Project restructuring to support the new direction

example/c/.gitignore

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+*.o
+scheme
+scheme.exe

example/c/Makefile

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+CFLAGS=-g
+
+all: scheme
+
+scheme: gc.o runtime.o

example/c/common.h

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+#ifndef _COMMON_H_
+#define _COMMON_H_
+
+#define SIZE 1024
+#define BROKEN_HEART 1
+#define CONS 2
+#define INTEGER 3
+#define SYMBOL 4
+#define BYE 5
+
+typedef struct box_t {
+  char type;
+  union {
+    int integer;
+    char* symbol;
+    struct cons_t* cons;
+  };
+} box_t;
+
+typedef struct cons_t {
+  box_t car;
+  box_t cdr;
+} cons_t;
+
+extern cons_t *the_empty_list;
+
+#endif // _COMMON_H_

example/c/gc.c

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+// Cheney style stop and copy garbage collector
+#include "gc.h"
+
+cons_t *the_empty_list = NULL;
+
+static cons_t *old, *new, *scanptr, *freeptr, *eom, *root;
+size_t tos;
+
+void gc_init() {
+  old = calloc(sizeof(cons_t), SIZE);
+  freeptr = old;
+  eom = old + (SIZE / 2);
+  new = eom + 1;
+  root = alloc();
+}
+
+cons_t *alloc() {
+  if (freeptr < eom) {
+    cons_t *retval = freeptr;
+    freeptr++;
+    return retval;
+  } else {
+    gc_run();
+    return alloc();
+  }
+}
+
+void gc_run() {
+  freeptr = new;
+  scanptr = new;
+  // Relocate root
+  relocate(root);
+  // Enter the main GC loop
+  gc_loop();
+  // Flip old and new;
+  cons_t *temp = old;
+  old = new;
+  new = temp;
+}
+
+void gc_loop() {
+  while (scanptr < freeptr) {
+    relocate(scanptr);
+    scanptr++;
+  }
+}
+
+void move(box_t box) {
+  if (box.type == CONS && box.cons != the_empty_list) {
+    if (box.cons->car.type == BROKEN_HEART) {
+      box.cons = box.cons->cdr.cons;
+    } else {
+      memcpy(freeptr, box.cons, sizeof(cons_t));
+      box.cons->car.type = BROKEN_HEART;
+      box.cons->cdr.cons = freeptr;
+      freeptr++;
+    }
+  }
+}
+
+void relocate(cons_t* cons) {
+  move(cons->car);
+  move(cons->cdr);
+}

example/c/gc.h

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+#ifndef _GC_H_
+#define _GC_H_
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include "common.h"
+
+void gc_init();
+cons_t *alloc();
+void gc_run();
+void gc_loop();
+void relocate(cons_t*);
+
+#endif // _GC_H_