Making the hashing buffer reusable instead of malloc every file

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 +21,6 @@ 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
-forcing xxhash to use the stack instead of the heap
+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
+Making the hashing buffer reusable instead of malloc every file

platform_windows.c

@@ -375,7 +375,7 @@ 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 +391,7 @@ 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);
+  // BYTE *buf = (BYTE *)malloc(READ_BLOCK);
   DWORD read = 0;
   BOOL ok;
   while (ReadFile(hFile, buf, READ_BLOCK, &read, NULL) && read > 0) {
@@ -400,7 +400,7 @@ static void xxh3_hash_file_stream(const char *path, char *out_hex) {
   }
   h = XXH3_128bits_digest(&state);
   CloseHandle(hFile);
-  free(buf);
+  // free(buf);
   snprintf(out_hex, HASH_STRLEN, "%016llx%016llx", (unsigned long long)h.high64,
            (unsigned long long)h.low64);
 }
@@ -411,6 +411,7 @@ 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 +419,7 @@ 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 +441,7 @@ static DWORD WINAPI hash_worker(LPVOID arg) {
     free(fe->path);
     free(fe);
   }
+  free(buf);
 
   return 0;
 }