started porting simple brainfuck interpreter

1 files changed, 133 insertions, 0 deletions

diff --git a/userspace/brainfuck.c b/userspace/brainfuck.c
new file mode 100644
index 0000000..03ce4f5
--- /dev/null
+++ b/userspace/brainfuck.c
@@ -0,0 +1,133 @@
+// taken from: http://it-ride.blogspot.com/2009/11/brainfuck-interpreter.html
+
+/* comment
+ * TODO
+ * You have a bug. You don't check for EOF while looking for square brackets.
+ */
+
+/*
+
+    A brainfuck intepreter written in C, complete with error checking so you
+    don't hurt yourself while, uh, brainfucking. Nothing really special about
+    the implementation and it is probably very poor performance-wise.
+    
+    Author: Felix Oghină
+    License: (brain)fuck licenses!
+
+*/
+
+// ADDED BY FOOLOS : foolos syscalls!
+#include "syscalls.c"
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+// by brainfuck standards (doesn't that sound funny?), the data pointer has
+// 30,000 bytes at its disposal, but I hate hard-coding such stuff.
+#define DATA_SIZE 30000
+
+void usage() {
+    puts(
+        "Usage: brainfuck FILE\n"
+        "If FILE is ommited or is '-', standard input is read"
+    );
+}
+
+int main(int argc, char **argv) {
+
+    // ADDED BY FOOLOS: we will show usage anyway
+     usage();
+
+    // used by the bf program
+    unsigned char *dataptr = malloc(sizeof(char) * DATA_SIZE);
+    // position of the data pointer
+    unsigned int datapos = 0;
+    // input file
+    FILE *input;
+    // level - deepness of brackets
+    // i - uh, you need explanation for this one?
+    unsigned int level, i;
+    // we will read chars from the input into r
+    unsigned char r;
+    
+    // determine input
+    if (argc == 2) {
+        if (strcmp(argv[1], "--help") == 0 || strcmp(argv[1], "-h") == 0) {
+            usage();
+            return EXIT_SUCCESS;
+        }
+        else {
+            input = fopen(argv[1], "r");
+            if (input == NULL) {
+                puts("Error opening input file");
+                return EXIT_FAILURE;
+            }
+        }
+    }
+    else {
+        usage();
+        return EXIT_FAILURE;
+    }
+    
+    // zero the data pointer
+    for (i=0; i < DATA_SIZE; i++) {
+        dataptr[i] = 0;
+    }
+    
+    // start interpreting
+    rewind(input);
+    while (!feof(input)) {
+        r = (unsigned char) fgetc(input);
+        switch(r) {
+        case '>':
+            if (datapos < DATA_SIZE - 1) datapos++;
+            else {
+                puts("brainfuck error: pointer overflow");
+                return EXIT_FAILURE;
+            }
+            break;
+        case '<':
+            if (datapos > 0) datapos--;
+            else {
+                puts("brainfuck error: pointer underflow");
+                return EXIT_FAILURE;
+            }
+            break;
+        case '+':
+            dataptr[datapos]++;
+            break;
+        case '-':
+            dataptr[datapos]--;
+            break;
+        case '.':
+            putchar(dataptr[datapos]);
+            break;
+        case ',':
+            dataptr[datapos] = getchar();
+            break;
+        case '[':
+            if (dataptr[datapos] == 0) {
+                level = 1;
+                while (level != 0) {
+                    r = (unsigned char) fgetc(input);
+                    if (r == '[') level ++;
+                    else if (r == ']') level --;
+                }
+            }
+            break;
+        case ']':
+            if (dataptr[datapos] != 0) {
+                level = 1;
+                while (level != 0) {
+                    fseek(input, -2, SEEK_CUR);
+                    r = (unsigned char) fgetc(input);
+                    if (r == ']') level ++;
+                    else if (r == '[') level --;
+                }
+            }
+            break;
+        }
+    }
+    return EXIT_SUCCESS;
+}