From f95ae41a9bb6dd30662997823b769e8255122a7a Mon Sep 17 00:00:00 2001
From: Marcus Holland-Moritz <github@mhxnet.de>
Date: Mon, 15 Jan 2024 22:07:13 +0100
Subject: [PATCH] test(filesystem): find_image_offset tests

---
 test/filesystem_test.cpp | 85 ++++++++++++++++++++++++++++++++++++++++
 1 file changed, 85 insertions(+)

diff --git a/test/filesystem_test.cpp b/test/filesystem_test.cpp
index 7527e591..eed28b61 100644
--- a/test/filesystem_test.cpp
+++ b/test/filesystem_test.cpp
@@ -26,9 +26,13 @@
 
 #include <fmt/format.h>
 
+#include <folly/Utility.h>
+
 #include "dwarfs/filesystem_v2.h"
+#include "dwarfs/fstypes.h"
 #include "dwarfs/mmap.h"
 
+#include "mmap_mock.h"
 #include "test_logger.h"
 
 using namespace dwarfs;
@@ -178,3 +182,84 @@ TEST(filesystem, metadata_symlink_unix) {
     EXPECT_EQ(-EINVAL, r.error());
   }
 }
+
+namespace {
+
+std::string valid_v1_header() {
+  section_header hdr;
+  hdr.type = section_type::BLOCK;
+  hdr.compression = compression_type_v1::NONE;
+  hdr.length = 1;
+  std::string buf;
+  buf.resize(8 + sizeof(hdr));
+  std::memcpy(buf.data(), "DWARFS\x02\x01", 8);
+  std::memcpy(buf.data() + 8, &hdr, sizeof(hdr));
+  return buf;
+}
+
+std::string valid_v2_header(uint32_t section_number = 0) {
+  section_header_v2 hdr;
+  std::memset(&hdr, 0, sizeof(hdr));
+  std::memcpy(hdr.magic, "DWARFS", 6);
+  hdr.major = 2;
+  hdr.minor = 3;
+  hdr.number = section_number;
+  hdr.type = folly::to_underlying(section_type::BLOCK);
+  hdr.compression = folly::to_underlying(compression_type::NONE);
+  hdr.length = 1;
+  std::string buf;
+  buf.resize(sizeof(hdr));
+  std::memcpy(buf.data(), &hdr, sizeof(hdr));
+  return buf;
+}
+
+} // namespace
+
+TEST(filesystem, find_image_offset) {
+  test::test_logger lgr;
+
+  auto make_fs =
+      [&](std::string data,
+          filesystem_options const& opt = {
+              .image_offset = filesystem_options::IMAGE_OFFSET_AUTO}) {
+        return filesystem_v2(
+            lgr, std::make_shared<test::mmap_mock>(std::move(data)), opt);
+      };
+
+  auto throws_rt_error = [](auto substr) {
+    return ::testing::ThrowsMessage<runtime_error>(
+        ::testing::HasSubstr(substr));
+  };
+
+  auto throws_no_fs_found = throws_rt_error("no filesystem found");
+  auto throws_no_schema = throws_rt_error("no metadata schema found");
+
+  std::string valid_fs;
+  {
+    mmap mm(test_dir / "unixlink.dwarfs");
+    auto data = mm.span<char>();
+    valid_fs.assign(data.data(), data.size());
+  }
+  auto v1_header = valid_v1_header();
+  auto v2_header = valid_v2_header();
+  auto prefix = "DWARFS\x02\x02 DWARFS\x02\x02 xxxxxxxxxxxxxxxxxxxxDWARFS\x02";
+
+  EXPECT_NO_THROW(make_fs(valid_fs));
+  EXPECT_NO_THROW(make_fs(prefix + valid_fs));
+
+  EXPECT_THAT([&] { make_fs("dwarfs"); }, throws_no_fs_found);
+  EXPECT_THAT([&] { make_fs(v1_header + "X"); }, throws_no_schema);
+  EXPECT_THAT([&] { make_fs(v2_header + "X"); }, throws_no_fs_found);
+  EXPECT_THAT([&] { make_fs(v2_header + "X" + valid_v2_header(1) + "X"); },
+              throws_no_schema);
+  EXPECT_THAT([&] { make_fs(prefix); }, throws_no_fs_found);
+
+  for (size_t len = 0; len < valid_fs.size() - 1; ++len) {
+    auto truncated = valid_fs.substr(0, len);
+    EXPECT_THAT([&] { make_fs(truncated); }, ::testing::Throws<runtime_error>())
+        << "len=" << len;
+    EXPECT_THAT([&] { make_fs(prefix + truncated); },
+                ::testing::Throws<runtime_error>())
+        << "len=" << len;
+  }
+}