util: Add function debug_get_option_cached os_get_option_cached

This is used to fixes DEBUG_GET_ONCE_*_OPTION macros latter

Signed-off-by: Yonggang Luo <luoyonggang@gmail.com>
Acked-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19554>

src/util/os_misc.c

@@ -26,9 +26,12 @@
  **************************************************************************/
 
 
+#include "hash_table.h"
+#include "macros.h"
 #include "os_misc.h"
 #include "os_file.h"
-#include "macros.h"
+#include "ralloc.h"
+#include "simple_mtx.h"
 
 #include <stdarg.h>
 
@@ -182,6 +185,49 @@ os_get_option(const char *name)
    return opt;
 }
 
+static struct hash_table *options_tbl;
+static simple_mtx_t options_tbl_mtx = SIMPLE_MTX_INITIALIZER;
+
+/**
+ * NOTE: The strings that allocated with ralloc_strdup(options_tbl, ...)
+ * are freed by _mesa_hash_table_destroy automatically
+ */
+static void
+options_tbl_fini(void)
+{
+   _mesa_hash_table_destroy(options_tbl, NULL);
+}
+
+const char *
+os_get_option_cached(const char *name)
+{
+   char *opt = NULL;
+   simple_mtx_lock(&options_tbl_mtx);
+   if (!options_tbl) {
+      options_tbl = _mesa_hash_table_create(NULL, _mesa_hash_string,
+            _mesa_key_string_equal);
+      if (options_tbl == NULL) {
+         goto exit_mutex;
+      }
+      atexit(options_tbl_fini);
+   }
+   struct hash_entry *entry = _mesa_hash_table_search(options_tbl, name);
+   if (entry) {
+      opt = entry->data;
+      goto exit_mutex;
+   }
+
+   char *name_dup = ralloc_strdup(options_tbl, name);
+   if (name_dup == NULL) {
+      goto exit_mutex;
+   }
+   opt = ralloc_strdup(options_tbl, os_get_option(name));
+   _mesa_hash_table_insert(options_tbl, name_dup, (void *)opt);
+exit_mutex:
+   simple_mtx_unlock(&options_tbl_mtx);
+   return opt;
+}
+
 /**
  * Return the size of the total physical memory.
  * \param size returns the size of the total physical memory

src/util/os_misc.h

@@ -90,6 +90,16 @@ os_log_message(const char *message);
 const char *
 os_get_option(const char *name);
 
+/*
+ * Get an option. Should return NULL if specified option is not set.
+ * It's will save the option into hash table for the first time, and
+ * for latter calling, it's will return the value comes from hash table
+ * directly, and the returned value will always be valid before program exit
+ * The disadvantage is that setenv, unsetenv, putenv won't take effect
+ * after this function is called
+ */
+const char *
+os_get_option_cached(const char *name);
 
 /*
  * Get the total amount of physical memory available on the system.

src/util/u_debug.c

@@ -166,6 +166,23 @@ debug_get_option(const char *name, const char *dfault)
 }
 
 
+const char *
+debug_get_option_cached(const char *name, const char *dfault)
+{
+   const char *result;
+
+   result = os_get_option_cached(name);
+   if (!result)
+      result = dfault;
+
+   if (debug_get_option_should_print())
+      debug_printf("%s: %s = %s\n", __FUNCTION__, name,
+                   result ? result : "(null)");
+
+   return result;
+}
+
+
 /**
  * Reads an environment variable and interprets its value as a boolean.
  * Recognizes 0/n/no/f/false case insensitive as false.

src/util/u_debug.h

@@ -355,6 +355,9 @@ comma_separated_list_contains(const char *list, const char *s);
 const char *
 debug_get_option(const char *name, const char *dfault);
 
+const char *
+debug_get_option_cached(const char *name, const char *dfault);
+
 bool
 debug_get_bool_option(const char *name, bool dfault);