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README.md

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+# A Branfuck interpreter in C
+
+This repo contains some demo brainfuck programs, most of which came from:
+(c) 2016 Daniel B. Cristofani
+http://brainfuck.org/
+

brainfuck.c

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+#include <stdio.h>
+#include <stdint.h>
+
+char instruction_buffer[30000] = {0};
+uint32_t instruction_pointer;
+uint32_t loop_stack[30000] = {0};
+uint32_t loop_stack_pointer;
+uint8_t cells[3000000] = {0};
+uint32_t data_pointer;
+
+void run_brainfuck()
+{
+    instruction_pointer = loop_stack_pointer = data_pointer = 0;
+
+    while(instruction_buffer[instruction_pointer])
+    {
+        // printf( "ip %d: ", instruction_pointer );
+        // printf( "i %c | ", instruction_buffer[instruction_pointer] );
+        // printf( "lsp %d: ", loop_stack_pointer );
+        // printf( "ls %d | ", loop_stack[loop_stack_pointer] );
+        // printf( "dp %d: ", data_pointer );
+        // printf( "c %d: ", cells[data_pointer] );
+        // printf( "\n" );
+
+        switch(instruction_buffer[instruction_pointer])
+        {
+            case '+':
+                cells[data_pointer]++;
+                break;
+            case '-':
+                cells[data_pointer]--;
+                break;
+            case '>':
+                data_pointer++;
+                break;
+            case '<':
+                data_pointer--;
+                break;
+            case '.':
+                putchar(cells[data_pointer]);
+                break;
+            case ',':
+                cells[data_pointer] = getchar();
+                break;
+            case '[':
+                if(cells[data_pointer])
+                {
+                    loop_stack[++loop_stack_pointer] = instruction_pointer;
+                }
+                else
+                {
+                    int skip_loop_stack = 0;
+                    while(instruction_buffer[++instruction_pointer] != ']' || skip_loop_stack)
+                    {
+                        if(instruction_buffer[instruction_pointer] == '[')
+                        {
+                            skip_loop_stack++;
+                        }
+                        else if(instruction_buffer[instruction_pointer] == ']')
+                        {
+                            skip_loop_stack--;
+                        }
+                    }
+                }
+                break;
+            case ']':
+                if(cells[data_pointer])
+                {
+                    instruction_pointer = loop_stack[loop_stack_pointer];
+                }
+                else
+                {
+                    loop_stack_pointer--;
+                }
+                break;
+        }
+        instruction_pointer++;
+        if (instruction_pointer == 30000)
+        {
+            break;
+        }
+    }
+    return;
+}
+
+int main(int argc, char *argv[])
+{
+    if(argc != 2)
+    {
+        printf("usage: %s <filename.bf>\n", argv[0]);
+        return 0;
+    }
+
+    FILE *file = fopen(argv[1], "r");
+
+    if(file == 0)
+    {
+        printf( "Could not open file\n" );
+        return 0;
+    }
+
+    instruction_pointer = 0;
+    char c;
+    while((c = fgetc(file)) != EOF && instruction_pointer < 30000)
+    {
+        if ( c == '+' || c == '-' || c == '>' || c == '<' ||
+             c == '[' || c == ']' || c == '.' || c == ',' )
+        {
+            instruction_buffer[instruction_pointer] = c;
+            instruction_pointer++;
+        }
+    }
+    fclose(file);
+
+    if (instruction_pointer == 30000)
+    {
+        printf( "Too many characters in your file\n" );
+        return 0;
+    }
+
+    run_brainfuck();
+
+    printf("\n"); // since most BF programs wont bother to end their outbut with a new line
+    return 0;
+}