unicodetext.h | Explore in Territory

// Copyright (C) 2006 Google Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Author: Jim Meehan

#ifndef UNICODETEXT_H_
#define UNICODETEXT_H_

#include <iterator>
#include <utility>

#include "base.h"

namespace chrome_lang_id {

// ***************************** UnicodeText **************************
//
// A UnicodeText object is a wrapper around a sequence of Unicode
// codepoint values that allows iteration over these values.
//
// The internal representation of the text is UTF-8. Since UTF-8 is a
// variable-width format, UnicodeText does not provide random access
// to the text, and changes to the text are permitted only at the end.
//
// The UnicodeText class defines a const_iterator. The dereferencing
// operator (*) returns a codepoint (int32). The iterator is a
// read-only iterator. It becomes invalid if the text is changed.
//
// Codepoints are integers in the range [0, 0xD7FF] or [0xE000,
// 0x10FFFF], but UnicodeText has the additional restriction that it
// can contain only those characters that are valid for interchange on
// the Web. This excludes all of the control codes except for carriage
// return, line feed, and horizontal tab.  It also excludes
// non-characters, but codepoints that are in the Private Use regions
// are allowed, as are codepoints that are unassigned. (See the
// Unicode reference for details.)
//
// MEMORY MANAGEMENT:
//
// PointToUTF8(buffer, size) creates an alias pointing to buffer.
//
// The purpose of an alias is to avoid making an unnecessary copy of a
// UTF-8 buffer while still providing access to the Unicode values
// within that text through iterators. The lifetime of an alias must not
// exceed the lifetime of the buffer from which it was constructed.
//
// Aliases should be used with care. If the source from which an alias
// was created is freed, or if the contents are changed, while the
// alias is still in use, fatal errors could result. But it can be
// quite useful to have a UnicodeText "window" through which to see a
// UTF-8 buffer without having to pay the price of making a copy.

// TODO(abakalov): Consider merging this class with the script detection
// code in the directory script_span.
class UnicodeText { … };

}  // namespace chrome_lang_id

#endif  // UNICODETEXT_H_
chromium/third_party/cld_3/src/src/unicodetext.h
