Merge "base: add API to remove file if it exists."

base/file.cpp

@@ -149,5 +149,32 @@ bool WriteFully(int fd, const void* data, size_t byte_count) {
   return true;
 }
 
+bool RemoveFileIfExists(const std::string& path, std::string* err) {
+  struct stat st;
+#if defined(_WIN32)
+  //TODO: Windows version can't handle symbol link correctly.
+  int result = stat(path.c_str(), &st);
+  bool file_type_removable = (result == 0 && S_ISREG(st.st_mode));
+#else
+  int result = lstat(path.c_str(), &st);
+  bool file_type_removable = (result == 0 && (S_ISREG(st.st_mode) || S_ISLNK(st.st_mode)));
+#endif
+  if (result == 0) {
+    if (!file_type_removable) {
+      if (err != nullptr) {
+        *err = "is not a regular or symbol link file";
+      }
+      return false;
+    }
+    if (unlink(path.c_str()) == -1) {
+      if (err != nullptr) {
+        *err = strerror(errno);
+      }
+      return false;
+    }
+  }
+  return true;
+}
+
 }  // namespace base
 }  // namespace android

base/file_test.cpp

@@ -96,3 +96,17 @@ TEST(file, WriteFully) {
   s.resize(1024);
   ASSERT_FALSE(android::base::ReadFully(tf.fd, &s[0], s.size()));
 }
+
+TEST(file, RemoveFileIfExist) {
+  TemporaryFile tf;
+  ASSERT_TRUE(tf.fd != -1);
+  close(tf.fd);
+  tf.fd = -1;
+  std::string err;
+  ASSERT_TRUE(android::base::RemoveFileIfExists(tf.path, &err)) << err;
+  ASSERT_TRUE(android::base::RemoveFileIfExists(tf.path));
+  TemporaryDir td;
+  ASSERT_FALSE(android::base::RemoveFileIfExists(td.path));
+  ASSERT_FALSE(android::base::RemoveFileIfExists(td.path, &err));
+  ASSERT_EQ("is not a regular or symbol link file", err);
+}

base/include/android-base/file.h

@@ -37,6 +37,8 @@ bool WriteStringToFile(const std::string& content, const std::string& path,
 bool ReadFully(int fd, void* data, size_t byte_count);
 bool WriteFully(int fd, const void* data, size_t byte_count);
 
+bool RemoveFileIfExists(const std::string& path, std::string* err = nullptr);
+
 }  // namespace base
 }  // namespace android