Move libsystemproperties to external

native/jni/external/systemproperties/include/system_properties/prop_info.h

@@ -0,0 +1,90 @@
+/*
+ * Copyright (C) 2008 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.
+ */
+
+#pragma once
+
+#include <stdatomic.h>
+#include <stdint.h>
+//#include <sys/system_properties.h>
+#include "../system_properties.h"
+
+#include "private/bionic_macros.h"
+
+// The C11 standard doesn't allow atomic loads from const fields,
+// though C++11 does.  Fudge it until standards get straightened out.
+static inline uint_least32_t load_const_atomic(const atomic_uint_least32_t* s, memory_order mo) {
+  atomic_uint_least32_t* non_const_s = const_cast<atomic_uint_least32_t*>(s);
+  return atomic_load_explicit(non_const_s, mo);
+}
+
+struct prop_info {
+  // Read only properties will not set anything but the bottom most bit of serial and the top byte.
+  // We borrow the 2nd from the top byte for extra flags, and use the bottom most bit of that for
+  // our first user, kLongFlag.
+  constexpr static uint32_t kLongFlag = 1 << 16;
+
+  // The error message fits in part of a union with the previous 92 char property value so there
+  // must be room left over after the error message for the offset to the new longer property value
+  // and future expansion fields if needed. Note that this value cannot ever increase.  The offset
+  // to the new longer property value appears immediately after it, so an increase of this size will
+  // break compatibility.
+  constexpr static size_t kLongLegacyErrorBufferSize = 56;
+
+ public:
+  atomic_uint_least32_t serial;
+  // we need to keep this buffer around because the property
+  // value can be modified whereas name is constant.
+  union {
+    char value[PROP_VALUE_MAX];
+    struct {
+      char error_message[kLongLegacyErrorBufferSize];
+      uint32_t offset;
+    } long_property;
+  };
+  char name[0];
+
+  bool is_long() const {
+    return (load_const_atomic(&serial, memory_order_relaxed) & kLongFlag) != 0;
+  }
+
+  const char* long_value() const {
+    // We can't store pointers here since this is shared memory that will have different absolute
+    // pointers in different processes.  We don't have data_ from prop_area, but since we know
+    // `this` is data_ + some offset and long_value is data_ + some other offset, we calculate the
+    // offset from `this` to long_value and store it as long_property.offset.
+    return reinterpret_cast<const char*>(this) + long_property.offset;
+  }
+
+  prop_info(const char* name, uint32_t namelen, const char* value, uint32_t valuelen);
+  prop_info(const char* name, uint32_t namelen, uint32_t long_offset);
+
+ private:
+  BIONIC_DISALLOW_IMPLICIT_CONSTRUCTORS(prop_info);
+};
+
+static_assert(sizeof(prop_info) == 96, "sizeof struct prop_info must be 96 bytes");