xpcom/ds/nsStringEnumerator.h
author Nicholas Nethercote <nnethercote@mozilla.com>
Thu, 28 Apr 2016 17:11:17 +1000
changeset 334688 1d99e6c5a2bf41b983658369b97c5d152649695b
parent 268263 2328731ef45354daf50eb21607a3c781ab79bc7c
child 493106 907a2b49e060213565f65c7b8b4ab4308b0ab93c
permissions -rw-r--r--
Bug 1268772 (part 5) - Use MOZ_MUST_USE in other parts of xpcom/ds/. r=erahm. As well as adding MOZ_MUST_USE to a number of functions, this patch: - Changes the return type of nsObserverList::GetObserverList() from |nsresult| to |void|, because it always returned NS_OK and none of the callers checked the result. - Removes an unnecessary |new| check in nsSupportsArray::Enumerate().

/* -*- 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/. */

#include "nsIStringEnumerator.h"
#include "nsStringFwd.h"
#include "nsTArrayForwardDeclare.h"

// nsIStringEnumerator/nsIUTF8StringEnumerator implementations
//
// Currently all implementations support both interfaces. The
// constructors below provide the most common interface for the given
// type (i.e. nsIStringEnumerator for char16_t* strings, and so
// forth) but any resulting enumerators can be queried to the other
// type. Internally, the enumerators will hold onto the type that was
// passed in and do conversion if GetNext() for the other type of
// string is called.

// There are a few different types of enumerators:

//
// These enumerators hold a pointer to the array. Be careful
// because modifying the array may confuse the iterator, especially if
// you insert or remove elements in the middle of the array.
//

// The non-adopting enumerator requires that the array sticks around
// at least as long as the enumerator does. These are for constant
// string arrays that the enumerator does not own, this could be used
// in VERY specialized cases such as when the provider KNOWS that the
// string enumerator will be consumed immediately, or will at least
// outlast the array.
// For example:
//
// nsTArray<nsCString> array;
// array.AppendCString("abc");
// array.AppendCString("def");
// NS_NewStringEnumerator(&enumerator, &array, true);
//
// // call some internal method which iterates the enumerator
// InternalMethod(enumerator);
// NS_RELEASE(enumerator);
//
MOZ_MUST_USE nsresult
NS_NewStringEnumerator(nsIStringEnumerator** aResult,
                       const nsTArray<nsString>* aArray,
                       nsISupports* aOwner);
MOZ_MUST_USE nsresult
NS_NewUTF8StringEnumerator(nsIUTF8StringEnumerator** aResult,
                           const nsTArray<nsCString>* aArray);

MOZ_MUST_USE nsresult
NS_NewStringEnumerator(nsIStringEnumerator** aResult,
                       const nsTArray<nsString>* aArray);

// Adopting string enumerators assume ownership of the array and will
// call |operator delete| on the array when the enumerator is destroyed
// this is useful when the provider creates an array solely for the
// purpose of creating the enumerator.
// For example:
//
// nsTArray<nsCString>* array = new nsTArray<nsCString>;
// array->AppendString("abcd");
// NS_NewAdoptingStringEnumerator(&result, array);
MOZ_MUST_USE nsresult
NS_NewAdoptingStringEnumerator(nsIStringEnumerator** aResult,
                               nsTArray<nsString>* aArray);

MOZ_MUST_USE nsresult
NS_NewAdoptingUTF8StringEnumerator(nsIUTF8StringEnumerator** aResult,
                                   nsTArray<nsCString>* aArray);


// these versions take a refcounted "owner" which will be addreffed
// when the enumerator is created, and destroyed when the enumerator
// is released. This allows providers to give non-owning pointers to
// ns*StringArray member variables without worrying about lifetime
// issues
// For example:
//
// nsresult MyClass::Enumerate(nsIUTF8StringEnumerator** aResult) {
//     mCategoryList->AppendString("abcd");
//     return NS_NewStringEnumerator(aResult, mCategoryList, this);
// }
//
MOZ_MUST_USE nsresult
NS_NewUTF8StringEnumerator(nsIUTF8StringEnumerator** aResult,
                           const nsTArray<nsCString>* aArray,
                           nsISupports* aOwner);