1 files changed, 194 insertions, 0 deletions

diff --git a/dc.c b/dc.c
new file mode 100644
index 000000000..37c7731d2
--- /dev/null
+++ b/dc.c
@@ -0,0 +1,194 @@
+/* vi: set sw=4 ts=4: */
+#include "internal.h"
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <math.h>
+
+/* Tiny RPN calculator, because "expr" didn't give me bitwise operations. */
+
+static const char dc_usage[] = "math expression ...\n"
+#ifndef BB_FEATURE_TRIVIAL_HELP
+                "\nThis is a Tiny RPN calculator that understands the\n"
+                "following operations: +, -, /, *, and, or, not, eor.\n"
+                "i.e. 'math 2 2 add' -> 4, and 'math 8 8 \\* 2 2 + /' -> 16\n"
+#endif
+                ;
+
+static double stack[100];
+static unsigned int pointer;
+
+static void push(double a)
+{
+        if (pointer >= (sizeof(stack) / sizeof(*stack))) {
+                fprintf(stderr, "math: stack overflow\n");
+                exit(-1);
+        } else
+                stack[pointer++] = a;
+}
+
+static double pop()
+{
+        if (pointer == 0) {
+                fprintf(stderr, "math: stack underflow\n");
+                exit(-1);
+        }
+        return stack[--pointer];
+}
+
+static void add()
+{
+        push(pop() + pop());
+}
+
+static void sub()
+{
+        double subtrahend = pop();
+
+        push(pop() - subtrahend);
+}
+
+static void mul()
+{
+        push(pop() * pop());
+}
+
+static void divide()
+{
+        double divisor = pop();
+
+        push(pop() / divisor);
+}
+
+static void and()
+{
+        push((unsigned int) pop() & (unsigned int) pop());
+}
+
+static void or()
+{
+        push((unsigned int) pop() | (unsigned int) pop());
+}
+
+static void eor()
+{
+        push((unsigned int) pop() ^ (unsigned int) pop());
+}
+
+static void not()
+{
+        push(~(unsigned int) pop());
+}
+
+static void print()
+{
+        printf("%g\n", pop());
+}
+
+struct op {
+        const char *name;
+        void (*function) ();
+};
+
+static const struct op operators[] = {
+        {"+",   add},
+        {"add", add},
+        {"-",   sub},
+        {"sub", sub},
+        {"*",   mul},
+        {"mul", mul},
+        {"/",   divide},
+        {"div", divide},
+        {"and", and},
+        {"or",  or},
+        {"not", not},
+        {"eor", eor},
+        {0,     0}
+};
+
+static void stack_machine(const char *argument)
+{
+        char *endPointer = 0;
+        double d;
+        const struct op *o = operators;
+
+        if (argument == 0) {
+                print();
+                return;
+        }
+
+        d = strtod(argument, &endPointer);
+
+        if (endPointer != argument) {
+                push(d);
+                return;
+        }
+
+        while (o->name != 0) {
+                if (strcmp(o->name, argument) == 0) {
+                        (*(o->function)) ();
+                        return;
+                }
+                o++;
+        }
+        fprintf(stderr, "math: %s: syntax error.\n", argument);
+        exit(-1);
+}
+
+/* return pointer to next token in buffer and set *buffer to one char
+ * past the end of the above mentioned token 
+ */
+static char *get_token(char **buffer)
+{
+        char *start   = NULL;
+        char *current = *buffer;
+
+        while (isspace(*current)) { current++; }
+        if (*current != 0) {
+                start = current;
+                while (!isspace(*current) && current != 0) { current++; }
+                *buffer = current;
+        }
+        return start;
+}
+
+/* In Perl one might say, scalar m|\s*(\S+)\s*|g */
+static int number_of_tokens(char *buffer)
+{
+        int   i = 0;
+        char *b = buffer;
+        while (get_token(&b)) { i++; }
+        return i;
+}
+
+int dc_main(int argc, char **argv)
+{
+        /* take stuff from stdin if no args are given */
+        if (argc <= 1) {
+                int i, len;
+                char *line   = NULL;
+                char *cursor = NULL;
+                char *token  = NULL;
+                while ((line = cstring_lineFromFile(stdin))) {
+                        cursor = line;
+                        len = number_of_tokens(line);
+                        for (i = 0; i < len; i++) {
+                                token = get_token(&cursor);
+                                *cursor++ = 0;
+                                stack_machine(token);
+                        }
+                        free(line);
+                }
+        } else {
+                if (*argv[1]=='-')
+                        usage(dc_usage);
+                while (argc >= 2) {
+                        stack_machine(argv[1]);
+                        argv++;
+                        argc--;
+                }
+        }
+        stack_machine(0);
+        return( TRUE);
+}