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json.cpp
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json.cpp
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#include "json.h"
#include <iterator>
namespace json {
namespace {
using namespace std::literals;
Node LoadNode(std::istream& input);
Node LoadString(std::istream& input);
std::string LoadLiteral(std::istream& input) {
std::string str;
while (std::isalpha(input.peek())) {
str.push_back(static_cast<char>(input.get()));
}
return str;
}
Node LoadArray(std::istream& input) {
std::vector<Node> result;
for (char current_char; input >> current_char && current_char != ']';) {
if (current_char != ',') {
input.putback(current_char);
}
result.push_back(LoadNode(input));
}
if (!input) {
throw ParsingError("Array parsing error"s);
}
return result;
}
Node LoadDict(std::istream& input) {
Dict dict;
for (char current_char; input >> current_char && current_char != '}';) {
if (current_char == '"') {
std::string key = LoadString(input).AsString();
if (input >> current_char && current_char == ':') {
if (dict.find(key) != dict.end()) {
throw ParsingError("Duplicate key '"s + key + "' have been found");
}
dict.emplace(std::move(key), LoadNode(input));
} else {
throw ParsingError(": is expected but '"s + current_char + "' has been found"s);
}
} else if (current_char != ',') {
throw ParsingError(R"(',' is expected but ')"s + current_char + "' has been found"s);
}
}
if (!input) {
throw ParsingError("Dictionary parsing error"s);
}
return dict;
}
Node LoadString(std::istream& input) {
auto it = std::istreambuf_iterator<char>(input);
auto end = std::istreambuf_iterator<char>();
std::string str;
while (true) {
if (it == end) {
throw ParsingError("String parsing error");
}
const char current_char = *it;
if (current_char == '"') {
++it;
break;
} else if (current_char == '\\') {
++it;
if (it == end) {
throw ParsingError("String parsing error");
}
const char escaped_char = *(it);
switch (escaped_char) {
case 'n':
str.push_back('\n');
break;
case 't':
str.push_back('\t');
break;
case 'r':
str.push_back('\r');
break;
case '"':
str.push_back('"');
break;
case '\\':
str.push_back('\\');
break;
default:
throw ParsingError("Unrecognized escape sequence \\"s + escaped_char);
}
} else if (current_char == '\n' || current_char == '\r') {
throw ParsingError("Unexpected end of line"s);
} else {
str.push_back(current_char);
}
++it;
}
return str;
}
Node LoadBool(std::istream& input) {
const auto str = LoadLiteral(input);
if (str == "true"sv) {
return Node{ true };
} else if (str == "false"sv) {
return Node{ false };
} else {
throw ParsingError("Failed to parse '"s + str + "' as bool"s);
}
}
Node LoadNull(std::istream& input) {
if (auto literal = LoadLiteral(input); literal == "null"sv) {
return Node{ nullptr };
} else {
throw ParsingError("Failed to parse '"s + literal + "' as null"s);
}
}
Node LoadNumber(std::istream& input) {
std::string parsed_num;
auto read_char = [&parsed_num, &input] {
parsed_num += static_cast<char>(input.get());
if (!input) {
throw ParsingError("Failed to read number from stream"s);
}
};
auto read_digits = [&input, read_char] {
if (!std::isdigit(input.peek())) {
throw ParsingError("A digit is expected"s);
}
while (std::isdigit(input.peek())) {
read_char();
}
};
if (input.peek() == '-') {
read_char();
}
if (input.peek() == '0') {
read_char();
} else {
read_digits();
}
bool is_int = true;
if (input.peek() == '.') {
read_char();
read_digits();
is_int = false;
}
if (int current_char = input.peek(); current_char == 'e' || current_char == 'E') {
read_char();
if (current_char = input.peek(); current_char == '+' || current_char == '-') {
read_char();
}
read_digits();
is_int = false;
}
try {
if (is_int) {
try {
return std::stoi(parsed_num);
} catch (...) {
}
}
return std::stod(parsed_num);
} catch (...) {
throw ParsingError("Failed to convert "s + parsed_num + " to number"s);
}
}
Node LoadNode(std::istream& input) {
char current_char;
if (!(input >> current_char)) {
throw ParsingError("Unexpected EOF"s);
}
switch (current_char) {
case '[':
return LoadArray(input);
case '{':
return LoadDict(input);
case '"':
return LoadString(input);
case 't': case 'f':
input.putback(current_char);
return LoadBool(input);
case 'n':
input.putback(current_char);
return LoadNull(input);
default:
input.putback(current_char);
return LoadNumber(input);
}
}
struct PrintContext {
std::ostream& out;
int indent_step = 4;
int indent = 0;
void PrintIndent() const {
for (int i = 0; i < indent; ++i) {
out.put(' ');
}
}
PrintContext Indented() const {
return { out, indent_step, indent_step + indent };
}
};
void PrintNode(const Node& node, const PrintContext& ctx);
template <typename Value>
void PrintValue(const Value& value, const PrintContext& ctx) {
ctx.out << value;
}
void PrintString(const std::string& value, std::ostream& out) {
out.put('"');
for (const char current_char : value) {
switch (current_char) {
case '\r':
out << "\\r"sv;
break;
case '\n':
out << "\\n"sv;
break;
case '"':
out << "\\\""sv;
break;
case '\\':
out << "\\\\"sv;
break;
default:
out.put(current_char);
break;
}
}
out.put('"');
}
template <>
void PrintValue<std::string>(const std::string& value, const PrintContext& ctx) {
PrintString(value, ctx.out);
}
template <>
void PrintValue<std::nullptr_t>(const std::nullptr_t&, const PrintContext& ctx) {
ctx.out << "null"sv;
}
template <>
void PrintValue<bool>(const bool& value, const PrintContext& ctx) {
ctx.out << (value ? "true"sv : "false"sv);
}
template <>
void PrintValue<Array>(const Array& nodes, const PrintContext& ctx) {
std::ostream& out = ctx.out;
out << "[\n"sv;
bool first = true;
auto inner_ctx = ctx.Indented();
for (const Node& node : nodes) {
if (first) {
first = false;
} else {
out << ",\n"sv;
}
inner_ctx.PrintIndent();
PrintNode(node, inner_ctx);
}
out.put('\n');
ctx.PrintIndent();
out.put(']');
}
template <>
void PrintValue<Dict>(const Dict& nodes, const PrintContext& ctx) {
std::ostream& out = ctx.out;
out << "{\n"sv;
bool first = true;
auto inner_ctx = ctx.Indented();
for (const auto& [key, node] : nodes) {
if (first) {
first = false;
} else {
out << ",\n"sv;
}
inner_ctx.PrintIndent();
PrintString(key, ctx.out);
out << ": "sv;
PrintNode(node, inner_ctx);
}
out.put('\n');
ctx.PrintIndent();
out.put('}');
}
void PrintNode(const Node& node, const PrintContext& ctx) {
std::visit(
[&ctx](const auto& value) {
PrintValue(value, ctx);
},
node.GetValue());
}
} // namespace
Document Load(std::istream& input) {
return Document{ LoadNode(input) };
}
void Print(const Document& doc, std::ostream& output) {
PrintNode(doc.GetRoot(), PrintContext{ output });
}
} // namespace json