/* * 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 * was re-ported from NetBSD and debianized. * * rewrite arith.y to micro stack based cryptic algorithm by * Copyright (c) 2001 Aaron Lehmann * * Modified by Paul Mundt (c) 2004 to support * dynamic variables. * * Modified by Vladimir Oleynik (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 * * 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 * * - 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 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 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 */ /* * 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(14,1) #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) 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; 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 arith_t 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 (VALID_NAME(t->var_name)) { const char *p = math_state->lookupvar(t->var_name); if (p) { 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 (strcmp(cur->var_name, t->var_name) == 0) { /* yes */ return "expression recursion loop detected"; } } /* push current var name */ remember.var_name = t->var_name; remember.next = math_state->list_of_recursed_names; math_state->list_of_recursed_names = &remember; /* recursively evaluate p as expression */ t->val = evaluate_string(math_state, p); /* pop current var name */ math_state->list_of_recursed_names = remember.next; return math_state->errmsg; } /* treat undefined var as 0 */ t->val = 0; } return NULL; } /* "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 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--; expr1->val = top_of_stack->val; expr1->var_name = NULL; return NULL; } 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 */ top_of_stack--; /* now points to left side */ if (math_state->evaluation_disabled) { dbg("binary op %02x skipped", op); goto ret_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. */ } 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_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 (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 == TOK_DIV || op == TOK_DIV_ASSIGN) rez /= right_side_val; else rez %= right_side_val; } } if (math_state->evaluation_disabled) { dbg("unary op %02x skipped", op); goto ret_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); math_state->setvar(top_of_stack->var_name, buf); /* After saving, make previous value for v++ or v-- */ if (op == TOK_POST_INC) rez--; if (op == TOK_POST_DEC) 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_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, '~', 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 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; for (;;) { unsigned digit = (unsigned)*nptr - '0'; if (digit >= 10 /* not 0..9 */ && digit <= 'z' - '0' /* needed to reject 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 = 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) - example where we need this? // break; } if (digit >= base) break; /* bash does not check for overflows */ n = n * base + digit; nptr++; } /* Note: we do not set errno on bad chars, we just set a pointer * to the first invalid char. For example, this allows * "N#" (empty "nnnn" part): 64#+1 is a valid expression, * it means 64# + 1, whereas 64#~... is not, since ~ is not a valid * operator. */ *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 //TODO: much better estimation than expr_len/2? Such as: //static unsigned estimate_nums_and_names(const char *expr) //{ // unsigned count = 0; // while (*(expr = skip_whitespace(expr)) != '\0') { // const char *p; // if (isdigit(*expr)) { // while (isdigit(*++expr)) // continue; // count++; // continue; // } // p = endofname(expr); // if (p != expr) { // expr = p; // count++; // continue; // } // } // return count; //} static arith_t evaluate_string(arith_state_t *math_state, const char *expr) { operator lasttok; const char *errmsg = NULL; const char *start_expr = expr = skip_whitespace(expr); unsigned expr_len = strlen(expr) + 2; /* Stack of integers/names */ /* There can be no more than strlen(startbuf)/2+1 * integers/names in any given correct or incorrect expression. * (modulo "09v09v09v09v09v" case, * but we have code to detect that early) */ 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 opstack = alloca(expr_len * sizeof(opstack[0])); operator *opstackptr = opstack; operator insert_op = 0xff; unsigned ternary_level = 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 */ goto syntax_err; } return numstack->val; } p = endofname(expr); if (p != expr) { /* Name */ if (!math_state->evaluation_disabled) { size_t var_name_size = (p - expr) + 1; /* +1 for NUL */ numstackptr->var_name = alloca(var_name_size); safe_strncpy(numstackptr->var_name, expr, var_name_size); dbg("[%d] var:'%s'", (int)(numstackptr - numstack), numstackptr->var_name); expr = skip_whitespace(p); /* If it is not followed by "=" operator... */ if (expr[0] != '=' /* not "=..." */ || expr[1] == '=' /* or "==..." */ ) { /* Evaluate variable to value */ errmsg = arith_lookup_val(math_state, numstackptr); if (errmsg) goto err_with_custom_msg; } } else { dbg("[%d] var:IGNORED", (int)(numstackptr - numstack)); numstackptr->var_name = NULL; numstackptr->val = 0; //paranoia, probably not needed expr = p; } push_num: numstackptr++; lasttok = TOK_NUM; continue; } if (isdigit(*expr)) { /* Number */ numstackptr->var_name = NULL; errno = 0; numstackptr->val = strto_arith_t(expr, (char**) &expr); dbg("[%d] val:%lld", (int)(numstackptr - numstack), numstackptr->val); /* 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. Example: 09v09v09v09v09v09v09v09v09v */ if (isalnum(*expr) || *expr == '_') goto syntax_err; if (errno) numstackptr->val = 0; /* bash compat */ goto push_num; } /* 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: /* 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; /* 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_NUM) { /* must be preceded by a num */ 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: (var) is just a number, for example, (var) = 1 is not valid */ numstackptr[-1].var_name = NULL; /* Any operator directly after a * close paren should consider itself binary */ lasttok = TOK_NUM; 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. */