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79f6b4823b
Have classes contain only a single private member of type PointerHolder<Members>. This makes it safe to change the structure of the Members class without breaking binary compatibility. Many of the classes already follow this pattern quite successfully. This brings in the rest of the class that are part of the public API.
102 lines
3.3 KiB
C++
102 lines
3.3 KiB
C++
// Copyright (c) 2005-2019 Jay Berkenbilt
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//
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// This file is part of qpdf.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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//
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// Versions of qpdf prior to version 7 were released under the terms
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// of version 2.0 of the Artistic License. At your option, you may
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// continue to consider qpdf to be licensed under those terms. Please
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// see the manual for additional information.
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// Generalized Pipeline interface. By convention, subclasses of
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// Pipeline are called Pl_Something.
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//
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// When an instance of Pipeline is created with a pointer to a next
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// pipeline, that pipeline writes its data to the next one when it
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// finishes with it. In order to make possible a usage style in which
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// a pipeline may be passed to a function which may stick other
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// pipelines in front of it, the allocator of a pipeline is
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// responsible for its destruction. In other words, one pipeline
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// object does not attempt to manage the memory of its successor.
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//
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// The client is required to call finish() before destroying a
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// Pipeline in order to avoid loss of data. A Pipeline class should
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// not throw an exception in the destructor if this hasn't been done
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// though since doing so causes too much trouble when deleting
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// pipelines during error conditions.
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//
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// Some pipelines are reusable (i.e., you can call write() after
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// calling finish() and can call finish() multiple times) while others
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// are not. It is up to the caller to use a pipeline according to its
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// own restrictions.
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#ifndef PIPELINE_HH
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#define PIPELINE_HH
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#include <qpdf/DLL.h>
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#include <qpdf/PointerHolder.hh>
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#include <string>
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class QPDF_DLL_CLASS Pipeline
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{
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public:
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QPDF_DLL
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Pipeline(char const* identifier, Pipeline* next);
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QPDF_DLL
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virtual ~Pipeline();
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// Subclasses should implement write and finish to do their jobs
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// and then, if they are not end-of-line pipelines, call
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// getNext()->write or getNext()->finish. It would be really nice
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// if write could take unsigned char const*, but this would make
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// it much more difficult to write pipelines around legacy
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// interfaces whose calls don't want pointers to const data. As a
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// rule, pipelines should generally not be modifying the data
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// passed to them. They should, instead, create new data to pass
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// downstream.
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QPDF_DLL
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virtual void write(unsigned char* data, size_t len) = 0;
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QPDF_DLL
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virtual void finish() = 0;
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protected:
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Pipeline* getNext(bool allow_null = false);
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std::string identifier;
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private:
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// Do not implement copy or assign
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Pipeline(Pipeline const&);
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Pipeline& operator=(Pipeline const&);
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class Members
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{
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friend class Pipeline;
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public:
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QPDF_DLL
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~Members();
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private:
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Members(Pipeline* next);
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Members(Members const&);
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Pipeline* next;
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};
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PointerHolder<Members> m;
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};
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#endif // PIPELINE_HH
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