ladybird/AK/JsonParser.cpp
Andreas Kling 587f9af960 AK: Make JSON parser return ErrorOr<JsonValue> (instead of Optional)
Also add slightly richer parse errors now that we can include a string
literal with returned errors.

This will allow us to use TRY() when working with JSON data.
2021-11-17 00:21:10 +01:00

348 lines
9.8 KiB
C++

/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/CharacterTypes.h>
#include <AK/JsonArray.h>
#include <AK/JsonObject.h>
#include <AK/JsonParser.h>
namespace AK {
constexpr bool is_space(int ch)
{
return ch == '\t' || ch == '\n' || ch == '\r' || ch == ' ';
}
ErrorOr<String> JsonParser::consume_and_unescape_string()
{
if (!consume_specific('"'))
return Error::from_string_literal("JsonParser: Expected '\"'"sv);
StringBuilder final_sb;
for (;;) {
size_t peek_index = m_index;
char ch = 0;
for (;;) {
if (peek_index == m_input.length())
break;
ch = m_input[peek_index];
if (ch == '"' || ch == '\\')
break;
if (is_ascii_c0_control(ch))
return Error::from_string_literal("JsonParser: Error while parsing string"sv);
++peek_index;
}
while (peek_index != m_index) {
final_sb.append(m_input[m_index]);
m_index++;
}
if (m_index == m_input.length())
break;
if (ch == '"')
break;
if (ch != '\\') {
final_sb.append(consume());
continue;
}
ignore();
if (next_is('"')) {
ignore();
final_sb.append('"');
continue;
}
if (next_is('\\')) {
ignore();
final_sb.append('\\');
continue;
}
if (next_is('/')) {
ignore();
final_sb.append('/');
continue;
}
if (next_is('n')) {
ignore();
final_sb.append('\n');
continue;
}
if (next_is('r')) {
ignore();
final_sb.append('\r');
continue;
}
if (next_is('t')) {
ignore();
final_sb.append('\t');
continue;
}
if (next_is('b')) {
ignore();
final_sb.append('\b');
continue;
}
if (next_is('f')) {
ignore();
final_sb.append('\f');
continue;
}
if (next_is('u')) {
ignore();
if (tell_remaining() < 4)
return Error::from_string_literal("JsonParser: EOF while parsing Unicode escape"sv);
auto code_point = AK::StringUtils::convert_to_uint_from_hex(consume(4));
if (code_point.has_value()) {
final_sb.append_code_point(code_point.value());
continue;
}
return Error::from_string_literal("JsonParser: Error while parsing Unicode escape"sv);
}
return Error::from_string_literal("JsonParser: Error while parsing string"sv);
}
if (!consume_specific('"'))
return Error::from_string_literal("JsonParser: Expected '\"'"sv);
return final_sb.to_string();
}
ErrorOr<JsonValue> JsonParser::parse_object()
{
JsonObject object;
if (!consume_specific('{'))
return Error::from_string_literal("JsonParser: Expected '{'"sv);
for (;;) {
ignore_while(is_space);
if (peek() == '}')
break;
ignore_while(is_space);
auto name = TRY(consume_and_unescape_string());
if (name.is_null())
return Error::from_string_literal("JsonParser: Expected object property name"sv);
ignore_while(is_space);
if (!consume_specific(':'))
return Error::from_string_literal("JsonParser: Expected ':'"sv);
ignore_while(is_space);
auto value = TRY(parse_helper());
object.set(name, move(value));
ignore_while(is_space);
if (peek() == '}')
break;
if (!consume_specific(','))
return Error::from_string_literal("JsonParser: Expected ','"sv);
ignore_while(is_space);
if (peek() == '}')
return Error::from_string_literal("JsonParser: Unexpected '}'"sv);
}
if (!consume_specific('}'))
return Error::from_string_literal("JsonParser: Expected '}'"sv);
return JsonValue { move(object) };
}
ErrorOr<JsonValue> JsonParser::parse_array()
{
JsonArray array;
if (!consume_specific('['))
return Error::from_string_literal("JsonParser: Expected '['"sv);
for (;;) {
ignore_while(is_space);
if (peek() == ']')
break;
auto element = TRY(parse_helper());
array.append(move(element));
ignore_while(is_space);
if (peek() == ']')
break;
if (!consume_specific(','))
return Error::from_string_literal("JsonParser: Expected ','"sv);
ignore_while(is_space);
if (peek() == ']')
return Error::from_string_literal("JsonParser: Unexpected ']'"sv);
}
ignore_while(is_space);
if (!consume_specific(']'))
return Error::from_string_literal("JsonParser: Expected ']'"sv);
return JsonValue { move(array) };
}
ErrorOr<JsonValue> JsonParser::parse_string()
{
auto string = TRY(consume_and_unescape_string());
return JsonValue(move(string));
}
ErrorOr<JsonValue> JsonParser::parse_number()
{
JsonValue value;
Vector<char, 128> number_buffer;
Vector<char, 128> fraction_buffer;
bool is_double = false;
for (;;) {
char ch = peek();
if (ch == '.') {
if (is_double)
return Error::from_string_literal("JsonParser: Multiple '.' in number"sv);
is_double = true;
++m_index;
continue;
}
if (ch == '-' || (ch >= '0' && ch <= '9')) {
if (is_double) {
if (ch == '-')
return Error::from_string_literal("JsonParser: Error while parsing number"sv);
fraction_buffer.append(ch);
} else {
if (number_buffer.size() > 0) {
if (number_buffer.at(0) == '0')
return Error::from_string_literal("JsonParser: Error while parsing number"sv);
}
if (number_buffer.size() > 1) {
if (number_buffer.at(0) == '-' && number_buffer.at(1) == '0')
return Error::from_string_literal("JsonParser: Error while parsing number"sv);
}
number_buffer.append(ch);
}
++m_index;
continue;
}
break;
}
StringView number_string(number_buffer.data(), number_buffer.size());
#ifndef KERNEL
if (is_double) {
// FIXME: This logic looks shaky.
int whole = 0;
auto to_signed_result = number_string.to_uint();
if (to_signed_result.has_value()) {
whole = to_signed_result.value();
} else {
auto number = number_string.to_int();
if (!number.has_value())
return Error::from_string_literal("JsonParser: Error while parsing number"sv);
whole = number.value();
}
StringView fraction_string(fraction_buffer.data(), fraction_buffer.size());
auto fraction_string_uint = fraction_string.to_uint();
if (!fraction_string_uint.has_value())
return Error::from_string_literal("JsonParser: Error while parsing number"sv);
int fraction = fraction_string_uint.value();
fraction *= (whole < 0) ? -1 : 1;
auto divider = 1;
for (size_t i = 0; i < fraction_buffer.size(); ++i) {
divider *= 10;
}
value = JsonValue((double)whole + ((double)fraction / divider));
} else {
#endif
auto to_unsigned_result = number_string.to_uint<u64>();
if (to_unsigned_result.has_value()) {
auto number = *to_unsigned_result;
if (number <= NumericLimits<u32>::max())
value = JsonValue((u32)number);
else
value = JsonValue(number);
} else {
auto number = number_string.to_int<i64>();
if (!number.has_value())
return Error::from_string_literal("JsonParser: Error while parsing number"sv);
if (number.value() <= NumericLimits<i32>::max()) {
value = JsonValue((i32)number.value());
} else {
value = JsonValue(number.value());
}
}
#ifndef KERNEL
}
#endif
return value;
}
ErrorOr<JsonValue> JsonParser::parse_true()
{
if (!consume_specific("true"))
return Error::from_string_literal("JsonParser: Expected 'true'"sv);
return JsonValue(true);
}
ErrorOr<JsonValue> JsonParser::parse_false()
{
if (!consume_specific("false"))
return Error::from_string_literal("JsonParser: Expected 'false'"sv);
return JsonValue(false);
}
ErrorOr<JsonValue> JsonParser::parse_null()
{
if (!consume_specific("null"))
return Error::from_string_literal("JsonParser: Expected 'null'"sv);
return JsonValue(JsonValue::Type::Null);
}
ErrorOr<JsonValue> JsonParser::parse_helper()
{
ignore_while(is_space);
auto type_hint = peek();
switch (type_hint) {
case '{':
return parse_object();
case '[':
return parse_array();
case '"':
return parse_string();
case '-':
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
return parse_number();
case 'f':
return parse_false();
case 't':
return parse_true();
case 'n':
return parse_null();
}
return Error::from_string_literal("JsonParser: Unexpected character"sv);
}
ErrorOr<JsonValue> JsonParser::parse()
{
auto result = TRY(parse_helper());
ignore_while(is_space);
if (!is_eof())
return Error::from_string_literal("JsonParser: Didn't consume all input"sv);
return result;
}
}