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);
+}