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busybox/shell/math.c
Denys Vlasenko c58d785b9d ash: fix BASE###nn bashism for bases 36..64 
function                                             old     new   delta
evaluate_string                                      876     932     +56

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
2019-09-22 23:40:10 +02:00

838 lines
25 KiB
C
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/*
* Arithmetic code ripped out of ash shell for code sharing.
*
* This code is derived from software contributed to Berkeley by
* Kenneth Almquist.
*
* Original BSD copyright notice is retained at the end of this file.
*
* Copyright (c) 1989, 1991, 1993, 1994
* The Regents of the University of California. All rights reserved.
*
* Copyright (c) 1997-2005 Herbert Xu <herbert@gondor.apana.org.au>
* was re-ported from NetBSD and debianized.
*
* rewrite arith.y to micro stack based cryptic algorithm by
* Copyright (c) 2001 Aaron Lehmann <aaronl@vitelus.com>
*
* Modified by Paul Mundt <lethal@linux-sh.org> (c) 2004 to support
* dynamic variables.
*
* Modified by Vladimir Oleynik <dzo@simtreas.ru> (c) 2001-2005 to be
* used in busybox and size optimizations,
* rewrote arith (see notes to this), added locale support,
* rewrote dynamic variables.
*
* Licensed under GPLv2 or later, see file LICENSE in this source tree.
*/
/* Copyright (c) 2001 Aaron Lehmann <aaronl@vitelus.com>
*
* Permission is hereby granted, free of charge, to any person obtaining
* a copy of this software and associated documentation files (the
* "Software"), to deal in the Software without restriction, including
* without limitation the rights to use, copy, modify, merge, publish,
* distribute, sublicense, and/or sell copies of the Software, and to
* permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be
* included in all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
* EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
* MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
* IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY
* CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT,
* TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
* SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
*/
/* This is my infix parser/evaluator. It is optimized for size, intended
* as a replacement for yacc-based parsers. However, it may well be faster
* than a comparable parser written in yacc. The supported operators are
* listed in #defines below. Parens, order of operations, and error handling
* are supported. This code is thread safe. The exact expression format should
* be that which POSIX specifies for shells.
*
* The code uses a simple two-stack algorithm. See
* http://www.onthenet.com.au/~grahamis/int2008/week02/lect02.html
* for a detailed explanation of the infix-to-postfix algorithm on which
* this is based (this code differs in that it applies operators immediately
* to the stack instead of adding them to a queue to end up with an
* expression).
*/
/*
* Aug 24, 2001 Manuel Novoa III
*
* Reduced the generated code size by about 30% (i386) and fixed several bugs.
*
* 1) In arith_apply():
* a) Cached values of *numptr and &(numptr[-1]).
* b) Removed redundant test for zero denominator.
*
* 2) In arith():
* a) Eliminated redundant code for processing operator tokens by moving
* to a table-based implementation. Also folded handling of parens
* into the table.
* b) Combined all 3 loops which called arith_apply to reduce generated
* code size at the cost of speed.
*
* 3) The following expressions were treated as valid by the original code:
* 1() , 0! , 1 ( *3 ) .
* These bugs have been fixed by internally enclosing the expression in
* parens and then checking that all binary ops and right parens are
* preceded by a valid expression (NUM_TOKEN).
*
* Note: It may be desirable to replace Aaron's test for whitespace with
* ctype's isspace() if it is used by another busybox applet or if additional
* whitespace chars should be considered. Look below the "#include"s for a
* precompiler test.
*/
/*
* Aug 26, 2001 Manuel Novoa III
*
* Return 0 for null expressions. Pointed out by Vladimir Oleynik.
*
* Merge in Aaron's comments previously posted to the busybox list,
* modified slightly to take account of my changes to the code.
*
*/
/*
* (C) 2003 Vladimir Oleynik <dzo@simtreas.ru>
*
* - allow access to variable,
* use recursive value indirection: c="2*2"; a="c"; echo $((a+=2)) produce 6
* - implement assign syntax (VAR=expr, +=, *= etc)
* - implement exponentiation (** operator)
* - implement comma separated - expr, expr
* - implement ++expr --expr expr++ expr--
* - implement expr ? expr : expr (but second expr is always calculated)
* - allow hexadecimal and octal numbers
* - restore lost XOR operator
* - protect $((num num)) as true zero expr (Manuel's error)
* - always use special isspace(), see comment from bash ;-)
*/
#include "libbb.h"
#include "math.h"
#define lookupvar (math_state->lookupvar)
#define setvar (math_state->setvar )
//#define endofname (math_state->endofname)
typedef unsigned char operator;
/* An operator's token id is a bit of a bitfield. The lower 5 bits are the
* precedence, and 3 high bits are an ID unique across operators of that
* precedence. The ID portion is so that multiple operators can have the
* same precedence, ensuring that the leftmost one is evaluated first.
* Consider * and /
*/
#define tok_decl(prec,id) (((id)<<5) | (prec))
#define PREC(op) ((op) & 0x1F)
#define TOK_LPAREN tok_decl(0,0)
#define TOK_COMMA tok_decl(1,0)
/* All assignments are right associative and have the same precedence,
* but there are 11 of them, which doesn't fit into 3 bits for unique id.
* Abusing another precedence level:
*/
#define TOK_ASSIGN tok_decl(2,0)
#define TOK_AND_ASSIGN tok_decl(2,1)
#define TOK_OR_ASSIGN tok_decl(2,2)
#define TOK_XOR_ASSIGN tok_decl(2,3)
#define TOK_PLUS_ASSIGN tok_decl(2,4)
#define TOK_MINUS_ASSIGN tok_decl(2,5)
#define TOK_LSHIFT_ASSIGN tok_decl(2,6)
#define TOK_RSHIFT_ASSIGN tok_decl(2,7)
#define TOK_MUL_ASSIGN tok_decl(3,0)
#define TOK_DIV_ASSIGN tok_decl(3,1)
#define TOK_REM_ASSIGN tok_decl(3,2)
#define fix_assignment_prec(prec) do { if (prec == 3) prec = 2; } while (0)
/* Ternary conditional operator is right associative too */
#define TOK_CONDITIONAL tok_decl(4,0)
#define TOK_CONDITIONAL_SEP tok_decl(4,1)
#define TOK_OR tok_decl(5,0)
#define TOK_AND tok_decl(6,0)
#define TOK_BOR tok_decl(7,0)
#define TOK_BXOR tok_decl(8,0)
#define TOK_BAND tok_decl(9,0)
#define TOK_EQ tok_decl(10,0)
#define TOK_NE tok_decl(10,1)
#define TOK_LT tok_decl(11,0)
#define TOK_GT tok_decl(11,1)
#define TOK_GE tok_decl(11,2)
#define TOK_LE tok_decl(11,3)
#define TOK_LSHIFT tok_decl(12,0)
#define TOK_RSHIFT tok_decl(12,1)
#define TOK_ADD tok_decl(13,0)
#define TOK_SUB tok_decl(13,1)
#define TOK_MUL tok_decl(14,0)
#define TOK_DIV tok_decl(14,1)
#define TOK_REM tok_decl(14,2)
/* Exponent is right associative */
#define TOK_EXPONENT tok_decl(15,1)
/* Unary operators */
#define UNARYPREC 16
#define TOK_BNOT tok_decl(UNARYPREC,0)
#define TOK_NOT tok_decl(UNARYPREC,1)
#define TOK_UMINUS tok_decl(UNARYPREC+1,0)
#define TOK_UPLUS tok_decl(UNARYPREC+1,1)
#define PREC_PRE (UNARYPREC+2)
#define TOK_PRE_INC tok_decl(PREC_PRE, 0)
#define TOK_PRE_DEC tok_decl(PREC_PRE, 1)
#define PREC_POST (UNARYPREC+3)
#define TOK_POST_INC tok_decl(PREC_POST, 0)
#define TOK_POST_DEC tok_decl(PREC_POST, 1)
#define SPEC_PREC (UNARYPREC+4)
#define TOK_NUM tok_decl(SPEC_PREC, 0)
#define TOK_RPAREN tok_decl(SPEC_PREC, 1)
static int
is_assign_op(operator op)
{
operator prec = PREC(op);
fix_assignment_prec(prec);
return prec == PREC(TOK_ASSIGN)
|| prec == PREC_PRE
|| prec == PREC_POST;
}
static int
is_right_associative(operator prec)
{
return prec == PREC(TOK_ASSIGN)
|| prec == PREC(TOK_EXPONENT)
|| prec == PREC(TOK_CONDITIONAL);
}
typedef struct {
arith_t val;
/* We acquire second_val only when "expr1 : expr2" part
* of ternary ?: op is evaluated.
* We treat ?: as two binary ops: (expr ? (expr1 : expr2)).
* ':' produces a new value which has two parts, val and second_val;
* then '?' selects one of them based on its left side.
*/
arith_t second_val;
char second_val_present;
/* If NULL then it's just a number, else it's a named variable */
char *var;
} var_or_num_t;
typedef struct remembered_name {
struct remembered_name *next;
const char *var;
} remembered_name;
static arith_t FAST_FUNC
evaluate_string(arith_state_t *math_state, const char *expr);
static const char*
arith_lookup_val(arith_state_t *math_state, var_or_num_t *t)
{
if (t->var) {
const char *p = lookupvar(t->var);
if (p) {
remembered_name *cur;
remembered_name cur_save;
/* did we already see this name?
* testcase: a=b; b=a; echo $((a))
*/
for (cur = math_state->list_of_recursed_names; cur; cur = cur->next) {
if (strcmp(cur->var, t->var) == 0) {
/* Yes */
return "expression recursion loop detected";
}
}
/* push current var name */
cur = math_state->list_of_recursed_names;
cur_save.var = t->var;
cur_save.next = cur;
math_state->list_of_recursed_names = &cur_save;
/* recursively evaluate p as expression */
t->val = evaluate_string(math_state, p);
/* pop current var name */
math_state->list_of_recursed_names = cur;
return math_state->errmsg;
}
/* treat undefined var as 0 */
t->val = 0;
}
return 0;
}
/* "Applying" a token means performing it on the top elements on the integer
* stack. For an unary operator it will only change the top element, but a
* binary operator will pop two arguments and push the result */
static NOINLINE const char*
arith_apply(arith_state_t *math_state, operator op, var_or_num_t *numstack, var_or_num_t **numstackptr)
{
#define NUMPTR (*numstackptr)
var_or_num_t *top_of_stack;
arith_t rez;
const char *err;
/* There is no operator that can work without arguments */
if (NUMPTR == numstack)
goto err;
top_of_stack = NUMPTR - 1;
/* Resolve name to value, if needed */
err = arith_lookup_val(math_state, top_of_stack);
if (err)
return err;
rez = top_of_stack->val;
if (op == TOK_UMINUS)
rez = -rez;
else if (op == TOK_NOT)
rez = !rez;
else if (op == TOK_BNOT)
rez = ~rez;
else if (op == TOK_POST_INC || op == TOK_PRE_INC)
rez++;
else if (op == TOK_POST_DEC || op == TOK_PRE_DEC)
rez--;
else if (op != TOK_UPLUS) {
/* Binary operators */
arith_t right_side_val;
char bad_second_val;
/* Binary operators need two arguments */
if (top_of_stack == numstack)
goto err;
/* ...and they pop one */
NUMPTR = top_of_stack; /* this decrements NUMPTR */
bad_second_val = top_of_stack->second_val_present;
if (op == TOK_CONDITIONAL) { /* ? operation */
/* Make next if (...) protect against
* $((expr1 ? expr2)) - that is, missing ": expr" */
bad_second_val = !bad_second_val;
}
if (bad_second_val) {
/* Protect against $((expr <not_?_op> expr1 : expr2)) */
return "malformed ?: operator";
}
top_of_stack--; /* now points to left side */
if (op != TOK_ASSIGN) {
/* Resolve left side value (unless the op is '=') */
err = arith_lookup_val(math_state, top_of_stack);
if (err)
return err;
}
right_side_val = rez;
rez = top_of_stack->val;
if (op == TOK_CONDITIONAL) /* ? operation */
rez = (rez ? right_side_val : top_of_stack[1].second_val);
else if (op == TOK_CONDITIONAL_SEP) { /* : operation */
if (top_of_stack == numstack) {
/* Protect against $((expr : expr)) */
return "malformed ?: operator";
}
top_of_stack->second_val_present = op;
top_of_stack->second_val = right_side_val;
}
else if (op == TOK_BOR || op == TOK_OR_ASSIGN)
rez |= right_side_val;
else if (op == TOK_OR)
rez = right_side_val || rez;
else if (op == TOK_BAND || op == TOK_AND_ASSIGN)
rez &= right_side_val;
else if (op == TOK_BXOR || op == TOK_XOR_ASSIGN)
rez ^= right_side_val;
else if (op == TOK_AND)
rez = rez && right_side_val;
else if (op == TOK_EQ)
rez = (rez == right_side_val);
else if (op == TOK_NE)
rez = (rez != right_side_val);
else if (op == TOK_GE)
rez = (rez >= right_side_val);
else if (op == TOK_RSHIFT || op == TOK_RSHIFT_ASSIGN)
rez >>= right_side_val;
else if (op == TOK_LSHIFT || op == TOK_LSHIFT_ASSIGN)
rez <<= right_side_val;
else if (op == TOK_GT)
rez = (rez > right_side_val);
else if (op == TOK_LT)
rez = (rez < right_side_val);
else if (op == TOK_LE)
rez = (rez <= right_side_val);
else if (op == TOK_MUL || op == TOK_MUL_ASSIGN)
rez *= right_side_val;
else if (op == TOK_ADD || op == TOK_PLUS_ASSIGN)
rez += right_side_val;
else if (op == TOK_SUB || op == TOK_MINUS_ASSIGN)
rez -= right_side_val;
else if (op == TOK_ASSIGN || op == TOK_COMMA)
rez = right_side_val;
else if (op == TOK_EXPONENT) {
arith_t c;
if (right_side_val < 0)
return "exponent less than 0";
c = 1;
while (--right_side_val >= 0)
c *= rez;
rez = c;
}
else if (right_side_val == 0)
return "divide by zero";
else if (op == TOK_DIV || op == TOK_DIV_ASSIGN
|| op == TOK_REM || op == TOK_REM_ASSIGN) {
/*
* bash 4.2.45 x86 64bit: SEGV on 'echo $((2**63 / -1))'
*
* MAX_NEGATIVE_INT / -1 = MAX_POSITIVE_INT+1
* and thus is not representable.
* Some CPUs segfault trying such op.
* Others overflow MAX_POSITIVE_INT+1 to
* MAX_NEGATIVE_INT (0x7fff+1 = 0x8000).
* Make sure to at least not SEGV here:
*/
if (right_side_val == -1
&& rez << 1 == 0 /* MAX_NEGATIVE_INT or 0 */
) {
right_side_val = 1;
}
if (op == TOK_DIV || op == TOK_DIV_ASSIGN)
rez /= right_side_val;
else {
rez %= right_side_val;
}
}
}
if (is_assign_op(op)) {
char buf[sizeof(arith_t)*3 + 2];
if (top_of_stack->var == NULL) {
/* Hmm, 1=2 ? */
//TODO: actually, bash allows ++7 but for some reason it evals to 7, not 8
goto err;
}
/* Save to shell variable */
sprintf(buf, ARITH_FMT, rez);
setvar(top_of_stack->var, buf);
/* After saving, make previous value for v++ or v-- */
if (op == TOK_POST_INC)
rez--;
else if (op == TOK_POST_DEC)
rez++;
}
top_of_stack->val = rez;
/* Erase var name, it is just a number now */
top_of_stack->var = NULL;
return NULL;
err:
return "arithmetic syntax error";
#undef NUMPTR
}
/* longest must be first */
static const char op_tokens[] ALIGN1 = {
'<','<','=',0, TOK_LSHIFT_ASSIGN,
'>','>','=',0, TOK_RSHIFT_ASSIGN,
'<','<', 0, TOK_LSHIFT,
'>','>', 0, TOK_RSHIFT,
'|','|', 0, TOK_OR,
'&','&', 0, TOK_AND,
'!','=', 0, TOK_NE,
'<','=', 0, TOK_LE,
'>','=', 0, TOK_GE,
'=','=', 0, TOK_EQ,
'|','=', 0, TOK_OR_ASSIGN,
'&','=', 0, TOK_AND_ASSIGN,
'*','=', 0, TOK_MUL_ASSIGN,
'/','=', 0, TOK_DIV_ASSIGN,
'%','=', 0, TOK_REM_ASSIGN,
'+','=', 0, TOK_PLUS_ASSIGN,
'-','=', 0, TOK_MINUS_ASSIGN,
'-','-', 0, TOK_POST_DEC,
'^','=', 0, TOK_XOR_ASSIGN,
'+','+', 0, TOK_POST_INC,
'*','*', 0, TOK_EXPONENT,
'!', 0, TOK_NOT,
'<', 0, TOK_LT,
'>', 0, TOK_GT,
'=', 0, TOK_ASSIGN,
'|', 0, TOK_BOR,
'&', 0, TOK_BAND,
'*', 0, TOK_MUL,
'/', 0, TOK_DIV,
'%', 0, TOK_REM,
'+', 0, TOK_ADD,
'-', 0, TOK_SUB,
'^', 0, TOK_BXOR,
/* uniq */
'~', 0, TOK_BNOT,
',', 0, TOK_COMMA,
'?', 0, TOK_CONDITIONAL,
':', 0, TOK_CONDITIONAL_SEP,
')', 0, TOK_RPAREN,
'(', 0, TOK_LPAREN,
0
};
#define ptr_to_rparen (&op_tokens[sizeof(op_tokens)-7])
#if ENABLE_FEATURE_SH_MATH_BASE
static arith_t strto_arith_t(const char *nptr, char **endptr)
{
unsigned base;
arith_t n;
# if ENABLE_FEATURE_SH_MATH_64
n = strtoull(nptr, endptr, 0);
# else
n = strtoul(nptr, endptr, 0);
# endif
if (**endptr != '#'
|| (*nptr < '1' || *nptr > '9')
|| (n < 2 || n > 64)
) {
return n;
}
/* It's "N#nnnn" or "NN#nnnn" syntax, NN can't start with 0,
* NN is in 2..64 range.
*/
base = (unsigned)n;
n = 0;
nptr = *endptr + 1;
/* bash allows "N#" (empty "nnnn" part) */
for (;;) {
unsigned digit = (unsigned)*nptr - '0';
if (digit >= 10) {
/* *nptr is not 0..9 */
if (*nptr > 'z')
break; /* this rejects e.g. $((64#~)) */
/* in bases up to 36, case does not matter for a-z */
digit = (unsigned)(*nptr | 0x20) - ('a' - 10);
if (base > 36 && *nptr <= '_') {
/* otherwise, A-Z,@,_ are 36..61,62,63 */
if (*nptr == '@')
digit = 62;
else if (*nptr == '_')
digit = 63;
else if (digit < 36) /* A-Z */
digit += 36 - 10;
else
break; /* error, such as [ or \ */
}
//bb_error_msg("ch:'%c'%d digit:%u", *nptr, *nptr, digit);
//if (digit < 10) - example where we need this?
// break;
}
if (digit >= base)
break;
/* bash does not check for overflows */
n = n * base + digit;
nptr++;
}
*endptr = (char*)nptr;
return n;
}
#else /* !ENABLE_FEATURE_SH_MATH_BASE */
# if ENABLE_FEATURE_SH_MATH_64
# define strto_arith_t(nptr, endptr) strtoull(nptr, endptr, 0)
# else
# define strto_arith_t(nptr, endptr) strtoul(nptr, endptr, 0)
# endif
#endif
static arith_t FAST_FUNC
evaluate_string(arith_state_t *math_state, const char *expr)
{
operator lasttok;
const char *errmsg;
const char *start_expr = expr = skip_whitespace(expr);
unsigned expr_len = strlen(expr) + 2;
/* Stack of integers */
/* The proof that there can be no more than strlen(startbuf)/2+1
* integers in any given correct or incorrect expression
* is left as an exercise to the reader. */
var_or_num_t *const numstack = alloca((expr_len / 2) * sizeof(numstack[0]));
var_or_num_t *numstackptr = numstack;
/* Stack of operator tokens */
operator *const stack = alloca(expr_len * sizeof(stack[0]));
operator *stackptr = stack;
/* Start with a left paren */
*stackptr++ = lasttok = TOK_LPAREN;
errmsg = NULL;
while (1) {
const char *p;
operator op;
operator prec;
char arithval;
expr = skip_whitespace(expr);
arithval = *expr;
if (arithval == '\0') {
if (expr == start_expr) {
/* Null expression */
numstack->val = 0;
goto ret;
}
/* This is only reached after all tokens have been extracted from the
* input stream. If there are still tokens on the operator stack, they
* are to be applied in order. At the end, there should be a final
* result on the integer stack */
if (expr != ptr_to_rparen + 1) {
/* If we haven't done so already,
* append a closing right paren
* and let the loop process it */
expr = ptr_to_rparen;
continue;
}
/* At this point, we're done with the expression */
if (numstackptr != numstack + 1) {
/* ...but if there isn't, it's bad */
goto err;
}
if (numstack->var) {
/* expression is $((var)) only, lookup now */
errmsg = arith_lookup_val(math_state, numstack);
}
goto ret;
}
p = endofname(expr);
if (p != expr) {
/* Name */
size_t var_name_size = (p-expr) + 1; /* +1 for NUL */
numstackptr->var = alloca(var_name_size);
safe_strncpy(numstackptr->var, expr, var_name_size);
expr = p;
num:
numstackptr->second_val_present = 0;
numstackptr++;
lasttok = TOK_NUM;
continue;
}
if (isdigit(arithval)) {
/* Number */
numstackptr->var = NULL;
errno = 0;
numstackptr->val = strto_arith_t(expr, (char**) &expr);
if (errno)
numstackptr->val = 0; /* bash compat */
goto num;
}
/* Should be an operator */
/* Special case: NUM-- and NUM++ are not recognized if NUM
* is a literal number, not a variable. IOW:
* "a+++v" is a++ + v.
* "7+++v" is 7 + ++v, not 7++ + v.
*/
if (lasttok == TOK_NUM && !numstackptr[-1].var /* number literal */
&& (expr[0] == '+' || expr[0] == '-')
&& (expr[1] == expr[0])
) {
//bb_error_msg("special %c%c", expr[0], expr[0]);
op = (expr[0] == '+' ? TOK_ADD : TOK_SUB);
expr += 1;
goto tok_found1;
}
p = op_tokens;
while (1) {
/* Compare expr to current op_tokens[] element */
const char *e = expr;
while (1) {
if (*p == '\0') {
/* Match: operator is found */
expr = e;
goto tok_found;
}
if (*p != *e)
break;
p++;
e++;
}
/* No match, go to next element of op_tokens[] */
while (*p)
p++;
p += 2; /* skip NUL and TOK_foo bytes */
if (*p == '\0') {
/* No next element, operator not found */
//math_state->syntax_error_at = expr;
goto err;
}
}
tok_found:
op = p[1]; /* fetch TOK_foo value */
tok_found1:
/* NB: expr now points past the operator */
/* post grammar: a++ reduce to num */
if (lasttok == TOK_POST_INC || lasttok == TOK_POST_DEC)
lasttok = TOK_NUM;
/* Plus and minus are binary (not unary) _only_ if the last
* token was a number, or a right paren (which pretends to be
* a number, since it evaluates to one). Think about it.
* It makes sense. */
if (lasttok != TOK_NUM) {
switch (op) {
case TOK_ADD:
op = TOK_UPLUS;
break;
case TOK_SUB:
op = TOK_UMINUS;
break;
case TOK_POST_INC:
op = TOK_PRE_INC;
break;
case TOK_POST_DEC:
op = TOK_PRE_DEC;
break;
}
}
/* We don't want an unary operator to cause recursive descent on the
* stack, because there can be many in a row and it could cause an
* operator to be evaluated before its argument is pushed onto the
* integer stack.
* But for binary operators, "apply" everything on the operator
* stack until we find an operator with a lesser priority than the
* one we have just extracted. If op is right-associative,
* then stop "applying" on the equal priority too.
* Left paren is given the lowest priority so it will never be
* "applied" in this way.
*/
prec = PREC(op);
if ((prec > 0 && prec < UNARYPREC) || prec == SPEC_PREC) {
/* not left paren or unary */
if (lasttok != TOK_NUM) {
/* binary op must be preceded by a num */
goto err;
}
while (stackptr != stack) {
operator prev_op = *--stackptr;
if (op == TOK_RPAREN) {
/* The algorithm employed here is simple: while we don't
* hit an open paren nor the bottom of the stack, pop
* tokens and apply them */
if (prev_op == TOK_LPAREN) {
/* Any operator directly after a
* close paren should consider itself binary */
lasttok = TOK_NUM;
goto next;
}
} else {
operator prev_prec = PREC(prev_op);
fix_assignment_prec(prec);
fix_assignment_prec(prev_prec);
if (prev_prec < prec
|| (prev_prec == prec && is_right_associative(prec))
) {
stackptr++;
break;
}
}
errmsg = arith_apply(math_state, prev_op, numstack, &numstackptr);
if (errmsg)
goto err_with_custom_msg;
}
if (op == TOK_RPAREN)
goto err;
}
/* Push this operator to the stack and remember it */
*stackptr++ = lasttok = op;
next: ;
} /* while (1) */
err:
errmsg = "arithmetic syntax error";
err_with_custom_msg:
numstack->val = -1;
ret:
math_state->errmsg = errmsg;
return numstack->val;
}
arith_t FAST_FUNC
arith(arith_state_t *math_state, const char *expr)
{
math_state->errmsg = NULL;
math_state->list_of_recursed_names = NULL;
return evaluate_string(math_state, expr);
}
/*
* Copyright (c) 1989, 1991, 1993, 1994
* The Regents of the University of California. All rights reserved.
*
* This code is derived from software contributed to Berkeley by
* Kenneth Almquist.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the University nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ''AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
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