apexd: make exception-free

Do not use APIs which can throw exceptions.
- add and use WalkDir() helper instead of directory_iterator
- use noexcept version of is_block_file()

Bug: 124662897
Test: atest apexservice_test
Test: adb shell pm list packages --apex-only (after restart)
Change-Id: Ie42ba763903521c43e21381e3ae9871cd71120fd

2 files changed, 32 insertions, 21 deletions

diff --git a/apexd/apex_database.cpp b/apexd/apex_database.cpp
index d386adbd..53793659 100644
--- a/apexd/apex_database.cpp
+++ b/apexd/apex_database.cpp
@@ -100,10 +100,15 @@ class BlockDevice {
 
   std::vector<BlockDevice> GetSlaves() const {
     std::vector<BlockDevice> slaves;
-    for (auto& p : fs::directory_iterator(SysPath() / "slaves")) {
-      if (fs::is_block_file(kDevBlock / p.path().filename())) {
-        slaves.emplace_back(p.path());
+    std::error_code ec;
+    auto status = WalkDir(SysPath() / "slaves", [&](const auto& entry) {
+      BlockDevice dev(entry);
+      if (fs::is_block_file(dev.DevPath(), ec)) {
+        slaves.push_back(dev);
       }
+    });
+    if (!status.Ok()) {
+      LOG(WARNING) << status.ErrorMessage();
     }
     return slaves;
   }
@@ -142,12 +147,12 @@ StatusOr<inode_t> inodeFor(const std::string& path) {
   return StatusOr<inode_t>(buf.st_dev, buf.st_ino);
 }
 
-// Flattened packages from builtin APEX dirs(/system/apex, /product/apex)
+// Flattened packages from builtin APEX dirs(/system/apex, /product/apex, ...)
 inode_map scanFlattendedPackages() {
   inode_map map;
 
   for (const auto& dir : kApexPackageBuiltinDirs) {
-    ReadDir(dir, [&](const fs::directory_entry& entry) {
+    WalkDir(dir, [&](const fs::directory_entry& entry) {
       const auto& path = entry.path();
       if (isFlattenedApex(path)) {
         auto inode = inodeFor(path);
@@ -155,7 +160,6 @@ inode_map scanFlattendedPackages() {
           map[*inode] = path;
         }
       }
-      return true;
     });
   }
 
diff --git a/apexd/apexd_utils.h b/apexd/apexd_utils.h
index 3ce80541..e97c0ba6 100644
--- a/apexd/apexd_utils.h
+++ b/apexd/apexd_utils.h
@@ -82,33 +82,40 @@ inline int ForkAndRun(const std::vector<std::string>& args,
   return rc;
 }
 
-template <typename FilterFn>
-StatusOr<std::vector<std::string>> ReadDir(const std::string& path,
-                                           FilterFn fn) {
+template <typename Fn>
+Status WalkDir(const std::string& path, Fn fn) {
   namespace fs = std::filesystem;
-  using Status = StatusOr<std::vector<std::string>>;
-
   std::error_code ec;
-  if (!fs::is_directory(path, ec) || ec) {
-    return Status::Fail(StringLog() << "Can't open " << path
-                                    << " for reading : " << ec.message());
-  }
-
-  std::vector<std::string> ret;
   auto it = fs::directory_iterator(path, ec);
   auto end = fs::directory_iterator();
   while (!ec && it != end) {
-    if (fn(*it)) {
-      ret.push_back(it->path());
-    }
+    fn(*it);
     it.increment(ec);
   }
   if (ec) {
     return Status::Fail(StringLog() << "Can't open " << path
                                     << " for reading : " << ec.message());
   }
+  return Status::Success();
+}
+
+template <typename FilterFn>
+StatusOr<std::vector<std::string>> ReadDir(const std::string& path,
+                                           FilterFn fn) {
+  namespace fs = std::filesystem;
+  using Status = StatusOr<std::vector<std::string>>;
+
+  std::vector<std::string> ret;
+  auto status = WalkDir(path, [&](const fs::directory_entry& entry) {
+    if (fn(entry)) {
+      ret.push_back(entry.path());
+    }
+  });
+  if (!status.Ok()) {
+    return Status::Fail(status.ErrorMessage());
+  }
   return Status(std::move(ret));
-}  // namespace apex
+}
 
 inline bool IsEmptyDirectory(const std::string& path) {
   auto res = ReadDir(path, [](auto _) { return true; });