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gimp/libgimpwidgets/gimpeevl.c

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/* LIBGIMP - The GIMP Library
* Copyright (C) 1995-1997 Peter Mattis and Spencer Kimball
*
* gimpeevl.c
* Copyright (C) 2008 Fredrik Alstromer <roe@excu.se>
* Copyright (C) 2008 Martin Nordholts <martinn@svn.gnome.org>
*
* 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/>.
*/
/* Introducing eevl eva, the 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 setjmp/longjmp
* for try/catch like pattern on error, 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 ::= ratio { ( '*' | '/' ) ratio }* ;
*
* ratio ::= signed factor { ':' signed factor }* ;
*
* signed factor ::= ( '+' | '-' )? factor ;
*
* factor ::= quantity ( '^' signed factor )? ;
*
* quantity ::= number unit? | '(' expression ')' ;
*
* number ::= ? what g_strtod() consumes ? ;
*
* unit ::= simple unit ( '^' signed factor )? ;
*
* simple 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.
*/
#include "config.h"
#include <setjmp.h>
#include <string.h>
#include <glib-object.h>
#include "libgimpmath/gimpmath.h"
#include "gimpeevl.h"
#include "gimpwidgets-error.h"
#include "libgimp/libgimp-intl.h"
typedef enum
{
GIMP_EEVL_TOKEN_NUM = 30000,
GIMP_EEVL_TOKEN_IDENTIFIER = 30001,
GIMP_EEVL_TOKEN_ANY = 40000,
GIMP_EEVL_TOKEN_END = 50000
} GimpEevlTokenType;
typedef struct
{
GimpEevlTokenType type;
union
{
gdouble fl;
struct
{
const gchar *c;
gint size;
};
} value;
} GimpEevlToken;
typedef struct
{
const gchar *string;
GimpEevlOptions options;
GimpEevlToken current_token;
const gchar *start_of_current_token;
jmp_buf catcher;
const gchar *error_message;
} GimpEevl;
static void gimp_eevl_init (GimpEevl *eva,
const gchar *string,
const GimpEevlOptions *options);
static GimpEevlQuantity gimp_eevl_complete (GimpEevl *eva);
static GimpEevlQuantity gimp_eevl_expression (GimpEevl *eva);
static GimpEevlQuantity gimp_eevl_term (GimpEevl *eva);
static GimpEevlQuantity gimp_eevl_ratio (GimpEevl *eva);
static GimpEevlQuantity gimp_eevl_signed_factor (GimpEevl *eva);
static GimpEevlQuantity gimp_eevl_factor (GimpEevl *eva);
static GimpEevlQuantity gimp_eevl_quantity (GimpEevl *eva);
static gboolean gimp_eevl_accept (GimpEevl *eva,
GimpEevlTokenType token_type,
GimpEevlToken *consumed_token);
static void gimp_eevl_lex (GimpEevl *eva);
static void gimp_eevl_lex_accept_count (GimpEevl *eva,
gint count,
GimpEevlTokenType token_type);
static void gimp_eevl_lex_accept_to (GimpEevl *eva,
gchar *to,
GimpEevlTokenType token_type);
static void gimp_eevl_move_past_whitespace (GimpEevl *eva);
static gboolean gimp_eevl_unit_identifier_start (gunichar c);
static gboolean gimp_eevl_unit_identifier_continue (gunichar c);
static gint gimp_eevl_unit_identifier_size (const gchar *s,
gint start);
static void gimp_eevl_expect (GimpEevl *eva,
GimpEevlTokenType token_type,
GimpEevlToken *value);
static void gimp_eevl_error (GimpEevl *eva,
gchar *msg);
/**
* gimp_eevl_evaluate:
* @string: The NULL-terminated string to be evaluated.
* @options: Evaluations options.
* @result: Result of evaluation.
* @error_pos: Will point to the position within the string,
* before which the parse / evaluation error
* occurred. Will be set to null of no error occurred.
* @error_message: Will point to a static string with a semi-descriptive
* error message if parsing / evaluation failed.
*
* Evaluates the given arithmetic expression, along with an optional dimension
* analysis, and basic unit conversions.
*
* All units conversions factors are relative to some implicit
* base-unit (which in GIMP is inches). This is also the unit of the
* returned value.
*
* Returns: A #GimpEevlQuantity with a value given in the base unit along with
* the order of the dimension (i.e. if the base unit is inches, a dimension
* order of two means in^2).
**/
gboolean
gimp_eevl_evaluate (const gchar *string,
const GimpEevlOptions *options,
GimpEevlQuantity *result,
const gchar **error_pos,
GError **error)
{
GimpEevl eva;
g_return_val_if_fail (g_utf8_validate (string, -1, NULL), FALSE);
g_return_val_if_fail (options != NULL, FALSE);
g_return_val_if_fail (options->unit_resolver_proc != NULL, FALSE);
g_return_val_if_fail (result != NULL, FALSE);
g_return_val_if_fail (error == NULL || *error == NULL, FALSE);
gimp_eevl_init (&eva,
string,
options);
if (!setjmp (eva.catcher)) /* try... */
{
*result = gimp_eevl_complete (&eva);
return TRUE;
}
else /* catch.. */
{
if (error_pos)
*error_pos = eva.start_of_current_token;
g_set_error_literal (error,
GIMP_WIDGETS_ERROR,
GIMP_WIDGETS_PARSE_ERROR,
eva.error_message);
return FALSE;
}
}
static void
gimp_eevl_init (GimpEevl *eva,
const gchar *string,
const GimpEevlOptions *options)
{
eva->string = string;
eva->options = *options;
eva->current_token.type = GIMP_EEVL_TOKEN_END;
eva->error_message = NULL;
/* Preload symbol... */
gimp_eevl_lex (eva);
}
static GimpEevlQuantity
gimp_eevl_complete (GimpEevl *eva)
{
GimpEevlQuantity result = {0, 0};
GimpEevlQuantity default_unit_factor;
/* Empty expression evaluates to 0 */
if (gimp_eevl_accept (eva, GIMP_EEVL_TOKEN_END, NULL))
return result;
result = gimp_eevl_expression (eva);
/* There should be nothing left to parse by now */
gimp_eevl_expect (eva, GIMP_EEVL_TOKEN_END, 0);
eva->options.unit_resolver_proc (NULL,
&default_unit_factor,
eva->options.data);
/* Entire expression is dimensionless, apply default unit if
* applicable
*/
if (result.dimension == 0 && default_unit_factor.dimension != 0)
{
result.value /= default_unit_factor.value;
result.dimension = default_unit_factor.dimension;
}
return result;
}
static GimpEevlQuantity
gimp_eevl_expression (GimpEevl *eva)
{
gboolean subtract;
GimpEevlQuantity evaluated_terms;
evaluated_terms = gimp_eevl_term (eva);
/* continue evaluating terms, chained with + or -. */
for (subtract = FALSE;
gimp_eevl_accept (eva, '+', NULL) ||
(subtract = gimp_eevl_accept (eva, '-', NULL));
subtract = FALSE)
{
GimpEevlQuantity new_term = gimp_eevl_term (eva);
/* If dimensions mismatch, attempt default unit assignment */
if (new_term.dimension != evaluated_terms.dimension)
{
GimpEevlQuantity default_unit_factor;
eva->options.unit_resolver_proc (NULL,
&default_unit_factor,
eva->options.data);
if (new_term.dimension == 0 &&
evaluated_terms.dimension == default_unit_factor.dimension)
{
new_term.value /= default_unit_factor.value;
new_term.dimension = default_unit_factor.dimension;
}
else if (evaluated_terms.dimension == 0 &&
new_term.dimension == default_unit_factor.dimension)
{
evaluated_terms.value /= default_unit_factor.value;
evaluated_terms.dimension = default_unit_factor.dimension;
}
else
{
gimp_eevl_error (eva, "Dimension mismatch during addition");
}
}
evaluated_terms.value += (subtract ? -new_term.value : new_term.value);
}
return evaluated_terms;
}
static GimpEevlQuantity
gimp_eevl_term (GimpEevl *eva)
{
gboolean division;
GimpEevlQuantity evaluated_ratios;
evaluated_ratios = gimp_eevl_ratio (eva);
for (division = FALSE;
gimp_eevl_accept (eva, '*', NULL) ||
(division = gimp_eevl_accept (eva, '/', NULL));
division = FALSE)
{
GimpEevlQuantity new_ratio = gimp_eevl_ratio (eva);
if (division)
{
evaluated_ratios.value /= new_ratio.value;
evaluated_ratios.dimension -= new_ratio.dimension;
}
else
{
evaluated_ratios.value *= new_ratio.value;
evaluated_ratios.dimension += new_ratio.dimension;
}
}
return evaluated_ratios;
}
static GimpEevlQuantity
gimp_eevl_ratio (GimpEevl *eva)
{
GimpEevlQuantity evaluated_signed_factors;
if (! eva->options.ratio_expressions)
return gimp_eevl_signed_factor (eva);
evaluated_signed_factors = gimp_eevl_signed_factor (eva);
while (gimp_eevl_accept (eva, ':', NULL))
{
GimpEevlQuantity new_signed_factor = gimp_eevl_signed_factor (eva);
if (eva->options.ratio_invert)
{
GimpEevlQuantity temp;
temp = evaluated_signed_factors;
evaluated_signed_factors = new_signed_factor;
new_signed_factor = temp;
}
evaluated_signed_factors.value *= eva->options.ratio_quantity.value /
new_signed_factor.value;
evaluated_signed_factors.dimension += eva->options.ratio_quantity.dimension -
new_signed_factor.dimension;
}
return evaluated_signed_factors;
}
static GimpEevlQuantity
gimp_eevl_signed_factor (GimpEevl *eva)
{
GimpEevlQuantity result;
gboolean negate = FALSE;
if (! gimp_eevl_accept (eva, '+', NULL))
negate = gimp_eevl_accept (eva, '-', NULL);
result = gimp_eevl_factor (eva);
if (negate) result.value = -result.value;
return result;
}
static GimpEevlQuantity
gimp_eevl_factor (GimpEevl *eva)
{
GimpEevlQuantity evaluated_factor;
evaluated_factor = gimp_eevl_quantity (eva);
if (gimp_eevl_accept (eva, '^', NULL))
{
GimpEevlQuantity evaluated_exponent;
evaluated_exponent = gimp_eevl_signed_factor (eva);
if (evaluated_exponent.dimension != 0)
gimp_eevl_error (eva, "Exponent is not a dimensionless quantity");
evaluated_factor.value = pow (evaluated_factor.value,
evaluated_exponent.value);
evaluated_factor.dimension *= evaluated_exponent.value;
}
return evaluated_factor;
}
static GimpEevlQuantity
gimp_eevl_quantity (GimpEevl *eva)
{
GimpEevlQuantity evaluated_quantity = { 0, 0 };
GimpEevlToken consumed_token;
if (gimp_eevl_accept (eva,
GIMP_EEVL_TOKEN_NUM,
&consumed_token))
{
evaluated_quantity.value = consumed_token.value.fl;
}
else if (gimp_eevl_accept (eva, '(', NULL))
{
evaluated_quantity = gimp_eevl_expression (eva);
gimp_eevl_expect (eva, ')', 0);
}
else
{
gimp_eevl_error (eva, "Expected number or '('");
}
if (eva->current_token.type == GIMP_EEVL_TOKEN_IDENTIFIER)
{
gchar *identifier;
GimpEevlQuantity result;
gimp_eevl_accept (eva,
GIMP_EEVL_TOKEN_ANY,
&consumed_token);
identifier = g_newa (gchar, consumed_token.value.size + 1);
strncpy (identifier, consumed_token.value.c, consumed_token.value.size);
identifier[consumed_token.value.size] = '\0';
if (eva->options.unit_resolver_proc (identifier,
&result,
eva->options.data))
{
if (gimp_eevl_accept (eva, '^', NULL))
{
GimpEevlQuantity evaluated_exponent;
evaluated_exponent = gimp_eevl_signed_factor (eva);
if (evaluated_exponent.dimension != 0)
{
gimp_eevl_error (eva,
"Exponent is not a dimensionless quantity");
}
result.value = pow (result.value, evaluated_exponent.value);
result.dimension *= evaluated_exponent.value;
}
evaluated_quantity.value /= result.value;
evaluated_quantity.dimension += result.dimension;
}
else
{
gimp_eevl_error (eva, "Unit was not resolved");
}
}
return evaluated_quantity;
}
static gboolean
gimp_eevl_accept (GimpEevl *eva,
GimpEevlTokenType token_type,
GimpEevlToken *consumed_token)
{
gboolean existed = FALSE;
if (token_type == eva->current_token.type ||
token_type == GIMP_EEVL_TOKEN_ANY)
{
existed = TRUE;
if (consumed_token)
*consumed_token = eva->current_token;
/* Parse next token */
gimp_eevl_lex (eva);
}
return existed;
}
static void
gimp_eevl_lex (GimpEevl *eva)
{
const gchar *s;
gimp_eevl_move_past_whitespace (eva);
s = eva->string;
eva->start_of_current_token = s;
if (! s || s[0] == '\0')
{
/* We're all done */
eva->current_token.type = GIMP_EEVL_TOKEN_END;
}
else if (s[0] == '+' || s[0] == '-')
{
/* Snatch these before the g_strtod() does, otherwise they might
* be used in a numeric conversion.
*/
gimp_eevl_lex_accept_count (eva, 1, s[0]);
}
else
{
/* Attempt to parse a numeric value */
gchar *endptr = NULL;
gdouble value = g_strtod (s, &endptr);
if (endptr && endptr != s)
{
/* A numeric could be parsed, use it */
eva->current_token.value.fl = value;
gimp_eevl_lex_accept_to (eva, endptr, GIMP_EEVL_TOKEN_NUM);
}
else if (gimp_eevl_unit_identifier_start (s[0]))
{
/* Unit identifier */
eva->current_token.value.c = s;
eva->current_token.value.size = gimp_eevl_unit_identifier_size (s, 0);
gimp_eevl_lex_accept_count (eva,
eva->current_token.value.size,
GIMP_EEVL_TOKEN_IDENTIFIER);
}
else
{
/* Everything else is a single character token */
gimp_eevl_lex_accept_count (eva, 1, s[0]);
}
}
}
static void
gimp_eevl_lex_accept_count (GimpEevl *eva,
gint count,
GimpEevlTokenType token_type)
{
eva->current_token.type = token_type;
eva->string += count;
}
static void
gimp_eevl_lex_accept_to (GimpEevl *eva,
gchar *to,
GimpEevlTokenType token_type)
{
eva->current_token.type = token_type;
eva->string = to;
}
static void
gimp_eevl_move_past_whitespace (GimpEevl *eva)
{
if (! eva->string)
return;
while (g_ascii_isspace (*eva->string))
eva->string++;
}
static gboolean
gimp_eevl_unit_identifier_start (gunichar c)
{
return (g_unichar_isalpha (c) ||
c == (gunichar) '%' ||
c == (gunichar) '\'');
}
static gboolean
gimp_eevl_unit_identifier_continue (gunichar c)
{
return (gimp_eevl_unit_identifier_start (c) ||
g_unichar_isdigit (c));
}
/**
* gimp_eevl_unit_identifier_size:
* @s:
* @start:
*
* Returns: Size of identifier in bytes (not including NULL
* terminator).
**/
static gint
gimp_eevl_unit_identifier_size (const gchar *string,
gint start_offset)
{
const gchar *start = g_utf8_offset_to_pointer (string, start_offset);
const gchar *s = start;
gunichar c = g_utf8_get_char (s);
gint length = 0;
if (gimp_eevl_unit_identifier_start (c))
{
s = g_utf8_next_char (s);
c = g_utf8_get_char (s);
length++;
while (gimp_eevl_unit_identifier_continue (c))
{
s = g_utf8_next_char (s);
c = g_utf8_get_char (s);
length++;
}
}
return g_utf8_offset_to_pointer (start, length) - start;
}
static void
gimp_eevl_expect (GimpEevl *eva,
GimpEevlTokenType token_type,
GimpEevlToken *value)
{
if (! gimp_eevl_accept (eva, token_type, value))
gimp_eevl_error (eva, "Unexpected token");
}
static void
gimp_eevl_error (GimpEevl *eva,
gchar *msg)
{
eva->error_message = msg;
longjmp (eva->catcher, 1);
}
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