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busybox/shell/math.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"
#if 1
# define dbg(...) ((void)0)
#else
# define dbg(...) bb_error_msg(__VA_ARGS__)
#endif
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 ID_SHIFT 5
#define PREC(op) ((op) & 0x1f)
#define PREC_LPAREN 0
#define TOK_LPAREN tok_decl(0,0)
/* Precedence value of RPAREN is used only to distinguish it from LPAREN */
#define TOK_RPAREN tok_decl(1,1)
#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 PREC_ASSIGN1 2
#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_ADD_ASSIGN tok_decl(2,4)
#define TOK_SUB_ASSIGN tok_decl(2,5)
#define TOK_LSHIFT_ASSIGN tok_decl(2,6)
#define TOK_RSHIFT_ASSIGN tok_decl(2,7)
#define PREC_ASSIGN2 3
#define TOK_MUL_ASSIGN tok_decl(3,0)
/* "/" and "/=" ops have the same id bits */
#define DIV_ID1 1
#define TOK_DIV_ASSIGN tok_decl(3,DIV_ID1)
#define TOK_REM_ASSIGN tok_decl(3,2)
#define fix_assignment_prec(prec) do { prec -= (prec == 3); } while (0)
/* Ternary conditional operator is right associative too */
/*
* bash documentation says that precedence order is:
* ...
* expr ? expr1 : expr2
* = *= /= %= += -= <<= >>= &= ^= |=
* exprA , exprB
* What it omits is that expr1 is parsed as if parenthesized
* (this matches the rules of ?: in C language):
* "v ? 1,2 : 3,4" is parsed as "(v ? (1,2) : 3),4"
* "v ? a=2 : b=4" is parsed as "(v ? (a=1) : b)=4" (thus, this is a syntax error)
*/
#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,DIV_ID1)
#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)
/* TOK_VALUE marks a number, name, name++/name--, or (EXPR):
* IOW: something which can be used as the left side of a binary op.
* Since it's never pushed to opstack, its precedence does not matter.
*/
#define TOK_VALUE tok_decl(PREC_POST,2)
static int
is_assign_op(operator op)
{
operator prec = PREC(op);
return prec == PREC_ASSIGN1
|| prec == PREC_ASSIGN2
|| 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;
const char *var_name;
} var_or_num_t;
#define VALID_NAME(name) (name)
#define NOT_NAME(name) (!(name))
typedef struct remembered_name {
struct remembered_name *next;
const char *var_name;
} remembered_name;
static ALWAYS_INLINE int isalnum_(int c)
{
return (isalnum(c) || c == '_');
}
static arith_t
evaluate_string(arith_state_t *math_state, const char *expr);
static arith_t
arith_lookup_val(arith_state_t *math_state, const char *name, char *endname)
{
char c;
const char *p;
c = *endname;
*endname = '\0';
p = math_state->lookupvar(name);
*endname = c;
if (p) {
arith_t val;
size_t len = endname - name;
remembered_name *cur;
remembered_name remember;
/* 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 (strncmp(cur->var_name, name, len) == 0
&& !isalnum_(cur->var_name[len])
) {
/* yes */
math_state->errmsg = "expression recursion loop detected";
return -1;
}
}
/* push current var name */
remember.var_name = name;
remember.next = math_state->list_of_recursed_names;
math_state->list_of_recursed_names = &remember;
/* recursively evaluate p as expression */
/* this sets math_state->errmsg on error */
val = evaluate_string(math_state, p);
/* pop current var name */
math_state->list_of_recursed_names = remember.next;
return val;
}
/* treat undefined var as 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,
* a binary operator will pop two arguments and push the result,
* the ternary ?: op will pop three 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 NUMSTACKPTR (*numstackptr)
var_or_num_t *top_of_stack;
arith_t rez;
/* There is no operator that can work without arguments */
if (NUMSTACKPTR == numstack)
goto syntax_err;
top_of_stack = NUMSTACKPTR - 1;
if (op == TOK_CONDITIONAL_SEP) {
/* "expr1 ? expr2 : expr3" operation */
var_or_num_t *expr1 = &top_of_stack[-2];
NUMSTACKPTR = expr1 + 1;
if (expr1 < numstack) /* Example: $((2:3)) */
return "malformed ?: operator";
if (expr1->val != 0) /* select expr2 or expr3 */
top_of_stack--;
rez = top_of_stack->val;
top_of_stack = expr1;
goto ret_rez;
}
if (op == TOK_CONDITIONAL) /* Example: $((a ? b)) */
return "malformed ?: operator";
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) - always true, we drop TOK_UPLUS earlier */ {
/* Binary operators */
arith_t right_side_val;
if (top_of_stack == numstack) /* have two arguments? */
goto syntax_err; /* no */
/* Pop numstack */
NUMSTACKPTR = top_of_stack; /* this decrements NUMSTACKPTR */
if (math_state->evaluation_disabled) {
dbg("binary op %02x skipped", op);
return NULL;
/* bash 5.2.12 does not execute "2/0" in disabled
* branches of ?: (and thus does not complain),
* but complains about negative exp: "2**-1".
* I don't think we need to emulate that.
*/
}
top_of_stack--; /* now points to left side */
right_side_val = rez;
rez = top_of_stack->val;
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_ADD_ASSIGN)
rez += right_side_val;
else if (op == TOK_SUB || op == TOK_SUB_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) {
if ((right_side_val & 1) == 0) {
/* this if() block is not necessary for correctness,
* but otherwise echo $((3**999999999999999999))
* takes a VERY LONG time
* (and it's not interruptible by ^C)
*/
rez *= rez;
right_side_val >>= 1;
}
c *= rez;
right_side_val--;
}
rez = c;
}
else /*if (op == TOK_DIV || op == TOK_DIV_ASSIGN
|| op == TOK_REM || op == TOK_REM_ASSIGN) - always true */
{
if (right_side_val == 0)
return "divide by zero";
/*
* 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 & (DIV_ID1 << ID_SHIFT)) /* DIV or DIV_ASSIGN? */
rez /= right_side_val;
else
rez %= right_side_val;
}
}
if (math_state->evaluation_disabled) {
dbg("unary op %02x skipped", op);
return NULL;
}
if (is_assign_op(op)) {
char buf[sizeof(arith_t)*3 + 2];
if (NOT_NAME(top_of_stack->var_name)) {
/* Hmm, 1=2 ? */
goto syntax_err;
}
/* Save to shell variable */
sprintf(buf, ARITH_FMT, rez);
{
char *e = (char*)endofname(top_of_stack->var_name);
char c = *e;
*e = '\0';
math_state->setvar(top_of_stack->var_name, buf);
*e = c;
}
/* VAR++ or VAR--? */
if (PREC(op) == PREC_POST) {
/* Do not store new value to stack (keep old value) */
goto ret_NULL;
}
}
ret_rez:
top_of_stack->val = rez;
ret_NULL:
/* Erase var name, it is just a number now */
top_of_stack->var_name = NULL;
return NULL;
syntax_err:
return "arithmetic syntax error";
#undef NUMSTACKPTR
}
/* 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_ADD_ASSIGN,
'-','=', 0, TOK_SUB_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,
'~', 0, TOK_BNOT,
',', 0, TOK_COMMA,
'?', 0, TOK_CONDITIONAL,
':', 0, TOK_CONDITIONAL_SEP,
')', 0, TOK_RPAREN,
'(', 0, TOK_LPAREN,
0
};
#define END_POINTER (&op_tokens[sizeof(op_tokens)-1])
#if ENABLE_FEATURE_SH_MATH_BASE
static arith_t parse_with_base(const char *nptr, char **endptr, unsigned base)
{
arith_t n = 0;
const char *start = nptr;
for (;;) {
unsigned digit = (unsigned)*nptr - '0';
if (digit >= 10 /* not 0..9 */
&& digit <= 'z' - '0' /* reject e.g. $((64#~)) */
) {
/* current char is one of :;<=>?@A..Z[\]^_`a..z */
/* in bases up to 36, case does not matter for a-z,
* map @A..Z and `a..z to 9..35: */
digit = (unsigned)(*nptr | 0x20) - ('a' - 10);
if (base > 36 && *nptr <= '_') {
/* base > 36: A-Z,@,_ are 36-61,62,63 */
if (*nptr == '_')
digit = 63;
else if (*nptr == '@')
digit = 62;
else if (digit < 36) /* A-Z */
digit += 36 - 10;
else
break; /* error: one of [\]^ */
}
//bb_error_msg("ch:'%c'%d digit:%u", *nptr, *nptr, digit);
if (digit < 10) /* reject e.g. $((36#@)) */
break;
}
if (digit >= base)
break;
/* bash does not check for overflows */
n = n * base + digit;
nptr++;
}
*endptr = (char*)nptr;
/* "64#" and "64#+1" used to be valid expressions, but bash 5.2.15
* no longer allow such, detect this:
*/
// NB: bash allows $((0x)), this is probably a bug...
if (nptr == start)
*endptr = NULL; /* there weren't any digits, bad */
return n;
}
static arith_t strto_arith_t(const char *nptr, char **endptr)
{
/* NB: we do not use strtoull here to be bash-compatible:
* $((99999999999999999999)) is 7766279631452241919
* (the 64-bit truncated value).
*/
unsigned base;
/* nptr[0] is '0'..'9' here */
base = nptr[0] - '0';
if (base == 0) { /* nptr[0] is '0' */
base = 8;
if ((nptr[1] | 0x20) == 'x') {
base = 16;
nptr += 2;
}
// NB: bash allows $((0x)), this is probably a bug...
return parse_with_base(nptr, endptr, base);
}
/* base is 1..9 here */
if (nptr[1] == '#') {
if (base > 1)
return parse_with_base(nptr + 2, endptr, base);
/* else: "1#NN", bash says "invalid arithmetic base" */
}
if (isdigit(nptr[1]) && nptr[2] == '#') {
base = 10 * base + (nptr[1] - '0');
/* base is at least 10 here */
if (base <= 64)
return parse_with_base(nptr + 3, endptr, base);
/* else: bash says "invalid arithmetic base" */
}
return parse_with_base(nptr, endptr, 10);
}
#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
evaluate_string(arith_state_t *math_state, const char *expr)
{
/* Stack of integers/names */
var_or_num_t *numstack, *numstackptr;
/* Stack of operator tokens */
operator *opstack, *opstackptr;
/* To detect whether we are after a "value": */
operator lasttok;
/* To insert implicit () in ?: ternary op: */
operator insert_op = 0xff;
unsigned ternary_level = 0;
const char *errmsg;
const char *start_expr = expr = skip_whitespace(expr);
{
unsigned expr_len = strlen(expr);
/* If LOTS of whitespace, do not blow up the estimation */
const char *p = expr;
while (*p) {
/* in a run of whitespace, count only 1st char */
if (isspace(*p)) {
while (p++, isspace(*p))
expr_len--;
} else {
p++;
}
}
dbg("expr:'%s' expr_len:%u", expr, expr_len);
/* expr_len deep opstack is needed. Think "------------7".
* Only "?" operator temporarily needs two opstack slots
* (IOW: more than one slot), but its second slot (LPAREN)
* is popped off when ":" is reached.
*/
expr_len++; /* +1 for 1st LPAREN. See what $((1?)) pushes to opstack */
opstackptr = opstack = alloca(expr_len * sizeof(opstack[0]));
/* There can be no more than (expr_len/2 + 1)
* integers/names in any given correct or incorrect expression.
* (modulo "09", "0v" cases where 2 chars are 2 ints/names,
* but we have code to detect that early)
*/
expr_len = (expr_len / 2)
+ 1 /* "1+2" has two nums, 2 = len/2+1, NOT len/2 */;
numstackptr = numstack = alloca(expr_len * sizeof(numstack[0]));
}
/* Start with a left paren */
dbg("(%d) op:TOK_LPAREN", (int)(opstackptr - opstack));
*opstackptr++ = lasttok = TOK_LPAREN;
while (1) {
const char *p;
operator op;
operator prec;
expr = skip_whitespace(expr);
if (*expr == '\0') {
if (expr == start_expr) {
/* Null expression */
return 0;
}
/* 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 != END_POINTER) {
/* If we haven't done so already,
* append a closing right paren
* and let the loop process it */
expr = END_POINTER;
op = TOK_RPAREN;
goto tok_found1;
}
/* At this point, we're done with the expression */
if (numstackptr != numstack + 1) {
/* if there is not exactly one result, it's bad */
/* Example: $((1 2)) */
goto syntax_err;
}
return numstack->val;
}
p = endofname(expr);
if (p != expr) {
/* Name */
if (!math_state->evaluation_disabled) {
numstackptr->var_name = expr;
dbg("[%d] var:'%.*s'", (int)(numstackptr - numstack), (int)(p - expr), expr);
expr = skip_whitespace(p);
/* If it is not followed by "=" operator... */
if (expr[0] != '=' /* not "=..." */
|| expr[1] == '=' /* or "==..." */
) {
/* Evaluate variable to value */
arith_t val = arith_lookup_val(math_state, numstackptr->var_name, (char*)p);
if (math_state->errmsg)
return val; /* -1 */
numstackptr->val = val;
}
} else {
dbg("[%d] var:IGNORED", (int)(numstackptr - numstack));
expr = p;
numstackptr->var_name = NULL; /* not needed, paranoia */
numstackptr->val = 0; /* not needed, paranoia */
}
push_value:
numstackptr++;
lasttok = TOK_VALUE;
continue;
}
if (isdigit(*expr)) {
/* Number */
char *end;
numstackptr->var_name = NULL;
/* code is smaller compared to using &expr here: */
numstackptr->val = strto_arith_t(expr, &end);
expr = end;
dbg("[%d] val:%lld", (int)(numstackptr - numstack), numstackptr->val);
if (!expr) /* example: $((10#)) */
goto syntax_err;
/* A number can't be followed by another number, or a variable name.
* We'd catch this later anyway, but this would require numstack[]
* to be ~twice as deep to handle strings where _every_ char is
* a new number or name.
* Examples: "09" is two numbers, "0v" is number and name.
*/
if (isalnum(*expr) || *expr == '_')
goto syntax_err;
goto push_value;
}
/* Should be an operator */
/* Special case: XYZ--, XYZ++, --XYZ, ++XYZ are recognized
* only if XYZ is a variable name, not a number or EXPR. IOW:
* "a+++v" is a++ + v.
* "(a)+++7" is ( a ) + + + 7.
* "7+++v" is 7 + ++v, not 7++ + v.
* "--7" is - - 7, not --7.
* "++++a" is + + ++a, not ++ ++a.
*/
if ((expr[0] == '+' || expr[0] == '-')
&& (expr[1] == expr[0])
) {
if (numstackptr == numstack || NOT_NAME(numstackptr[-1].var_name)) {
/* not a VAR++ */
char next = skip_whitespace(expr + 2)[0];
if (!(isalpha(next) || next == '_')) {
/* not a ++VAR */
op = (expr[0] == '+' ? TOK_ADD : TOK_SUB);
expr++;
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 syntax_err;
}
}
/* NB: expr now points past the operator */
tok_found:
op = p[1]; /* fetch TOK_foo value */
/* Special rule for "? EXPR :"
* "EXPR in the middle of ? : is parsed as if parenthesized"
* (this quirk originates in C grammar, I think).
*/
if (op == TOK_CONDITIONAL) {
insert_op = TOK_LPAREN;
dbg("insert_op=%02x", insert_op);
}
if (op == TOK_CONDITIONAL_SEP) {
insert_op = op;
op = TOK_RPAREN;
dbg("insert_op=%02x op=%02x", insert_op, op);
}
tok_found1:
/* NAME++ is a "value" (something suitable for a binop) */
if (PREC(lasttok) == PREC_POST)
lasttok = TOK_VALUE;
/* Plus and minus are binary (not unary) _only_ if the last
* token was a "value". Think about it. It makes sense.
*/
if (lasttok != TOK_VALUE) {
switch (op) {
case TOK_ADD:
//op = TOK_UPLUS;
//break;
/* Unary plus does nothing, do not even push it to opstack */
continue;
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 will never be "applied" in this way.
*/
prec = PREC(op);
if (prec != PREC_LPAREN && prec < UNARYPREC) {
/* Binary, ternary or RPAREN */
if (lasttok != TOK_VALUE) {
/* Must be preceded by a value.
* $((2 2 + * 3)) would be accepted without this.
*/
goto syntax_err;
}
/* if op is RPAREN:
* while opstack is not empty:
* pop prev_op
* if prev_op is LPAREN (finished evaluating (EXPR)):
* goto N
* evaluate prev_op on top of numstack
* BUG (unpaired RPAREN)
* else (op is not RPAREN):
* while opstack is not empty:
* pop prev_op
* if can't evaluate prev_op (it is lower precedence than op):
* push prev_op back
* goto C
* evaluate prev_op on top of numstack
* C:if op is "?": check result, set disable flag if needed
* push op
* N:loop to parse the rest of string
*/
while (opstackptr != opstack) {
operator prev_op = *--opstackptr;
if (op == TOK_RPAREN) {
if (prev_op == TOK_LPAREN) {
/* Erase var name: for example, (VAR) = 1 is not valid */
numstackptr[-1].var_name = NULL;
/* (EXPR) is a "value": next operator directly after
* close paren should be considered binary
*/
lasttok = TOK_VALUE;
goto next;
}
/* Not (y), but ...x~y). Fall through to evaluate x~y */
} 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))
) {
/* ...x~y@. push @ on opstack */
opstackptr++; /* undo removal of ~ op */
goto check_cond;
}
/* else: ...x~y@. Evaluate x~y, replace it on stack with result. Then repeat */
}
dbg("arith_apply(prev_op:%02x, numstack:%d)", prev_op, (int)(numstackptr - numstack));
errmsg = arith_apply(math_state, prev_op, numstack, &numstackptr);
if (errmsg)
goto err_with_custom_msg;
dbg(" numstack:%d val:%lld '%s'", (int)(numstackptr - numstack), numstackptr[-1].val, numstackptr[-1].var_name);
if (prev_op == TOK_CONDITIONAL_SEP) {
/* We just executed ":" */
/* Remove "?" from opstack too, not just ":" */
opstackptr--;
if (*opstackptr != TOK_CONDITIONAL) {
/* Example: $((1,2:3)) */
errmsg = "malformed ?: operator";
goto err_with_custom_msg;
}
/* Example: a=1?2:3,a. We just executed ":".
* Prevent assignment from being still disabled.
*/
if (ternary_level == math_state->evaluation_disabled) {
math_state->evaluation_disabled = 0;
dbg("':' executed: evaluation_disabled=CLEAR");
}
ternary_level--;
}
} /* while (opstack not empty) */
if (op == TOK_RPAREN) /* unpaired RPAREN? */
goto syntax_err;
check_cond:
if (op == TOK_CONDITIONAL) {
/* We just now evaluated EXPR before "?".
* Should we disable evaluation now?
*/
ternary_level++;
if (numstackptr[-1].val == 0 && !math_state->evaluation_disabled) {
math_state->evaluation_disabled = ternary_level;
dbg("'?' entered: evaluation_disabled=%u", math_state->evaluation_disabled);
}
}
} /* if */
/* else: LPAREN or UNARY: push it on opstack */
/* Push this operator to opstack */
dbg("(%d) op:%02x insert_op:%02x", (int)(opstackptr - opstack), op, insert_op);
*opstackptr++ = lasttok = op;
next:
if (insert_op != 0xff) {
op = insert_op;
insert_op = 0xff;
dbg("inserting %02x", op);
if (op == TOK_CONDITIONAL_SEP) {
/* The next token is ":". Toggle "do not evaluate" state */
if (!math_state->evaluation_disabled) {
math_state->evaluation_disabled = ternary_level;
dbg("':' entered: evaluation_disabled=%u", math_state->evaluation_disabled);
} else if (ternary_level == math_state->evaluation_disabled) {
math_state->evaluation_disabled = 0;
dbg("':' entered: evaluation_disabled=CLEAR");
} /* else: ternary_level > evaluation_disabled && evaluation_disabled != 0 */
/* We are in nested "?:" while in outer "?:" disabled branch */
/* do_nothing */
}
goto tok_found1;
}
} /* while (1) */
syntax_err:
errmsg = "arithmetic syntax error";
err_with_custom_msg:
math_state->errmsg = errmsg;
return -1;
}
arith_t FAST_FUNC
arith(arith_state_t *math_state, const char *expr)
{
math_state->evaluation_disabled = 0;
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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