1 files changed, 76 insertions, 0 deletions
diff --git a/libc/bionic/sysprop_helpers.cpp b/libc/bionic/sysprop_helpers.cpp
new file mode 100644
index 000000000..edae6cc84
--- /dev/null
+++ b/libc/bionic/sysprop_helpers.cpp
@@ -0,0 +1,76 @@
+/*
+ * Copyright (C) 2021 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include "sysprop_helpers.h"
+
+#include <assert.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include "sys/system_properties.h"
+
+static bool get_property_value(const char* property_name, char* dest, size_t dest_size) {
+  assert(property_name && dest && dest_size != 0);
+  const prop_info* prop = __system_property_find(property_name);
+  if (!prop) return false;
+
+  struct PropCbCookie {
+    char* dest;
+    size_t size;
+  };
+  *dest = '\0';
+  PropCbCookie cb_cookie = {dest, dest_size};
+
+  __system_property_read_callback(
+      prop,
+      [](void* cookie, const char* /* name */, const char* value, uint32_t /* serial */) {
+        auto* cb_cookie = reinterpret_cast<PropCbCookie*>(cookie);
+        strncpy(cb_cookie->dest, value, cb_cookie->size);
+      },
+      &cb_cookie);
+  if (*dest != '\0' && *dest != '0') return true;
+
+  return false;
+}
+
+bool get_config_from_env_or_sysprops(const char* env_var_name, const char* const* sys_prop_names,
+                                     size_t sys_prop_names_size, char* options,
+                                     size_t options_size) {
+  const char* env = getenv(env_var_name);
+  if (env && *env != '\0') {
+    strncpy(options, env, options_size);
+    options[options_size - 1] = '\0';  // Ensure null-termination.
+    return true;
+  }
+
+  for (size_t i = 0; i < sys_prop_names_size; ++i) {
+    if (sys_prop_names[i] == nullptr) continue;
+    if (get_property_value(sys_prop_names[i], options, options_size)) return true;
+  }
+  return false;
+}