fuzz_parse.cpp

// Copyright 2025 ByteDance Ltd. and/or its affiliates. All rights reserved.
// Licensed under the Apache License, Version 2.0 (the "License");

#include "fuzz_util.h"

#include <cstddef>
#include <cstdint>
#include <string>

using ByteDance::pjson;

namespace {

    // DOM parsing and serialization invariants.

    // Exercises one parser configuration and checks successful
    // values across both compact and pretty serialization modes.
    void exerciseParser(const uint8_t* data, size_t size, size_t variantOffset) {
        const pjson::ParseOptions options =
            pjson_fuzz::parseOptionsVariant(data, size, variantOffset);
        pjson::ParseError error;
        pjson::unique_ptr value = pjson::parse(pjson_fuzz::bytes(data, size), size, error, options);
        // The returned value and explicit status must agree on whether parsing succeeded.
        pjson_fuzz::require(static_cast<bool>(value) == error.ok);
        if (!value)
            return;

        // Compact output must be a stable, value-preserving representation.
        const std::string compact = value->toString();
        pjson::ParseOptions compactOptions = options;
        compactOptions.maxInputBytes = compact.size();
        pjson::ParseError compactError;
        pjson::unique_ptr reparsed = pjson::parse(compact, compactError, compactOptions);
        pjson_fuzz::require(reparsed != nullptr);
        pjson_fuzz::require(compactError.ok);
        pjson_fuzz::require(*reparsed == *value);
        pjson_fuzz::require(reparsed->toString() == compact);

        // Pretty printing may change whitespace, but never the represented JSON value.
        const std::string pretty = value->toString(pjson::SerializeOptions::prettyPrinted());
        pjson::ParseOptions prettyOptions = options;
        prettyOptions.maxInputBytes = pretty.size();
        pjson::unique_ptr prettyParsed = pjson::parse(pretty, prettyOptions);
        pjson_fuzz::require(prettyParsed != nullptr);
        pjson_fuzz::require(*prettyParsed == *value);
    }

} // namespace

// libFuzzer entry point.

// Bounds each test case and exercises the same bytes under several
// duplicate-policy/resource-budget variants.
extern "C" int LLVMFuzzerTestOneInput(const uint8_t* data, size_t size) {
    if (size > pjson_fuzz::kMaxInputBytes)
        return 0;
    exerciseParser(data, size, 0U);
    exerciseParser(data, size, 4U);
    exerciseParser(data, size, 8U);
    return 0;
}