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Diffstat (limited to 'src/libs/xpcom18a4/xpcom/string/public/nsTPromiseFlatString.h')
| -rw-r--r-- | src/libs/xpcom18a4/xpcom/string/public/nsTPromiseFlatString.h | 158 |
1 files changed, 158 insertions, 0 deletions
diff --git a/src/libs/xpcom18a4/xpcom/string/public/nsTPromiseFlatString.h b/src/libs/xpcom18a4/xpcom/string/public/nsTPromiseFlatString.h new file mode 100644 index 00000000..6cf82f60 --- /dev/null +++ b/src/libs/xpcom18a4/xpcom/string/public/nsTPromiseFlatString.h @@ -0,0 +1,158 @@ +/* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */ +/* vim:set ts=2 sw=2 sts=2 et cindent: */ +/* ***** BEGIN LICENSE BLOCK ***** + * Version: MPL 1.1/GPL 2.0/LGPL 2.1 + * + * The contents of this file are subject to the Mozilla Public License Version + * 1.1 (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.mozilla.org/MPL/ + * + * Software distributed under the License is distributed on an "AS IS" basis, + * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License + * for the specific language governing rights and limitations under the + * License. + * + * The Original Code is Mozilla. + * + * The Initial Developer of the Original Code is IBM Corporation. + * Portions created by IBM Corporation are Copyright (C) 2003 + * IBM Corporation. All Rights Reserved. + * + * Contributor(s): + * Scott Collins <scc@mozilla.org> (original author) + * Darin Fisher <darin@meer.net> + * + * Alternatively, the contents of this file may be used under the terms of + * either the GNU General Public License Version 2 or later (the "GPL"), or + * the GNU Lesser General Public License Version 2.1 or later (the "LGPL"), + * in which case the provisions of the GPL or the LGPL are applicable instead + * of those above. If you wish to allow use of your version of this file only + * under the terms of either the GPL or the LGPL, and not to allow others to + * use your version of this file under the terms of the MPL, indicate your + * decision by deleting the provisions above and replace them with the notice + * and other provisions required by the GPL or the LGPL. If you do not delete + * the provisions above, a recipient may use your version of this file under + * the terms of any one of the MPL, the GPL or the LGPL. + * + * ***** END LICENSE BLOCK ***** */ + + + /** + * NOTE: + * + * Try to avoid flat strings. |PromiseFlat[C]String| will help you as a last + * resort, and this may be necessary when dealing with legacy or OS calls, + * but in general, requiring a null-terminated array of characters kills many + * of the performance wins the string classes offer. Write your own code to + * use |nsA[C]String&|s for parameters. Write your string proccessing + * algorithms to exploit iterators. If you do this, you will benefit from + * being able to chain operations without copying or allocating and your code + * will be significantly more efficient. Remember, a function that takes an + * |const nsA[C]String&| can always be passed a raw character pointer by + * wrapping it (for free) in a |nsDependent[C]String|. But a function that + * takes a character pointer always has the potential to force allocation and + * copying. + * + * + * How to use it: + * + * A |nsPromiseFlat[C]String| doesn't necessarily own the characters it + * promises. You must never use it to promise characters out of a string + * with a shorter lifespan. The typical use will be something like this: + * + * SomeOSFunction( PromiseFlatCString(aCString).get() ); // GOOD + * + * Here's a BAD use: + * + * const char* buffer = PromiseFlatCString(aCString).get(); + * SomeOSFunction(buffer); // BAD!! |buffer| is a dangling pointer + * + * The only way to make one is with the function |PromiseFlat[C]String|, + * which produce a |const| instance. ``What if I need to keep a promise + * around for a little while?'' you might ask. In that case, you can keep a + * reference, like so + * + * const nsPromiseFlatString& flat = PromiseFlatString(aString); + * // this reference holds the anonymous temporary alive, but remember, + * // it must _still_ have a lifetime shorter than that of |aString| + * + * SomeOSFunction(flat.get()); + * SomeOtherOSFunction(flat.get()); + * + * + * How does it work? + * + * A |nsPromiseFlat[C]String| is just a wrapper for another string. If you + * apply it to a string that happens to be flat, your promise is just a + * dependent reference to the string's data. If you apply it to a non-flat + * string, then a temporary flat string is created for you, by allocating and + * copying. In the event that you end up assigning the result into a sharing + * string (e.g., |nsTString|), the right thing happens. + */ + +class nsTPromiseFlatString_CharT : public nsTString_CharT + { + public: + + typedef nsTPromiseFlatString_CharT self_type; + + private: + + NS_COM void Init( const substring_type& ); + NS_COM void Init( const abstract_string_type& ); + + // NOT TO BE IMPLEMENTED + void operator=( const self_type& ); + + // NOT TO BE IMPLEMENTED + nsTPromiseFlatString_CharT(); + + public: + + explicit + nsTPromiseFlatString_CharT( const substring_type& str ) + : string_type() + { + Init(str); + } + + explicit + nsTPromiseFlatString_CharT( const abstract_string_type& readable ) + : string_type() + { + Init(readable); + } + + explicit + nsTPromiseFlatString_CharT( const substring_tuple_type& tuple ) + : string_type() + { + // nothing else to do here except assign the value of the tuple + // into ourselves. + Assign(tuple); + } + }; + +inline +const nsTPromiseFlatString_CharT +TPromiseFlatString_CharT( const nsTAString_CharT& str ) + { + return nsTPromiseFlatString_CharT(str); + } + + // e.g., PromiseFlatCString(Substring(s)) +inline +const nsTPromiseFlatString_CharT +TPromiseFlatString_CharT( const nsTSubstring_CharT& frag ) + { + return nsTPromiseFlatString_CharT(frag); + } + + // e.g., PromiseFlatCString(a + b) +inline +const nsTPromiseFlatString_CharT +TPromiseFlatString_CharT( const nsTSubstringTuple_CharT& tuple ) + { + return nsTPromiseFlatString_CharT(tuple); + } |