gecko/xpcom/string/nsTPromiseFlatString.h
Birunthan Mohanathas da2394e67f Bug 1028559 - Flatten xpcom/string/{public,src}/ directories. r=dbaron
--HG--
rename : xpcom/string/public/nsAString.h => xpcom/string/nsAString.h
rename : xpcom/string/public/nsAlgorithm.h => xpcom/string/nsAlgorithm.h
rename : xpcom/string/public/nsCharTraits.h => xpcom/string/nsCharTraits.h
rename : xpcom/string/src/nsDependentString.cpp => xpcom/string/nsDependentString.cpp
rename : xpcom/string/public/nsDependentString.h => xpcom/string/nsDependentString.h
rename : xpcom/string/src/nsDependentSubstring.cpp => xpcom/string/nsDependentSubstring.cpp
rename : xpcom/string/public/nsDependentSubstring.h => xpcom/string/nsDependentSubstring.h
rename : xpcom/string/public/nsEmbedString.h => xpcom/string/nsEmbedString.h
rename : xpcom/string/public/nsLiteralString.h => xpcom/string/nsLiteralString.h
rename : xpcom/string/public/nsPrintfCString.h => xpcom/string/nsPrintfCString.h
rename : xpcom/string/src/nsPromiseFlatString.cpp => xpcom/string/nsPromiseFlatString.cpp
rename : xpcom/string/public/nsPromiseFlatString.h => xpcom/string/nsPromiseFlatString.h
rename : xpcom/string/src/nsReadableUtils.cpp => xpcom/string/nsReadableUtils.cpp
rename : xpcom/string/public/nsReadableUtils.h => xpcom/string/nsReadableUtils.h
rename : xpcom/string/src/nsString.cpp => xpcom/string/nsString.cpp
rename : xpcom/string/public/nsString.h => xpcom/string/nsString.h
rename : xpcom/string/public/nsStringBuffer.h => xpcom/string/nsStringBuffer.h
rename : xpcom/string/src/nsStringComparator.cpp => xpcom/string/nsStringComparator.cpp
rename : xpcom/string/public/nsStringFwd.h => xpcom/string/nsStringFwd.h
rename : xpcom/string/public/nsStringIterator.h => xpcom/string/nsStringIterator.h
rename : xpcom/string/src/nsStringObsolete.cpp => xpcom/string/nsStringObsolete.cpp
rename : xpcom/string/src/nsSubstring.cpp => xpcom/string/nsSubstring.cpp
rename : xpcom/string/public/nsSubstring.h => xpcom/string/nsSubstring.h
rename : xpcom/string/src/nsSubstringTuple.cpp => xpcom/string/nsSubstringTuple.cpp
rename : xpcom/string/public/nsSubstringTuple.h => xpcom/string/nsSubstringTuple.h
rename : xpcom/string/src/nsTDependentString.cpp => xpcom/string/nsTDependentString.cpp
rename : xpcom/string/public/nsTDependentString.h => xpcom/string/nsTDependentString.h
rename : xpcom/string/src/nsTDependentSubstring.cpp => xpcom/string/nsTDependentSubstring.cpp
rename : xpcom/string/public/nsTDependentSubstring.h => xpcom/string/nsTDependentSubstring.h
rename : xpcom/string/public/nsTLiteralString.h => xpcom/string/nsTLiteralString.h
rename : xpcom/string/src/nsTPromiseFlatString.cpp => xpcom/string/nsTPromiseFlatString.cpp
rename : xpcom/string/public/nsTPromiseFlatString.h => xpcom/string/nsTPromiseFlatString.h
rename : xpcom/string/src/nsTString.cpp => xpcom/string/nsTString.cpp
rename : xpcom/string/public/nsTString.h => xpcom/string/nsTString.h
rename : xpcom/string/src/nsTStringComparator.cpp => xpcom/string/nsTStringComparator.cpp
rename : xpcom/string/src/nsTStringObsolete.cpp => xpcom/string/nsTStringObsolete.cpp
rename : xpcom/string/src/nsTSubstring.cpp => xpcom/string/nsTSubstring.cpp
rename : xpcom/string/public/nsTSubstring.h => xpcom/string/nsTSubstring.h
rename : xpcom/string/src/nsTSubstringTuple.cpp => xpcom/string/nsTSubstringTuple.cpp
rename : xpcom/string/public/nsTSubstringTuple.h => xpcom/string/nsTSubstringTuple.h
rename : xpcom/string/public/nsUTF8Utils.h => xpcom/string/nsUTF8Utils.h
rename : xpcom/string/src/nsUTF8UtilsSSE2.cpp => xpcom/string/nsUTF8UtilsSSE2.cpp
rename : xpcom/string/public/nsXPCOMStrings.h => xpcom/string/nsXPCOMStrings.h
rename : xpcom/string/public/nsXPIDLString.h => xpcom/string/nsXPIDLString.h
rename : xpcom/string/public/string-template-def-char.h => xpcom/string/string-template-def-char.h
rename : xpcom/string/public/string-template-def-unichar.h => xpcom/string/string-template-def-unichar.h
rename : xpcom/string/public/string-template-undef.h => xpcom/string/string-template-undef.h
2014-06-25 15:08:54 -07:00

107 lines
3.6 KiB
C++

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
* License, v. 2.0. If a copy of the MPL was not distributed with this
* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
/**
* 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(aCSubstring).get() ); // GOOD
*
* Here's a BAD use:
*
* const char* buffer = PromiseFlatCString(aCSubstring).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 nsCString& flat = PromiseFlatString(aCSubstring);
* // this reference holds the anonymous temporary alive, but remember,
* // it must _still_ have a lifetime shorter than that of |aCSubstring|
*
* 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:
void Init(const substring_type&);
// NOT TO BE IMPLEMENTED
void operator=(const self_type&) MOZ_DELETE;
// NOT TO BE IMPLEMENTED
nsTPromiseFlatString_CharT() MOZ_DELETE;
// NOT TO BE IMPLEMENTED
nsTPromiseFlatString_CharT(const string_type& aStr) MOZ_DELETE;
public:
explicit
nsTPromiseFlatString_CharT(const substring_type& aStr)
: string_type()
{
Init(aStr);
}
explicit
nsTPromiseFlatString_CharT(const substring_tuple_type& aTuple)
: string_type()
{
// nothing else to do here except assign the value of the tuple
// into ourselves.
Assign(aTuple);
}
};
// We template this so that the constructor is chosen based on the type of the
// parameter. This allows us to reject attempts to promise a flat flat string.
template<class T>
const nsTPromiseFlatString_CharT
TPromiseFlatString_CharT(const T& aString)
{
return nsTPromiseFlatString_CharT(aString);
}