tests: Add fuzzing harness for CAutoFile (streams.h)

src/test/fuzz/autofile.cpp

@@ -0,0 +1,72 @@
+// Copyright (c) 2020 The Bitcoin Core developers
+// Distributed under the MIT software license, see the accompanying
+// file COPYING or http://www.opensource.org/licenses/mit-license.php.
+
+#include <optional.h>
+#include <streams.h>
+#include <test/fuzz/FuzzedDataProvider.h>
+#include <test/fuzz/fuzz.h>
+#include <test/fuzz/util.h>
+
+#include <array>
+#include <cstdint>
+#include <iostream>
+#include <optional>
+#include <string>
+#include <vector>
+
+void test_one_input(const std::vector<uint8_t>& buffer)
+{
+    FuzzedDataProvider fuzzed_data_provider{buffer.data(), buffer.size()};
+    FuzzedAutoFileProvider fuzzed_auto_file_provider = ConsumeAutoFile(fuzzed_data_provider);
+    CAutoFile auto_file = fuzzed_auto_file_provider.open();
+    while (fuzzed_data_provider.ConsumeBool()) {
+        switch (fuzzed_data_provider.ConsumeIntegralInRange<int>(0, 5)) {
+        case 0: {
+            std::array<uint8_t, 4096> arr{};
+            try {
+                auto_file.read((char*)arr.data(), fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096));
+            } catch (const std::ios_base::failure&) {
+            }
+            break;
+        }
+        case 1: {
+            const std::array<uint8_t, 4096> arr{};
+            try {
+                auto_file.write((const char*)arr.data(), fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096));
+            } catch (const std::ios_base::failure&) {
+            }
+            break;
+        }
+        case 2: {
+            try {
+                auto_file.ignore(fuzzed_data_provider.ConsumeIntegralInRange<size_t>(0, 4096));
+            } catch (const std::ios_base::failure&) {
+            }
+            break;
+        }
+        case 3: {
+            auto_file.fclose();
+            break;
+        }
+        case 4: {
+            ReadFromStream(fuzzed_data_provider, auto_file);
+            break;
+        }
+        case 5: {
+            WriteToStream(fuzzed_data_provider, auto_file);
+            break;
+        }
+        }
+    }
+    (void)auto_file.Get();
+    (void)auto_file.GetType();
+    (void)auto_file.GetVersion();
+    (void)auto_file.IsNull();
+    if (fuzzed_data_provider.ConsumeBool()) {
+        FILE* f = auto_file.release();
+        if (f != nullptr) {
+            fclose(f);
+        }
+    }
+}