merge(3p/immer): Subtree merge at 'ad3e3556d' as 'third_party/immer'

Change-Id: I9636a41ad44b4218293833fd3e9456d9b07c731b

third_party/immer/extra/fuzzer/fuzzer_input.hpp

@@ -0,0 +1,62 @@
+//
+// immer: immutable data structures for C++
+// Copyright (C) 2016, 2017, 2018 Juan Pedro Bolivar Puente
+//
+// This software is distributed under the Boost Software License, Version 1.0.
+// See accompanying file LICENSE or copy at http://boost.org/LICENSE_1_0.txt
+//
+
+#pragma once
+
+#include <cstdint>
+#include <stdexcept>
+
+struct no_more_input : std::exception
+{};
+
+struct fuzzer_input
+{
+    const std::uint8_t* data_;
+    std::size_t size_;
+
+    const std::uint8_t* next(std::size_t size)
+    {
+        if (size_ < size)
+            throw no_more_input{};
+        auto r = data_;
+        data_ += size;
+        size_ -= size;
+        return r;
+    }
+
+    const std::uint8_t* next(std::size_t size, std::size_t align)
+    {
+        auto rem = size % align;
+        if (rem)
+            next(align - rem);
+        return next(size);
+    }
+
+    template <typename Fn>
+    int run(Fn step)
+    {
+        try {
+            while (step(*this))
+                continue;
+        } catch (const no_more_input&) {};
+        return 0;
+    }
+};
+
+template <typename T>
+const T& read(fuzzer_input& fz)
+{
+    return *reinterpret_cast<const T*>(fz.next(sizeof(T), alignof(T)));
+}
+
+template <typename T, typename Cond>
+T read(fuzzer_input& fz, Cond cond)
+{
+    auto x = read<T>(fz);
+    return cond(x) ? x : read<T>(fz, cond);
+}