ladybird/AK/JsonParser.cpp

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/*
* Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
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#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 {
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constexpr bool is_space(int ch)
{
return ch == '\t' || ch == '\n' || ch == '\r' || ch == ' ';
}
ErrorOr<DeprecatedString> 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;
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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();
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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');
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continue;
}
if (next_is('r')) {
ignore();
final_sb.append('\r');
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continue;
}
if (next_is('t')) {
ignore();
final_sb.append('\t');
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continue;
}
if (next_is('b')) {
ignore();
final_sb.append('\b');
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continue;
}
if (next_is('f')) {
ignore();
final_sb.append('\f');
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continue;
}
if (next_is('u')) {
ignore();
if (tell_remaining() < 4)
return Error::from_string_literal("JsonParser: EOF while parsing Unicode escape");
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auto code_point = AK::StringUtils::convert_to_uint_from_hex(consume(4));
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if (code_point.has_value()) {
final_sb.append_code_point(code_point.value());
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continue;
}
return Error::from_string_literal("JsonParser: Error while parsing Unicode escape");
}
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return Error::from_string_literal("JsonParser: Error while parsing string");
}
if (!consume_specific('"'))
return Error::from_string_literal("JsonParser: Expected '\"'");
return final_sb.to_deprecated_string();
}
ErrorOr<JsonValue> JsonParser::parse_object()
{
JsonObject object;
if (!consume_specific('{'))
return Error::from_string_literal("JsonParser: Expected '{'");
for (;;) {
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ignore_while(is_space);
if (peek() == '}')
break;
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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");
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ignore_while(is_space);
if (!consume_specific(':'))
return Error::from_string_literal("JsonParser: Expected ':'");
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ignore_while(is_space);
auto value = TRY(parse_helper());
object.set(name, move(value));
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ignore_while(is_space);
if (peek() == '}')
break;
if (!consume_specific(','))
return Error::from_string_literal("JsonParser: Expected ','");
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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 (;;) {
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ignore_while(is_space);
if (peek() == ']')
break;
auto element = TRY(parse_helper());
array.append(move(element));
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ignore_while(is_space);
if (peek() == ']')
break;
if (!consume_specific(','))
return Error::from_string_literal("JsonParser: Expected ','");
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ignore_while(is_space);
if (peek() == ']')
return Error::from_string_literal("JsonParser: Unexpected ']'");
}
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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");
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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");
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return fallback_to_double_parse();
}
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if (is_ascii_digit(ch)) {
if (ch != '0')
all_zero = false;
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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()
{
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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());
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ignore_while(is_space);
if (!is_eof())
return Error::from_string_literal("JsonParser: Didn't consume all input");
return result;
}
}