Add FuzzedDataProvider helper class / single header library.

[Dor1s]

Summary

This class is useful for writing fuzz target that have multiple inputs.

Current CL imports the existing FuzzedDataProvider from Chromium
without any modifications. Feel free to review it thoroughly, if you're
interested, but I'd prefer changing the class in a follow up CL.

The CL also introduces an exhaustive test for the library, as the behavior
of FuzzedDataProvider must not change over time.

In follow up CLs I'm planning on changing some implementation details
(I can share a doc with some comments to be addressed). After that, we
will document how FuzzedDataProvider should be used.

I have tested this on Linux, Windows and Mac platforms.

[Dor1s]

WIP

[Dor1s]

Add the tests.

[Dor1s]

Remove commented line

[Dor1s]

Workaround Windows-specific linking issue.

[Dor1s]

Nico, Reid, Jonathan, I'd greatly appreciate your Windows expertise here. If I remove lines 11-16 from lib/fuzzer/tests/FuzzedDataProviderUnittest.cpp, I'm getting the following link errors on Windows:

C:\src\llvm\build>ninja -v check-fuzzer-unit
[1/3] cmd.exe /C "cd /D C:\src\llvm\build\projects\compiler-rt\lib\fuzzer\tests && C:\src\llvm\build\.\bin\clang.exe -DWIN32 -D_WINDOWS -Wno-unknown-warning-option -DGTEST_NO_LLVM_RAW_OSTREAM=1 -DGTEST_HAS_RTTI=0 -IC:/src/llvm/llvm/utils/unittest/googletest/include -IC:/src/llvm/llvm/utils/unittest/googletest -Wno-deprecated-declarations -IC:/src/llvm/llvm/projects/compiler-rt/lib/fuzzer -fno-rtti -O2 -c -o FuzzedDataProviderTestObjects.FuzzedDataProviderUnittest.cpp.x86_64.o C:/src/llvm/llvm/projects/compiler-rt/lib/fuzzer/tests/FuzzedDataProviderUnittest.cpp"
[2/3] cmd.exe /C "cd /D C:\src\llvm\build\projects\compiler-rt\lib\fuzzer\tests && C:\src\llvm\build\.\bin\clang.exe FuzzedDataProviderTestObjects.FuzzedDataProviderUnittest.cpp.x86_64.o FuzzedDataProviderTestObjects.gtest-all.cc.x86_64.o C:/src/llvm/build/projects/compiler-rt/lib/fuzzer/tests/RTFuzzerTest.x86_64.lib -o C:/src/llvm/build/projects/compiler-rt/lib/fuzzer/tests/./FuzzerUtils-x86_64-Test.exe --driver-mode=g++"
FAILED: projects/compiler-rt/lib/fuzzer/tests/FuzzerUtils-x86_64-Test.exe
cmd.exe /C "cd /D C:\src\llvm\build\projects\compiler-rt\lib\fuzzer\tests && C:\src\llvm\build\.\bin\clang.exe FuzzedDataProviderTestObjects.FuzzedDataProviderUnittest.cpp.x86_64.o FuzzedDataProviderTestObjects.gtest-all.cc.x86_64.o C:/src/llvm/build/projects/compiler-rt/lib/fuzzer/tests/RTFuzzerTest.x86_64.lib -o C:/src/llvm/build/projects/compiler-rt/lib/fuzzer/tests/./FuzzerUtils-x86_64-Test.exe --driver-mode=g++"
   Creating library C:/src/llvm/build/projects/compiler-rt/lib/fuzzer/tests/./FuzzerUtils-x86_64-Test.lib and object C:/src/llvm/build/projects/compiler-rt/lib/fuzzer/tests/./FuzzerUtils-x86_64-Test.exp
FuzzedDataProviderTestObjects.gtest-all.cc.x86_64.o : error LNK2019: unresolved external symbol fdopen referenced in function "void __cdecl testing::internal::DeathTestAbort(class std::basic_string<char,struct std::char_traits<char>,class std::allocator<char> > const &)" (?DeathTestAbort@internal@testing@@YAXAEBV?$basic_string@DU?$char_traits@D@std@@V?$allocator@D@2@@std@@@Z)
FuzzedDataProviderTestObjects.gtest-all.cc.x86_64.o : error LNK2019: unresolved external symbol read referenced in function "protected: void __cdecl testing::internal::DeathTestImpl::ReadAndInterpretStatusByte(void)" (?ReadAndInterpretStatusByte@DeathTestImpl@internal@testing@@IEAAXXZ)
FuzzedDataProviderTestObjects.gtest-all.cc.x86_64.o : error LNK2019: unresolved external symbol close referenced in function "protected: void __cdecl testing::internal::DeathTestImpl::ReadAndInterpretStatusByte(void)" (?ReadAndInterpretStatusByte@DeathTestImpl@internal@testing@@IEAAXXZ)
FuzzedDataProviderTestObjects.gtest-all.cc.x86_64.o : error LNK2019: unresolved external symbol write referenced in function "protected: virtual void __cdecl testing::internal::DeathTestImpl::Abort(enum testing::internal::DeathTest::AbortReason)" (?Abort@DeathTestImpl@internal@testing@@MEAAXW4AbortReason@DeathTest@23@@Z)
FuzzedDataProviderTestObjects.gtest-all.cc.x86_64.o : error LNK2019: unresolved external symbol dup referenced in function "public: __cdecl testing::internal::CapturedStream::CapturedStream(int)" (??0CapturedStream@internal@testing@@QEAA@H@Z)
FuzzedDataProviderTestObjects.gtest-all.cc.x86_64.o : error LNK2019: unresolved external symbol creat referenced in function "public: __cdecl testing::internal::CapturedStream::CapturedStream(int)" (??0CapturedStream@internal@testing@@QEAA@H@Z)
FuzzedDataProviderTestObjects.gtest-all.cc.x86_64.o : error LNK2019: unresolved external symbol dup2 referenced in function "public: __cdecl testing::internal::CapturedStream::CapturedStream(int)" (??0CapturedStream@internal@testing@@QEAA@H@Z)
C:/src/llvm/build/projects/compiler-rt/lib/fuzzer/tests/./FuzzerUtils-x86_64-Test.exe : fatal error LNK1120: 7 unresolved externals
clang: error: linker command failed with exit code 1120 (use -v to see invocation)
ninja: build stopped: subcommand failed.

To me the issue looks like libc (or whatever equivalent it has on Windows) isn't specified as a gtest dependency, that's why symbols like read, write, or dup2 are unresolved. It also looks like libFuzzer has the correct dependencies specified on Windows, and that's why everything works fine if my FuzzedDataProviderUnittest depends on libFuzzer (and actually uses it). However, I was not able to track this down and find any magic dependency that I should specify in the CMakeLists.txt for FuzzedDataProviderUnittest.

Does this look familiar at all? My FuzzedDataProviderUnittest doesn't really need libFuzzer (aka RTFuzzer), it actually needs only lib/fuzzer/utils/FuzzedDataProvider.h and gtest.

[rnk]

In D62733#1535103, @Dor1s wrote:

Nico, Reid, Jonathan, I'd greatly appreciate your Windows expertise here. If I remove lines 11-16 from lib/fuzzer/tests/FuzzedDataProviderUnittest.cpp, I'm getting the following link errors on Windows:

Typically the CRT gets pulled into the link by /defaultlib:libcmt flags in the .drective section of the object file. Objects compiled with clang-cl and cl will have these directives, but objects compiled by plain clang will not, because clang has no flag that the user can use to indicate whether the static or dynamic CRT should be used (/MT vs /MD). That spelling obviously conflicts with the .d file related options -MD, and we never invented a GCC-style spelling, so it doesn't exist, and we also didn't try guessing which CRT is in use. I think that's what's going on here: objects in RTFuzzer are compiled by MSVC, but the unittests build configuration uses clang because they were designed to test compiler instrumentation.

As a fix, try adding /defaultlib:libcmt to link flags.

[Dor1s]

In D62733#1536561, @rnk wrote:

As a fix, try adding /defaultlib:libcmt to link flags.

Reid, thanks so much for taking a look. Adding -Wl,-defaultlib:libcmt,-defaultlib:oldnames indeed does the trick! I'll update the patch to remove that hacky dependency on RTFuzzer.

[Dor1s]

Fix linking on Windows, get rid of unnecessary RTFuzzer dependency.

[Dor1s]

Yay, the current version works across Linux / Windows / Mac without any hacks. Thanks again, Reid!

Matt and Kostya, I need your approval on the directory structure and CMake changes. Reviewing the tests / library is not necessary, but would be helpful of course :)

[morehouse]

lib/fuzzer/tests/CMakeLists.txt

26 ↗

(On Diff #203878)

Nit: Let's invert the if-condition:

if(WIN32) 
  ...
else()
 ...

[Dor1s]

Fix CMakeLists.txt as per Matt's comment

lib/fuzzer/utils/FuzzedDataProvider.h

+//===- FuzzedDataProvider.h - Utility header for fuzz targets ---*- C++ -* ===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// A single header library providing an utility class to break up an array of
+// bytes (supposedly provided by a fuzzing engine) for multiple consumers.
+// Whenever run on the same input, provides the same output, as long as its
+// methods are called in the same order, with the same arguments.
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_FUZZER_FUZZED_DATA_PROVIDER_H_
+#define LLVM_FUZZER_FUZZED_DATA_PROVIDER_H_
+
+#include <limits.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include <algorithm>
+#include <cstring>
+#include <string>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+class FuzzedDataProvider {
+ public:
+  typedef uint8_t data_type;
+
+  // |data| is an array of length |size| that the FuzzedDataProvider wraps to
+  // provide more granular access. |data| must outlive the FuzzedDataProvider.
+  FuzzedDataProvider(const uint8_t* data, size_t size)
+      : data_ptr_(data), remaining_bytes_(size) {}
+  ~FuzzedDataProvider() = default;
+
+  // Returns a std::vector containing |num_bytes| of input data. If fewer than
+  // |num_bytes| of data remain, returns a shorter std::vector containing all
+  // of the data that's left.
+  template <typename T = data_type>
+  std::vector<T> ConsumeBytes(size_t num_bytes) {
+    static_assert(sizeof(T) == sizeof(data_type), "Incompatible data type.");
+
+    num_bytes = std::min(num_bytes, remaining_bytes_);
+
+    // The point of using the size-based constructor below is to increase the
+    // odds of having a vector object with capacity being equal to the length.
+    // That part is always implementation specific, but at least both libc++ and
+    // libstdc++ allocate the requested number of bytes in that constructor,
+    // which seems to be a natual choice for other implementations as well.
+    // To increase the odds even more, we also call |shrink_to_fit| below.
+    std::vector<T> result(num_bytes);
+    std::memcpy(result.data(), data_ptr_, num_bytes);
+    Advance(num_bytes);
+
+    // Even though |shrink_to_fit| is also implementation specific, we expect it
+    // to provide an additional assurance in case vector's constructor allocated
+    // a buffer which is larger than the actual amount of data we put inside it.
+    result.shrink_to_fit();
+    return result;
+  }
+
+  // Prefer using |ConsumeBytes| unless you actually need a std::string object.
+  // Returns a std::string containing |num_bytes| of input data. If fewer than
+  // |num_bytes| of data remain, returns a shorter std::string containing all
+  // of the data that's left.
+  std::string ConsumeBytesAsString(size_t num_bytes) {
+    static_assert(sizeof(std::string::value_type) == sizeof(data_type),
+                  "ConsumeBytesAsString cannot convert the data to a string.");
+
+    num_bytes = std::min(num_bytes, remaining_bytes_);
+    std::string result(
+        reinterpret_cast<const std::string::value_type*>(data_ptr_), num_bytes);
+    Advance(num_bytes);
+    return result;
+  }
+
+  // Returns a number in the range [min, max] by consuming bytes from the input
+  // data. The value might not be uniformly distributed in the given range. If
+  // there's no input data left, always returns |min|. |min| must be less than
+  // or equal to |max|.
+  template <typename T>
+  T ConsumeIntegralInRange(T min, T max) {
+    static_assert(std::is_integral<T>::value, "An integral type is required.");
+    static_assert(sizeof(T) <= sizeof(uint64_t), "Unsupported integral type.");
+
+    if (min > max)
+      abort();
+
+    // Use the biggest type possible to hold the range and the result.
+    uint64_t range = static_cast<uint64_t>(max) - min;
+    uint64_t result = 0;
+    size_t offset = 0;
+
+    while (offset < sizeof(T) * CHAR_BIT && (range >> offset) > 0 &&
+           remaining_bytes_ != 0) {
+      // Pull bytes off the end of the seed data. Experimentally, this seems to
+      // allow the fuzzer to more easily explore the input space. This makes
+      // sense, since it works by modifying inputs that caused new code to run,
+      // and this data is often used to encode length of data read by
+      // |ConsumeBytes|. Separating out read lengths makes it easier modify the
+      // contents of the data that is actually read.
+      --remaining_bytes_;
+      result = (result << CHAR_BIT) | data_ptr_[remaining_bytes_];
+      offset += CHAR_BIT;
+    }
+
+    // Avoid division by 0, in the case |range + 1| results in overflow.
+    if (range != std::numeric_limits<decltype(range)>::max())
+      result = result % (range + 1);
+
+    return static_cast<T>(min + result);
+  }
+
+  // Returns a std::string of length from 0 to |max_length|. When it runs out of
+  // input data, returns what remains of the input. Designed to be more stable
+  // with respect to a fuzzer inserting characters than just picking a random
+  // length and then consuming that many bytes with |ConsumeBytes|.
+  std::string ConsumeRandomLengthString(size_t max_length) {
+    // Reads bytes from the start of |data_ptr_|. Maps "\\" to "\", and maps "\"
+    // followed by anything else to the end of the string. As a result of this
+    // logic, a fuzzer can insert characters into the string, and the string
+    // will be lengthened to include those new characters, resulting in a more
+    // stable fuzzer than picking the length of a string independently from
+    // picking its contents.
+    std::string result;
+    for (size_t i = 0; i < max_length && remaining_bytes_ != 0; ++i) {
+      char next = static_cast<char>(data_ptr_[0]);
+      Advance(1);
+      if (next == '\\' && remaining_bytes_ != 0) {
+        next = static_cast<char>(data_ptr_[0]);
+        Advance(1);
+        if (next != '\\')
+          return result;
+      }
+      result += next;
+    }
+
+    result.shrink_to_fit();
+    return result;
+  }
+
+  // Returns a std::vector containing all remaining bytes of the input data.
+  template <typename T = data_type>
+  std::vector<T> ConsumeRemainingBytes() {
+    return ConsumeBytes<T>(remaining_bytes_);
+  }
+
+  // Prefer using |ConsumeRemainingBytes| unless you actually need a std::string
+  // object.
+  // Returns a std::vector containing all remaining bytes of the input data.
+  std::string ConsumeRemainingBytesAsString() {
+    return ConsumeBytesAsString(remaining_bytes_);
+  }
+
+  // Returns a number in the range [Type's min, Type's max]. The value might
+  // not be uniformly distributed in the given range. If there's no input data
+  // left, always returns |min|.
+  template <typename T>
+  T ConsumeIntegral() {
+    return ConsumeIntegralInRange(std::numeric_limits<T>::min(),
+                                  std::numeric_limits<T>::max());
+  }
+
+  // Reads one byte and returns a bool, or false when no data remains.
+  bool ConsumeBool() { return 1 & ConsumeIntegral<uint8_t>(); }
+
+  // Returns a value from |array|, consuming as many bytes as needed to do so.
+  // |array| must be a fixed-size array.
+  template <typename T, size_t size>
+  T PickValueInArray(T (&array)[size]) {
+    return array[ConsumeIntegralInRange<size_t>(0, size - 1)];
+  }
+
+  // Return an enum value. The enum must start at 0 and be contiguous. It must
+  // also contain kMaxValue aliased to its largest (inclusive) value. Such as:
+  // enum class Foo { SomeValue, OtherValue, kMaxValue = OtherValue };
+  template <typename T>
+  T ConsumeEnum() {
+    static_assert(std::is_enum<T>::value, "|T| must be an enum type.");
+    return static_cast<T>(ConsumeIntegralInRange<uint32_t>(
+        0, static_cast<uint32_t>(T::kMaxValue)));
+  }
+
+  // Reports the remaining bytes available for fuzzed input.
+  size_t remaining_bytes() { return remaining_bytes_; }
+
+ private:
+  FuzzedDataProvider(const FuzzedDataProvider&) = delete;
+  FuzzedDataProvider& operator=(const FuzzedDataProvider&) = delete;
+
+  void Advance(size_t num_bytes) {
+    if (num_bytes > remaining_bytes_)
+      abort();
+
+    data_ptr_ += num_bytes;
+    remaining_bytes_ -= num_bytes;
+  }
+
+  const data_type* data_ptr_;
+  size_t remaining_bytes_;
+};
+
+#endif  // LLVM_FUZZER_FUZZED_DATA_PROVIDER_H_
+                                                                                
 No newline at end of file

lib/fuzzer/utils/FuzzedDataProviderTest.cpp

+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "utils/FuzzedDataProvider.h"
+
+/* A random 1KB buffer generated by:
+$ python -c "import os; print '\n'.join([', '.join(['0x%02X' % ord(i) for i \
+      in list(os.urandom(8))]) for _ in xrange(128)])"
+*/
+const uint8_t Data[] = {
+  0xA6, 0x02, 0xDD, 0x13, 0x44, 0xFF, 0xF5, 0xFA
+  0xF6, 0xB5, 0xDD, 0xEE, 0x77, 0x30, 0xEB, 0x83
+  0x95, 0xBE, 0x3C, 0xED, 0x73, 0x1B, 0x64, 0x0B
+  0x77, 0x35, 0xCB, 0x8C, 0x4C, 0x62, 0x61, 0x4C
+  0x5B, 0x61, 0x3C, 0xFA, 0xA0, 0x96, 0x06, 0xB7
+  0x73, 0x73, 0x56, 0x1B, 0xB5, 0xDC, 0x87, 0x44
+  0x96, 0x69, 0xF2, 0xC7, 0x98, 0xCA, 0x3E, 0xBF
+  0x3C, 0x7D, 0xDE, 0x8B, 0xD5, 0x2E, 0x41, 0x6E
+  0xCE, 0x92, 0x2E, 0x34, 0xC8, 0x97, 0x7E, 0xD6
+  0x79, 0x21, 0x09, 0x84, 0xCA, 0x3F, 0x96, 0xA0
+  0x8D, 0x82, 0xF5, 0x13, 0x94, 0x17, 0x18, 0xA2
+  0x10, 0x58, 0x15, 0xAA, 0xC8, 0xD8, 0xA1, 0x08
+  0x66, 0xAA, 0x31, 0xAC, 0x0A, 0x9D, 0xD1, 0x22
+  0x3E, 0x61, 0xAE, 0xC4, 0x97, 0xD5, 0xC1, 0xD0
+  0x25, 0x3A, 0x69, 0x3D, 0x36, 0x2D, 0x5D, 0x17
+  0x51, 0x9B, 0x3E, 0x05, 0x3A, 0x45, 0x51, 0xBA
+  0xB5, 0x68, 0x37, 0x3F, 0xE1, 0x2F, 0xA3, 0x19
+  0x66, 0x1C, 0x3D, 0xC6, 0xB3, 0x5A, 0x3E, 0xA5
+  0x12, 0x08, 0x24, 0xC3, 0x73, 0x1D, 0xDE, 0x82
+  0xCC, 0xD9, 0xCC, 0x26, 0xD0, 0x7C, 0x7E, 0xB9
+  0xD2, 0x41, 0x77, 0x3B, 0xE4, 0xBE, 0xE9, 0x92
+  0x5F, 0x91, 0x59, 0x37, 0x9F, 0xCF, 0xF3, 0xC8
+  0xF2, 0x2B, 0x77, 0x35, 0x0B, 0xF1, 0x77, 0xDC
+  0x9E, 0x76, 0x93, 0x18, 0x66, 0xE3, 0xE4, 0x2F
+  0x0F, 0x9F, 0x71, 0xEA, 0x9A, 0x98, 0x42, 0xF7
+  0x23, 0x7B, 0x5E, 0xFA, 0xD2, 0x61, 0xFD, 0xB6
+  0x8A, 0xD9, 0x81, 0x96, 0x6C, 0x6C, 0xF8, 0x82
+  0x8F, 0x08, 0x29, 0x61, 0x15, 0x10, 0x36, 0xD3
+  0x5A, 0x25, 0x93, 0x43, 0xDE, 0x52, 0x2C, 0xC3
+  0x3C, 0x25, 0x8C, 0x12, 0x82, 0x93, 0xAC, 0x3C
+  0x55, 0xB1, 0x62, 0xFE, 0x57, 0xB9, 0xA6, 0xA9
+  0x28, 0x58, 0x27, 0xA0, 0xBF, 0x7B, 0xC1, 0x87
+  0xDB, 0x98, 0x24, 0x7D, 0xFC, 0xFA, 0xF3, 0xD1
+  0xFF, 0xC7, 0xB6, 0x39, 0x60, 0x3A, 0xE8, 0xE1
+  0x64, 0x46, 0xFB, 0xDC, 0xF3, 0x8F, 0x25, 0xDD
+  0xCD, 0x62, 0x7B, 0x28, 0x24, 0xD4, 0x85, 0x34
+  0xAA, 0xF0, 0xE0, 0xB0, 0xD6, 0xC4, 0xA7, 0x15
+  0x44, 0x30, 0x98, 0xFE, 0xF9, 0x3E, 0x37, 0x0F
+  0x06, 0x79, 0xD8, 0x0A, 0x4C, 0xEE, 0x26, 0x30
+  0x36, 0x16, 0x75, 0x59, 0xCA, 0xE0, 0x42, 0xCB
+  0xF1, 0x65, 0x43, 0x4D, 0x16, 0x41, 0x89, 0x96
+  0xCB, 0xA1, 0xFA, 0xF1, 0xAE, 0x89, 0xEB, 0x83
+  0x82, 0xA4, 0x92, 0x6F, 0xE2, 0x9D, 0xA3, 0x58
+  0x24, 0x09, 0x32, 0x70, 0x10, 0xF6, 0xAE, 0x6D
+  0x0C, 0x25, 0x47, 0x55, 0x09, 0xDE, 0x73, 0xA5
+  0x77, 0xF8, 0x31, 0x44, 0xD7, 0xF4, 0xA7, 0xEF
+  0x87, 0x36, 0xA7, 0x43, 0x79, 0xDB, 0x08, 0x68
+  0x71, 0x31, 0x32, 0xA0, 0x30, 0x18, 0x9F, 0xD0
+  0x94, 0x6D, 0x79, 0x0C, 0x0A, 0x3B, 0xB8, 0xF1
+  0x60, 0xBD, 0x53, 0xD7, 0x88, 0x69, 0xCF, 0xCB
+  0x5E, 0x0C, 0xC5, 0x26, 0xF1, 0x89, 0x64, 0xBC
+  0x9C, 0x20, 0xF8, 0x41, 0xF0, 0xFF, 0x14, 0xE9
+  0x21, 0xE4, 0x15, 0x2F, 0x73, 0xCC, 0x40, 0xF1
+  0x36, 0x2F, 0xBD, 0x7C, 0x12, 0x50, 0xE3, 0x1F
+  0x7E, 0xE2, 0x69, 0x1F, 0xC8, 0x11, 0xDB, 0xA4
+  0x70, 0xFC, 0xED, 0xCD, 0x0A, 0x9D, 0x25, 0x77
+  0xED, 0xF9, 0x4B, 0x67, 0xFA, 0x1D, 0xAA, 0xA1
+  0x6A, 0x24, 0x9F, 0x31, 0x5D, 0xD9, 0x9E, 0xEE
+  0x3A, 0x8E, 0x00, 0xF3, 0x85, 0xB9, 0x2D, 0xE4
+  0x24, 0x67, 0x09, 0xDF, 0x6A, 0x84, 0x65, 0xB6
+  0xE9, 0xD2, 0x9E, 0xC8, 0xCB, 0x32, 0x17, 0xD8
+  0x0C, 0x6B, 0x3E, 0xD6, 0xF6, 0x56, 0x38, 0x48
+  0xF5, 0x05, 0x2F, 0x9C, 0xD1, 0xCC, 0xBD, 0x8C
+  0x5B, 0xCD, 0x94, 0x73, 0xD9, 0x22, 0x10, 0x3D
+  0x36, 0x9B, 0x1A, 0xA5, 0x03, 0xA6, 0xC2, 0x2F
+  0x81, 0x96, 0x97, 0xDC, 0xEE, 0xEE, 0xDD, 0x13
+  0x7F, 0xFF, 0x26, 0xBF, 0x30, 0x67, 0xAC, 0x2D
+  0x2F, 0xD8, 0x3E, 0x35, 0x90, 0x27, 0xC5, 0xA2
+  0x77, 0x37, 0x4B, 0x52, 0xD5, 0x18, 0x4F, 0xA4
+  0xBB, 0xAA, 0xBC, 0xC9, 0xF9, 0x34, 0x43, 0xA9
+  0x46, 0x70, 0x61, 0x03, 0x8C, 0x8C, 0xB9, 0x9A
+  0xC8, 0x8B, 0xC1, 0x5D, 0x7C, 0xEF, 0xEF, 0xA6
+  0xAD, 0xD0, 0x57, 0x03, 0x0C, 0x79, 0xD7, 0xC6
+  0xB3, 0x08, 0x6A, 0xFB, 0x56, 0x3D, 0xB9, 0x7C
+  0x5B, 0xCF, 0x62, 0x84, 0x2C, 0x32, 0x7B, 0x56
+  0xBF, 0xFD, 0x67, 0xEF, 0xC2, 0xB2, 0x44, 0xCC
+  0xC3, 0x34, 0x18, 0xA0, 0xDA, 0x10, 0x81, 0xB0
+  0x48, 0xDB, 0xFC, 0xE6, 0xB2, 0x87, 0x4C, 0x82
+  0x70, 0x6E, 0x97, 0xA4, 0x97, 0x3D, 0x30, 0xB5
+  0x01, 0x09, 0xFA, 0xD0, 0x0F, 0xA6, 0xE7, 0xE3
+  0x0D, 0x60, 0x88, 0xA1, 0x5C, 0x05, 0x54, 0x03
+  0x69, 0x62, 0x1E, 0x48, 0x21, 0xB4, 0x3D, 0x0F
+  0x5B, 0x82, 0x01, 0x73, 0x8B, 0x13, 0x30, 0x57
+  0xD2, 0xB6, 0xD6, 0x0A, 0x89, 0x45, 0x0C, 0xD0
+  0x1C, 0x7C, 0xFD, 0x19, 0x56, 0xFB, 0x3F, 0xED
+  0x76, 0x1F, 0x19, 0xC0, 0xBD, 0xBE, 0xA6, 0xB0
+  0x36, 0x0F, 0xFA, 0x54, 0x1D, 0x77, 0x2B, 0xAF
+  0xAE, 0x77, 0x0C, 0x93, 0x1D, 0x1F, 0x1A, 0x78
+  0x92, 0x15, 0x59, 0x0D, 0xEA, 0xE3, 0xCD, 0xEE
+  0x33, 0x4C, 0xCD, 0xD2, 0xE7, 0x21, 0x92, 0x4B
+  0xC8, 0x6D, 0xF2, 0x9A, 0x52, 0x57, 0x8F, 0xC3
+  0x68, 0x0D, 0x61, 0x18, 0x50, 0x12, 0xCC, 0x9C
+  0x1A, 0xFF, 0x78, 0xA4, 0xF4, 0xFB, 0xC0, 0xFA
+  0x58, 0xAC, 0x67, 0x5C, 0x38, 0xEA, 0x1E, 0x70
+  0xAC, 0xEB, 0x76, 0x63, 0x0B, 0xDC, 0xE3, 0x32
+  0x95, 0x6E, 0xCB, 0xAC, 0x0D, 0x44, 0x8E, 0x7F
+  0xD9, 0x16, 0x30, 0xE1, 0x87, 0xD0, 0x35, 0xA9
+  0x44, 0xD9, 0x2D, 0x98, 0x67, 0x63, 0x4B, 0xD4
+  0x3B, 0x08, 0x9B, 0x80, 0x46, 0x61, 0xEA, 0x35
+  0x2D, 0x8B, 0x14, 0x5A, 0x77, 0x84, 0x72, 0xFC
+  0xDD, 0xA0, 0x9E, 0x6A, 0xDD, 0xAE, 0xBD, 0x11
+  0x63, 0xCA, 0x96, 0x37, 0x8C, 0x35, 0xBD, 0x66
+  0xBD, 0x00, 0x02, 0x3D, 0xE0, 0xDC, 0x87, 0x00
+  0xC8, 0x44, 0xDA, 0xD3, 0x62, 0x91, 0xBB, 0xB3
+  0x96, 0x03, 0x20, 0xD2, 0x07, 0x07, 0x8B, 0x5A
+  0x43, 0x12, 0x9C, 0x2C, 0x39, 0x93, 0x63, 0x70
+  0x79, 0x07, 0xF8, 0x06, 0x50, 0x4F, 0xBC, 0x4A
+  0x63, 0x11, 0x83, 0xA0, 0xC7, 0x2F, 0xBE, 0xE8
+  0x7E, 0xCA, 0x04, 0x9E, 0x1F, 0x3B, 0x97, 0x4F
+  0x40, 0xC1, 0x7E, 0x2D, 0xCE, 0x4F, 0x7D, 0xA2
+  0x47, 0x42, 0xE2, 0xB8, 0x00, 0x73, 0xCE, 0x75
+  0xB5, 0xCF, 0x24, 0x44, 0x27, 0xC7, 0x8B, 0xB0
+  0x23, 0x7A, 0xCC, 0x7F, 0xE2, 0xBA, 0xB8, 0xBD
+  0xA9, 0x6E, 0x71, 0x63, 0x3F, 0x36, 0xC7, 0x4F
+  0x04, 0xE3, 0x7C, 0x69, 0x60, 0x52, 0xF1, 0x84
+  0x5B, 0x25, 0xA1, 0x0B, 0x80, 0xD8, 0x10, 0x0F
+  0x07, 0x1A, 0xA6, 0x6F, 0xD0, 0x41, 0xA4, 0x92
+  0x09, 0x41, 0x57, 0xC2, 0xDC, 0xDE, 0x86, 0x9A
+  0x0A, 0x61, 0x14, 0x04, 0xD0, 0x25, 0xCD, 0x89
+  0xAA, 0xCB, 0x2B, 0x4F, 0x5D, 0x33, 0xA5, 0xDF
+  0x3D, 0x35, 0xB7, 0xA1, 0x78, 0xA0, 0xDE, 0x34
+  0x93, 0xB4, 0x33, 0x47, 0xA4, 0xFD, 0xD9, 0x82
+  0xC6, 0x72, 0x91, 0xD0, 0xA6, 0x82, 0x17, 0x25
+  0xEF, 0xD1, 0x95, 0x9F, 0x85, 0x31, 0x05, 0xBB
+  0x46, 0xF3, 0x86, 0x02, 0x71, 0xF5, 0xC0, 0xB9
+  0xF8, 0xB3, 0x6C, 0x79, 0xBF, 0x9C, 0x2C, 0xAA
+  0x60, 0xEA, 0xC7, 0x97, 0xCB, 0x20, 0x0D, 0x90
+  0xD5, 0x9B, 0xDB, 0x9C, 0xE4, 0x3D, 0x80, 0xA7
+};
+
+
+// int main(int argc, char *argv[]) {
+  
+//   FuzzedDataProvider DataProv(Data, sizeof(data));
+
+  // template <typename T = data_type>
+  // std::vector<T> ConsumeBytes(size_t num_bytes)
+  // char, signed char, unsigned char, uint8_t
+//  std::vector<char> Chars = DataProv.ConsumeBytes(5);
+
+  // std::string ConsumeBytesAsString(size_t num_bytes)
+
+  // template <typename T>
+  // T ConsumeIntegralInRange(T min, T max)
+
+  // std::string ConsumeRandomLengthString(size_t max_length) {
+
+  // template <typename T = data_type>
+  // std::vector<T> ConsumeRemainingBytes() {
+  //   return ConsumeBytes<T>(remaining_bytes_);
+  // }
+
+  // std::string ConsumeRemainingBytesAsString() {
+  //   return ConsumeBytesAsString(remaining_bytes_);
+  // }
+
+  // template <typename T>
+  // T ConsumeIntegral() {
+
+  // bool ConsumeBool() 
+
+  // template <typename T, size_t size>
+  // T PickValueInArray(T (&array)[size]) {
+
+  // template <typename T>
+  // T ConsumeEnum() 
+
+  // size_t remaining_bytes() 
+
+  // return 0;
+// }
+
+TEST(Fuzzer, Basename) {
+  FuzzedDataProvider DataProv(Data, sizeof(data));
+  EXPECT_EQ(DataProv.ConsumeBytes<char>(1), std::vector<char>(1, 0xA6));
+  // EXPECT_EQ(Basename("bar"), "bar");
+  // EXPECT_EQ(Basename("/bar"), "bar");
+  // EXPECT_EQ(Basename("foo/x"), "x");
+  // EXPECT_EQ(Basename("foo/"), "");
+}
+
+int main(int argc, char **argv) {
+  testing::InitGoogleTest(&argc, argv);
+  return RUN_ALL_TESTS();
+}