source: branches/3.2/mindi-busybox/shell/math.c @ 3232

Last change on this file since 3232 was 3232, checked in by bruno, 5 years ago
  • Update mindi-busybox to 1.21.1
  • Property svn:eol-style set to native
File size: 22.8 KB
Line 
1/*
2 * Arithmetic code ripped out of ash shell for code sharing.
3 *
4 * This code is derived from software contributed to Berkeley by
5 * Kenneth Almquist.
6 *
7 * Original BSD copyright notice is retained at the end of this file.
8 *
9 * Copyright (c) 1989, 1991, 1993, 1994
10 *      The Regents of the University of California.  All rights reserved.
11 *
12 * Copyright (c) 1997-2005 Herbert Xu <herbert@gondor.apana.org.au>
13 * was re-ported from NetBSD and debianized.
14 *
15 * rewrite arith.y to micro stack based cryptic algorithm by
16 * Copyright (c) 2001 Aaron Lehmann <aaronl@vitelus.com>
17 *
18 * Modified by Paul Mundt <lethal@linux-sh.org> (c) 2004 to support
19 * dynamic variables.
20 *
21 * Modified by Vladimir Oleynik <dzo@simtreas.ru> (c) 2001-2005 to be
22 * used in busybox and size optimizations,
23 * rewrote arith (see notes to this), added locale support,
24 * rewrote dynamic variables.
25 *
26 * Licensed under GPLv2 or later, see file LICENSE in this source tree.
27 */
28/* Copyright (c) 2001 Aaron Lehmann <aaronl@vitelus.com>
29 *
30 * Permission is hereby granted, free of charge, to any person obtaining
31 * a copy of this software and associated documentation files (the
32 * "Software"), to deal in the Software without restriction, including
33 * without limitation the rights to use, copy, modify, merge, publish,
34 * distribute, sublicense, and/or sell copies of the Software, and to
35 * permit persons to whom the Software is furnished to do so, subject to
36 * the following conditions:
37 *
38 * The above copyright notice and this permission notice shall be
39 * included in all copies or substantial portions of the Software.
40 *
41 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
42 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
43 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
44 * IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
45 * CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
46 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
47 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
48 */
49
50/* This is my infix parser/evaluator. It is optimized for size, intended
51 * as a replacement for yacc-based parsers. However, it may well be faster
52 * than a comparable parser written in yacc. The supported operators are
53 * listed in #defines below. Parens, order of operations, and error handling
54 * are supported. This code is thread safe. The exact expression format should
55 * be that which POSIX specifies for shells.
56 *
57 * The code uses a simple two-stack algorithm. See
58 * http://www.onthenet.com.au/~grahamis/int2008/week02/lect02.html
59 * for a detailed explanation of the infix-to-postfix algorithm on which
60 * this is based (this code differs in that it applies operators immediately
61 * to the stack instead of adding them to a queue to end up with an
62 * expression).
63 */
64
65/*
66 * Aug 24, 2001              Manuel Novoa III
67 *
68 * Reduced the generated code size by about 30% (i386) and fixed several bugs.
69 *
70 * 1) In arith_apply():
71 *    a) Cached values of *numptr and &(numptr[-1]).
72 *    b) Removed redundant test for zero denominator.
73 *
74 * 2) In arith():
75 *    a) Eliminated redundant code for processing operator tokens by moving
76 *       to a table-based implementation.  Also folded handling of parens
77 *       into the table.
78 *    b) Combined all 3 loops which called arith_apply to reduce generated
79 *       code size at the cost of speed.
80 *
81 * 3) The following expressions were treated as valid by the original code:
82 *       1()  ,    0!  ,    1 ( *3 )   .
83 *    These bugs have been fixed by internally enclosing the expression in
84 *    parens and then checking that all binary ops and right parens are
85 *    preceded by a valid expression (NUM_TOKEN).
86 *
87 * Note: It may be desirable to replace Aaron's test for whitespace with
88 * ctype's isspace() if it is used by another busybox applet or if additional
89 * whitespace chars should be considered.  Look below the "#include"s for a
90 * precompiler test.
91 */
92/*
93 * Aug 26, 2001              Manuel Novoa III
94 *
95 * Return 0 for null expressions.  Pointed out by Vladimir Oleynik.
96 *
97 * Merge in Aaron's comments previously posted to the busybox list,
98 * modified slightly to take account of my changes to the code.
99 *
100 */
101/*
102 *  (C) 2003 Vladimir Oleynik <dzo@simtreas.ru>
103 *
104 * - allow access to variable,
105 *   use recursive value indirection: c="2*2"; a="c"; echo $((a+=2)) produce 6
106 * - implement assign syntax (VAR=expr, +=, *= etc)
107 * - implement exponentiation (** operator)
108 * - implement comma separated - expr, expr
109 * - implement ++expr --expr expr++ expr--
110 * - implement expr ? expr : expr (but second expr is always calculated)
111 * - allow hexadecimal and octal numbers
112 * - restore lost XOR operator
113 * - protect $((num num)) as true zero expr (Manuel's error)
114 * - always use special isspace(), see comment from bash ;-)
115 */
116#include "libbb.h"
117#include "math.h"
118
119#define lookupvar (math_state->lookupvar)
120#define setvar    (math_state->setvar   )
121//#define endofname (math_state->endofname)
122
123typedef unsigned char operator;
124
125/* An operator's token id is a bit of a bitfield. The lower 5 bits are the
126 * precedence, and 3 high bits are an ID unique across operators of that
127 * precedence. The ID portion is so that multiple operators can have the
128 * same precedence, ensuring that the leftmost one is evaluated first.
129 * Consider * and /
130 */
131#define tok_decl(prec,id)       (((id)<<5) | (prec))
132#define PREC(op)                ((op) & 0x1F)
133
134#define TOK_LPAREN              tok_decl(0,0)
135
136#define TOK_COMMA               tok_decl(1,0)
137
138/* All assignments are right associative and have the same precedence,
139 * but there are 11 of them, which doesn't fit into 3 bits for unique id.
140 * Abusing another precedence level:
141 */
142#define TOK_ASSIGN              tok_decl(2,0)
143#define TOK_AND_ASSIGN          tok_decl(2,1)
144#define TOK_OR_ASSIGN           tok_decl(2,2)
145#define TOK_XOR_ASSIGN          tok_decl(2,3)
146#define TOK_PLUS_ASSIGN         tok_decl(2,4)
147#define TOK_MINUS_ASSIGN        tok_decl(2,5)
148#define TOK_LSHIFT_ASSIGN       tok_decl(2,6)
149#define TOK_RSHIFT_ASSIGN       tok_decl(2,7)
150
151#define TOK_MUL_ASSIGN          tok_decl(3,0)
152#define TOK_DIV_ASSIGN          tok_decl(3,1)
153#define TOK_REM_ASSIGN          tok_decl(3,2)
154
155#define fix_assignment_prec(prec) do { if (prec == 3) prec = 2; } while (0)
156
157/* Ternary conditional operator is right associative too */
158#define TOK_CONDITIONAL         tok_decl(4,0)
159#define TOK_CONDITIONAL_SEP     tok_decl(4,1)
160
161#define TOK_OR                  tok_decl(5,0)
162
163#define TOK_AND                 tok_decl(6,0)
164
165#define TOK_BOR                 tok_decl(7,0)
166
167#define TOK_BXOR                tok_decl(8,0)
168
169#define TOK_BAND                tok_decl(9,0)
170
171#define TOK_EQ                  tok_decl(10,0)
172#define TOK_NE                  tok_decl(10,1)
173
174#define TOK_LT                  tok_decl(11,0)
175#define TOK_GT                  tok_decl(11,1)
176#define TOK_GE                  tok_decl(11,2)
177#define TOK_LE                  tok_decl(11,3)
178
179#define TOK_LSHIFT              tok_decl(12,0)
180#define TOK_RSHIFT              tok_decl(12,1)
181
182#define TOK_ADD                 tok_decl(13,0)
183#define TOK_SUB                 tok_decl(13,1)
184
185#define TOK_MUL                 tok_decl(14,0)
186#define TOK_DIV                 tok_decl(14,1)
187#define TOK_REM                 tok_decl(14,2)
188
189/* Exponent is right associative */
190#define TOK_EXPONENT            tok_decl(15,1)
191
192/* Unary operators */
193#define UNARYPREC               16
194#define TOK_BNOT                tok_decl(UNARYPREC,0)
195#define TOK_NOT                 tok_decl(UNARYPREC,1)
196
197#define TOK_UMINUS              tok_decl(UNARYPREC+1,0)
198#define TOK_UPLUS               tok_decl(UNARYPREC+1,1)
199
200#define PREC_PRE                (UNARYPREC+2)
201
202#define TOK_PRE_INC             tok_decl(PREC_PRE, 0)
203#define TOK_PRE_DEC             tok_decl(PREC_PRE, 1)
204
205#define PREC_POST               (UNARYPREC+3)
206
207#define TOK_POST_INC            tok_decl(PREC_POST, 0)
208#define TOK_POST_DEC            tok_decl(PREC_POST, 1)
209
210#define SPEC_PREC               (UNARYPREC+4)
211
212#define TOK_NUM                 tok_decl(SPEC_PREC, 0)
213#define TOK_RPAREN              tok_decl(SPEC_PREC, 1)
214
215static int
216is_assign_op(operator op)
217{
218    operator prec = PREC(op);
219    fix_assignment_prec(prec);
220    return prec == PREC(TOK_ASSIGN)
221    || prec == PREC_PRE
222    || prec == PREC_POST;
223}
224
225static int
226is_right_associative(operator prec)
227{
228    return prec == PREC(TOK_ASSIGN)
229    || prec == PREC(TOK_EXPONENT)
230    || prec == PREC(TOK_CONDITIONAL);
231}
232
233
234typedef struct {
235    arith_t val;
236    /* We acquire second_val only when "expr1 : expr2" part
237     * of ternary ?: op is evaluated.
238     * We treat ?: as two binary ops: (expr ? (expr1 : expr2)).
239     * ':' produces a new value which has two parts, val and second_val;
240     * then '?' selects one of them based on its left side.
241     */
242    arith_t second_val;
243    char second_val_present;
244    /* If NULL then it's just a number, else it's a named variable */
245    char *var;
246} var_or_num_t;
247
248typedef struct remembered_name {
249    struct remembered_name *next;
250    const char *var;
251} remembered_name;
252
253
254static arith_t FAST_FUNC
255evaluate_string(arith_state_t *math_state, const char *expr);
256
257static const char*
258arith_lookup_val(arith_state_t *math_state, var_or_num_t *t)
259{
260    if (t->var) {
261        const char *p = lookupvar(t->var);
262        if (p) {
263            remembered_name *cur;
264            remembered_name cur_save;
265
266            /* did we already see this name?
267             * testcase: a=b; b=a; echo $((a))
268             */
269            for (cur = math_state->list_of_recursed_names; cur; cur = cur->next) {
270                if (strcmp(cur->var, t->var) == 0) {
271                    /* Yes */
272                    return "expression recursion loop detected";
273                }
274            }
275
276            /* push current var name */
277            cur = math_state->list_of_recursed_names;
278            cur_save.var = t->var;
279            cur_save.next = cur;
280            math_state->list_of_recursed_names = &cur_save;
281
282            /* recursively evaluate p as expression */
283            t->val = evaluate_string(math_state, p);
284
285            /* pop current var name */
286            math_state->list_of_recursed_names = cur;
287
288            return math_state->errmsg;
289        }
290        /* treat undefined var as 0 */
291        t->val = 0;
292    }
293    return 0;
294}
295
296/* "Applying" a token means performing it on the top elements on the integer
297 * stack. For an unary operator it will only change the top element, but a
298 * binary operator will pop two arguments and push the result */
299static NOINLINE const char*
300arith_apply(arith_state_t *math_state, operator op, var_or_num_t *numstack, var_or_num_t **numstackptr)
301{
302#define NUMPTR (*numstackptr)
303
304    var_or_num_t *top_of_stack;
305    arith_t rez;
306    const char *err;
307
308    /* There is no operator that can work without arguments */
309    if (NUMPTR == numstack)
310        goto err;
311
312    top_of_stack = NUMPTR - 1;
313
314    /* Resolve name to value, if needed */
315    err = arith_lookup_val(math_state, top_of_stack);
316    if (err)
317        return err;
318
319    rez = top_of_stack->val;
320    if (op == TOK_UMINUS)
321        rez = -rez;
322    else if (op == TOK_NOT)
323        rez = !rez;
324    else if (op == TOK_BNOT)
325        rez = ~rez;
326    else if (op == TOK_POST_INC || op == TOK_PRE_INC)
327        rez++;
328    else if (op == TOK_POST_DEC || op == TOK_PRE_DEC)
329        rez--;
330    else if (op != TOK_UPLUS) {
331        /* Binary operators */
332        arith_t right_side_val;
333        char bad_second_val;
334
335        /* Binary operators need two arguments */
336        if (top_of_stack == numstack)
337            goto err;
338        /* ...and they pop one */
339        NUMPTR = top_of_stack; /* this decrements NUMPTR */
340
341        bad_second_val = top_of_stack->second_val_present;
342        if (op == TOK_CONDITIONAL) { /* ? operation */
343            /* Make next if (...) protect against
344             * $((expr1 ? expr2)) - that is, missing ": expr" */
345            bad_second_val = !bad_second_val;
346        }
347        if (bad_second_val) {
348            /* Protect against $((expr <not_?_op> expr1 : expr2)) */
349            return "malformed ?: operator";
350        }
351
352        top_of_stack--; /* now points to left side */
353
354        if (op != TOK_ASSIGN) {
355            /* Resolve left side value (unless the op is '=') */
356            err = arith_lookup_val(math_state, top_of_stack);
357            if (err)
358                return err;
359        }
360
361        right_side_val = rez;
362        rez = top_of_stack->val;
363        if (op == TOK_CONDITIONAL) /* ? operation */
364            rez = (rez ? right_side_val : top_of_stack[1].second_val);
365        else if (op == TOK_CONDITIONAL_SEP) { /* : operation */
366            if (top_of_stack == numstack) {
367                /* Protect against $((expr : expr)) */
368                return "malformed ?: operator";
369            }
370            top_of_stack->second_val_present = op;
371            top_of_stack->second_val = right_side_val;
372        }
373        else if (op == TOK_BOR || op == TOK_OR_ASSIGN)
374            rez |= right_side_val;
375        else if (op == TOK_OR)
376            rez = right_side_val || rez;
377        else if (op == TOK_BAND || op == TOK_AND_ASSIGN)
378            rez &= right_side_val;
379        else if (op == TOK_BXOR || op == TOK_XOR_ASSIGN)
380            rez ^= right_side_val;
381        else if (op == TOK_AND)
382            rez = rez && right_side_val;
383        else if (op == TOK_EQ)
384            rez = (rez == right_side_val);
385        else if (op == TOK_NE)
386            rez = (rez != right_side_val);
387        else if (op == TOK_GE)
388            rez = (rez >= right_side_val);
389        else if (op == TOK_RSHIFT || op == TOK_RSHIFT_ASSIGN)
390            rez >>= right_side_val;
391        else if (op == TOK_LSHIFT || op == TOK_LSHIFT_ASSIGN)
392            rez <<= right_side_val;
393        else if (op == TOK_GT)
394            rez = (rez > right_side_val);
395        else if (op == TOK_LT)
396            rez = (rez < right_side_val);
397        else if (op == TOK_LE)
398            rez = (rez <= right_side_val);
399        else if (op == TOK_MUL || op == TOK_MUL_ASSIGN)
400            rez *= right_side_val;
401        else if (op == TOK_ADD || op == TOK_PLUS_ASSIGN)
402            rez += right_side_val;
403        else if (op == TOK_SUB || op == TOK_MINUS_ASSIGN)
404            rez -= right_side_val;
405        else if (op == TOK_ASSIGN || op == TOK_COMMA)
406            rez = right_side_val;
407        else if (op == TOK_EXPONENT) {
408            arith_t c;
409            if (right_side_val < 0)
410                return "exponent less than 0";
411            c = 1;
412            while (--right_side_val >= 0)
413                c *= rez;
414            rez = c;
415        }
416        else if (right_side_val == 0)
417            return "divide by zero";
418        else if (op == TOK_DIV || op == TOK_DIV_ASSIGN)
419            rez /= right_side_val;
420        else if (op == TOK_REM || op == TOK_REM_ASSIGN)
421            rez %= right_side_val;
422    }
423
424    if (is_assign_op(op)) {
425        char buf[sizeof(arith_t)*3 + 2];
426
427        if (top_of_stack->var == NULL) {
428            /* Hmm, 1=2 ? */
429//TODO: actually, bash allows ++7 but for some reason it evals to 7, not 8
430            goto err;
431        }
432        /* Save to shell variable */
433        sprintf(buf, ARITH_FMT, rez);
434        setvar(top_of_stack->var, buf);
435        /* After saving, make previous value for v++ or v-- */
436        if (op == TOK_POST_INC)
437            rez--;
438        else if (op == TOK_POST_DEC)
439            rez++;
440    }
441
442    top_of_stack->val = rez;
443    /* Erase var name, it is just a number now */
444    top_of_stack->var = NULL;
445    return NULL;
446 err:
447    return "arithmetic syntax error";
448#undef NUMPTR
449}
450
451/* longest must be first */
452static const char op_tokens[] ALIGN1 = {
453    '<','<','=',0, TOK_LSHIFT_ASSIGN,
454    '>','>','=',0, TOK_RSHIFT_ASSIGN,
455    '<','<',    0, TOK_LSHIFT,
456    '>','>',    0, TOK_RSHIFT,
457    '|','|',    0, TOK_OR,
458    '&','&',    0, TOK_AND,
459    '!','=',    0, TOK_NE,
460    '<','=',    0, TOK_LE,
461    '>','=',    0, TOK_GE,
462    '=','=',    0, TOK_EQ,
463    '|','=',    0, TOK_OR_ASSIGN,
464    '&','=',    0, TOK_AND_ASSIGN,
465    '*','=',    0, TOK_MUL_ASSIGN,
466    '/','=',    0, TOK_DIV_ASSIGN,
467    '%','=',    0, TOK_REM_ASSIGN,
468    '+','=',    0, TOK_PLUS_ASSIGN,
469    '-','=',    0, TOK_MINUS_ASSIGN,
470    '-','-',    0, TOK_POST_DEC,
471    '^','=',    0, TOK_XOR_ASSIGN,
472    '+','+',    0, TOK_POST_INC,
473    '*','*',    0, TOK_EXPONENT,
474    '!',        0, TOK_NOT,
475    '<',        0, TOK_LT,
476    '>',        0, TOK_GT,
477    '=',        0, TOK_ASSIGN,
478    '|',        0, TOK_BOR,
479    '&',        0, TOK_BAND,
480    '*',        0, TOK_MUL,
481    '/',        0, TOK_DIV,
482    '%',        0, TOK_REM,
483    '+',        0, TOK_ADD,
484    '-',        0, TOK_SUB,
485    '^',        0, TOK_BXOR,
486    /* uniq */
487    '~',        0, TOK_BNOT,
488    ',',        0, TOK_COMMA,
489    '?',        0, TOK_CONDITIONAL,
490    ':',        0, TOK_CONDITIONAL_SEP,
491    ')',        0, TOK_RPAREN,
492    '(',        0, TOK_LPAREN,
493    0
494};
495#define ptr_to_rparen (&op_tokens[sizeof(op_tokens)-7])
496
497const char* FAST_FUNC
498endofname(const char *name)
499{
500    if (!is_name(*name))
501        return name;
502    while (*++name) {
503        if (!is_in_name(*name))
504            break;
505    }
506    return name;
507}
508
509static arith_t FAST_FUNC
510evaluate_string(arith_state_t *math_state, const char *expr)
511{
512    operator lasttok;
513    const char *errmsg;
514    const char *start_expr = expr = skip_whitespace(expr);
515    unsigned expr_len = strlen(expr) + 2;
516    /* Stack of integers */
517    /* The proof that there can be no more than strlen(startbuf)/2+1
518     * integers in any given correct or incorrect expression
519     * is left as an exercise to the reader. */
520    var_or_num_t *const numstack = alloca((expr_len / 2) * sizeof(numstack[0]));
521    var_or_num_t *numstackptr = numstack;
522    /* Stack of operator tokens */
523    operator *const stack = alloca(expr_len * sizeof(stack[0]));
524    operator *stackptr = stack;
525
526    /* Start with a left paren */
527    *stackptr++ = lasttok = TOK_LPAREN;
528    errmsg = NULL;
529
530    while (1) {
531        const char *p;
532        operator op;
533        operator prec;
534        char arithval;
535
536        expr = skip_whitespace(expr);
537        arithval = *expr;
538        if (arithval == '\0') {
539            if (expr == start_expr) {
540                /* Null expression */
541                numstack->val = 0;
542                goto ret;
543            }
544
545            /* This is only reached after all tokens have been extracted from the
546             * input stream. If there are still tokens on the operator stack, they
547             * are to be applied in order. At the end, there should be a final
548             * result on the integer stack */
549
550            if (expr != ptr_to_rparen + 1) {
551                /* If we haven't done so already,
552                 * append a closing right paren
553                 * and let the loop process it */
554                expr = ptr_to_rparen;
555                continue;
556            }
557            /* At this point, we're done with the expression */
558            if (numstackptr != numstack + 1) {
559                /* ...but if there isn't, it's bad */
560                goto err;
561            }
562            if (numstack->var) {
563                /* expression is $((var)) only, lookup now */
564                errmsg = arith_lookup_val(math_state, numstack);
565            }
566            goto ret;
567        }
568
569        p = endofname(expr);
570        if (p != expr) {
571            /* Name */
572            size_t var_name_size = (p-expr) + 1;  /* +1 for NUL */
573            numstackptr->var = alloca(var_name_size);
574            safe_strncpy(numstackptr->var, expr, var_name_size);
575            expr = p;
576 num:
577            numstackptr->second_val_present = 0;
578            numstackptr++;
579            lasttok = TOK_NUM;
580            continue;
581        }
582
583        if (isdigit(arithval)) {
584            /* Number */
585            numstackptr->var = NULL;
586            errno = 0;
587            numstackptr->val = strto_arith_t(expr, (char**) &expr, 0);
588            if (errno)
589                numstackptr->val = 0; /* bash compat */
590            goto num;
591        }
592
593        /* Should be an operator */
594        p = op_tokens;
595        while (1) {
596// TODO: bash allows 7+++v, treats it as 7 + ++v
597// we treat it as 7++ + v and reject
598            /* Compare expr to current op_tokens[] element */
599            const char *e = expr;
600            while (1) {
601                if (*p == '\0') {
602                    /* Match: operator is found */
603                    expr = e;
604                    goto tok_found;
605                }
606                if (*p != *e)
607                    break;
608                p++;
609                e++;
610            }
611            /* No match, go to next element of op_tokens[] */
612            while (*p)
613                p++;
614            p += 2; /* skip NUL and TOK_foo bytes */
615            if (*p == '\0') {
616                /* No next element, operator not found */
617                //math_state->syntax_error_at = expr;
618                goto err;
619            }
620        }
621 tok_found:
622        op = p[1]; /* fetch TOK_foo value */
623        /* NB: expr now points past the operator */
624
625        /* post grammar: a++ reduce to num */
626        if (lasttok == TOK_POST_INC || lasttok == TOK_POST_DEC)
627            lasttok = TOK_NUM;
628
629        /* Plus and minus are binary (not unary) _only_ if the last
630         * token was a number, or a right paren (which pretends to be
631         * a number, since it evaluates to one). Think about it.
632         * It makes sense. */
633        if (lasttok != TOK_NUM) {
634            switch (op) {
635            case TOK_ADD:
636                op = TOK_UPLUS;
637                break;
638            case TOK_SUB:
639                op = TOK_UMINUS;
640                break;
641            case TOK_POST_INC:
642                op = TOK_PRE_INC;
643                break;
644            case TOK_POST_DEC:
645                op = TOK_PRE_DEC;
646                break;
647            }
648        }
649        /* We don't want an unary operator to cause recursive descent on the
650         * stack, because there can be many in a row and it could cause an
651         * operator to be evaluated before its argument is pushed onto the
652         * integer stack.
653         * But for binary operators, "apply" everything on the operator
654         * stack until we find an operator with a lesser priority than the
655         * one we have just extracted. If op is right-associative,
656         * then stop "applying" on the equal priority too.
657         * Left paren is given the lowest priority so it will never be
658         * "applied" in this way.
659         */
660        prec = PREC(op);
661        if ((prec > 0 && prec < UNARYPREC) || prec == SPEC_PREC) {
662            /* not left paren or unary */
663            if (lasttok != TOK_NUM) {
664                /* binary op must be preceded by a num */
665                goto err;
666            }
667            while (stackptr != stack) {
668                operator prev_op = *--stackptr;
669                if (op == TOK_RPAREN) {
670                    /* The algorithm employed here is simple: while we don't
671                     * hit an open paren nor the bottom of the stack, pop
672                     * tokens and apply them */
673                    if (prev_op == TOK_LPAREN) {
674                        /* Any operator directly after a
675                         * close paren should consider itself binary */
676                        lasttok = TOK_NUM;
677                        goto next;
678                    }
679                } else {
680                    operator prev_prec = PREC(prev_op);
681                    fix_assignment_prec(prec);
682                    fix_assignment_prec(prev_prec);
683                    if (prev_prec < prec
684                     || (prev_prec == prec && is_right_associative(prec))
685                    ) {
686                        stackptr++;
687                        break;
688                    }
689                }
690                errmsg = arith_apply(math_state, prev_op, numstack, &numstackptr);
691                if (errmsg)
692                    goto err_with_custom_msg;
693            }
694            if (op == TOK_RPAREN)
695                goto err;
696        }
697
698        /* Push this operator to the stack and remember it */
699        *stackptr++ = lasttok = op;
700 next: ;
701    } /* while (1) */
702
703 err:
704    errmsg = "arithmetic syntax error";
705 err_with_custom_msg:
706    numstack->val = -1;
707 ret:
708    math_state->errmsg = errmsg;
709    return numstack->val;
710}
711
712arith_t FAST_FUNC
713arith(arith_state_t *math_state, const char *expr)
714{
715    math_state->errmsg = NULL;
716    math_state->list_of_recursed_names = NULL;
717    return evaluate_string(math_state, expr);
718}
719
720/*
721 * Copyright (c) 1989, 1991, 1993, 1994
722 *      The Regents of the University of California.  All rights reserved.
723 *
724 * This code is derived from software contributed to Berkeley by
725 * Kenneth Almquist.
726 *
727 * Redistribution and use in source and binary forms, with or without
728 * modification, are permitted provided that the following conditions
729 * are met:
730 * 1. Redistributions of source code must retain the above copyright
731 *    notice, this list of conditions and the following disclaimer.
732 * 2. Redistributions in binary form must reproduce the above copyright
733 *    notice, this list of conditions and the following disclaimer in the
734 *    documentation and/or other materials provided with the distribution.
735 * 3. Neither the name of the University nor the names of its contributors
736 *    may be used to endorse or promote products derived from this software
737 *    without specific prior written permission.
738 *
739 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
740 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
741 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
742 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
743 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
744 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
745 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
746 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
747 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
748 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
749 * SUCH DAMAGE.
750 */
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