wip: working on extern in VM

- Feat: add writer externs writing fns
- Feat: add VM reader functions

src/vm/reader/vm_rd_extern_libs.c

@@ -0,0 +1,49 @@
+#include <common/fzl_extern.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <vm/internals/reader.h>
+
+// Read external lib names
+bool vm_rd_extern_libs(fzl_vm_reader_t *reader, FILE *fd)
+{
+  if (!reader || !fd)
+    return false;
+
+  uint16_t libs_count = reader->extern_libs_count;
+  if (!libs_count)
+    return true;
+
+  reader->extern_libs = malloc(sizeof(char *) * libs_count);
+  if (!reader->extern_libs)
+    return false;
+
+  memset(reader->extern_libs, 0, sizeof(char *) * libs_count);
+
+  bool ok          = false;
+  uint16_t name_sz = 0;
+  char name[256];
+  for (uint16_t i = 0; i < libs_count; i++)
+  {
+    memset(name, 0, sizeof(name));
+
+    ok = vm_rd_u16(fd, 1, &name_sz);
+    if (!ok || name_sz < 1)
+      return false;
+
+    ok = vm_rd_char(fd, name_sz, name);
+    if (!ok)
+      return false;
+
+    char *val = malloc(sizeof(char) * name_sz);
+    if (!val)
+      return false;
+
+    memset(val, 0, sizeof(char) * name_sz);
+    memcpy(val, name, sizeof(char) * name_sz);
+    reader->extern_libs[i] = val;
+  }
+
+  return true;
+}