chromium/base/json/json_reader.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// A JSON parser, converting from a std::string_view to a base::Value.
//
// The JSON spec is:
// https://tools.ietf.org/rfc/rfc8259.txt
// which obsoletes the earlier RFCs 4627, 7158 and 7159.
//
// This RFC should be equivalent to the informal spec:
// https://www.json.org/json-en.html
//
// Implementation choices permitted by the RFC:
// - Nesting is limited (to a configurable depth, 200 by default).
// - Numbers are limited to those representable by a finite double. The
//   conversion from a JSON number (in the std::string_view input) to a
//   double-flavored base::Value may also be lossy.
// - The input (which must be UTF-8) may begin with a BOM (Byte Order Mark).
// - Duplicate object keys (strings) are silently allowed. Last key-value pair
//   wins. Previous pairs are discarded.
//
// Configurable (see the JSONParserOptions type) deviations from the RFC:
// - Allow trailing commas: "[1,2,]".
// - Replace invalid Unicode with U+FFFD REPLACEMENT CHARACTER.
// - Allow "// etc\n" and "/* etc */" C-style comments.
// - Allow ASCII control characters, including literal (not escaped) NUL bytes
//   and new lines, within a JSON string.
// - Allow "\\v" escapes within a JSON string, producing a vertical tab.
// - Allow "\\x23" escapes within a JSON string. Subtly, the 2-digit hex value
//   is a Unicode code point, not a UTF-8 byte. For example, "\\xFF" in the
//   JSON source decodes to a base::Value whose string contains "\xC3\xBF", the
//   UTF-8 encoding of U+00FF LATIN SMALL LETTER Y WITH DIAERESIS. Converting
//   from UTF-8 to UTF-16, e.g. via UTF8ToWide, will recover a 16-bit 0x00FF.

#ifndef BASE_JSON_JSON_READER_H_
#define BASE_JSON_JSON_READER_H_

#include <optional>
#include <string>
#include <string_view>

#include "base/base_export.h"
#include "base/json/json_common.h"
#include "base/strings/string_number_conversions.h"
#include "base/types/expected.h"
#include "base/values.h"

namespace base {

enum JSONParserOptions { … };

class BASE_EXPORT JSONReader { … };

}  // namespace base

#endif  // BASE_JSON_JSON_READER_H_