mirror of https://github.com/qpdf/qpdf.git
111 lines
4.1 KiB
C++
111 lines
4.1 KiB
C++
// Copyright (c) 2005-2024 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"); you may not use this file except
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// in compliance with the License. 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 distributed under the License
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// is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express
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// or implied. See the License for the specific language governing permissions and limitations under
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// the License.
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//
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// Versions of qpdf prior to version 7 were released under the terms of version 2.0 of the Artistic
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// License. At your option, you may continue to consider qpdf to be licensed under those terms.
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// Please see the manual for additional information.
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// Generalized Pipeline interface. By convention, subclasses of 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 pipeline, that pipeline writes
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// its data to the next one when it finishes with it. In order to make possible a usage style in
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// which a pipeline may be passed to a function which may stick other pipelines in front of it, the
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// allocator of a pipeline is responsible for its destruction. In other words, one pipeline object
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// 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 Pipeline in order to avoid loss of
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// data. A Pipeline class should 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 pipelines during error conditions.
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//
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// Some pipelines are reusable (i.e., you can call write() after calling finish() and can call
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// finish() multiple times) while others are not. It is up to the caller to use a pipeline
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// according to its 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> // unused -- remove in qpdf 12 (see #785)
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#include <memory>
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#include <string>
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// Remember to use QPDF_DLL_CLASS on anything derived from Pipeline so it will work with
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// dynamic_cast across the shared object boundary.
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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() = default;
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// Subclasses should implement write and finish to do their jobs and then, if they are not
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// end-of-line pipelines, call getNext()->write or getNext()->finish.
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QPDF_DLL
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virtual void write(unsigned char const* data, size_t len) = 0;
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QPDF_DLL
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virtual void finish() = 0;
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QPDF_DLL
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std::string getIdentifier() const;
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// These are convenience methods for making it easier to write certain other types of data to
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// pipelines without having to cast. The methods that take char const* expect null-terminated C
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// strings and do not write the null terminators.
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QPDF_DLL
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void writeCStr(char const* cstr);
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QPDF_DLL
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void writeString(std::string const&);
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// This allows *p << "x" << "y" but is not intended to be a general purpose << compatible with
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// ostream and does not have local awareness or the ability to be "imbued" with properties.
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QPDF_DLL
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Pipeline& operator<<(char const* cstr);
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QPDF_DLL
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Pipeline& operator<<(std::string const&);
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QPDF_DLL
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Pipeline& operator<<(short);
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QPDF_DLL
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Pipeline& operator<<(int);
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QPDF_DLL
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Pipeline& operator<<(long);
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QPDF_DLL
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Pipeline& operator<<(long long);
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QPDF_DLL
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Pipeline& operator<<(unsigned short);
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QPDF_DLL
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Pipeline& operator<<(unsigned int);
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QPDF_DLL
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Pipeline& operator<<(unsigned long);
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QPDF_DLL
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Pipeline& operator<<(unsigned long long);
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// Overloaded write to reduce casting
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QPDF_DLL
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void write(char const* data, size_t len);
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protected:
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QPDF_DLL
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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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Pipeline(Pipeline const&) = delete;
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Pipeline& operator=(Pipeline const&) = delete;
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Pipeline* next;
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};
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#endif // PIPELINE_HH
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