hashers now use thread local arena

Instead of writing directly to file_hashes.txt, hash_workers now are
using a local arena, writing everything once at the end

using #pragma once to ensure that a given header file is included only
once in a single compilation unit

platform.h

@@ -1,39 +1,10 @@
-#pragma once
+#pragma once // ensure that a given header file is included only once in a
+             // single compilation unit
 
-#include <immintrin.h>
-#include <stdatomic.h>
-#include <stdint.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <time.h>
-
-#if defined(_WIN32) || defined(_WIN64)
-#define PLATFORM_WINDOWS 1
-#include <aclapi.h>
-#include <fcntl.h>
-#include <io.h>
-#include <sys/stat.h>
-#include <sys/types.h>
-#include <windows.h>
-
-#define strdup _strdup
-#else
-#include <dirent.h>
-#include <fcntl.h>
-#include <pthread.h>
-#include <pwd.h>
-#include <sys/stat.h>
-#include <unistd.h>
-#endif
-
-#define XXH_VECTOR                                                             \
-  XXH_AVX2 // not recommanded to compile with gcc see xxhash.h line 4082
-           // Must compile with /arch:AVX2 in clang-cl or -mavx2 in clang/gcc
-#define XXH_INLINE_ALL
-#include "xxhash.c"
-#include "xxhash.h"
+#include "arena.h"
+#include "base.h"
 
+#include "arena.c"
 // ----------------------------- Config -------------------------------------
 #define FILE_HASHES_TXT "file_hashes.txt"
 #define HASH_STRLEN 33 // 128-bit hex (32 chars) + null
@@ -124,6 +95,11 @@ typedef struct {
 
 static MPMCQueue g_file_queue;
 
+typedef struct {
+  MPMCQueue *queue;
+  mem_arena *arena;
+} WorkerContext;
+
 /* Scan folders */
 typedef struct DirQueue DirQueue;