[util] Add current_date_str() platform method

Will be used for metadata on new presets.

avs/platform.h

@@ -62,6 +62,13 @@ uint64_t timer_us();
  */
 double timer_us_precision();
 
+/**
+ * Return a string pointer with the current date in the format "YYYY-MM-DD" (11 bytes).
+ * The data is stored in a static buffer, so the return pointer is always the same, but
+ * its contents are not guaranteed to stay the same between calls to this function.
+ */
+const char* current_date_str();
+
 /**
  * Create a new lock object.
  */

avs/platform_linux.c

@@ -12,7 +12,7 @@
 #include <sys/mman.h>  // mprotect flags
 #include <sys/stat.h>  // mkdir()
 
-/* timers */
+/* timers & time */
 
 uint64_t timer_ms() {
     struct timespec ts;
@@ -38,6 +38,19 @@ double timer_us_precision() {
     return ts.tv_sec * 1000.0 * 1000.0 + (double)ts.tv_nsec / 1000.0;
 }
 
+const char* current_date_str() {
+    static char date_str[11];
+    time_t t = time(NULL);
+    struct tm date = *localtime(&t);
+    snprintf(date_str,
+             11,
+             "%04d-%02d-%02d",
+             date.tm_year + 1900,
+             date.tm_mon + 1,
+             date.tm_mday);
+    return date_str;
+}
+
 /* locking */
 
 #define PTHREAD_LOCK(lock) ((pthread_mutex_t*)(lock))

avs/platform_win32.c

@@ -5,7 +5,7 @@
 #include <stdio.h>
 #include <windowsx.h>
 
-/* timers */
+/* timers & time */
 
 static int64_t timer_highres_ticks_per_us = 0;
 
@@ -36,6 +36,14 @@ double timer_us_precision() {
     return 1.0f / (double)timer_highres_ticks_per_us;
 }
 
+const char* current_date_str() {
+    static char date_str[11];
+    SYSTEMTIME date;
+    GetLocalTime(&date);
+    snprintf(date_str, 11, "%04d-%02d-%02d", date.wYear, date.wMonth, date.wDay);
+    return date_str;
+}
+
 /* locking */
 
 #define WIN_LOCK(lock) ((CRITICAL_SECTION*)(lock))