mirror of https://github.com/qpdf/qpdf.git
30 lines
1.1 KiB
C++
30 lines
1.1 KiB
C++
// This is an example of how to write C++ functions and make them usable with the qpdf C API. It
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// consists of three files:
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// - extend-c-api.h -- a plain C header file
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// - extend-c-api.c -- a C program that calls the function
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// - extend-c-api.cc -- a C++ file that implements the function
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#include "extend-c-api.h"
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// Here, we add a function to get the number of pages in a PDF file and make it callable through the
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// C API.
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// This is a normal C++ function that works with QPDF in a normal way. It doesn't do anything
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// special to be callable from C.
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int
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numPages(std::shared_ptr<QPDF> qpdf)
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{
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return qpdf->getRoot().getKey("/Pages").getKey("/Count").getIntValueAsInt();
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}
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// Now we define the glue that makes our function callable using the C API.
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// This is the C++ implementation of the C function.
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QPDF_ERROR_CODE
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num_pages(qpdf_data qc, int* npages)
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{
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// Call qpdf_c_wrap to convert any exception our function might through to a QPDF_ERROR_CODE
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// and attach it to the qpdf_data object in the same way as other functions in the C API.
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return qpdf_c_wrap(qc, [&qc, &npages]() { *npages = numPages(qpdf_c_get_qpdf(qc)); });
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}
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