mirror of
https://github.com/sheumann/hush.git
synced 2024-12-22 14:30:31 +00:00
Commit my changes to arith.c which fixed a couple of bugs and decreased
code size. Please read the TODO comments regarding accessing shell variables from the arith() funciton.
This commit is contained in:
Manuel Novoa III
parent
f6ecaccf92
commit
6a9d1f652b
398
libbb/arith.c
398
libbb/arith.c
@ -24,19 +24,88 @@
|
||||
* as a replacement for yacc-based parsers. However, it may well be faster
|
||||
* than a comparable parser writen in yacc. The supported operators are
|
||||
* listed in #defines below. Parens, order of operations, and error handling
|
||||
* are supported. This code is threadsafe. */
|
||||
* 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 */
|
||||
|
||||
/* To use the routine, call it with an expression string. It returns an
|
||||
* integer result. You will also need to define an "error" function
|
||||
* that takes printf arguments and _does not return_, or modify the code
|
||||
* to use another error mechanism. */
|
||||
/*
|
||||
* 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 desireable 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 vodz.
|
||||
*
|
||||
* Merge in Aaron's comments previously posted to the busybox list,
|
||||
* modified slightly to take account of my changes to the code.
|
||||
*
|
||||
* TODO: May want to allow access to variables in the arith code.
|
||||
* This would:
|
||||
* 1) allow us to evaluate $A as 0 if A isn't set (although this
|
||||
* would require changes to ash.c too).
|
||||
* 2) allow us to write expressions as $(( A + 2 )).
|
||||
* This could be done using a callback function passed to the
|
||||
* arith() function of by requiring such a function with fixed
|
||||
* name as an extern.
|
||||
*/
|
||||
|
||||
#include <stdlib.h>
|
||||
#include <string.h>
|
||||
#include <ctype.h>
|
||||
#include "libbb.h"
|
||||
|
||||
/*
|
||||
* Use "#if 1" below for Aaron's original test for whitespace.
|
||||
* Use "#if 0" for ctype's isspace().
|
||||
* */
|
||||
#if 1
|
||||
#undef isspace
|
||||
#define isspace(arithval) \
|
||||
(arithval == ' ' || arithval == '\n' || arithval == '\t')
|
||||
#endif
|
||||
|
||||
typedef char operator;
|
||||
|
||||
/* An operator's token id is a bit of a bitfield. The lower 5 bits are the
|
||||
* precedence, and high 3 are an ID unique accross 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)
|
||||
|
||||
@ -70,194 +139,235 @@ typedef char operator;
|
||||
#define TOK_DIV tok_decl(10,1)
|
||||
#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 */
|
||||
#define UNARYPREC 14
|
||||
#define TOK_BNOT tok_decl(UNARYPREC,0)
|
||||
#define TOK_NOT tok_decl(UNARYPREC,1)
|
||||
#define TOK_UMINUS tok_decl(UNARYPREC,2)
|
||||
#define TOK_UPLUS tok_decl(UNARYPREC,3)
|
||||
|
||||
#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 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)
|
||||
{
|
||||
if (NUMPTR == numstack) goto err;
|
||||
if (op == TOK_UMINUS)
|
||||
NUMPTR[-1] *= -1;
|
||||
else if (op == TOK_NOT)
|
||||
NUMPTR[-1] = !(NUMPTR[-1]);
|
||||
else if (op == TOK_BNOT)
|
||||
NUMPTR[-1] = ~(NUMPTR[-1]);
|
||||
long numptr_val;
|
||||
long *NUMPTR_M1;
|
||||
|
||||
if (NUMPTR == numstack) goto err; /* There is no operator that can work
|
||||
without arguments */
|
||||
NUMPTR_M1 = NUMPTR - 1;
|
||||
if (op == TOK_UMINUS)
|
||||
*NUMPTR_M1 *= -1;
|
||||
else if (op == TOK_NOT)
|
||||
*NUMPTR_M1 = !(*NUMPTR_M1);
|
||||
else if (op == TOK_BNOT)
|
||||
*NUMPTR_M1 = ~(*NUMPTR_M1);
|
||||
else if (op != TOK_UPLUS) {
|
||||
/* Binary operators */
|
||||
else {
|
||||
if (NUMPTR-1 == numstack) goto err;
|
||||
--NUMPTR;
|
||||
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[-1] |= *NUMPTR;
|
||||
*NUMPTR_M1 |= numptr_val;
|
||||
else if (op == TOK_OR)
|
||||
NUMPTR[-1] = *NUMPTR || NUMPTR[-1];
|
||||
*NUMPTR_M1 = numptr_val || *NUMPTR_M1;
|
||||
else if (op == TOK_BAND)
|
||||
NUMPTR[-1] &= *NUMPTR;
|
||||
*NUMPTR_M1 &= numptr_val;
|
||||
else if (op == TOK_AND)
|
||||
NUMPTR[-1] = NUMPTR[-1] && *NUMPTR;
|
||||
*NUMPTR_M1 = *NUMPTR_M1 && numptr_val;
|
||||
else if (op == TOK_EQ)
|
||||
NUMPTR[-1] = (NUMPTR[-1] == *NUMPTR);
|
||||
*NUMPTR_M1 = (*NUMPTR_M1 == numptr_val);
|
||||
else if (op == TOK_NE)
|
||||
NUMPTR[-1] = (NUMPTR[-1] != *NUMPTR);
|
||||
*NUMPTR_M1 = (*NUMPTR_M1 != numptr_val);
|
||||
else if (op == TOK_GE)
|
||||
NUMPTR[-1] = (NUMPTR[-1] >= *NUMPTR);
|
||||
*NUMPTR_M1 = (*NUMPTR_M1 >= numptr_val);
|
||||
else if (op == TOK_RSHIFT)
|
||||
NUMPTR[-1] >>= *NUMPTR;
|
||||
*NUMPTR_M1 >>= numptr_val;
|
||||
else if (op == TOK_LSHIFT)
|
||||
NUMPTR[-1] <<= *NUMPTR;
|
||||
*NUMPTR_M1 <<= numptr_val;
|
||||
else if (op == TOK_GT)
|
||||
NUMPTR[-1] = (NUMPTR[-1] > *NUMPTR);
|
||||
*NUMPTR_M1 = (*NUMPTR_M1 > numptr_val);
|
||||
else if (op == TOK_LT)
|
||||
NUMPTR[-1] = (NUMPTR[-1] < *NUMPTR);
|
||||
*NUMPTR_M1 = (*NUMPTR_M1 < numptr_val);
|
||||
else if (op == TOK_LE)
|
||||
NUMPTR[-1] = (NUMPTR[-1] <= *NUMPTR);
|
||||
*NUMPTR_M1 = (*NUMPTR_M1 <= numptr_val);
|
||||
else if (op == TOK_MUL)
|
||||
NUMPTR[-1] *= *NUMPTR;
|
||||
else if (op == TOK_DIV) {
|
||||
if(*NUMPTR==0)
|
||||
return -2;
|
||||
NUMPTR[-1] /= *NUMPTR;
|
||||
}
|
||||
else if (op == TOK_REM) {
|
||||
if(*NUMPTR==0)
|
||||
return -2;
|
||||
NUMPTR[-1] %= *NUMPTR;
|
||||
}
|
||||
*NUMPTR_M1 *= numptr_val;
|
||||
else if (op == TOK_ADD)
|
||||
NUMPTR[-1] += *NUMPTR;
|
||||
*NUMPTR_M1 += numptr_val;
|
||||
else if (op == TOK_SUB)
|
||||
NUMPTR[-1] -= *NUMPTR;
|
||||
*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! */
|
||||
}
|
||||
return 0;
|
||||
err: return(-1);
|
||||
}
|
||||
|
||||
extern long arith (const char *startbuf, int *errcode)
|
||||
{
|
||||
register char arithval;
|
||||
const char *expr = startbuf;
|
||||
static const char endexpression[] = ")";
|
||||
|
||||
operator lasttok = TOK_MUL, op;
|
||||
size_t datasizes = strlen(startbuf);
|
||||
/* + and - (in that order) must be last */
|
||||
static const char op_char[] = "!<>=|&*/%~()+-";
|
||||
static const char op_token[] = {
|
||||
/* paired with equal */
|
||||
TOK_NE, TOK_LE, TOK_GE,
|
||||
/* 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,
|
||||
TOK_MUL, TOK_DIV, TOK_REM, TOK_BNOT, TOK_LPAREN, TOK_RPAREN,
|
||||
TOK_ADD, TOK_SUB, TOK_UPLUS, TOK_UMINUS
|
||||
};
|
||||
|
||||
#define NUM_PAIR_EQUAL 3
|
||||
#define NUM_PAIR_SAME 6
|
||||
|
||||
extern long arith (const char *expr, int *errcode)
|
||||
{
|
||||
register char arithval; /* Current character under analysis */
|
||||
operator lasttok, op;
|
||||
unsigned char prec;
|
||||
|
||||
long *numstack, *numstackptr;
|
||||
operator *stack = alloca(datasizes * sizeof(operator)), *stackptr = stack;
|
||||
const char *p = endexpression;
|
||||
|
||||
*errcode = 0;
|
||||
numstack = alloca((datasizes/2+1)*sizeof(long)), numstackptr = numstack;
|
||||
size_t datasizes = strlen(expr);
|
||||
|
||||
while ((arithval = *expr)) {
|
||||
if (arithval == ' ' || arithval == '\n' || arithval == '\t')
|
||||
goto prologue;
|
||||
/* 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;
|
||||
/* Stack of operator tokens */
|
||||
operator *stack = alloca((datasizes+1) * sizeof(operator)),
|
||||
*stackptr = stack;
|
||||
|
||||
*stackptr++ = lasttok = TOK_LPAREN; /* start off with a left paren */
|
||||
|
||||
loop:
|
||||
if ((arithval = *expr) == 0) {
|
||||
if (p == endexpression) { /* Null expression. */
|
||||
return (*errcode = 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 != endexpression + 1) { /* If we haven't done so already, */
|
||||
expr = endexpression; /* append a closing right paren */
|
||||
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:
|
||||
return (*errcode = -1);
|
||||
/* NOTREACHED */
|
||||
}
|
||||
return *numstack;
|
||||
} else {
|
||||
/* Continue processing the expression. */
|
||||
if (isspace(arithval)) {
|
||||
goto prologue; /* Skip whitespace */
|
||||
}
|
||||
if ((unsigned)arithval-'0' <= 9) /* isdigit */ {
|
||||
*numstackptr++ = strtol(expr, (char **) &expr, 10);
|
||||
lasttok = TOK_NUM;
|
||||
continue;
|
||||
} if (arithval == '(') {
|
||||
*stackptr++ = TOK_LPAREN;
|
||||
lasttok = TOK_LPAREN;
|
||||
goto prologue;
|
||||
} if (arithval == ')') {
|
||||
lasttok = TOK_NUM;
|
||||
while (stackptr != stack) {
|
||||
op = *--stackptr;
|
||||
if (op == TOK_LPAREN)
|
||||
goto prologue;
|
||||
*errcode = ARITH_APPLY(op);
|
||||
if(*errcode) return *errcode;
|
||||
goto loop;
|
||||
}
|
||||
#if 1
|
||||
if ((p = strchr(op_char, arithval)) == NULL) {
|
||||
goto err;
|
||||
}
|
||||
#else
|
||||
for ( p=op_char ; *p != arithval ; p++ ) {
|
||||
if (!*p) {
|
||||
goto err;
|
||||
}
|
||||
goto err; /* Mismatched parens */
|
||||
} if (arithval == '|') {
|
||||
if (*++expr == '|')
|
||||
op = TOK_OR;
|
||||
else {
|
||||
}
|
||||
#endif
|
||||
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;
|
||||
op = TOK_BOR;
|
||||
if (arithval == '=') { /* single = */
|
||||
goto err;
|
||||
}
|
||||
p += NUM_PAIR_SAME;
|
||||
/* Plus and minus are binary (not unary) _only_ if the last
|
||||
* token was as 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)
|
||||
&& (p >= op_token + NUM_PAIR_SAME + NUM_PAIR_EQUAL
|
||||
+ sizeof(op_char) - 2)) {
|
||||
p += 2; /* Unary plus or minus */
|
||||
}
|
||||
}
|
||||
} else if (arithval == '&') {
|
||||
if (*++expr == '&')
|
||||
op = TOK_AND;
|
||||
else {
|
||||
--expr;
|
||||
op = TOK_BAND;
|
||||
}
|
||||
} else if (arithval == '=') {
|
||||
if (*++expr != '=') goto err; /* Unknown token */
|
||||
op = TOK_EQ;
|
||||
} else if (arithval == '!') {
|
||||
if (*++expr == '=')
|
||||
op = TOK_NE;
|
||||
else {
|
||||
--expr;
|
||||
op = TOK_NOT;
|
||||
}
|
||||
} else if (arithval == '>') {
|
||||
switch (*++expr) {
|
||||
case '=':
|
||||
op = TOK_GE;
|
||||
break;
|
||||
case '>':
|
||||
op = TOK_RSHIFT;
|
||||
break;
|
||||
default:
|
||||
--expr;
|
||||
op = TOK_GT;
|
||||
}
|
||||
} else if (arithval == '<') {
|
||||
switch (*++expr) {
|
||||
case '=':
|
||||
op = TOK_LE;
|
||||
break;
|
||||
case '<':
|
||||
op = TOK_LSHIFT;
|
||||
break;
|
||||
default:
|
||||
--expr;
|
||||
op = TOK_LT;
|
||||
}
|
||||
} else if (arithval == '*')
|
||||
op = TOK_MUL;
|
||||
else if (arithval == '/')
|
||||
op = TOK_DIV;
|
||||
else if (arithval == '%')
|
||||
op = TOK_REM;
|
||||
else if (arithval == '+') {
|
||||
if (lasttok != TOK_NUM) goto prologue; /* Unary plus */
|
||||
op = TOK_ADD;
|
||||
} else if (arithval == '-')
|
||||
op = (lasttok == TOK_NUM) ? TOK_SUB : TOK_UMINUS;
|
||||
else if (arithval == '~')
|
||||
op = TOK_BNOT;
|
||||
else goto err; /* Unknown token */
|
||||
}
|
||||
op = *p;
|
||||
|
||||
/* We don't want a 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. */
|
||||
/* Left paren is given the lowest priority so it will never be
|
||||
* "applied" in this way */
|
||||
prec = PREC(op);
|
||||
if (prec != UNARYPREC)
|
||||
while (stackptr != stack && PREC(stackptr[-1]) >= prec) {
|
||||
if ((prec > 0) && (prec != UNARYPREC)) { /* not left paren or unary */
|
||||
if (lasttok != TOK_NUM) { /* binary op must be preceded by a num */
|
||||
goto err;
|
||||
}
|
||||
while (stackptr != stack) {
|
||||
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 (stackptr[-1] == TOK_LPAREN) {
|
||||
--stackptr;
|
||||
lasttok = TOK_NUM; /* Any operator directly after a */
|
||||
/* close paren should consider itself binary */
|
||||
goto prologue;
|
||||
}
|
||||
} else if (PREC(stackptr[-1]) < prec) {
|
||||
break;
|
||||
}
|
||||
*errcode = ARITH_APPLY(*--stackptr);
|
||||
if(*errcode) return *errcode;
|
||||
}
|
||||
*stackptr++ = op;
|
||||
lasttok = op;
|
||||
prologue: ++expr;
|
||||
} /* yay */
|
||||
if (op == TOK_RPAREN) {
|
||||
goto err;
|
||||
}
|
||||
}
|
||||
|
||||
while (stackptr != stack) {
|
||||
*errcode = ARITH_APPLY(*--stackptr);
|
||||
if(*errcode) return *errcode;
|
||||
}
|
||||
if (numstackptr != numstack+1) {
|
||||
err:
|
||||
*errcode = -1;
|
||||
return -1;
|
||||
/* NOTREACHED */
|
||||
}
|
||||
/* Push this operator to the stack and remember it. */
|
||||
*stackptr++ = lasttok = op;
|
||||
|
||||
return *numstack;
|
||||
prologue:
|
||||
++expr;
|
||||
goto loop;
|
||||
}
|
||||
}
|
||||
|
||||
Loading…
Reference in New Issue
Block a user