/*
* 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 == ' ';
}
// ECMA-404 9 String
// Boils down to
// STRING = "\"" *("[^\"\\]" | "\\" ("[\"\\bfnrt]" | "u[0-9A-Za-z]{4}")) "\""
// │├── " ──╮───────────────────────────────────────────────╭── " ──┤│
// │ │
// │ ╭───────────────────<─────────────────────╮ │
// │ │ │ │
// ╰──╰──╮───────────── [^"\\] ──────────────╭──╯──╯
// │ │
// ╰── \ ───╮──── ["\\bfnrt] ───────╭──╯
// │ │
// ╰─── u[0-9A-Za-z]{4} ──╯
//
ErrorOr<ByteString> JsonParser::consume_and_unescape_string()
{
if (!consume_specific('"'))
return Error::from_string_literal("JsonParser: Expected '\"'");
StringBuilder final_sb;
for (;;) {
// OPTIMIZATION: We try to append as many literal characters as possible at a time
// This also pre-checks some error conditions
// Note: All utf8 characters are either plain ascii, or have their most signifiant bit set,
// which puts the, above plain ascii in value, so they will always consist
// of a set of "legal" non-special bytes,
// hence we don't need to bother with a code-point iterator,
// as a simple byte iterator suffices, which GenericLexer provides by default
size_t literal_characters = 0;
for (;;) {
char ch = peek(literal_characters);
// Note: We get a 0 byte when we hit EOF
if (ch == 0)
return Error::from_string_literal("JsonParser: EOF while parsing String");
// Spec: All code points may be placed within the quotation marks except
// for the code points that must be escaped: quotation mark (U+0022),
// reverse solidus (U+005C), and the control characters U+0000 to U+001F.
// There are two-character escape sequence representations of some characters.
if (is_ascii_c0_control(ch))
return Error::from_string_literal("JsonParser: ASCII control sequence encountered");
if (ch == '"' || ch == '\\')
break;
++literal_characters;
}
final_sb.append(consume(literal_characters));
// We have checked all cases except end-of-string and escaped characters in the loop above,
// so we now only have to handle those two cases
char ch = peek();
if (ch == '"') {
consume();
break;
}
ignore(); // '\'
switch (peek()) {
case '\0':
return Error::from_string_literal("JsonParser: EOF while parsing String");
case '"':
case '\\':
case '/':
final_sb.append(consume());
break;
case 'b':
ignore();
final_sb.append('\b');
break;
case 'f':
ignore();
final_sb.append('\f');
break;
case 'n':
ignore();
final_sb.append('\n');
break;
case 'r':
ignore();
final_sb.append('\r');
break;
case 't':
ignore();
final_sb.append('\t');
break;
case 'u': {
ignore(); // 'u'
// https://ecma-international.org/wp-content/uploads/ECMA-404_2nd_edition_december_2017.pdf
//
// To escape a code point that is not in the Basic Multilingual Plane, the character may be represented as a
// twelve-character sequence, encoding the UTF-16 surrogate pair corresponding to the code point. So for
// example, a string containing only the G clef character (U+1D11E) may be represented as "\uD834\uDD1E".
// However, whether a processor of JSON texts interprets such a surrogate pair as a single code point or as an
// explicit surrogate pair is a semantic decision that is determined by the specific processor.
auto code_point = decode_single_or_paired_surrogate();
if (code_point.is_error())
return Error::from_string_literal("JsonParser: Error while parsing Unicode escape");
final_sb.append_code_point(code_point.value());
break;
}
default:
dbgln("JsonParser: Invalid escaped character '{}' ({:#x}) ", peek(), peek());
return Error::from_string_literal("JsonParser: Invalid escaped character");
}
}
return final_sb.to_byte_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());
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());
TRY(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());
if (auto number = number_string.to_number<u64>(); number.has_value())
return JsonValue(*number);
if (auto number = number_string.to_number<i64>(); number.has_value())
return JsonValue(*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"sv))
return Error::from_string_literal("JsonParser: Expected 'true'");
return JsonValue(true);
}
ErrorOr<JsonValue> JsonParser::parse_false()
{
if (!consume_specific("false"sv))
return Error::from_string_literal("JsonParser: Expected 'false'");
return JsonValue(false);
}
ErrorOr<JsonValue> JsonParser::parse_null()
{
if (!consume_specific("null"sv))
return Error::from_string_literal("JsonParser: Expected 'null'");
return JsonValue {};
}
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;
}
}
