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https://github.com/qpdf/qpdf.git
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Implement page manipulation APIs
This commit is contained in:
Jay Berkenbilt
parent
e01ae1968b
commit
eb802cfa8c
@ -22,7 +22,8 @@ enum qpdf_error_code_e
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qpdf_e_system, /* I/O error, memory error, etc. */
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qpdf_e_unsupported, /* PDF feature not (yet) supported by qpdf */
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qpdf_e_password, /* incorrect password for encrypted file */
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qpdf_e_damaged_pdf /* syntax errors or other damage in PDF */
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qpdf_e_damaged_pdf, /* syntax errors or other damage in PDF */
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qpdf_e_pages, /* erroneous or unsupported pages structure */
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};
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/* Write Parameters */
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@ -340,14 +340,26 @@ class QPDF
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// Convenience routines for common functions. See also
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// QPDFObjectHandle.hh for additional convenience routines.
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// Traverse page tree return all /Page objects.
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// Page handling API
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// Traverse page tree return all /Page objects. Note that calls
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// to page manipulation APIs will change the internal vector that
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// this routine returns a pointer to. If you don't want that,
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// assign this to a regular vector rather than a const reference.
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QPDF_DLL
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std::vector<QPDFObjectHandle> const& getAllPages();
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// QPDF internally caches the /Pages tree. This method will clear
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// the cache when e.g. direct modifications have been made.
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// This method synchronizes QPDF's cache of the page structure
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// with the actual /Pages tree. If you restrict changes to the
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// /Pages tree, including addition, removal, or replacement of
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// pages or changes to any /Pages objects, to calls to these page
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// handling APIs, you never need to call this method. If you
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// modify /Pages structures directly, you must call this method
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// afterwards. This method updates the internal list of pages, so
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// after calling this method, any previous references returned by
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// getAllPages() will be valid again.
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QPDF_DLL
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void clearPagesCache();
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void updateAllPagesCache();
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// Add new page at the beginning or the end of the current pdf
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QPDF_DLL
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@ -356,11 +368,11 @@ class QPDF
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// Add new page before or after refpage
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QPDF_DLL
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void addPageAt(QPDFObjectHandle newpage, bool before,
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QPDFObjectHandle const& refpage);
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QPDFObjectHandle refpage);
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// Remove pageoh from the pdf.
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// Remove page from the pdf.
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QPDF_DLL
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void removePage(QPDFObjectHandle const& pageoh);
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void removePage(QPDFObjectHandle page);
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// Resolver class is restricted to QPDFObjectHandle so that only
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// it can resolve indirect references.
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@ -541,12 +553,12 @@ class QPDF
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void getAllPagesInternal(QPDFObjectHandle cur_pages,
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std::vector<QPDFObjectHandle>& result);
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// creates pageobj_to_pages_pos if necessary
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// returns position, or -1 if not found
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void insertPage(QPDFObjectHandle newpage, int pos);
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int findPage(int objid, int generation);
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int findPage(QPDFObjectHandle const& pageoh); // convenience
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int findPage(QPDFObjectHandle& page);
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void flattenPagesTree();
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void insertPageobjToPage(QPDFObjectHandle const& obj, int pos,
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bool check_duplicate);
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// methods to support encryption -- implemented in QPDF_encryption.cc
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encryption_method_e interpretCF(QPDFObjectHandle);
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@ -6,6 +6,40 @@
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#include <qpdf/QUtil.hh>
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#include <qpdf/QPDFExc.hh>
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// In support of page manipulation APIs, these methods internally
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// maintain state about pages in a pair of data structures: all_pages,
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// which is a vector of page objects, and pageobj_to_pages_pos, which
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// maps a page object to its position in the all_pages array.
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// Unfortunately, the getAllPages() method returns a const reference
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// to all_pages and has been in the public API long before the
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// introduction of mutation APIs, so we're pretty much stuck with it.
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// Anyway, there are lots of calls to it in the library, so the
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// efficiency of having it cached is probably worth keeping it.
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// The goal of this code is to ensure that the all_pages vector, which
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// users may have a reference to, and the pageobj_to_pages_pos map,
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// which users will not have access to, remain consistent outside of
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// any call to the library. As long as users only touch the /Pages
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// structure through page-specific API calls, they never have to worry
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// about anything, and this will also stay consistent. If a user
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// touches anything about the /Pages structure outside of these calls
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// (such as by directly looking up and manipulating the underlying
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// objects), they can call updatePagesCache() to bring things back in
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// sync.
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// If the user doesn't ever use the page manipulation APIs, then qpdf
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// leaves the /Pages structure alone. If the user does use the APIs,
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// then we push all inheritable objects down and flatten the /Pages
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// tree. This makes it easier for us to keep /Pages, all_pages, and
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// pageobj_to_pages_pos internally consistent at all times.
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// Responsibility for keeping all_pages, pageobj_to_pages_pos, and the
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// Pages structure consistent should remain in as few places as
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// possible. As of initial writing, only flattenPagesTree,
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// insertPage, and removePage, along with methods they call, are
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// concerned with it. Everything else goes through one of those
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// methods.
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std::vector<QPDFObjectHandle> const&
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QPDF::getAllPages()
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{
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@ -44,152 +78,173 @@ QPDF::getAllPagesInternal(QPDFObjectHandle cur_pages,
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}
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}
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// FIXXX here down
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void
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QPDF::clearPagesCache()
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QPDF::updateAllPagesCache()
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{
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// Force regeneration of the pages cache. We force immediate
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// recalculation of all_pages since users may have references to
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// it that they got from calls to getAllPages(). We can defer
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// recalculation of pageobj_to_pages_pos until needed.
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QTC::TC("qpdf", "QPDF updateAllPagesCache");
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this->all_pages.clear();
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this->pageobj_to_pages_pos.clear();
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getAllPages();
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}
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void
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QPDF::flattenPagesTree()
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{
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clearPagesCache();
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// If not already done, flatten the /Pages structure and
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// initialize pageobj_to_pages_pos.
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// FIXME: more specific method, we don't want to generate the extra stuff.
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// We also need cheap fixup after addPage/removePage.
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// no compressed objects to be produced here...
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std::map<int, int> object_stream_data;
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optimize(object_stream_data); // push down inheritance
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std::vector<QPDFObjectHandle> kids = this->getAllPages();
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QPDFObjectHandle pages = this->trailer.getKey("/Root").getKey("/Pages");
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const int len = kids.size();
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for (int pos = 0; pos < len; ++pos)
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if (! this->pageobj_to_pages_pos.empty())
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{
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// populate pageobj_to_pages_pos
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ObjGen og(kids[pos].getObjectID(), kids[pos].getGeneration());
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if (! this->pageobj_to_pages_pos.insert(std::make_pair(og, pos)).second)
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{
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// insert failed: duplicate entry found
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*out_stream << "WARNING: duplicate page reference found, "
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<< "but currently not fully supported." << std::endl;
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}
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// fix parent links
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kids[pos].replaceKey("/Parent", pages);
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return;
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}
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pages.replaceKey("/Kids", QPDFObjectHandle::newArray(kids));
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// Push inherited objects down to the /Page level
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optimizePagesTree(true);
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getAllPages();
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QPDFObjectHandle pages = this->trailer.getKey("/Root").getKey("/Pages");
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int const len = (int)this->all_pages.size();
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for (int pos = 0; pos < len; ++pos)
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{
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// populate pageobj_to_pages_pos and fix parent pointer
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insertPageobjToPage(this->all_pages[pos], pos, true);
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this->all_pages[pos].replaceKey("/Parent", pages);
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}
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pages.replaceKey("/Kids", QPDFObjectHandle::newArray(this->all_pages));
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// /Count has not changed
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assert(pages.getKey("/Count").getIntValue() == len);
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}
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int
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QPDF::findPage(int objid, int generation)
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void
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QPDF::insertPageobjToPage(QPDFObjectHandle const& obj, int pos,
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bool check_duplicate)
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{
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if (this->pageobj_to_pages_pos.empty())
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ObjGen og(obj.getObjectID(), obj.getGeneration());
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bool duplicate =
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(! this->pageobj_to_pages_pos.insert(std::make_pair(og, pos)).second);
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if (duplicate && check_duplicate)
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{
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flattenPagesTree();
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QTC::TC("qpdf", "QPDF duplicate page reference");
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setLastObjectDescription("page " + QUtil::int_to_string(pos) +
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" (numbered from zero)",
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og.obj, og.gen);
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throw QPDFExc(qpdf_e_pages, this->file->getName(),
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this->last_object_description, 0,
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"duplicate page reference found;"
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" this would cause loss of data");
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}
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std::map<ObjGen, int>::iterator it =
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this->pageobj_to_pages_pos.find(ObjGen(objid, generation));
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if (it != this->pageobj_to_pages_pos.end())
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{
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return (*it).second;
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}
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return -1; // throw?
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}
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int
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QPDF::findPage(QPDFObjectHandle const& pageoh)
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{
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if (!pageoh.isInitialized())
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{
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return -1;
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// TODO? throw
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}
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return findPage(pageoh.getObjectID(), pageoh.getGeneration());
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}
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void
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QPDF::addPage(QPDFObjectHandle newpage, bool first)
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QPDF::insertPage(QPDFObjectHandle newpage, int pos)
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{
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if (this->pageobj_to_pages_pos.empty())
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{
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flattenPagesTree();
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}
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newpage.assertPageObject(); // FIXME: currently private
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QPDFObjectHandle pages = this->trailer.getKey("/Root").getKey("/Pages");
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QPDFObjectHandle kids = pages.getKey("/Kids");
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newpage.replaceKey("/Parent", pages);
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if (first)
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{
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kids.insertItem(0, newpage);
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}
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else
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{
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kids.appendItem(newpage);
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}
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pages.replaceKey("/Count",
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QPDFObjectHandle::newInteger(kids.getArrayNItems()));
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// FIXME: this is overkill, but cache is now stale
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clearPagesCache();
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}
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void
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QPDF::addPageAt(QPDFObjectHandle newpage, bool before,
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QPDFObjectHandle const &refpage)
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{
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int refpos = findPage(refpage); // also ensures flat /Pages
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if (refpos == -1)
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{
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throw "Could not find refpage";
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}
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// pos is numbered from 0, so pos = 0 inserts at the begining and
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// pos = npages adds to the end.
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flattenPagesTree();
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newpage.assertPageObject();
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QTC::TC("qpdf", "QPDF insert page",
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(pos == 0) ? 0 : // insert at beginning
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(pos == ((int)this->all_pages.size())) ? 1 : // insert at end
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2); // insert in middle
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QPDFObjectHandle pages = this->trailer.getKey("/Root").getKey("/Pages");
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QPDFObjectHandle kids = pages.getKey("/Kids");
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if (! before)
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{
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++refpos;
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}
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assert ((pos >= 0) && (pos <= (int)this->all_pages.size()));
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newpage.replaceKey("/Parent", pages);
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kids.insertItem(refpos, newpage);
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pages.replaceKey("/Count",
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QPDFObjectHandle::newInteger(kids.getArrayNItems()));
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// FIXME: this is overkill, but cache is now stale
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clearPagesCache();
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kids.insertItem(pos, newpage);
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int npages = kids.getArrayNItems();
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pages.replaceKey("/Count", QPDFObjectHandle::newInteger(npages));
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this->all_pages.insert(this->all_pages.begin() + pos, newpage);
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assert((int)this->all_pages.size() == npages);
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for (int i = pos + 1; i < npages; ++i)
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{
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insertPageobjToPage(this->all_pages[i], i, false);
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}
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insertPageobjToPage(newpage, pos, true);
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assert((int)this->pageobj_to_pages_pos.size() == npages);
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}
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void
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QPDF::removePage(QPDFObjectHandle const& pageoh)
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QPDF::removePage(QPDFObjectHandle page)
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{
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int pos = findPage(pageoh); // also ensures flat /Pages
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if (pos == -1)
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{
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throw "Can't remove non-existing page";
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}
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int pos = findPage(page); // also ensures flat /Pages
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QTC::TC("qpdf", "QPDF remove page",
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(pos == 0) ? 0 : // remove at beginning
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(pos == ((int)this->all_pages.size() - 1)) ? 1 : // remove at end
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2); // remove in middle
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QPDFObjectHandle pages = this->trailer.getKey("/Root").getKey("/Pages");
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QPDFObjectHandle kids = pages.getKey("/Kids");
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kids.eraseItem(pos);
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pages.replaceKey("/Count",
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QPDFObjectHandle::newInteger(kids.getArrayNItems()));
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// FIXME: this is overkill, but cache is now stale
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clearPagesCache();
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int npages = kids.getArrayNItems();
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pages.replaceKey("/Count", QPDFObjectHandle::newInteger(npages));
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this->all_pages.erase(this->all_pages.begin() + pos);
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assert((int)this->all_pages.size() == npages);
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this->pageobj_to_pages_pos.erase(
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ObjGen(page.getObjectID(), page.getGeneration()));
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assert((int)this->pageobj_to_pages_pos.size() == npages);
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for (int i = pos; i < npages; ++i)
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{
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insertPageobjToPage(this->all_pages[i], i, false);
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}
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}
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void
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QPDF::addPageAt(QPDFObjectHandle newpage, bool before,
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QPDFObjectHandle refpage)
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{
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int refpos = findPage(refpage);
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if (! before)
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{
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++refpos;
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}
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insertPage(newpage, refpos);
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}
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void
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QPDF::addPage(QPDFObjectHandle newpage, bool first)
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{
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getAllPages();
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if (first)
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{
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insertPage(newpage, 0);
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}
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else
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{
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insertPage(newpage, (int)this->all_pages.size());
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}
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}
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int
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QPDF::findPage(QPDFObjectHandle& page)
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{
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page.assertPageObject();
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return findPage(page.getObjectID(), page.getGeneration());
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}
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int
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QPDF::findPage(int objid, int generation)
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{
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flattenPagesTree();
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std::map<ObjGen, int>::iterator it =
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this->pageobj_to_pages_pos.find(ObjGen(objid, generation));
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if (it == this->pageobj_to_pages_pos.end())
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{
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setLastObjectDescription("page object", objid, generation);
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QPDFExc(qpdf_e_pages, this->file->getName(),
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this->last_object_description, 0,
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"page object not referenced in /Pages tree");
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}
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return (*it).second;
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}
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@ -203,3 +203,7 @@ qpdf-c called qpdf_init_write_memory 0
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exercise processFile(name) 0
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exercise processFile(FILE*) 0
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exercise processMemoryFile 0
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QPDF duplicate page reference 0
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QPDF remove page 2
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QPDF insert page 2
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QPDF updateAllPagesCache 0
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