Keep the ReadFileToString/ReadFdToString overhead down.
Bug: https://code.google.com/p/android/issues/detail?id=258500
Bug: http://b/36046324
Test: ran tests
Change-Id: I40e76a6dd164ea9a5e8e18159f543e1bb221dcba
diff --git a/base/file_test.cpp b/base/file_test.cpp
index 266131e..02b431d 100644
--- a/base/file_test.cpp
+++ b/base/file_test.cpp
@@ -214,3 +214,46 @@
EXPECT_EQ(".", android::base::Dirname("sh"));
EXPECT_EQ("/system/bin", android::base::Dirname("/system/bin/sh/"));
}
+
+TEST(file, ReadFileToString_capacity) {
+ TemporaryFile tf;
+ ASSERT_TRUE(tf.fd != -1);
+
+ // For a huge file, the overhead should still be small.
+ std::string s;
+ size_t size = 16 * 1024 * 1024;
+ ASSERT_TRUE(android::base::WriteStringToFile(std::string(size, 'x'), tf.path));
+ ASSERT_TRUE(android::base::ReadFileToString(tf.path, &s));
+ EXPECT_EQ(size, s.size());
+ EXPECT_LT(s.capacity(), size + 16);
+
+ // Even for weird badly-aligned sizes.
+ size += 12345;
+ ASSERT_TRUE(android::base::WriteStringToFile(std::string(size, 'x'), tf.path));
+ ASSERT_TRUE(android::base::ReadFileToString(tf.path, &s));
+ EXPECT_EQ(size, s.size());
+ EXPECT_LT(s.capacity(), size + 16);
+
+ // We'll shrink an enormous string if you read a small file into it.
+ size = 64;
+ ASSERT_TRUE(android::base::WriteStringToFile(std::string(size, 'x'), tf.path));
+ ASSERT_TRUE(android::base::ReadFileToString(tf.path, &s));
+ EXPECT_EQ(size, s.size());
+ EXPECT_LT(s.capacity(), size + 16);
+}
+
+TEST(file, ReadFileToString_capacity_0) {
+ TemporaryFile tf;
+ ASSERT_TRUE(tf.fd != -1);
+
+ // Because /proc reports its files as zero-length, we don't actually trust
+ // any file that claims to be zero-length. Rather than add increasingly
+ // complex heuristics for shrinking the passed-in string in that case, we
+ // currently leave it alone.
+ std::string s;
+ size_t initial_capacity = s.capacity();
+ ASSERT_TRUE(android::base::WriteStringToFile("", tf.path));
+ ASSERT_TRUE(android::base::ReadFileToString(tf.path, &s));
+ EXPECT_EQ(0U, s.size());
+ EXPECT_EQ(initial_capacity, s.capacity());
+}