Validate correct string data in fuzz test

src/fuzz.cpp

@@ -1,14 +1,17 @@
 #include "callbacks.h"
+#include "json_value.h"
 #include "parser3.h"
 
 #include <simdjson.h>
 
-std::pair<std::string, parser3::Status> runStreaming(std::string copy) {
+std::pair<std::string, parser3::Status> runStreaming(std::string copy,
+                                                     int stride) {
   SerializeState state;
   auto c = serializeCallbacks();
   parser3::Parser3 parser(&c, &state);
-  for (int i = 0; i < copy.size(); ++i) {
-    auto s = parser.parse(copy.data() + i, 1);
+  for (int i = 0; i < copy.size(); i += stride) {
+    auto s =
+        parser.parse(copy.data() + i, std::min<int>(stride, copy.size() - i));
     if (s != parser3::S_AGAIN) {
       return {state.result, s};
     }
@@ -36,20 +39,23 @@ std::pair<std::string, parser3::Status> runBatch(std::string copy) {
 }
 
 void testStreaming(std::string const &json) {
-  auto streaming = runStreaming(json);
   auto batch = runBatch(json);
-  if (streaming != batch) {
-    if (streaming.second == batch.second && streaming.second != parser3::S_OK) {
-      // It's ok if the processed data doesn't match if parsing failed
-      return;
+  for (int stride = 1; stride < 16; ++stride) {
+    auto streaming = runStreaming(json, stride);
+    if (streaming != batch) {
+      if (streaming.second == batch.second &&
+          streaming.second != parser3::S_OK) {
+        // It's ok if the processed data doesn't match if parsing failed
+        return;
+      }
+      printf("streaming: %s, %s\n",
+             streaming.second == parser3::S_OK ? "accept" : "reject",
+             streaming.first.c_str());
+      printf("batch: %s, %s\n",
+             streaming.second == parser3::S_OK ? "accept" : "reject",
+             batch.first.c_str());
+      abort();
     }
-    printf("streaming: %s, %s\n",
-           streaming.second == parser3::S_OK ? "accept" : "reject",
-           streaming.first.c_str());
-    printf("batch: %s, %s\n",
-           streaming.second == parser3::S_OK ? "accept" : "reject",
-           batch.first.c_str());
-    abort();
   }
 }
 
@@ -92,9 +98,27 @@ void compareWithSimdjson(std::string const &json) {
   }
 }
 
+void testStringRoundTrip(std::string_view s) {
+  if (!simdjson::validate_utf8(s.data(), s.size())) {
+    // You can't encode non utf-8 data in a json string, even with escaping
+    return;
+  }
+  for (int stride = 0; stride < 16; ++stride) {
+    auto escaped = "\"" + escapeAsJsonString(s) + "\"";
+    auto parsed = toValue(std::move(escaped));
+    if (!parsed.has_value()) {
+      abort();
+    }
+    if (std::get<std::string>(*parsed) != s) {
+      abort();
+    }
+  }
+}
+
 extern "C" int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
   auto s = std::string((const char *)data, size);
   testStreaming(s);
   compareWithSimdjson(s);
+  testStringRoundTrip(s);
   return 0;
 }