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// Copyright 2019 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#ifndef UTIL_JSON_JSON_HELPERS_H_
#define UTIL_JSON_JSON_HELPERS_H_
#include <chrono>
#include <cmath>
#include <functional>
#include <string>
#include <utility>
#include <vector>
#include "absl/strings/string_view.h"
#include "json/value.h"
#include "platform/base/error.h"
#include "util/chrono_helpers.h"
#include "util/json/json_serialization.h"
#include "util/simple_fraction.h"
// This file contains helper methods for parsing JSON, in an attempt to
// reduce boilerplate code when working with JsonCpp.
namespace openscreen {
namespace json {
inline bool TryParseBool(const Json::Value& value, bool* out) {
if (!value.isBool()) {
return false;
}
*out = value.asBool();
return true;
}
// A general note about parsing primitives. "Validation" in this context
// generally means ensuring that the values are non-negative, excepting doubles
// which may be negative in some cases.
inline bool TryParseDouble(const Json::Value& value,
double* out,
bool allow_negative = false) {
if (!value.isDouble()) {
return false;
}
const double d = value.asDouble();
if (std::isnan(d)) {
return false;
}
if (!allow_negative && d < 0) {
return false;
}
*out = d;
return true;
}
inline bool TryParseInt(const Json::Value& value, int* out) {
if (!value.isInt()) {
return false;
}
int i = value.asInt();
if (i < 0) {
return false;
}
*out = i;
return true;
}
inline bool TryParseUint(const Json::Value& value, uint32_t* out) {
if (!value.isUInt()) {
return false;
}
*out = value.asUInt();
return true;
}
inline bool TryParseString(const Json::Value& value, std::string* out) {
if (!value.isString()) {
return false;
}
*out = value.asString();
return true;
}
// We want to be more robust when we parse fractions then just
// allowing strings, this will parse numeral values such as
// value: 50 as well as value: "50" and value: "100/2".
inline bool TryParseSimpleFraction(const Json::Value& value,
SimpleFraction* out) {
if (value.isInt()) {
int parsed = value.asInt();
if (parsed < 0) {
return false;
}
*out = SimpleFraction{parsed, 1};
return true;
}
if (value.isString()) {
auto fraction_or_error = SimpleFraction::FromString(value.asString());
if (!fraction_or_error) {
return false;
}
if (!fraction_or_error.value().is_positive() ||
!fraction_or_error.value().is_defined()) {
return false;
}
*out = std::move(fraction_or_error.value());
return true;
}
return false;
}
inline bool TryParseMilliseconds(const Json::Value& value, milliseconds* out) {
int out_ms;
if (!TryParseInt(value, &out_ms) || out_ms < 0) {
return false;
}
*out = milliseconds(out_ms);
return true;
}
template <typename T>
using Parser = std::function<bool(const Json::Value&, T*)>;
// NOTE: array parsing methods reset the output vector to an empty vector in
// any error case. This is especially useful for optional arrays.
template <typename T>
bool TryParseArray(const Json::Value& value,
Parser<T> parser,
std::vector<T>* out) {
out->clear();
if (!value.isArray() || value.empty()) {
return false;
}
out->reserve(value.size());
for (Json::ArrayIndex i = 0; i < value.size(); ++i) {
T v;
if (!parser(value[i], &v)) {
out->clear();
return false;
}
out->push_back(v);
}
return true;
}
inline bool TryParseIntArray(const Json::Value& value, std::vector<int>* out) {
return TryParseArray<int>(value, TryParseInt, out);
}
inline bool TryParseUintArray(const Json::Value& value,
std::vector<uint32_t>* out) {
return TryParseArray<uint32_t>(value, TryParseUint, out);
}
inline bool TryParseStringArray(const Json::Value& value,
std::vector<std::string>* out) {
return TryParseArray<std::string>(value, TryParseString, out);
}
} // namespace json
} // namespace openscreen
#endif // UTIL_JSON_JSON_HELPERS_H_
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