96 lines
2.2 KiB
D
96 lines
2.2 KiB
D
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// Copyright Ferdinand Majerech 2011.
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// Distributed under the Boost Software License, Version 1.0.
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// (See accompanying file LICENSE_1_0.txt or copy at
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// http://www.boost.org/LICENSE_1_0.txt)
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module dyaml.fastcharsearch;
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import std.algorithm;
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import std.conv;
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package:
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/**
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* Mixin used for fast searching for a character in string.
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*
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* Creates a lookup table to quickly determine if a character
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* is present in the string. Size of the lookup table is limited;
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* any characters not represented in the table will be checked
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* by ordinary equality comparison.
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*
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* Params: chars = String to search in.
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* tableSize = Maximum number of bytes used by the table.
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*
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* Generated method:
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* bool canFind(dchar c)
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*
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* Determines if a character is in the string.
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*/
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template FastCharSearch(dstring chars, uint tableSize = 256)
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{
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private mixin(searchCode!(chars, tableSize)());
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}
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/// Generate the search table and the canFind method.
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string searchCode(dstring chars, uint tableSize)()
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{
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import std.string;
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const tableSizeStr = tableSize.to!string;
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ubyte[tableSize] table;
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table[] = 0;
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//Characters that don't fit in the table.
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dchar[] specialChars;
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foreach(c; chars)
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{
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if(c < tableSize) { table[c] = 1; }
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else { specialChars ~= c; }
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}
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string specialCharsCode()
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{
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return specialChars.map!(c => q{cast(uint)c == %s}.format(cast(uint)c)).join(q{ || });
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}
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const caseInTable =
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q{
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if(c < %s)
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{
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return cast(immutable(bool))table_[c];
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}
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}.format(tableSize);
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string code;
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if(tableSize)
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{
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code ~=
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q{
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static immutable ubyte[%s] table_ = [
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%s];
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}.format(tableSize, table[].map!(c => c ? q{true} : q{false}).join(q{, }));
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}
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code ~=
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q{
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bool canFind(const dchar c) @safe pure nothrow @nogc
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{
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%s
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return %s;
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}
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}.format(tableSize ? caseInTable : "",
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specialChars.length ? specialCharsCode() : q{false});
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return code;
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}
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@safe unittest
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{
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mixin FastCharSearch!("+", 128) search;
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assert(search.canFind('+'));
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}
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