527 lines
9.8 KiB
C
527 lines
9.8 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* Mini expr implementation for busybox
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*
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* based on GNU expr Mike Parker.
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* Copyright (C) 86, 1991-1997, 1999 Free Software Foundation, Inc.
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*
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* Busybox modifications
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* Copyright (c) 2000 Edward Betts <edward@debian.org>.
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* Aug 2003 Vladimir Oleynik - reduced 464 bytes.
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*
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* this program is free software; you can redistribute it and/or modify
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* it under the terms of the gnu general public license as published by
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* the free software foundation; either version 2 of the license, or
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* (at your option) any later version.
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*
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* this program is distributed in the hope that it will be useful,
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* but without any warranty; without even the implied warranty of
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* merchantability or fitness for a particular purpose. see the gnu
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* general public license for more details.
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*
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* you should have received a copy of the gnu general public license
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* along with this program; if not, write to the free software
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* foundation, inc., 59 temple place, suite 330, boston, ma 02111-1307 usa
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*
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*/
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/* This program evaluates expressions. Each token (operator, operand,
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* parenthesis) of the expression must be a seperate argument. The
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* parser used is a reasonably general one, though any incarnation of
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* it is language-specific. It is especially nice for expressions.
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*
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* No parse tree is needed; a new node is evaluated immediately.
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* One function can handle multiple operators all of equal precedence,
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* provided they all associate ((x op x) op x). */
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/* no getopt needed */
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#include <stdio.h>
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#include <string.h>
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#include <stdlib.h>
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#include <regex.h>
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#include <sys/types.h>
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#include <errno.h>
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#include "busybox.h"
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/* The kinds of value we can have. */
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enum valtype {
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integer,
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string
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};
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typedef enum valtype TYPE;
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/* A value is.... */
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struct valinfo {
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TYPE type; /* Which kind. */
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union { /* The value itself. */
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int i;
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char *s;
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} u;
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};
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typedef struct valinfo VALUE;
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/* The arguments given to the program, minus the program name. */
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static char **args;
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static VALUE *docolon (VALUE *sv, VALUE *pv);
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static VALUE *eval (void);
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static VALUE *int_value (int i);
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static VALUE *str_value (char *s);
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static int nextarg (char *str);
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static int null (VALUE *v);
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static int toarith (VALUE *v);
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static void freev (VALUE *v);
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static void tostring (VALUE *v);
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int expr_main (int argc, char **argv)
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{
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VALUE *v;
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if (argc == 1) {
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bb_error_msg_and_die("too few arguments");
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}
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args = argv + 1;
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v = eval ();
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if (*args)
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bb_error_msg_and_die ("syntax error");
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if (v->type == integer)
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printf ("%d\n", v->u.i);
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else
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puts (v->u.s);
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exit (null (v));
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}
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/* Return a VALUE for I. */
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static VALUE *int_value (int i)
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{
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VALUE *v;
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v = xmalloc (sizeof(VALUE));
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v->type = integer;
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v->u.i = i;
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return v;
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}
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/* Return a VALUE for S. */
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static VALUE *str_value (char *s)
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{
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VALUE *v;
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v = xmalloc (sizeof(VALUE));
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v->type = string;
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v->u.s = strdup (s);
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return v;
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}
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/* Free VALUE V, including structure components. */
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static void freev (VALUE *v)
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{
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if (v->type == string)
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free (v->u.s);
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free (v);
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}
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/* Return nonzero if V is a null-string or zero-number. */
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static int null (VALUE *v)
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{
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switch (v->type) {
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case integer:
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return v->u.i == 0;
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default: /* string: */
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return v->u.s[0] == '\0' || strcmp (v->u.s, "0") == 0;
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}
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}
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/* Coerce V to a string value (can't fail). */
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static void tostring (VALUE *v)
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{
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if (v->type == integer) {
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bb_xasprintf (&(v->u.s), "%d", v->u.i);
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v->type = string;
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}
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}
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/* Coerce V to an integer value. Return 1 on success, 0 on failure. */
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static int toarith (VALUE *v)
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{
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if(v->type == string) {
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int i;
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/* Don't interpret the empty string as an integer. */
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if (v->u.s == 0)
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return 0;
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i = atoi(v->u.s);
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free (v->u.s);
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v->u.i = i;
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v->type = integer;
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}
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return 1;
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}
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/* Return nonzero if the next token matches STR exactly.
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STR must not be NULL. */
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static int
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nextarg (char *str)
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{
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if (*args == NULL)
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return 0;
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return strcmp (*args, str) == 0;
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}
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/* The comparison operator handling functions. */
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static int cmp_common (VALUE *l, VALUE *r, int op)
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{
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int cmpval;
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if (l->type == string || r->type == string) {
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tostring (l);
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tostring (r);
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cmpval = strcmp (l->u.s, r->u.s);
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}
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else
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cmpval = l->u.i - r->u.i;
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switch(op) {
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case '<':
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return cmpval < 0;
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case ('L'+'E'):
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return cmpval <= 0;
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case '=':
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return cmpval == 0;
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case '!':
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return cmpval != 0;
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case '>':
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return cmpval > 0;
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default: /* >= */
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return cmpval >= 0;
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}
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}
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/* The arithmetic operator handling functions. */
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static int arithmetic_common (VALUE *l, VALUE *r, int op)
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{
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int li, ri;
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if (!toarith (l) || !toarith (r))
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bb_error_msg_and_die ("non-numeric argument");
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li = l->u.i;
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ri = r->u.i;
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if((op == '/' || op == '%') && ri == 0)
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bb_error_msg_and_die ( "division by zero");
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switch(op) {
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case '+':
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return li + ri;
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case '-':
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return li - ri;
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case '*':
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return li * ri;
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case '/':
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return li / ri;
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default:
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return li % ri;
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}
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}
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/* Do the : operator.
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SV is the VALUE for the lhs (the string),
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PV is the VALUE for the rhs (the pattern). */
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static VALUE *docolon (VALUE *sv, VALUE *pv)
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{
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VALUE *v;
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const char *errmsg;
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struct re_pattern_buffer re_buffer;
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struct re_registers re_regs;
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int len;
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tostring (sv);
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tostring (pv);
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if (pv->u.s[0] == '^') {
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fprintf (stderr, "\
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warning: unportable BRE: `%s': using `^' as the first character\n\
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of a basic regular expression is not portable; it is being ignored",
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pv->u.s);
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}
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len = strlen (pv->u.s);
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memset (&re_buffer, 0, sizeof (re_buffer));
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memset (&re_regs, 0, sizeof (re_regs));
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re_buffer.allocated = 2 * len;
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re_buffer.buffer = (unsigned char *) xmalloc (re_buffer.allocated);
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re_buffer.translate = 0;
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re_syntax_options = RE_SYNTAX_POSIX_BASIC;
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errmsg = re_compile_pattern (pv->u.s, len, &re_buffer);
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if (errmsg) {
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bb_error_msg_and_die("%s", errmsg);
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}
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len = re_match (&re_buffer, sv->u.s, strlen (sv->u.s), 0, &re_regs);
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if (len >= 0) {
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/* Were \(...\) used? */
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if (re_buffer.re_nsub > 0) { /* was (re_regs.start[1] >= 0) */
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sv->u.s[re_regs.end[1]] = '\0';
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v = str_value (sv->u.s + re_regs.start[1]);
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}
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else
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v = int_value (len);
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}
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else {
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/* Match failed -- return the right kind of null. */
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if (re_buffer.re_nsub > 0)
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v = str_value ("");
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else
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v = int_value (0);
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}
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free (re_buffer.buffer);
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return v;
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}
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/* Handle bare operands and ( expr ) syntax. */
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static VALUE *eval7 (void)
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{
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VALUE *v;
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if (!*args)
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bb_error_msg_and_die ( "syntax error");
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if (nextarg ("(")) {
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args++;
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v = eval ();
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if (!nextarg (")"))
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bb_error_msg_and_die ( "syntax error");
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args++;
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return v;
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}
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if (nextarg (")"))
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bb_error_msg_and_die ( "syntax error");
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return str_value (*args++);
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}
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/* Handle match, substr, index, length, and quote keywords. */
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static VALUE *eval6 (void)
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{
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VALUE *l, *r, *v, *i1, *i2;
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if (nextarg ("quote")) {
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args++;
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if (!*args)
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bb_error_msg_and_die ( "syntax error");
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return str_value (*args++);
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}
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else if (nextarg ("length")) {
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args++;
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r = eval6 ();
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tostring (r);
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v = int_value (strlen (r->u.s));
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freev (r);
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return v;
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}
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else if (nextarg ("match")) {
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args++;
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l = eval6 ();
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r = eval6 ();
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v = docolon (l, r);
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freev (l);
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freev (r);
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return v;
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}
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else if (nextarg ("index")) {
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args++;
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l = eval6 ();
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r = eval6 ();
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tostring (l);
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tostring (r);
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v = int_value (strcspn (l->u.s, r->u.s) + 1);
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if (v->u.i == (int) strlen (l->u.s) + 1)
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v->u.i = 0;
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freev (l);
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freev (r);
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return v;
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}
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else if (nextarg ("substr")) {
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args++;
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l = eval6 ();
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i1 = eval6 ();
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i2 = eval6 ();
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tostring (l);
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if (!toarith (i1) || !toarith (i2)
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|| i1->u.i > (int) strlen (l->u.s)
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|| i1->u.i <= 0 || i2->u.i <= 0)
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v = str_value ("");
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else {
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v = xmalloc (sizeof(VALUE));
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v->type = string;
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v->u.s = bb_xstrndup(l->u.s + i1->u.i - 1, i2->u.i);
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}
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freev (l);
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freev (i1);
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freev (i2);
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return v;
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}
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else
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return eval7 ();
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}
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/* Handle : operator (pattern matching).
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Calls docolon to do the real work. */
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static VALUE *eval5 (void)
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{
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VALUE *l, *r, *v;
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l = eval6 ();
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while (nextarg (":")) {
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args++;
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r = eval6 ();
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v = docolon (l, r);
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freev (l);
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freev (r);
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l = v;
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}
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return l;
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}
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/* Handle *, /, % operators. */
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static VALUE *eval4 (void)
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{
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VALUE *l, *r;
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int op, val;
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l = eval5 ();
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while (1) {
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if (nextarg ("*"))
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op = '*';
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else if (nextarg ("/"))
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op = '/';
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else if (nextarg ("%"))
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op = '%';
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else
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return l;
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args++;
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r = eval5 ();
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val = arithmetic_common (l, r, op);
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freev (l);
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freev (r);
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l = int_value (val);
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}
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}
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/* Handle +, - operators. */
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static VALUE *eval3 (void)
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{
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VALUE *l, *r;
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int op, val;
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l = eval4 ();
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while (1) {
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if (nextarg ("+"))
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op = '+';
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else if (nextarg ("-"))
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op = '-';
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else
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return l;
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args++;
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r = eval4 ();
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val = arithmetic_common (l, r, op);
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freev (l);
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freev (r);
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l = int_value (val);
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}
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}
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/* Handle comparisons. */
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static VALUE *eval2 (void)
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{
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VALUE *l, *r;
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int op, val;
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l = eval3 ();
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while (1) {
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if (nextarg ("<"))
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op = '<';
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else if (nextarg ("<="))
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op = 'L'+'E';
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else if (nextarg ("=") || nextarg ("=="))
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op = '=';
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else if (nextarg ("!="))
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op = '!';
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else if (nextarg (">="))
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op = 'G'+'E';
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else if (nextarg (">"))
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op = '>';
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else
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return l;
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args++;
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r = eval3 ();
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toarith (l);
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toarith (r);
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val = cmp_common (l, r, op);
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freev (l);
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freev (r);
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l = int_value (val);
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}
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}
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/* Handle &. */
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static VALUE *eval1 (void)
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{
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VALUE *l, *r;
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l = eval2 ();
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while (nextarg ("&")) {
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args++;
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r = eval2 ();
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if (null (l) || null (r)) {
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freev (l);
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freev (r);
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l = int_value (0);
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}
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else
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freev (r);
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}
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return l;
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}
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/* Handle |. */
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static VALUE *eval (void)
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{
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VALUE *l, *r;
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l = eval1 ();
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while (nextarg ("|")) {
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args++;
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r = eval1 ();
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if (null (l)) {
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freev (l);
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l = r;
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}
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else
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freev (r);
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}
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return l;
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}
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