base/i18n/streaming_utf8_validator.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 // A streaming validator for UTF-8. Validation is based on the definition in
   6 // RFC-3629. In particular, it does not reject the invalid characters rejected
   7 // by base::IsStringUTF8().
   8 //
   9 // The implementation detects errors on the first possible byte.
  10
  11 #ifndef BASE_I18N_STREAMING_UTF8_VALIDATOR_H_
  12 #define BASE_I18N_STREAMING_UTF8_VALIDATOR_H_
  13
  14 #include <string>
  15
  16 #include "base/basictypes.h"
  17 #include "base/i18n/base_i18n_export.h"
  18
  19 namespace base {
  20
  21 class BASE_I18N_EXPORT StreamingUtf8Validator {
  22  public:
  23   // The validator exposes 3 states. It starts in state VALID_ENDPOINT. As it
  24   // processes characters it alternates between VALID_ENDPOINT and
  25   // VALID_MIDPOINT. If it encounters an invalid byte or UTF-8 sequence the
  26   // state changes permanently to INVALID.
  27   enum State {
  28     VALID_ENDPOINT,
  29     VALID_MIDPOINT,
  30     INVALID
  31   };
  32
  33   StreamingUtf8Validator() : state_(0u) {}
  34   // Trivial destructor intentionally omitted.
  35
  36   // Validate |size| bytes starting at |data|. If the concatenation of all calls
  37   // to AddBytes() since this object was constructed or reset is a valid UTF-8
  38   // string, returns VALID_ENDPOINT. If it could be the prefix of a valid UTF-8
  39   // string, returns VALID_MIDPOINT. If an invalid byte or UTF-8 sequence was
  40   // present, returns INVALID.
  41   State AddBytes(const char* data, size_t size);
  42
  43   // Return the object to a freshly-constructed state so that it can be re-used.
  44   void Reset();
  45
  46   // Validate a complete string using the same criteria. Returns true if the
  47   // string only contains complete, valid UTF-8 codepoints.
  48   static bool Validate(const std::string& string);
  49
  50  private:
  51   // The current state of the validator. Value 0 is the initial/valid state.
  52   // The state is stored as an offset into |kUtf8ValidatorTables|. The special
  53   // state |kUtf8InvalidState| is invalid.
  54   uint8 state_;
  55
  56   // This type could be made copyable but there is currently no use-case for
  57   // it.
  58   DISALLOW_COPY_AND_ASSIGN(StreamingUtf8Validator);
  59 };
  60
  61 }  // namespace base
  62
  63 #endif  // BASE_I18N_STREAMING_UTF8_VALIDATOR_H_