aflags: read protos from all containers

Create one library for reading protos from all containers, instead of
having numerous libraries perform the same logic. For Java, we will
create a similar library reusing the same
partition_aconfig_flags_paths.txt.

Bug: 324436145
Test: adb shell aflags list # Confirm that various containers appear
Change-Id: I924e281a50f9a609e1c07c03267eebe3dce52752

tools/aconfig/aconfig_device_paths/Android.bp

@@ -0,0 +1,38 @@
+// Copyright (C) 2024 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.
+
+package {
+    default_applicable_licenses: ["Android-Apache-2.0"],
+}
+
+rust_defaults {
+    name: "libaconfig_device_paths.defaults",
+    edition: "2021",
+    clippy_lints: "android",
+    lints: "android",
+    srcs: ["src/lib.rs"],
+    rustlibs: [
+        "libaconfig_protos",
+        "libanyhow",
+        "libprotobuf",
+        "libregex",
+    ],
+}
+
+rust_library {
+    name: "libaconfig_device_paths",
+    crate_name: "aconfig_device_paths",
+    host_supported: true,
+    defaults: ["libaconfig_device_paths.defaults"],
+}

tools/aconfig/aconfig_device_paths/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "aconfig_device_paths"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0.82"

tools/aconfig/aconfig_device_paths/partition_aconfig_flags_paths.txt

@@ -0,0 +1,6 @@
+[
+    "/system/etc/aconfig_flags.pb",
+    "/system_ext/etc/aconfig_flags.pb",
+    "/product/etc/aconfig_flags.pb",
+    "/vendor/etc/aconfig_flags.pb",
+]

tools/aconfig/aconfig_device_paths/src/lib.rs

@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2024 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.
+ */
+
+//! Library for finding all aconfig on-device protobuf file paths.
+
+use anyhow::Result;
+use std::path::PathBuf;
+
+use std::fs;
+
+/// Determine all paths that contain an aconfig protobuf file.
+pub fn parsed_flags_proto_paths() -> Result<Vec<PathBuf>> {
+    let mut result: Vec<PathBuf> = include!("../partition_aconfig_flags_paths.txt")
+        .map(|s| PathBuf::from(s.to_string()))
+        .to_vec();
+    for dir in fs::read_dir("/apex")? {
+        let dir = dir?;
+
+        // Only scan the currently active version of each mainline module; skip the @version dirs.
+        if dir.file_name().as_encoded_bytes().iter().any(|&b| b == b'@') {
+            continue;
+        }
+
+        let mut path = PathBuf::from("/apex");
+        path.push(dir.path());
+        path.push("etc");
+        path.push("aconfig_flags.pb");
+        if path.exists() {
+            result.push(path);
+        }
+    }
+
+    Ok(result)
+}