gecko/xpcom/string/public/nsStringBuffer.h

175 lines
7.0 KiB
C++

/* -*- 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):
* 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 ***** */
#ifndef nsStringBuffer_h__
#define nsStringBuffer_h__
/**
* This structure precedes the string buffers "we" allocate. It may be the
* case that nsTAString::mData does not point to one of these special
* buffers. The mFlags member variable distinguishes the buffer type.
*
* When this header is in use, it enables reference counting, and capacity
* tracking. NOTE: A string buffer can be modified only if its reference
* count is 1.
*/
class nsStringBuffer
{
private:
friend class CheckStaticAtomSizes;
PRInt32 mRefCount;
PRUint32 mStorageSize;
public:
/**
* Allocates a new string buffer, with given size in bytes and a
* reference count of one. When the string buffer is no longer needed,
* it should be released via Release.
*
* It is up to the caller to set the bytes corresponding to the string
* buffer by calling the Data method to fetch the raw data pointer. Care
* must be taken to properly null terminate the character array. The
* storage size can be greater than the length of the actual string
* (i.e., it is not required that the null terminator appear in the last
* storage unit of the string buffer's data).
*
* @return new string buffer or null if out of memory.
*/
NS_COM static nsStringBuffer* Alloc(size_t storageSize);
/**
* Resizes the given string buffer to the specified storage size. This
* method must not be called on a readonly string buffer. Use this API
* carefully!!
*
* This method behaves like the ANSI-C realloc function. (i.e., If the
* allocation fails, null will be returned and the given string buffer
* will remain unmodified.)
*
* @see IsReadonly
*/
NS_COM static nsStringBuffer* Realloc(nsStringBuffer* buf, size_t storageSize);
/**
* Increment the reference count on this string buffer.
*/
NS_COM void NS_FASTCALL AddRef();
/**
* Decrement the reference count on this string buffer. The string
* buffer will be destroyed when its reference count reaches zero.
*/
NS_COM void NS_FASTCALL Release();
/**
* This method returns the string buffer corresponding to the given data
* pointer. The data pointer must have been returned previously by a
* call to the nsStringBuffer::Data method.
*/
static nsStringBuffer* FromData(void* data)
{
return reinterpret_cast<nsStringBuffer*> (data) - 1;
}
/**
* This method returns the data pointer for this string buffer.
*/
void* Data() const
{
return const_cast<char*> (reinterpret_cast<const char*> (this + 1));
}
/**
* This function returns the storage size of a string buffer in bytes.
* This value is the same value that was originally passed to Alloc (or
* Realloc).
*/
PRUint32 StorageSize() const
{
return mStorageSize;
}
/**
* If this method returns false, then the caller can be sure that their
* reference to the string buffer is the only reference to the string
* buffer, and therefore it has exclusive access to the string buffer and
* associated data. However, if this function returns true, then other
* consumers may rely on the data in this buffer being immutable and
* other threads may access this buffer simultaneously.
*/
PRBool IsReadonly() const
{
return mRefCount > 1;
}
/**
* The FromString methods return a string buffer for the given string
* object or null if the string object does not have a string buffer.
* The reference count of the string buffer is NOT incremented by these
* methods. If the caller wishes to hold onto the returned value, then
* the returned string buffer must have its reference count incremented
* via a call to the AddRef method.
*/
NS_COM static nsStringBuffer* FromString(const nsAString &str);
NS_COM static nsStringBuffer* FromString(const nsACString &str);
/**
* The ToString methods assign this string buffer to a given string
* object. If the string object does not support sharable string
* buffers, then its value will be set to a copy of the given string
* buffer. Otherwise, these methods increment the reference count of the
* given string buffer. It is important to specify the length (in
* storage units) of the string contained in the string buffer since the
* length of the string may be less than its storage size. The string
* must have a null terminator at the offset specified by |len|.
*
* NOTE: storage size is measured in bytes even for wide strings;
* however, string length is always measured in storage units
* (2-byte units for wide strings).
*/
NS_COM void ToString(PRUint32 len, nsAString &str,
PRBool aMoveOwnership = PR_FALSE);
NS_COM void ToString(PRUint32 len, nsACString &str,
PRBool aMoveOwnership = PR_FALSE);
};
#endif /* !defined(nsStringBuffer_h__ */