string_escape.h

// Copyright (c) 2011 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This file defines utility functions for escaping strings suitable for JSON.

#ifndef BASE_JSON_STRING_ESCAPE_H_
#define BASE_JSON_STRING_ESCAPE_H_

#include <string>

#include "base/base_export.h"
#include "base/strings/string_piece.h"

namespace base {

// Appends to |dest| an escaped version of |str|. Valid UTF-8 code units and
// characters will pass through from the input to the output. Invalid code
// units and characters will be replaced with the U+FFFD replacement character.
// This function returns true if no replacement was necessary and false if
// there was a lossy replacement. On return, |dest| will contain a valid UTF-8
// JSON string.
//
// Non-printing control characters will be escaped as \uXXXX sequences for
// readability.
//
// If |put_in_quotes| is true, then a leading and trailing double-quote mark
// will be appended to |dest| as well.
BASE_EXPORT bool EscapeJSONString(StringPiece str,
                                  bool put_in_quotes,
                                  std::string* dest);

// Performs a similar function to the UTF-8 StringPiece version above,
// converting UTF-16 code units to UTF-8 code units and escaping non-printing
// control characters. On return, |dest| will contain a valid UTF-8 JSON string.
BASE_EXPORT bool EscapeJSONString(StringPiece16 str,
                                  bool put_in_quotes,
                                  std::string* dest);

// Helper functions that wrap the above two functions but return the value
// instead of appending. |put_in_quotes| is always true.
BASE_EXPORT std::string GetQuotedJSONString(StringPiece str);
BASE_EXPORT std::string GetQuotedJSONString(StringPiece16 str);

// Given an arbitrary byte string |str|, this will escape all non-ASCII bytes
// as \uXXXX escape sequences. This function is *NOT* meant to be used with
// Unicode strings and does not validate |str| as one.
//
// CAVEAT CALLER: The output of this function may not be valid JSON, since
// JSON requires escape sequences to be valid UTF-16 code units. This output
// will be mangled if passed to to the base::JSONReader, since the reader will
// interpret it as UTF-16 and convert it to UTF-8.
//
// The output of this function takes the *appearance* of JSON but is not in
// fact valid according to RFC 8259.
BASE_EXPORT std::string EscapeBytesAsInvalidJSONString(StringPiece str,
                                                       bool put_in_quotes);

}  // namespace base

#endif  // BASE_JSON_STRING_ESCAPE_H_