1 files changed, 182 insertions, 0 deletions
diff --git a/xpcom/tests/gtest/TestLogging.cpp b/xpcom/tests/gtest/TestLogging.cpp
new file mode 100644
index 0000000000..0eb2b7a152
--- /dev/null
+++ b/xpcom/tests/gtest/TestLogging.cpp
@@ -0,0 +1,182 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "mozilla/Logging.h"
+#include "mozilla/Sprintf.h"
+#include "gtest/gtest.h"
+
+namespace mozilla::detail {
+bool LimitFileToLessThanSize(const char* aFilename, uint32_t aSize,
+                             uint16_t aLongLineSize);
+}
+
+// These format strings result in 1024 byte lines on disk regardless
+// of OS, which makes various file sizes OS-agnostic.
+#ifdef XP_WIN
+#  define WHOLE_LINE "%01022d\n"
+#  define SHORT_LINE "%0510d\n"
+#else
+#  define WHOLE_LINE "%01023d\n"
+#  define SHORT_LINE "%0511d\n"
+#endif
+
+// Write the given number of 1k lines to the given file name.
+void WriteTestLogFile(const char* name, uint32_t numLines) {
+  FILE* f = fopen(name, "w");
+  ASSERT_NE(f, (FILE*)nullptr);
+
+  for (uint32_t i = 0; i < numLines; i++) {
+    char buf[1024 + 1];
+    SprintfLiteral(buf, WHOLE_LINE, i);
+    EXPECT_TRUE(fputs(buf, f) >= 0);
+  }
+
+  uint64_t size = static_cast<uint64_t>(ftell(f));
+
+  // Close before asserting.
+  EXPECT_FALSE(fclose(f));
+
+  ASSERT_EQ(numLines * 1024, size);
+}
+
+// Assert that the given file name has the expected size and that its
+// first line is the expected line.
+void AssertSizeAndFirstLine(const char* name, uint32_t expectedSize,
+                            const char* expectedLine) {
+  FILE* f = fopen(name, "r");
+  ASSERT_NE(f, (FILE*)nullptr);
+
+  EXPECT_FALSE(fseek(f, 0, SEEK_END));
+  uint64_t size = static_cast<uint64_t>(ftell(f));
+
+  EXPECT_FALSE(fseek(f, 0, SEEK_SET));
+
+  char line[1024 + 1];
+  const char* result = fgets(line, sizeof(line), f);
+
+  // Close before asserting.
+  EXPECT_FALSE(fclose(f));
+
+  ASSERT_NE(result, nullptr);
+  ASSERT_EQ(expectedSize, size);
+  ASSERT_STREQ(expectedLine, line);
+}
+
+TEST(Logging, DoesNothingWhenNotNeededExact)
+{
+  char nameBuf[2048];
+  SprintfLiteral(
+      nameBuf, "%s_%s.moz_log",
+      testing::UnitTest::GetInstance()->current_test_info()->test_case_name(),
+      testing::UnitTest::GetInstance()->current_test_info()->name());
+
+  WriteTestLogFile(nameBuf, 256);
+
+  // Here the log file is exactly the allowed size.  It shouldn't be limited.
+  ASSERT_TRUE(
+      mozilla::detail::LimitFileToLessThanSize(nameBuf, 256 * 1024, 1024));
+
+  char expectedLine[1024 + 1];
+  SprintfLiteral(expectedLine, WHOLE_LINE, 0);
+
+  AssertSizeAndFirstLine(nameBuf, 256 * 1024, expectedLine);
+
+  EXPECT_FALSE(remove(nameBuf));
+}
+
+TEST(Logging, DoesNothingWhenNotNeededInexact)
+{
+  char nameBuf[2048];
+  SprintfLiteral(
+      nameBuf, "%s_%s.moz_log",
+      testing::UnitTest::GetInstance()->current_test_info()->test_case_name(),
+      testing::UnitTest::GetInstance()->current_test_info()->name());
+
+  WriteTestLogFile(nameBuf, 200);
+
+  // Here the log file is strictly less than the allowed size.  It shouldn't be
+  // limited.
+  ASSERT_TRUE(
+      mozilla::detail::LimitFileToLessThanSize(nameBuf, 256 * 1024, 1024));
+
+  char expectedLine[1024 + 1];
+  SprintfLiteral(expectedLine, WHOLE_LINE, 0);
+
+  AssertSizeAndFirstLine(nameBuf, 200 * 1024, expectedLine);
+
+  EXPECT_FALSE(remove(nameBuf));
+}
+
+TEST(Logging, LimitsToLessThanSize)
+{
+  char nameBuf[2048];
+  SprintfLiteral(
+      nameBuf, "%s_%s.moz_log",
+      testing::UnitTest::GetInstance()->current_test_info()->test_case_name(),
+      testing::UnitTest::GetInstance()->current_test_info()->name());
+
+  WriteTestLogFile(nameBuf, 300);
+
+  ASSERT_TRUE(
+      mozilla::detail::LimitFileToLessThanSize(nameBuf, 256 * 1024, 1024));
+
+  char expectedLine[1024 + 1];
+  SprintfLiteral(expectedLine, WHOLE_LINE, 300 - 256);
+
+  AssertSizeAndFirstLine(nameBuf, 256 * 1024, expectedLine);
+
+  EXPECT_FALSE(remove(nameBuf));
+}
+
+TEST(Logging, MayCutLongLinesExact)
+{
+  char nameBuf[2048];
+  SprintfLiteral(
+      nameBuf, "%s_%s.moz_log",
+      testing::UnitTest::GetInstance()->current_test_info()->test_case_name(),
+      testing::UnitTest::GetInstance()->current_test_info()->name());
+
+  WriteTestLogFile(nameBuf, 300);
+
+  char expectedLine[1024 + 1];
+
+  ASSERT_TRUE(mozilla::detail::LimitFileToLessThanSize(
+      nameBuf, (256 * 1024) - 512, 512));
+
+  SprintfLiteral(expectedLine, SHORT_LINE, 300 - 256);
+
+  // The line to be cut ends "...044\n."  We read 512 bytes (the
+  // buffer size), so we're left with 512 bytes, one of which is the
+  // newline.
+  AssertSizeAndFirstLine(nameBuf, 256 * 1024 - 512, expectedLine);
+
+  EXPECT_FALSE(remove(nameBuf));
+}
+
+TEST(Logging, MayCutLongLinesInexact)
+{
+  char nameBuf[2048];
+  SprintfLiteral(
+      nameBuf, "%s_%s.moz_log",
+      testing::UnitTest::GetInstance()->current_test_info()->test_case_name(),
+      testing::UnitTest::GetInstance()->current_test_info()->name());
+
+  WriteTestLogFile(nameBuf, 300);
+
+  char expectedLine[1024 + 1];
+
+  ASSERT_TRUE(mozilla::detail::LimitFileToLessThanSize(
+      nameBuf, (256 * 1024) - 512, 512));
+
+  SprintfLiteral(expectedLine, SHORT_LINE, 300 - 256);
+
+  // We read 512 bytes (the buffer size), so we're left with 512
+  // bytes, one of which is the newline.  Notice that the limited size
+  // is smaller than the requested size.
+  AssertSizeAndFirstLine(nameBuf, 256 * 1024 - 512, expectedLine);
+
+  EXPECT_FALSE(remove(nameBuf));
+}