malloc: added functions to find and request memory

Makefile

@@ -1,7 +1,7 @@
 CC     = gcc
 CFLAGS = -O3 -Wall -Wextra -Wpedantic
 
-SRCS = main.c vm.c gc.c
+SRCS = main.c vm.c gc.c galloc.c
 OBJS = $(SRCS:.c=.o)
 EXE  = gc
 

gc_alloc.c

@@ -0,0 +1,49 @@
+#include <stdio.h>
+#include <unistd.h>
+
+#include "gc_alloc.h"
+
+static void *allocHead = NULL;
+
+struct gcHeader *findFree(struct gcHeader **prev, size_t size) {
+  struct gcHeader *curr = allocHead;
+
+  while (curr && !(curr->free && curr->size >= size)) {
+    *prev = curr;
+    curr = curr->next;
+  }
+
+  return curr;
+}
+
+struct gcHeader *requestMem(struct gcHeader *prev, size_t size) {
+  struct gcHeader *block;
+  void *request;
+
+  block = sbrk(0);
+  if (block == (void *)-1) {
+    perror("sbrk block");
+    return NULL;
+  }
+
+  request = sbrk(size + sizeof(struct gcHeader));
+  if (request == (void *)-1) {
+    perror("sbrk request");
+    return NULL;
+  }
+
+  if ((void *)block != request) {
+    fprintf(stderr, "gcHeader: block != request");
+    return NULL;
+  }
+
+  if (prev) {
+    prev->next = block;
+  }
+
+  block->size = size;
+  block->next = NULL;
+  block->free = 0;
+
+  return block;
+}

gc_alloc.h

@@ -0,0 +1,26 @@
+#ifndef GALLOC_H
+#define GALLOC_H
+
+#include <stdio.h>
+
+// Metadata for allocated memory - Headers are stored in a linked list to keep
+// track of alloc's and free's
+struct gcHeader {
+  size_t size;
+  int free;
+  struct gcHeader *next;
+};
+
+// Iterates over the galloc linked list attempting to find free space
+struct gcHeader *findFree(struct gcHeader **prev, size_t size);
+
+// Requests more memory from the kernel
+struct gcHeader *requestMem(struct gcHeader *prev, size_t size);
+
+// Performs allocations
+void *galloc(size_t size);
+
+// Frees memory allocated with galloc()
+void gfree(void *ptr);
+
+#endif /* GALLOC_H */