[libFuzzer] actually make the dictionaries work (+docs)

llvm-svn: 246825
diff --git a/llvm/lib/Fuzzer/test/SimpleDictionaryTest.cpp b/llvm/lib/Fuzzer/test/SimpleDictionaryTest.cpp
new file mode 100644
index 0000000..20c8067
--- /dev/null
+++ b/llvm/lib/Fuzzer/test/SimpleDictionaryTest.cpp
@@ -0,0 +1,25 @@
+// Simple test for a fuzzer.
+// The fuzzer must find a string based on dictionary words:
+//   "Elvis"
+//   "Presley"
+#include <cstdint>
+#include <cstdlib>
+#include <cstddef>
+#include <cstring>
+#include <iostream>
+
+static volatile int Zero = 0;
+
+extern "C" void LLVMFuzzerTestOneInput(const uint8_t *Data, size_t Size) {
+  const char *Expected = "ElvisPresley";
+  if (Size < strlen(Expected)) return;
+  size_t Match = 0;
+  for (size_t i = 0; Expected[i]; i++)
+    if (Expected[i] + Zero == Data[i])
+      Match++;
+  if (Match == strlen(Expected)) {
+    std::cout << "BINGO; Found the target, exiting\n";
+    exit(1);
+  }
+}
+