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ladybird/AK/JsonParser.cpp
davidot c9aa664eb0 AK: Make the JsonParser use the new double parser for numbers 
Because we still support u64 and i64 (on top of i32 and u32) we do still
have to parse the number ourself first. Then if we determine that the
number is a floating point or is outside of the range of i64 and u64 we
fallback and parse it as a double.

Before JsonParser had ifdefs guarding the double computation, but it
just build when we error on ifdef KERNEL so JsonParser is no longer
usable in the Kernel. This can be remedied fairly easily but since
it is not needed we #error on that for now.
2022-10-23 15:48:45 +02:00

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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#include <AK/CharacterTypes.h>
#include <AK/FloatingPointStringConversions.h>
#include <AK/JsonArray.h>
#include <AK/JsonObject.h>
#include <AK/JsonParser.h>
#include <math.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 '\"'");
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");
++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");
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");
}
return Error::from_string_literal("JsonParser: Error while parsing string");
}
if (!consume_specific('"'))
return Error::from_string_literal("JsonParser: Expected '\"'");
return final_sb.to_string();
}
ErrorOr<JsonValue> JsonParser::parse_object()
{
JsonObject object;
if (!consume_specific('{'))
return Error::from_string_literal("JsonParser: Expected '{'");
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");
ignore_while(is_space);
if (!consume_specific(':'))
return Error::from_string_literal("JsonParser: Expected ':'");
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 ','");
ignore_while(is_space);
if (peek() == '}')
return Error::from_string_literal("JsonParser: Unexpected '}'");
}
if (!consume_specific('}'))
return Error::from_string_literal("JsonParser: Expected '}'");
return JsonValue { move(object) };
}
ErrorOr<JsonValue> JsonParser::parse_array()
{
JsonArray array;
if (!consume_specific('['))
return Error::from_string_literal("JsonParser: Expected '['");
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 ','");
ignore_while(is_space);
if (peek() == ']')
return Error::from_string_literal("JsonParser: Unexpected ']'");
}
ignore_while(is_space);
if (!consume_specific(']'))
return Error::from_string_literal("JsonParser: Expected ']'");
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()
{
Vector<char, 32> number_buffer;
auto start_index = tell();
bool negative = false;
if (peek() == '-') {
number_buffer.append('-');
++m_index;
negative = true;
if (!is_ascii_digit(peek()))
return Error::from_string_literal("JsonParser: Unexpected '-' without further digits");
}
auto fallback_to_double_parse = [&]() -> ErrorOr<JsonValue> {
#ifdef KERNEL
# error JSONParser is currently not available for the Kernel because it disallows floating point. \
If you want to make this KERNEL compatible you can just make this fallback_to_double \
function fail with an error in KERNEL mode.
#endif
// FIXME: Since we know all the characters so far are ascii digits (and one . or e) we could
// use that in the floating point parser.
// The first part should be just ascii digits
StringView view = m_input.substring_view(start_index);
char const* start = view.characters_without_null_termination();
auto parse_result = parse_first_floating_point(start, start + view.length());
if (parse_result.parsed_value()) {
auto characters_parsed = parse_result.end_ptr - start;
m_index = start_index + characters_parsed;
return JsonValue(parse_result.value);
}
return Error::from_string_literal("JsonParser: Invalid floating point");
};
if (peek() == '0') {
if (is_ascii_digit(peek(1)))
return Error::from_string_literal("JsonParser: Cannot have leading zeros");
// Leading zeros are not allowed, however we can have a '.' or 'e' with
// valid digits after just a zero. These cases will be detected by having the next element
// start with a '.' or 'e'.
}
bool all_zero = true;
for (;;) {
char ch = peek();
if (ch == '.') {
if (!is_ascii_digit(peek(1)))
return Error::from_string_literal("JsonParser: Must have digits after decimal point");
return fallback_to_double_parse();
}
if (ch == 'e' || ch == 'E') {
char next = peek(1);
if (!is_ascii_digit(next) && ((next != '+' && next != '-') || !is_ascii_digit(peek(2))))
return Error::from_string_literal("JsonParser: Must have digits after exponent with an optional sign inbetween");
return fallback_to_double_parse();
}
if (is_ascii_digit(ch)) {
if (ch != '0')
all_zero = false;
number_buffer.append(ch);
++m_index;
continue;
}
break;
}
// Negative zero is always a double
if (negative && all_zero)
return JsonValue(-0.0);
StringView number_string(number_buffer.data(), number_buffer.size());
auto to_unsigned_result = number_string.to_uint<u64>();
if (to_unsigned_result.has_value()) {
if (*to_unsigned_result <= NumericLimits<u32>::max())
return JsonValue((u32)*to_unsigned_result);
return JsonValue(*to_unsigned_result);
} else if (auto signed_number = number_string.to_int<i64>(); signed_number.has_value()) {
if (*signed_number <= NumericLimits<i32>::max())
return JsonValue((i32)*signed_number);
return JsonValue(*signed_number);
}
// It's possible the unsigned value is bigger than u64 max
return fallback_to_double_parse();
}
ErrorOr<JsonValue> JsonParser::parse_true()
{
if (!consume_specific("true"))
return Error::from_string_literal("JsonParser: Expected 'true'");
return JsonValue(true);
}
ErrorOr<JsonValue> JsonParser::parse_false()
{
if (!consume_specific("false"))
return Error::from_string_literal("JsonParser: Expected 'false'");
return JsonValue(false);
}
ErrorOr<JsonValue> JsonParser::parse_null()
{
if (!consume_specific("null"))
return Error::from_string_literal("JsonParser: Expected 'null'");
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");
}
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");
return result;
}
}
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