Add beef Befunge-93 interpreter

4 files changed, 238 insertions, 0 deletions

diff --git a/bin/.gitignore b/bin/.gitignore
index b7d25952..311e3ccb 100644
--- a/bin/.gitignore
+++ b/bin/.gitignore
@@ -1,5 +1,6 @@
 *.o
 atch
+beef
 bri
 brot
 dtch
diff --git a/bin/Makefile b/bin/Makefile
index 4576de7e..a0487a17 100644
--- a/bin/Makefile
+++ b/bin/Makefile
@@ -24,6 +24,7 @@ BINS += ttpre
 BINS += wake
 BINS += xx
 
+BINS_BSD += beef
 BINS_BSD += wat
 
 BINS_LINUX += bri
diff --git a/bin/beef.c b/bin/beef.c
new file mode 100644
index 00000000..556742d9
--- /dev/null
+++ b/bin/beef.c
@@ -0,0 +1,139 @@
+/* Copyright (C) 2019  C. McEnroe <june@causal.agency>
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 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 Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include <err.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sysexits.h>
+
+enum {
+	Cols = 80,
+	Rows = 25,
+};
+static char page[Rows][Cols];
+
+static char get(int y, int x) {
+	if (y < 0 || y >= Rows) return 0;
+	if (x < 0 || x >= Cols) return 0;
+	return page[y][x];
+}
+static void put(int y, int x, char v) {
+	if (y < 0 || y >= Rows) return;
+	if (x < 0 || x >= Cols) return;
+	page[y][x] = v;
+}
+
+enum { StackLen = 1024 };
+static long stack[StackLen];
+static size_t top = StackLen;
+
+static void push(long val) {
+	if (!top) errx(EX_SOFTWARE, "stack overflow");
+	stack[--top] = val;
+}
+static long pop(void) {
+	if (top == StackLen) return 0;
+	return stack[top++];
+}
+
+static struct {
+	int y, x;
+	int dy, dx;
+} pc = { .dx = 1 };
+
+static void inc(void) {
+	pc.y += pc.dy;
+	pc.x += pc.dx;
+	if (pc.y == -1) pc.y += Rows;
+	if (pc.x == -1) pc.x += Cols;
+	if (pc.y == Rows) pc.y -= Rows;
+	if (pc.x == Cols) pc.x -= Cols;
+}
+
+static bool string;
+
+static bool step(void) {
+	char ch = page[pc.y][pc.x];
+
+	if (ch == '"') {
+		string ^= true;
+	} else if (string) {
+		push(ch);
+		inc();
+		return true;
+	}
+
+	if (ch == '?') ch = "><^v"[arc4random_uniform(4)];
+
+	long x, y, v;
+	switch (ch) {
+		break; case '+': push(pop() + pop());
+		break; case '-': y = pop(); x = pop(); push(x - y);
+		break; case '*': push(pop() * pop());
+		break; case '/': y = pop(); x = pop(); push(x / y);
+		break; case '%': y = pop(); x = pop(); push(x % y);
+		break; case '!': push(!pop());
+		break; case '`': y = pop(); x = pop(); push(x > y);
+		break; case '>': pc.dy = 0; pc.dx = +1;
+		break; case '<': pc.dy = 0; pc.dx = -1;
+		break; case '^': pc.dy = -1; pc.dx = 0;
+		break; case 'v': pc.dy = +1; pc.dx = 0;
+		break; case '_': pc.dy = 0; pc.dx = (pop() ? -1 : +1);
+		break; case '|': pc.dx = 0; pc.dy = (pop() ? -1 : +1);
+		break; case ':': x = pop(); push(x); push(x);
+		break; case '\\': y = pop(); x = pop(); push(y); push(x);
+		break; case '$': pop();
+		break; case '.': printf("%ld ", pop()); fflush(stdout);
+		break; case ',': printf("%c", (char)pop()); fflush(stdout);
+		break; case '#': inc();
+		break; case 'g': y = pop(); x = pop(); push(get(y, x));
+		break; case 'p': y = pop(); x = pop(); v = pop(); put(y, x, v);
+		break; case '&': x = EOF; scanf("%ld", &x); push(x);
+		break; case '~': push(getchar());
+		break; case '@': return false;
+		break; default:  if (ch >= '0' && ch <= '9') push(ch - '0');
+	}
+
+	inc();
+	return true;
+}
+
+int main(int argc, char *argv[]) {
+	memset(page, ' ', sizeof(page));
+
+	FILE *file = stdin;
+	if (argc > 1) {
+		file = fopen(argv[1], "r");
+		if (!file) err(EX_NOINPUT, "%s", argv[1]);
+	}
+
+	int y = 0;
+	char *line = NULL;
+	size_t cap = 0;
+	while (y < Rows && 0 < getline(&line, &cap, file)) {
+		for (int x = 0; x < Cols; ++x) {
+			if (line[x] == '\n' || !line[x]) break;
+			page[y][x] = line[x];
+		}
+		y++;
+	}
+	free(line);
+
+	while (step());
+	return pop();
+}
diff --git a/bin/man1/beef.1 b/bin/man1/beef.1
new file mode 100644
index 00000000..c42152d8
--- /dev/null
+++ b/bin/man1/beef.1
@@ -0,0 +1,97 @@
+.Dd January 26, 2019
+.Dt BEEF 1
+.Os
+.
+.Sh NAME
+.Nm beef
+.Nd Befunge-93 interpreter
+.
+.Sh SYNOPSIS
+.Nm
+.Op Ar file
+.
+.Sh DESCRIPTION
+.Nm
+is a Befunge-93 interpreter.
+If no
+.Ar file
+is provided,
+the program is read from standard input.
+.
+.Ss Befunge-93 Command Summary
+.Bl -tag -width "0-9" -compact
+.It \(dq
+toggle string mode
+.It 0-9
+push value
+.It +
+add
+.It -
+subtract
+.It *
+multiply
+.It /
+divide
+.It %
+modulo
+.It !
+not
+.It `
+greater than
+.It >
+right
+.It <
+left
+.It ^
+up
+.It v
+down
+.It ?
+random
+.It _
+horizontal (left) if
+.It |
+vertical (up) if
+.It :
+duplicate
+.It \e
+swap
+.It $
+drop
+.It .
+output integer
+.It ,
+output ASCII
+.It #
+bridge
+.It g
+get (y, x)
+.It p
+put (y, x) = v
+.It &
+input integer
+.It ~
+input ASCII
+.It @
+exit
+.El
+.
+.Sh EXIT STATUS
+.Nm
+exits with the top value left on the stack,
+or 0 if the stack is left empty.
+.
+.Sh STANDARDS
+.Rs
+.%A Chris Pressey
+.%Q Cat's Eye Technologies
+.%T Befunge-93
+.%D September, 1993
+.%U https://github.com/catseye/Befunge-93/blob/master/doc/Befunge-93.markdown
+.Re
+.
+.Sh CAVEATS
+.Nm
+does not support Linux
+since it uses
+.Xr arc4random_uniform 3 .