Making the hashing buffer reusable instead of malloc every file

arena.h

@@ -293,7 +293,8 @@ typedef enum arena_commit_policy {
 typedef struct arena_params {
   u64 reserve_size; // size of one arena block
   u64 commit_size;  // initial commit size
-  u64 align;        // allocation alignment (0 = default)
+  u64 align; // allocation alignment, 0 to disable and ARENA_ALIGN to align
+             // according to architecture
 
   // Element size rules:
   // - stack mode        : push_size > 0 (mandatory)

binaries/changelog.txt

@@ -7,7 +7,6 @@ v2.0: Multi threaded scan
 v2.1: Uses AVX2 instead of SSE2
 
 v3.0: Simple mutex/critical section based MPMC queue
-reusable hashing buffer
 
 v3.1: Lock free MPMC queue Vyukov-style
 
@@ -22,5 +21,7 @@ Reorder helper functions
 v3.4: Rewriting hash_worker() to export file_hashes.txt
 
 v4.0: 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
+Using #pragma once to ensure that a given header file is included only once in a single compilation unit
-forcing xxhash to use the stack instead of the heap
+Forcing xxhash to use the stack instead of the heap
+Making the hashing buffer reusable instead of malloc every file
+Implementing a general purpose arena to replace small allocations

platform.h

@@ -21,29 +21,6 @@ typedef struct FileEntry {
   char owner[128];        // resolved owner name
 } FileEntry;
 
-/* File path and metadata */
-static void normalize_path(char *p) {
-  char *src = p;
-  char *dst = p;
-  int prev_slash = 0;
-
-  while (*src) {
-    char c = *src++;
-
-    if (c == '\\' || c == '/') {
-      if (!prev_slash) {
-        *dst++ = '/';
-        prev_slash = 1;
-      }
-    } else {
-      *dst++ = c;
-      prev_slash = 0;
-    }
-  }
-
-  *dst = '\0';
-}
-
 void platform_get_file_times(const char *path, uint64_t *out_created,
                              uint64_t *out_modified);
 void platform_get_file_owner(const char *path, char *out_owner,
@@ -68,7 +45,7 @@ static double timer_stop(HiResTimer *t) {
 }
 
 // ============================================================
-// Simple Mutex-Based MPMC Queue (FileEntry*)
+// Simple lock free MPMC Queue
 // ============================================================
 
 typedef struct {
@@ -127,25 +104,3 @@ typedef struct DirQueue {
   pthread_cond_t cond;
 #endif
 } DirQueue;
-
-/* Hashing */
-typedef struct Job {
-  FileEntry *file;
-  struct Job *next;
-} Job;
-
-typedef struct {
-  Job *head;
-  Job *tail;
-  CRITICAL_SECTION cs;
-  CONDITION_VARIABLE cv;
-  atomic_size_t count; // queued jobs
-  int stop;
-} JobQueue;
-
-typedef struct {
-  JobQueue *queue;
-  atomic_size_t *done_counter;
-  size_t total_jobs;
-  atomic_int *live_workers;
-} WorkerArg;

platform_windows.c

@@ -1,3 +1,4 @@
+#include "arena.h"
 #include "platform.h"
 
 // ----------------------------- Globals ------------------------------------
@@ -5,19 +6,29 @@ static atomic_uint_fast64_t g_files_found = 0;
 static atomic_uint_fast64_t g_files_hashed = 0;
 static atomic_uint_fast64_t g_bytes_processed = 0;
 static atomic_int g_scan_done = 0;
-// __________________________________________________________________________
 
-// ----------------------------- Utils --------------------------------------
+// ============================= Utils ======================================
-static void perror_exit(const char *msg) {
+// ----------------------------- Normalize path --------------
-  perror(msg);
+static void normalize_path(char *p) {
-  exit(1);
+  char *src = p;
+  char *dst = p;
+  int prev_slash = 0;
+
+  while (*src) {
+    char c = *src++;
+
+    if (c == '\\' || c == '/') {
+      if (!prev_slash) {
+        *dst++ = '/';
+        prev_slash = 1;
+      }
+    } else {
+      *dst++ = c;
+      prev_slash = 0;
+    }
   }
 
-static void *xmalloc(size_t n) {
+  *dst = '\0';
-  void *p = malloc(n);
-  if (!p)
-    perror_exit("malloc");
-  return p;
 }
 
 // ----------------------------- Convert filetime to epoch --------------
@@ -29,7 +40,6 @@ static uint64_t filetime_to_epoch(const FILETIME *ft) {
   // Windows epoch (1601) → Unix epoch (1970)
   return (ull.QuadPart - 116444736000000000ULL) / 10000000ULL;
 }
-
 // ----------------------------- Format time helper -------------------------
 static void format_time(uint64_t t, char *out, size_t out_sz) {
   if (t == 0) {
@@ -258,6 +268,7 @@ FileEntry *mpmc_pop(MPMCQueue *q) {
   return data;
 }
 
+// --------------- parallel directory scanning ----------------
 // Add queue helper functions
 static void dirqueue_push(DirQueue *q, const char *path) {
   EnterCriticalSection(&q->cs);
@@ -375,7 +386,7 @@ void scan_folder_windows_parallel(const char *base, DirQueue *q) {
 }
 
 // ----------------------------- Hashing helpers -----------------------------
-static void xxh3_hash_file_stream(const char *path, char *out_hex) {
+static void xxh3_hash_file_stream(const char *path, char *out_hex, BYTE *buf) {
   // compute XXH3_128 over file. POSIX and Windows use standard reads in this
   // helper.
   // On Windows try to use overlapped synchronous chunked reads for higher
@@ -391,7 +402,6 @@ static void xxh3_hash_file_stream(const char *path, char *out_hex) {
   XXH3_state_t state;
   XXH3_128bits_reset(&state);
 
-  BYTE *buf = (BYTE *)malloc(READ_BLOCK);
   DWORD read = 0;
   BOOL ok;
   while (ReadFile(hFile, buf, READ_BLOCK, &read, NULL) && read > 0) {
@@ -400,7 +410,6 @@ static void xxh3_hash_file_stream(const char *path, char *out_hex) {
   }
   h = XXH3_128bits_digest(&state);
   CloseHandle(hFile);
-  free(buf);
   snprintf(out_hex, HASH_STRLEN, "%016llx%016llx", (unsigned long long)h.high64,
            (unsigned long long)h.low64);
 }
@@ -411,6 +420,7 @@ static DWORD WINAPI hash_worker(LPVOID arg) {
   WorkerContext *ctx = (WorkerContext *)arg;
   MPMCQueue *q = ctx->queue;
   mem_arena *local_arena = ctx->arena;
+  BYTE *buf = (BYTE *)malloc(READ_BLOCK);
 
   for (;;) {
     FileEntry *fe = mpmc_pop(q);
@@ -418,7 +428,7 @@ static DWORD WINAPI hash_worker(LPVOID arg) {
       break;
 
     char hash[HASH_STRLEN];
-    xxh3_hash_file_stream(fe->path, hash);
+    xxh3_hash_file_stream(fe->path, hash, buf);
 
     char created[32], modified[32];
     format_time(fe->created_time, created, sizeof(created));
@@ -440,6 +450,7 @@ static DWORD WINAPI hash_worker(LPVOID arg) {
     free(fe->path);
     free(fe);
   }
+  free(buf);
 
   return 0;
 }
@@ -587,6 +598,23 @@ int main(int argc, char **argv) {
     printf("  - %s\n", folders[i]);
   }
 
+  // -------------------------------
+  // Creating a general purpose arena
+  // -------------------------------
+  arena_params params = {
+      .reserve_size = GiB(1),
+      .commit_size = MiB(16),
+      .align = 0,
+      .push_size = 0,
+      .allow_free_list = true,
+      .allow_swapback = false,
+      .growth_policy = ARENA_GROWTH_NORMAL,
+      .commit_policy = ARENA_COMMIT_LAZY,
+      .max_nbre_blocks = 1,
+  };
+
+  mem_arena *gp_arena = arena_create(&params);
+
   // -------------------------------
   // Detect hardware threads (CPU cores)
   // -------------------------------
@@ -596,7 +624,7 @@ int main(int argc, char **argv) {
   GetLogicalProcessorInformation(NULL, &len);
 
   SYSTEM_LOGICAL_PROCESSOR_INFORMATION *buf =
-      (SYSTEM_LOGICAL_PROCESSOR_INFORMATION *)malloc(len);
+      (SYSTEM_LOGICAL_PROCESSOR_INFORMATION *)arena_push(&gp_arena, len, true);
 
   if (GetLogicalProcessorInformation(buf, &len)) {
     DWORD count = 0;
@@ -608,7 +636,7 @@ int main(int argc, char **argv) {
     if (count > 0)
       hw_threads = count;
   }
-  free(buf);
+  arena_free(&gp_arena, (u8 **)&buf, len);
 
   // Add some extra threads to overlap I/O more aggressively
   size_t num_threads = hw_threads * 2;
@@ -628,19 +656,6 @@ int main(int argc, char **argv) {
   q.active = 0;
 
   // starting hash threads
-
-  arena_params params = {
-      .reserve_size = GiB(1),
-      .commit_size = MiB(16),
-      .align = 0,
-      .push_size = 0,
-      .allow_free_list = true,
-      .allow_swapback = false,
-      .growth_policy = ARENA_GROWTH_NORMAL,
-      .commit_policy = ARENA_COMMIT_LAZY,
-      .max_nbre_blocks = 0,
-  };
-
   WorkerContext workers[num_threads];
 
   for (int i = 0; i < num_threads; i++) {
@@ -648,7 +663,8 @@ int main(int argc, char **argv) {
     workers[i].arena = arena_create(&params);
   }
 
-  HANDLE *hash_threads = malloc(sizeof(HANDLE) * num_threads);
+  HANDLE *hash_threads =
+      arena_push(&gp_arena, sizeof(HANDLE) * num_threads, true);
 
   for (size_t i = 0; i < num_threads; ++i) {
     hash_threads[i] = CreateThread(NULL, 0, hash_worker, &workers[i], 0, NULL);
@@ -665,7 +681,9 @@ int main(int argc, char **argv) {
   if (scan_threads < 2)
     scan_threads = 2;
 
-  HANDLE *scan_tids = malloc(sizeof(HANDLE) * scan_threads);
+  HANDLE *scan_tids =
+      arena_push(&gp_arena, sizeof(HANDLE) * scan_threads, true);
+
   for (size_t i = 0; i < scan_threads; ++i) {
     scan_tids[i] =
         CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)scan_worker, &q, 0, NULL);
@@ -673,7 +691,6 @@ int main(int argc, char **argv) {
 
   WaitForMultipleObjects((DWORD)scan_threads, scan_tids, TRUE, INFINITE);
 
-  // debug
   for (size_t i = 0; i < num_threads; i++) {
     mpmc_push(&g_file_queue, NULL);
   }
@@ -682,7 +699,8 @@ int main(int argc, char **argv) {
 
   for (size_t i = 0; i < scan_threads; ++i)
     CloseHandle(scan_tids[i]);
-  free(scan_tids);
+
+  arena_free(&gp_arena, (u8 **)&scan_tids, sizeof(HANDLE) * scan_threads);
 
   double scan_seconds = timer_stop(&scan_timer);
   size_t total_found = atomic_load(&g_files_found);
@@ -703,7 +721,7 @@ int main(int argc, char **argv) {
   for (size_t i = 0; i < num_threads; ++i)
     CloseHandle(hash_threads[i]);
 
-  free(hash_threads);
+  arena_free(&gp_arena, (u8 **)&hash_threads, sizeof(HANDLE) * num_threads);
 
   WaitForSingleObject(progress, INFINITE);
   CloseHandle(progress);
@@ -727,14 +745,14 @@ int main(int argc, char **argv) {
 
   for (int i = 0; i < num_threads; i++) {
 
-    mem_arena *arena = workers[i].arena;
+    mem_arena *local_hash_arena = workers[i].arena;
 
     DWORD written;
 
-    u8 *arena_base =
+    u8 *arena_base = (u8 *)local_hash_arena +
-        (u8 *)arena + ALIGN_UP_POW2(sizeof(mem_arena), arena->align);
+                     ALIGN_UP_POW2(sizeof(mem_arena), local_hash_arena->align);
 
-    WriteFile(h, arena_base, (DWORD)arena->pos, &written, NULL);
+    WriteFile(h, arena_base, (DWORD)local_hash_arena->pos, &written, NULL);
   }
 
   // done time