interpreter works

4 files changed, 239 insertions, 0 deletions

diff --git a/README b/README
new file mode 100644
index 0000000..843ec8f
--- /dev/null
+++ b/README
@@ -0,0 +1,9 @@
+a simple brainfuck interpreter
+
+```
+make
+./brainfuck numwarp.bf
+```
+type a number then press enter
+
+
diff --git a/brainfuck.c b/brainfuck.c
new file mode 100644
index 0000000..3cddd02
--- /dev/null
+++ b/brainfuck.c
@@ -0,0 +1,204 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <stdint.h>
+#include <assert.h>
+
+#define MEMORY_SIZE 30000
+#define MAX_PROGRAM_SIZE 4096
+#define STACK_SIZE 512
+
+#define STACK_PUSH(x)   (stack[sp++] = x)
+#define STACK_POP()     (sp--)
+#define STACK_EMPTY()   (sp == 0)
+#define STACK_FULL()    (sp == STACK_SIZE)
+#define STACK_PEEK()	(stack[sp-1])
+
+void die(const char *msg) { perror(msg); exit(EXIT_FAILURE); }
+
+void usage (char *argv[]) { printf("usage: %s script\n", argv[0]); exit(EXIT_SUCCESS); }
+
+uint8_t memory[MEMORY_SIZE] = {0};
+uint8_t program[MAX_PROGRAM_SIZE] = {0};
+uint32_t stack[STACK_SIZE] = {0};
+uint32_t sp = 0; // stack pointer
+
+char *bf_file;
+int bf_fd;
+
+void
+load(void)
+{
+	size_t i = 0;
+	char c;
+	while ((read(bf_fd, &c, 1)) > 0)
+	{
+		switch (c)
+		{
+			case '>':
+			case '<':
+			case '+':
+			case '-':
+			case '.':
+			case ',':
+			case '[':
+			case ']':
+				program[i] = c;
+				i++;
+				break;
+
+			default: break;
+		}
+	}
+}
+
+ssize_t
+find_closing_bracket(size_t pos)
+{
+	/*
+	 * find closing ] for opening [ at location pos in program, return its position
+	 * -1 on not found
+	 *
+	 *  count each opening [ and closing ] until the numbers match, that will be our closing bracket
+	 */
+	ssize_t close_pos = -1;
+	size_t open_count = 0;
+	size_t close_count = 0;
+
+	if (pos > MAX_PROGRAM_SIZE)
+	{
+		return -1;
+	}
+	if (program[pos] != '[')
+	{
+		fprintf(stderr, "instruction not [ at %zu\n", pos);
+		exit(EXIT_FAILURE);
+	}
+
+	uint8_t c;
+	while ((c = program[pos]) != 0)
+	{
+		switch (c)
+		{
+			case '[':
+
+				open_count++;
+				break;
+			case ']':
+				close_count++;
+				break;
+			default: break;
+		}
+		if (open_count == close_count)
+		{
+			close_pos = pos;
+			break;
+		}
+		pos++;
+		if (pos > MAX_PROGRAM_SIZE)
+			break;
+	}
+
+	assert(close_pos != -1);
+	return close_pos;
+}
+
+void
+run(void)
+{
+	int pc = 0; // program counter
+	size_t datap = 0; // data pointer into memory
+	uint8_t i; // current instruction
+	while ((i = program[pc]) != 0)
+	{
+		/*
+		size_t in;
+		int x = 0;
+		printf("PC = %d\n", pc);
+		while ((in = program[x]) != 0)
+		{
+			if (x == pc)
+				putchar('A');
+			putchar(in);
+			if (x == pc)
+				putchar('A');
+			x++;
+		}
+		getchar();
+		*/
+		switch (i)
+		{
+		case '>':
+			datap++;
+			pc++;
+			break;
+		case '<':
+			datap--;
+			pc++;
+			break;
+		case '+':
+			memory[datap]++;
+			pc++;
+			break;
+		case '-':memory[datap]--;
+			pc++;
+			break;
+
+		case '.':
+			putchar(memory[datap]);
+			fflush(stdout);
+			pc++;
+			break;
+		case ',':
+			memory[datap] = (char)getchar();
+			pc++;
+			break;
+		case '[':
+		{
+			if (memory[datap] == 0)
+			{
+				uint32_t end = find_closing_bracket(pc);
+				pc = end+1;
+			}
+			else
+			{
+				STACK_PUSH(pc+1);
+				pc++;
+			}
+			break;
+		}
+		case ']':
+			if (memory[datap] != 0)
+			{
+				pc = STACK_PEEK();
+			}
+			else
+			{
+				STACK_POP();
+				pc++;
+			}
+			break;
+
+		default: die("unknown instruction"); break;
+		}
+	}
+}
+
+int
+main(int argc, char *argv[])
+{
+	if (argc < 2)
+		usage(argv);
+
+	bf_file = argv[1];
+	if ((bf_fd = open(bf_file, O_RDONLY)) < 0)
+		die("open");
+
+	load();
+	
+	run();
+
+	close(bf_fd);
+	return EXIT_SUCCESS;
+}
diff --git a/makefile b/makefile
new file mode 100644
index 0000000..7b21de5
--- /dev/null
+++ b/makefile
@@ -0,0 +1,25 @@
+TARGET = brainfuck
+LIBS = 
+CC = gcc
+CFLAGS = -std=c99 -g -Wextra -Wall -Werror -Wno-unused-variable -Wimplicit-fallthrough 
+
+.PHONY: default all
+
+default: $(TARGET)
+all: default
+
+OBJECTS = $(patsubst %.c, %.o, $(wildcard *.c))
+HEADERS = $(wildcard *.h)
+
+%.o: %.c $(HEADERS)
+	$(CC) $(CFLAGS) -c $< -o $@
+
+.PRECIOUS: $(TARGET) $(OBJECTS)
+
+$(TARGET): $(OBJECTS)
+	$(CC) $(OBJECTS) -Wall $(CFLAGS) $(LIBS) -o $@
+
+clean:
+	-rm -f *.o
+	-rm -f *.tmp
+	-rm -f $(TARGET)
diff --git a/numwarp.bf b/numwarp.bf
new file mode 100644
index 0000000..3118ccd
--- /dev/null
+++ b/numwarp.bf
@@ -0,0 +1 @@
+>>>>+>+++>+++>>>>>+++[>,+>++++[>++++<-]>[<<[-[->]]>[<]>-]<<[>+>+>>+>+[<<<<]<+>>[+<]<[>]>+[[>>>]>>+[<<<<]>-]+<+>>>-[<<+[>]>>+<<<+<+<--------[<<-<<+[>]>+<<-<<-[<<<+<-[>>]<-<-<<<-<----[<<<->>>>+<-[<<<+[>]>+<<+<-<-[<<+<-<+[>>]<+<<<<+<-[<<-[>]>>-<<<-<-<-[<<<+<-[>>]<+<<<+<+<-[<<<<+[>]<-<<-[<<+[>]>>-<<<<-<-[>>>>>+<-<<<+<-[>>+<<-[<<-<-[>]>+<<-<-<-[<<+<+[>]<+<+<-[>>-<-<-[<<-[>]<+<++++[<-------->-]++<[<<+[>]>>-<-<<<<-[<<-<<->>>>-[<<<<+[>]>+<<<<-[<<+<<-[>>]<+<<<<<-[>>>>-<<<-<-]]]]]]]]]]]]]]]]]]]]]]>[>[[[<<<<]>+>>[>>>>>]<-]<]>>>+>>>>>>>+>]<]<[-]<<<<<<<++<+++<+++[[>]>>>>>>++++++++[<<++++>++++++>-]<-<<[-[<+>>.<-]]<<<<[-[-[>+<-]>]>>>>>[.[>]]<<[<+>-]>>>[<<++[<+>--]>>-]<<[->+<[<++>-]]<<<[<+>-]<<<<]>>+>>>--[<+>---]<.>>[[-]<<]<]