||
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(c >= '\uE000' && c <= '\uFFFD')))
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{
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return false;
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}
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