From 54568c8a5460925bf9201d0252915288d88ac4bb Mon Sep 17 00:00:00 2001
From: Mart Lubbers <mart@martlubbers.net>
Date: Thu, 25 Aug 2016 15:20:17 +0200
Subject: [PATCH] initial commit

---
 .gitignore |  1 +
 Makefile   |  7 +++++
 bf.c       | 87 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 95 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Makefile
 create mode 100644 bf.c

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..292a768
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+bf
diff --git a/Makefile b/Makefile
new file mode 100644
index 0000000..a8f241a
--- /dev/null
+++ b/Makefile
@@ -0,0 +1,7 @@
+PROGRAM:=bf
+CFLAGS:=-Wall -Werror -g
+
+all: $(PROGRAM)
+
+clean:
+	$(RM) -v $(PROGRAM)
diff --git a/bf.c b/bf.c
new file mode 100644
index 0000000..c095176
--- /dev/null
+++ b/bf.c
@@ -0,0 +1,87 @@
+#include <stdlib.h>
+#include <string.h>
+#include <stdio.h>
+
+struct nest {
+	long pos;
+	struct nest *next;
+};
+
+int main(int argc, char *argv[])
+{
+	size_t offset, stacksize = 1;
+	char *b = malloc(stacksize);
+	b[0] = 0;
+	char *ptr = b;
+	struct nest *t, *callstack = NULL;
+	FILE *in;
+
+	if(argc != 2){
+		fprintf(stderr, "Usage: %s PROGRAM\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+	
+	if((in = fopen(argv[1], "r")) == NULL){
+		perror("fopen");
+		return EXIT_FAILURE;
+	}
+
+	while(1){
+		switch(fgetc(in)){
+			case EOF:
+				return EXIT_SUCCESS;
+			case '>':
+				++ptr;
+				if(ptr > b+stacksize){
+					offset = ptr-b;
+					b = realloc(b, stacksize *= 2);
+					ptr = b+offset;
+					memset(ptr, 0, stacksize/2);
+				}
+				break;
+			case '<':
+				if(ptr == b){
+					fprintf(stderr, "There is no stack position -1...\n");
+					return EXIT_FAILURE;
+				}
+				--ptr;
+				break;
+			case '+':
+				++*ptr;
+				break;
+			case '-':
+				--*ptr;
+				break;
+			case '.':
+				putchar(*ptr);
+				break;
+			case ',':
+				*ptr = getchar();
+				break;
+			case '[':
+				if(*ptr){
+					t = callstack;
+					callstack = malloc(sizeof(struct nest));
+					callstack->next = t;
+					if((callstack->pos = ftell(in)) == -1){
+						perror("ftell");
+						return EXIT_FAILURE;
+					}
+				} else {
+					while(fgetc(in) != ']');
+				}
+				break;
+			case ']':
+				if(fseek(in, callstack->pos-1, SEEK_SET) == -1){
+					perror("fseek");
+					return EXIT_FAILURE;
+				}
+				t = callstack;
+				callstack = callstack->next;
+				free(t);
+				break;
+			default:
+				break;
+		}
+	}
+}
-- 
2.20.1