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/JsonArray.h>
#include <AK/JsonObject.h>
#include <AK/JsonParser.h>
namespace AK {
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constexpr bool is_space(int ch)
{
return ch == '\t' || ch == '\n' || ch == '\r' || ch == ' ';
}
String JsonParser::consume_and_unescape_string()
{
if (!consume_specific('"'))
return {};
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 {};
++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 {};
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;
} else {
return {};
}
}
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return {};
}
if (!consume_specific('"'))
return {};
return final_sb.to_string();
}
Optional<JsonValue> JsonParser::parse_object()
{
JsonObject object;
if (!consume_specific('{'))
return {};
for (;;) {
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ignore_while(is_space);
if (peek() == '}')
break;
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ignore_while(is_space);
auto name = consume_and_unescape_string();
if (name.is_null())
return {};
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ignore_while(is_space);
if (!consume_specific(':'))
return {};
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ignore_while(is_space);
auto value = parse_helper();
if (!value.has_value())
return {};
object.set(name, value.release_value());
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ignore_while(is_space);
if (peek() == '}')
break;
if (!consume_specific(','))
return {};
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ignore_while(is_space);
if (peek() == '}')
return {};
}
if (!consume_specific('}'))
return {};
return JsonValue { move(object) };
}
Optional<JsonValue> JsonParser::parse_array()
{
JsonArray array;
if (!consume_specific('['))
return {};
for (;;) {
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ignore_while(is_space);
if (peek() == ']')
break;
auto element = parse_helper();
if (!element.has_value())
return {};
array.append(element.release_value());
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ignore_while(is_space);
if (peek() == ']')
break;
if (!consume_specific(','))
return {};
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ignore_while(is_space);
if (peek() == ']')
return {};
}
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ignore_while(is_space);
if (!consume_specific(']'))
return {};
return JsonValue { move(array) };
}
Optional<JsonValue> JsonParser::parse_string()
{
auto result = consume_and_unescape_string();
if (result.is_null())
return {};
return JsonValue(result);
}
Optional<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 == '.') {
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if (is_double)
return {};
is_double = true;
++m_index;
continue;
}
if (ch == '-' || (ch >= '0' && ch <= '9')) {
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if (is_double) {
if (ch == '-')
return {};
fraction_buffer.append(ch);
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} else {
if (number_buffer.size() > 0) {
if (number_buffer.at(0) == '0')
return {};
}
if (number_buffer.size() > 1) {
if (number_buffer.at(0) == '-' && number_buffer.at(1) == '0')
return {};
}
number_buffer.append(ch);
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}
++m_index;
continue;
}
break;
}
StringView number_string(number_buffer.data(), number_buffer.size());
StringView fraction_string(fraction_buffer.data(), fraction_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 {};
whole = number.value();
}
auto fraction_string_uint = fraction_string.to_uint();
if (!fraction_string_uint.has_value())
return {};
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 {};
if (number.value() <= NumericLimits<i32>::max()) {
value = JsonValue((i32)number.value());
} else {
value = JsonValue(number.value());
}
}
#ifndef KERNEL
}
#endif
return value;
}
Optional<JsonValue> JsonParser::parse_true()
{
if (!consume_specific("true"))
return {};
return JsonValue(true);
}
Optional<JsonValue> JsonParser::parse_false()
{
if (!consume_specific("false"))
return {};
return JsonValue(false);
}
Optional<JsonValue> JsonParser::parse_null()
{
if (!consume_specific("null"))
return {};
return JsonValue(JsonValue::Type::Null);
}
Optional<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 {};
}
Optional<JsonValue> JsonParser::parse()
{
auto result = parse_helper();
if (!result.has_value())
return {};
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ignore_while(is_space);
if (!is_eof())
return {};
return result;
}
}