From 33a47d5c3c4402d8d94b00ed9b3aa2c339203d2f Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Tue, 2 Nov 2021 18:12:39 -0400
Subject: [PATCH] Make QPDF::findPage public (fixes #516)

This was originally not public because I wanted to get rid fo the
pages cache, but I recently realized there were deep reasons not to do
that, and the author of pikepdf wanted this, so I decided to make it
public.
---
 ChangeLog             |  4 ++++
 include/qpdf/QPDF.hh  | 11 +++++++++--
 libqpdf/QPDF_pages.cc |  1 +
 qpdf/qpdf.testcov     |  1 +
 4 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index c64f18ae..efb2173a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,9 @@
 2021-11-02  Jay Berkenbilt  <ejb@ql.org>
 
+	* Add QPDF::findPage to the public API. This is primarily to help
+	improve the efficiency of code that wraps the qpdf library, such
+	as pikepdf. Fixes #516.
+
 	* zlib-flate: warn and exit with code 3 when there is corrupted
 	input data even when decompression is possible. We do this in the
 	zlib-flate CLI so that it can be more reliably used to test the
diff --git a/include/qpdf/QPDF.hh b/include/qpdf/QPDF.hh
index 48b92137..941004cc 100644
--- a/include/qpdf/QPDF.hh
+++ b/include/qpdf/QPDF.hh
@@ -605,6 +605,15 @@ class QPDF
     QPDF_DLL
     std::vector<QPDFObjectHandle> const& getAllPages();
 
+    // These methods, given a page object or its object/generation
+    // number, returns the 0-based index into the array returned by
+    // getAllPages() for that page. An exception is thrown if the page
+    // is not found.
+    QPDF_DLL
+    int findPage(QPDFObjGen const& og);
+    QPDF_DLL
+    int findPage(QPDFObjectHandle& page);
+
     // This method synchronizes QPDF's cache of the page structure
     // with the actual /Pages tree.  If you restrict changes to the
     // /Pages tree, including addition, removal, or replacement of
@@ -990,8 +999,6 @@ class QPDF
                              std::set<QPDFObjGen>& visited,
                              std::set<QPDFObjGen>& seen);
     void insertPage(QPDFObjectHandle newpage, int pos);
-    int findPage(QPDFObjGen const& og);
-    int findPage(QPDFObjectHandle& page);
     void flattenPagesTree();
     void insertPageobjToPage(QPDFObjectHandle const& obj, int pos,
                              bool check_duplicate);
diff --git a/libqpdf/QPDF_pages.cc b/libqpdf/QPDF_pages.cc
index 8b55e0ef..eeb13029 100644
--- a/libqpdf/QPDF_pages.cc
+++ b/libqpdf/QPDF_pages.cc
@@ -345,6 +345,7 @@ QPDF::findPage(QPDFObjGen const& og)
         this->m->pageobj_to_pages_pos.find(og);
     if (it == this->m->pageobj_to_pages_pos.end())
     {
+        QTC::TC("qpdf", "QPDF_pages findPage not found");
         setLastObjectDescription("page object", og.getObj(), og.getGen());
         throw QPDFExc(qpdf_e_pages, this->m->file->getName(),
                       this->m->last_object_description, 0,
diff --git a/qpdf/qpdf.testcov b/qpdf/qpdf.testcov
index 331547cd..0cb56525 100644
--- a/qpdf/qpdf.testcov
+++ b/qpdf/qpdf.testcov
@@ -595,3 +595,4 @@ QPDF resolve duplicated page in insert 0
 QPDFWriter preserve object streams 1
 QPDFWriter exclude from object stream 0
 check unclosed --pages 1
+QPDF_pages findPage not found 0