commit a29f3c029a4c62e1140382800d1505c1f3f4a98d
author Yurii Zubrytskyi <zyy@google.com> Fri May 12 16:05:13 2023 -0700
committer Yurii Zubrytskyi <zyy@google.com> Fri May 12 16:05:13 2023 -0700
tree ae5f88560aaeeafe69c836aa2a6147c54922b1f9
parent 7d70bc534c01699acd0b9a59d4c2a6da5564dd48

idmap2 code cleanup

- proper use of random number generators in FileUtils
- get rid of <iostream> include where possible
- replace std::endl with '\n' as we don't really need stream
  flushes
- added a few missed moves

Bug: 282215580
Test: build, UTs and boot
Change-Id: I2dbe5e7c240acd0f344158ae6d9f2ee2b9c2c6ab

cmds/idmap2/libidmap2/FileUtils.cpp

diff --git a/cmds/idmap2/libidmap2/FileUtils.cpp b/cmds/idmap2/libidmap2/FileUtils.cpp
index 98a4cea..bc5654a 100644
--- a/cmds/idmap2/libidmap2/FileUtils.cpp
+++ b/cmds/idmap2/libidmap2/FileUtils.cpp
@@ -16,11 +16,13 @@
 
 #include "idmap2/FileUtils.h"
 
+#include <random>
 #include <string>
+#include <string_view>
 
 #include "android-base/file.h"
 #include "android-base/macros.h"
-#include "android-base/stringprintf.h"
+#include "android-base/strings.h"
 #include "private/android_filesystem_config.h"
 
 namespace android::idmap2::utils {
@@ -33,9 +35,9 @@
     return false;
   }
 
-  const std::string cache_subdir = base::StringPrintf("%s/", kIdmapCacheDir);
-  if (canonical_path == kIdmapCacheDir ||
-      canonical_path.compare(0, cache_subdir.size(), cache_subdir) == 0) {
+  if (base::StartsWith(canonical_path, kIdmapCacheDir) &&
+      (canonical_path.size() == kIdmapCacheDir.size() ||
+       canonical_path[kIdmapCacheDir.size()] == '/')) {
     // limit access to /data/resource-cache to root and system
     return uid == AID_ROOT || uid == AID_SYSTEM;
   }
@@ -47,17 +49,17 @@
 }
 #endif
 
-std::string RandomStringForPath(const size_t length) {
-  constexpr char kChars[] = "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
-  constexpr size_t kCharLastIndex = sizeof(kChars) - 1;
+std::string RandomStringForPath(size_t length) {
+  constexpr std::string_view kChars =
+      "0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
 
   std::string out_rand;
-  out_rand.reserve(length);
+  out_rand.resize(length);
 
-  std::random_device rd;
-  std::uniform_int_distribution<int> dist(0, kCharLastIndex);
+  static thread_local std::random_device rd;
+  std::uniform_int_distribution<int> dist(0, kChars.size() - 1);
   for (size_t i = 0; i < length; i++) {
-    out_rand[i] = kChars[dist(rd) % (kCharLastIndex)];
+    out_rand[i] = kChars[dist(rd)];
   }
   return out_rand;
 }