Added expr, from Edward Betts <edward@debian.org>, with some fixups

and docs added by me.
 -Erik

1 files changed, 531 insertions, 0 deletions

diff --git a/expr.c b/expr.c
new file mode 100644
index 000000000..9e3c04a11
--- /dev/null
+++ b/expr.c
@@ -0,0 +1,531 @@
+/* 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). */
+
+#include "internal.h"
+#include <stdio.h>
+#include <sys/types.h>
+
+#include <regex.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) {
+                fatalError("too few arguments\n");
+        }
+
+        args = argv + 1;
+
+        v = eval ();
+        if (*args)
+                fatalError ("syntax error\n");
+
+        if (v->type == integer)
+                printf ("%d\n", v->u.i);
+        else 
+                printf ("%s\n", 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))             \
+    fatalError ("non-numeric argument\n");      \
+  return l->u.i op r->u.i;                      \
+}
+
+#define arithdivf(name, op)                     \
+int name (l, r) VALUE *l; VALUE *r;             \
+{                                               \
+  if (!toarith (l) || !toarith (r))             \
+    fatalError ( "non-numeric argument\n");     \
+  if (r->u.i == 0)                              \
+    fatalError ( "division by zero\n");         \
+  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) {
+                fatalError("%s\n", 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)
+                fatalError ( "syntax error\n");
+
+        if (nextarg ("(")) {
+                args++;
+                v = eval ();
+                if (!nextarg (")"))
+                        fatalError ( "syntax error\n");
+                        args++;
+                        return v;
+                }
+
+        if (nextarg (")"))
+                fatalError ( "syntax error\n");
+
+        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)
+                        fatalError ( "syntax error\n");
+                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;
+}