Add `persistprops` to edit persistent properties offline

cmds/Android.bp

@@ -123,3 +123,19 @@ cc_binary {
 		"libhidlbase",
 	],
 }
+
+cc_binary {
+	name: "persistprops",
+	srcs: [
+		"persistent_properties.proto",
+		"persistprops.cpp",
+	],
+	static_executable: true,
+	proto: {
+		type: "lite",
+		static: true,
+	},
+	static_libs: [
+		"libprotobuf-cpp-lite"
+	],
+}

cmds/persistent_properties.proto

@@ -0,0 +1,27 @@
+/*
+ * Copyright (C) 2017 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+syntax = "proto2";
+option optimize_for = LITE_RUNTIME;
+
+message PersistentProperties {
+    message PersistentPropertyRecord {
+        optional string name = 1;
+        optional string value = 2;
+    }
+
+    repeated PersistentPropertyRecord properties = 1;
+}

cmds/persistprops.cpp

@@ -0,0 +1,55 @@
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include "device/phh/treble/cmds/persistent_properties.pb.h"
+#include <algorithm>
+#include <iostream>
+
+int main(int argc, char **argv) {
+	int fd = open("persistent_properties", O_RDWR);
+	off_t size = lseek(fd, 0, SEEK_END);
+	lseek(fd, 0, SEEK_SET);
+	char *data = (char*) malloc(size);
+	int ret = read(fd, data, size);
+
+	PersistentProperties props;
+	bool parsed = props.ParseFromArray(data, size);
+	std::cout << "Currently has " << props.properties_size() << " props." << std::endl;
+	for(auto prop: props.properties()) {
+		std::cout << prop.name() << ":" << prop.value() << std::endl;
+	}
+
+	if(argc == 1) {
+		close(fd);
+		return 0;
+	}
+	if(argc != 3) {
+		std::cout << "Usage: " << argv[0] << " [prop value]" << std::endl;
+		return -1;
+	}
+
+	std::string property(argv[1]);
+	std::string value(argv[2]);
+
+	auto p = props.mutable_properties();
+	auto it = std::find_if(p->begin(), p->end(), [=](const auto& v) { return v.name() == property; });
+	if(it == p->end()) {
+		std::cout << "Property not found, adding it" << std::endl;
+		auto *record = p->Add();;
+		record->set_name(property);
+		record->set_value(value);
+	} else {
+		std::cout << "Property found, replacing it" << std::endl;
+		it->set_value(value);
+	}
+
+	size_t write_size = props.ByteSize();
+	char *write_buffer = (char*) malloc(write_size);
+	props.SerializeToArray(write_buffer, write_size);
+	ftruncate(fd, 0);
+	lseek(fd, 0, SEEK_SET);
+	write(fd, write_buffer, write_size);
+	close(fd);
+}