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