* listed in #defines below. Parens, order of operations, and error handling
* are supported. This code is threadsafe. 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 explaination 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). */
-
+
/* To use the routine, call it with an expression string and error return
* pointer */
#define TOK_REM tok_decl(10,2)
/* For now all unary operators have the same precedence, and that's used to
- * identify them as unary operators */
+ * identify them as unary operators
+ */
#define UNARYPREC 14
#define TOK_BNOT tok_decl(UNARYPREC,0)
#define TOK_NOT tok_decl(UNARYPREC,1)
#define TOK_NUM tok_decl(15,0)
#define TOK_RPAREN tok_decl(15,1)
-#define TOK_ERROR tok_decl(15,2) /* just a place-holder really */
+#define TOK_ERROR tok_decl(15,2) /* just a place-holder really */
#define ARITH_APPLY(op) arith_apply(op, numstack, &numstackptr)
#define NUMPTR (*numstackptr)
/* "applying" a token means performing it on the top elements on the integer
* stack. For a unary operator it will only change the top element, but a
- * binary operator will pop two arguments and push a result */
-static short arith_apply(operator op, long *numstack, long **numstackptr)
+ * binary operator will pop two arguments and push a result
+ */
+static short arith_apply(operator op, long *numstack, long **numstackptr)
{
long numptr_val;
long *NUMPTR_M1;
- if (NUMPTR == numstack) goto err; /* There is no operator that can work
- without arguments */
+ /* There is no operator that can work without arguments */
+ if (NUMPTR == numstack) {
+ goto err;
+ }
+
NUMPTR_M1 = NUMPTR - 1;
- if (op == TOK_UMINUS)
+ if (op == TOK_UMINUS) {
*NUMPTR_M1 *= -1;
- else if (op == TOK_NOT)
+ } else if (op == TOK_NOT) {
*NUMPTR_M1 = !(*NUMPTR_M1);
- else if (op == TOK_BNOT)
+ } else if (op == TOK_BNOT) {
*NUMPTR_M1 = ~(*NUMPTR_M1);
- else if (op != TOK_UPLUS) {
- /* Binary operators */
- if (NUMPTR_M1 == numstack) goto err; /* ... and binary operators need two
- arguments */
- numptr_val = *--NUMPTR; /* ... and they pop one */
- NUMPTR_M1 = NUMPTR - 1;
- if (op == TOK_BOR)
- *NUMPTR_M1 |= numptr_val;
- else if (op == TOK_OR)
- *NUMPTR_M1 = numptr_val || *NUMPTR_M1;
- else if (op == TOK_BAND)
- *NUMPTR_M1 &= numptr_val;
- else if (op == TOK_AND)
- *NUMPTR_M1 = *NUMPTR_M1 && numptr_val;
- else if (op == TOK_EQ)
- *NUMPTR_M1 = (*NUMPTR_M1 == numptr_val);
- else if (op == TOK_NE)
- *NUMPTR_M1 = (*NUMPTR_M1 != numptr_val);
- else if (op == TOK_GE)
- *NUMPTR_M1 = (*NUMPTR_M1 >= numptr_val);
- else if (op == TOK_RSHIFT)
- *NUMPTR_M1 >>= numptr_val;
- else if (op == TOK_LSHIFT)
- *NUMPTR_M1 <<= numptr_val;
- else if (op == TOK_GT)
- *NUMPTR_M1 = (*NUMPTR_M1 > numptr_val);
- else if (op == TOK_LT)
- *NUMPTR_M1 = (*NUMPTR_M1 < numptr_val);
- else if (op == TOK_LE)
- *NUMPTR_M1 = (*NUMPTR_M1 <= numptr_val);
- else if (op == TOK_MUL)
- *NUMPTR_M1 *= numptr_val;
- else if (op == TOK_ADD)
- *NUMPTR_M1 += numptr_val;
- else if (op == TOK_SUB)
- *NUMPTR_M1 -= numptr_val;
- else if(numptr_val==0) /* zero divisor check */
- return -2;
- else if (op == TOK_DIV)
- *NUMPTR_M1 /= numptr_val;
- else if (op == TOK_REM)
- *NUMPTR_M1 %= numptr_val;
- /* WARNING!!! WARNING!!! WARNING!!! */
- /* Any new operators should be added BEFORE the zero divisor check! */
+ } else if (op != TOK_UPLUS) {
+ /* Binary operators */
+
+ /* ... and binary operators need two arguments */
+ if (NUMPTR_M1 == numstack) {
+ goto err;
+ }
+ /* ... and they pop one */
+ numptr_val = *--NUMPTR;
+
+ NUMPTR_M1 = NUMPTR - 1;
+
+ if (op == TOK_BOR) {
+ *NUMPTR_M1 |= numptr_val;
+ } else if (op == TOK_OR) {
+ *NUMPTR_M1 = numptr_val || *NUMPTR_M1;
+ } else if (op == TOK_BAND) {
+ *NUMPTR_M1 &= numptr_val;
+ } else if (op == TOK_AND) {
+ *NUMPTR_M1 = *NUMPTR_M1 && numptr_val;
+ } else if (op == TOK_EQ) {
+ *NUMPTR_M1 = (*NUMPTR_M1 == numptr_val);
+ } else if (op == TOK_NE) {
+ *NUMPTR_M1 = (*NUMPTR_M1 != numptr_val);
+ } else if (op == TOK_GE) {
+ *NUMPTR_M1 = (*NUMPTR_M1 >= numptr_val);
+ } else if (op == TOK_RSHIFT) {
+ *NUMPTR_M1 >>= numptr_val;
+ } else if (op == TOK_LSHIFT) {
+ *NUMPTR_M1 <<= numptr_val;
+ } else if (op == TOK_GT) {
+ *NUMPTR_M1 = (*NUMPTR_M1 > numptr_val);
+ } else if (op == TOK_LT) {
+ *NUMPTR_M1 = (*NUMPTR_M1 < numptr_val);
+ } else if (op == TOK_LE) {
+ *NUMPTR_M1 = (*NUMPTR_M1 <= numptr_val);
+ } else if (op == TOK_MUL) {
+ *NUMPTR_M1 *= numptr_val;
+ } else if (op == TOK_ADD) {
+ *NUMPTR_M1 += numptr_val;
+ } else if (op == TOK_SUB) {
+ *NUMPTR_M1 -= numptr_val;
+ }
+ /* zero divisor check */
+ else if (numptr_val == 0) {
+ return -2;
+ } else if (op == TOK_DIV) {
+ *NUMPTR_M1 /= numptr_val;
+ } else if (op == TOK_REM) {
+ *NUMPTR_M1 %= numptr_val;
+ }
+ /* WARNING!!! WARNING!!! WARNING!!! */
+ /* Any new operators should be added BEFORE the zero divisor check! */
}
return 0;
-err: return(-1);
+ err:
+ return (-1);
}
static const char endexpression[] = ")";
static const char op_token[] = {
/* paired with equal */
TOK_NE, TOK_LE, TOK_GE,
- /* paired with self -- note: ! is special-cased below*/
+ /* paired with self -- note: ! is special-cased below */
TOK_ERROR, TOK_LSHIFT, TOK_RSHIFT, TOK_EQ, TOK_OR, TOK_AND,
/* singles */
TOK_NOT, TOK_LT, TOK_GT, TOK_ERROR, TOK_BOR, TOK_BAND,
#define NUM_PAIR_EQUAL 3
#define NUM_PAIR_SAME 6
-extern long arith (const char *expr, int *errcode)
+extern long arith(const char *expr, int *errcode)
{
- register char arithval; /* Current character under analysis */
- operator lasttok, op;
+ register char arithval; /* Current character under analysis */
+ operator lasttok, op;
unsigned char prec;
-
const char *p = endexpression;
-
size_t datasizes = strlen(expr);
/* 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 excersize to
* the reader. */
- long *numstack = alloca((datasizes/2)*sizeof(long)),
- *numstackptr = numstack;
+ long *numstack = alloca(((datasizes + 1) / 2) * sizeof(long));
+ long *numstackptr = numstack;
+
/* Stack of operator tokens */
- operator *stack = alloca((datasizes+1) * sizeof(operator)),
- *stackptr = stack;
+ operator * stack = alloca((datasizes + 1) * sizeof(operator));
+ operator * stackptr = stack;
- *stackptr++ = lasttok = TOK_LPAREN; /* start off with a left paren */
+ /* start off with a left paren */
+ *stackptr++ = lasttok = TOK_LPAREN;
- loop:
+ loop:
if ((arithval = *expr) == 0) {
- if (p == endexpression) { /* Null expression. */
+ /* Null expression. */
+ if (p == endexpression) {
return (*errcode = 0);
}
* are to be applied in order. At the end, there should be a final
* result on the integer stack */
- if (expr != endexpression + 1) { /* If we haven't done so already, */
+ if (expr != endexpression + 1) { /* If we haven't done so already, */
expr = endexpression; /* append a closing right paren */
- goto loop; /* and let the loop process it. */
+ goto loop; /* and let the loop process it. */
}
/* At this point, we're done with the expression. */
- if (numstackptr != numstack+1) {/* ... but if there isn't, it's bad */
- err:
+ if (numstackptr != numstack + 1) { /* ... but if there isn't, it's bad */
+ err:
return (*errcode = -1);
/* NOTREACHED */
}
return *numstack;
} else {
/* Continue processing the expression. */
+ /* Skip whitespace */
if (isspace(arithval)) {
- goto prologue; /* Skip whitespace */
+ goto prologue;
}
- if ((unsigned)arithval-'0' <= 9) /* isdigit */ {
+ /* isdigit ? */
+ if ((unsigned) arithval - '0' <= 9) {
*numstackptr++ = strtol(expr, (char **) &expr, 10);
lasttok = TOK_NUM;
goto loop;
goto err;
}
#else
- for ( p=op_char ; *p != arithval ; p++ ) {
+ for (p = op_char; *p != arithval; p++) {
if (!*p) {
goto err;
}
}
#endif
- p = op_token + (int)(p - op_char);
+ p = op_token + (int) (p - op_char);
++expr;
if ((p >= op_token + NUM_PAIR_EQUAL) || (*expr != '=')) {
p += NUM_PAIR_EQUAL;
if ((p >= op_token + NUM_PAIR_SAME + NUM_PAIR_EQUAL)
|| (*expr != arithval) || (arithval == '!')) {
--expr;
- if (arithval == '=') { /* single = */
+ /* single = */
+ if (arithval == '=') {
goto err;
}
p += NUM_PAIR_SAME;
* a number, since it evaluates to one). Think about it.
* It makes sense. */
if ((lasttok != TOK_NUM)
- && (p >= op_token + NUM_PAIR_SAME + NUM_PAIR_EQUAL
- + sizeof(op_char) - 2)) {
- p += 2; /* Unary plus or minus */
+ && (p >=
+ (op_token + NUM_PAIR_SAME + NUM_PAIR_EQUAL +
+ sizeof(op_char) - 2))) {
+ /* Unary plus or minus */
+ p += 2;
}
}
}
/* Left paren is given the lowest priority so it will never be
* "applied" in this way */
prec = PREC(op);
- if ((prec > 0) && (prec != UNARYPREC)) { /* not left paren or unary */
- if (lasttok != TOK_NUM) { /* binary op must be preceded by a num */
+
+ /* not left paren or unary */
+ if ((prec > 0) && (prec != UNARYPREC)) {
+ /* binary op must be preceded by a num */
+ if (lasttok != TOK_NUM) {
goto err;
}
while (stackptr != stack) {
* tokens and apply them */
if (stackptr[-1] == TOK_LPAREN) {
--stackptr;
- lasttok = TOK_NUM; /* Any operator directly after a */
- /* close paren should consider itself binary */
+
+ /* Any operator directly after a */
+ lasttok = TOK_NUM;
+
+ /* close paren should consider itself binary */
goto prologue;
}
} else if (PREC(stackptr[-1]) < prec) {
break;
}
*errcode = ARITH_APPLY(*--stackptr);
- if(*errcode) return *errcode;
+ if (*errcode) {
+ return *errcode;
+ }
}
if (op == TOK_RPAREN) {
goto err;
/* Push this operator to the stack and remember it. */
*stackptr++ = lasttok = op;
- prologue:
+ prologue:
++expr;
goto loop;
}
projects / oweals / busybox.git / commitdiff