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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:24:48 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 18:24:48 +0000 |
commit | cca66b9ec4e494c1d919bff0f71a820d8afab1fa (patch) | |
tree | 146f39ded1c938019e1ed42d30923c2ac9e86789 /src/util/expression-evaluator.h | |
parent | Initial commit. (diff) | |
download | inkscape-upstream.tar.xz inkscape-upstream.zip |
Adding upstream version 1.2.2.upstream/1.2.2upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to '')
-rw-r--r-- | src/util/expression-evaluator.h | 196 |
1 files changed, 196 insertions, 0 deletions
diff --git a/src/util/expression-evaluator.h b/src/util/expression-evaluator.h new file mode 100644 index 0000000..a45ad5a --- /dev/null +++ b/src/util/expression-evaluator.h @@ -0,0 +1,196 @@ +// SPDX-License-Identifier: LGPL-3.0-or-later +/** @file + * TODO: insert short description here + */ +/* LIBGIMP - The GIMP Library + * Copyright (C) 1995-1997 Peter Mattis and Spencer Kimball + * + * Original file from libgimpwidgets: gimpeevl.h + * Copyright (C) 2008-2009 Fredrik Alstromer <roe@excu.se> + * Copyright (C) 2008-2009 Martin Nordholts <martinn@svn.gnome.org> + * Modified for Inkscape by Johan Engelen + * Copyright (C) 2011 Johan Engelen + * Copyright (C) 2013 Matthew Petroff + * + * This library is free software: you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 3 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library. If not, see + * <http://www.gnu.org/licenses/>. + */ + +#ifndef INKSCAPE_UTIL_EXPRESSION_EVALUATOR_H +#define INKSCAPE_UTIL_EXPRESSION_EVALUATOR_H + +#include "util/units.h" + +#include <exception> +#include <sstream> +#include <string> + +/** + * @file + * Expression evaluator: A straightforward recursive + * descent parser, no fuss, no new dependencies. The lexer is hand + * coded, tedious, not extremely fast but works. It evaluates the + * expression as it goes along, and does not create a parse tree or + * anything, and will not optimize anything. It uses doubles for + * precision, with the given use case, that's enough to combat any + * rounding errors (as opposed to optimizing the evaluation). + * + * It relies on external unit resolving through a callback and does + * elementary dimensionality constraint check (e.g. "2 mm + 3 px * 4 + * in" is an error, as L + L^2 is a mismatch). It uses g_strtod() for numeric + * conversions and it's non-destructive in terms of the parameters, and + * it's reentrant. + * + * EBNF: + * + * expression ::= term { ('+' | '-') term }* | + * <empty string> ; + * + * term ::= exponent { ( '*' | '/' ) exponent }* ; + * + * exponent ::= signed factor { '^' signed factor }* ; + * + * signed factor ::= ( '+' | '-' )? factor ; + * + * unit factor ::= factor unit? ; + * + * factor ::= number | '(' expression ')' ; + * + * number ::= ? what g_strtod() consumes ? ; + * + * unit ::= ? what not g_strtod() consumes and not whitespace ? ; + * + * The code should match the EBNF rather closely (except for the + * non-terminal unit factor, which is inlined into factor) for + * maintainability reasons. + * + * It will allow 1++1 and 1+-1 (resulting in 2 and 0, respectively), + * but I figured one might want that, and I don't think it's going to + * throw anyone off. + */ + +namespace Inkscape { +namespace Util { + +class Unit; + +/** + * EvaluatorQuantity: + * @param value In reference units. + * @param dimension mm has a dimension of 1, mm^2 has a dimension of 2, etc. + */ +class EvaluatorQuantity +{ +public: + EvaluatorQuantity(double value = 0, unsigned int dimension = 0); + + double value; + unsigned int dimension; +}; + +/** + * TokenType + */ +enum { + TOKEN_NUM = 30000, + TOKEN_IDENTIFIER = 30001, + TOKEN_ANY = 40000, + TOKEN_END = 50000 +}; +typedef int TokenType; + +/** + * EvaluatorToken + */ +class EvaluatorToken +{ +public: + EvaluatorToken(); + + TokenType type; + + union { + double fl; + struct { + const char *c; + int size; + }; + } value; +}; + +/** + * ExpressionEvaluator + * @param string NULL terminated input string to evaluate + * @param unit Unit output should be in + */ +class ExpressionEvaluator +{ +public: + ExpressionEvaluator(const char *string, Unit const *unit = nullptr); + + EvaluatorQuantity evaluate(); + +private: + const char *string; + Unit const *unit; + + EvaluatorToken current_token; + const char *start_of_current_token; + + EvaluatorQuantity evaluateExpression(); + EvaluatorQuantity evaluateTerm(); + EvaluatorQuantity evaluateExpTerm(); + EvaluatorQuantity evaluateSignedFactor(); + EvaluatorQuantity evaluateFactor(); + + bool acceptToken(TokenType token_type, EvaluatorToken *consumed_token); + void parseNextToken(); + void acceptTokenCount(int count, TokenType token_type); + void isExpected(TokenType token_type, EvaluatorToken *value); + + void movePastWhiteSpace(); + + static bool isUnitIdentifierStart(gunichar c); + static int getIdentifierSize(const char *s, int start); + + static bool resolveUnit(const char *identifier, EvaluatorQuantity *result, Unit const *unit); + + void throwError(const char *msg); +}; + +/** + * Special exception class for the expression evaluator. + */ +class EvaluatorException : public std::exception { +public: + EvaluatorException(const char *message, const char *at_position) { + std::ostringstream os; + const char *token = at_position ? at_position : "<End of input>"; + os << "Expression evaluator error: " << message << " at '" << token << "'"; + msgstr = os.str(); + } + + ~EvaluatorException() noexcept override = default; // necessary to destroy the string object!!! + + const char *what() const noexcept override { + return msgstr.c_str(); + } +protected: + std::string msgstr; +}; + +} +} + +#endif // INKSCAPE_UTIL_EXPRESSION_EVALUATOR_H |