Add functional versions of QPDFObjectHandle::replaceStreamData

Also fix a bug in checking consistency of length for stream data
providers. Length should not be checked or recorded if the provider
says it failed to generate the data.

ChangeLog

@@ -1,3 +1,11 @@
+2021-02-14  Jay Berkenbilt  <ejb@ql.org>
+
+	* Add new versions of QPDFObjectHandle::replaceStreamData that
+	take std::function objects for cases when you need something
+	between a static string and a full-fledged StreamDataProvider.
+	Using this with QUtil::file_provider is a very easy way to create
+	a stream from the contents of a file.
+
 2021-02-12  Jay Berkenbilt  <ejb@ql.org>
 
 	* Move formerly internal QPDFMatrix class to the public API. This

include/qpdf/QPDFObjectHandle.hh

@@ -30,6 +30,7 @@
 #include <vector>
 #include <set>
 #include <map>
+#include <functional>
 
 #include <qpdf/QPDFObjGen.hh>
 #include <qpdf/PointerHolder.hh>
@@ -986,6 +987,26 @@ class QPDFObjectHandle
 			   QPDFObjectHandle const& filter,
 			   QPDFObjectHandle const& decode_parms);
 
+    // Starting in qpdf 10.2, you can use C++-11 function objects
+    // instead of StreamDataProvider.
+
+    // The provider should write the stream data to the pipeline. For
+    // a one-liner to replace stream data with the contents of a file,
+    // pass QUtil::file_provider(filename) as provider.
+    QPDF_DLL
+    void replaceStreamData(std::function<void(Pipeline*)> provider,
+			   QPDFObjectHandle const& filter,
+			   QPDFObjectHandle const& decode_parms);
+    // The provider should write the stream data to the pipeline,
+    // returning true if it succeeded without errors.
+    QPDF_DLL
+    void replaceStreamData(
+        std::function<bool(Pipeline*,
+                           bool suppress_warnings,
+                           bool will_retry)> provider,
+        QPDFObjectHandle const& filter,
+        QPDFObjectHandle const& decode_parms);
+
     // Access object ID and generation.  For direct objects, return
     // object ID 0.
 

libqpdf/QPDFObjectHandle.cc

@@ -1347,6 +1347,62 @@ QPDFObjectHandle::replaceStreamData(PointerHolder<StreamDataProvider> provider,
 	provider, filter, decode_parms);
 }
 
+class FunctionProvider: public QPDFObjectHandle::StreamDataProvider
+{
+  public:
+    FunctionProvider(std::function<void(Pipeline*)> provider) :
+        StreamDataProvider(false),
+        p1(provider),
+        p2(nullptr)
+    {
+    }
+    FunctionProvider(std::function<bool(Pipeline*, bool, bool)> provider) :
+        StreamDataProvider(true),
+        p1(nullptr),
+        p2(provider)
+    {
+    }
+
+    virtual void provideStreamData(int, int, Pipeline* pipeline) override
+    {
+        p1(pipeline);
+    }
+
+    virtual bool provideStreamData(int, int, Pipeline* pipeline,
+                                   bool suppress_warnings,
+                                   bool will_retry) override
+    {
+        return p2(pipeline, suppress_warnings, will_retry);
+    }
+
+  private:
+    std::function<void(Pipeline*)> p1;
+    std::function<bool(Pipeline*, bool, bool)> p2;
+};
+
+void
+QPDFObjectHandle::replaceStreamData(std::function<void(Pipeline*)> provider,
+                                    QPDFObjectHandle const& filter,
+                                    QPDFObjectHandle const& decode_parms)
+{
+    assertStream();
+    PointerHolder<StreamDataProvider> sdp = new FunctionProvider(provider);
+    dynamic_cast<QPDF_Stream*>(obj.getPointer())->replaceStreamData(
+	sdp, filter, decode_parms);
+}
+
+void
+QPDFObjectHandle::replaceStreamData(
+    std::function<bool(Pipeline*, bool, bool)> provider,
+    QPDFObjectHandle const& filter,
+    QPDFObjectHandle const& decode_parms)
+{
+    assertStream();
+    PointerHolder<StreamDataProvider> sdp = new FunctionProvider(provider);
+    dynamic_cast<QPDF_Stream*>(obj.getPointer())->replaceStreamData(
+	sdp, filter, decode_parms);
+}
+
 QPDFObjGen
 QPDFObjectHandle::getObjGen() const
 {

libqpdf/QPDF_Stream.cc

@@ -533,7 +533,7 @@ QPDF_Stream::pipeStreamData(Pipeline* pipeline, bool* filterp,
         }
 	qpdf_offset_t actual_length = count.getCount();
 	qpdf_offset_t desired_length = 0;
-        if (this->stream_dict.hasKey("/Length"))
+        if (success && this->stream_dict.hasKey("/Length"))
         {
 	    desired_length = this->stream_dict.getKey("/Length").getIntValue();
             if (actual_length == desired_length)
@@ -555,7 +555,7 @@ QPDF_Stream::pipeStreamData(Pipeline* pipeline, bool* filterp,
                     QUtil::int_to_string(desired_length) + " bytes");
             }
         }
-        else
+        else if (success)
         {
             QTC::TC("qpdf", "QPDF_Stream provider length not provided");
             this->stream_dict.replaceKey(

manual/qpdf-manual.xml

@@ -5211,6 +5211,17 @@ print "\n";
           contents of a file through a pipeline as binary data.
          </para>
         </listitem>
+        <listitem>
+         <para>
+	  Add new versions of
+	  <function>QPDFObjectHandle::replaceStreamData</function>
+	  that take <classname>std::function</classname> objects for
+	  cases when you need something between a static string and a
+	  full-fledged StreamDataProvider. Using this with
+	  QUtil::file_provider is a very easy way to create a stream
+	  from the contents of a file.
+         </para>
+        </listitem>
         <listitem>
          <para>
           Add option to <function>QUtil::double_to_string</function>

qpdf/qtest/qpdf.test

@@ -717,7 +717,7 @@ $td->runtest("check dates",
 show_ntests();
 # ----------
 $td->notify("--- Stream Replacement Tests ---");
-$n_tests += 8;
+$n_tests += 10;
 
 $td->runtest("replace stream data",
 	     {$td->COMMAND => "test_driver 7 qstream.pdf"},
@@ -747,6 +747,13 @@ $td->runtest("add page contents",
 $td->runtest("new stream",
 	     {$td->FILE => "a.pdf"},
 	     {$td->FILE => "add-contents.pdf"});
+$td->runtest("functional replace stream data",
+	     {$td->COMMAND => "test_driver 78 minimal.pdf"},
+	     {$td->FILE => "test78.out", $td->EXIT_STATUS => 0},
+	     $td->NORMALIZE_NEWLINES);
+$td->runtest("check output",
+	     {$td->FILE => "a.pdf"},
+	     {$td->FILE => "test78.pdf"});
 
 show_ntests();
 # ----------

qpdf/qtest/qpdf/test78.out

@@ -0,0 +1,10 @@
+piping with warning suppression
+f2
+f2 done
+writing
+f2
+failing
+f2
+warning
+f2 done
+test 78 done

qpdf/qtest/qpdf/test78.pdf

@@ -0,0 +1,139 @@
+%PDF-1.3
+%¿÷¢þ
+%QDF-1.0
+
+%% Original object ID: 1 0
+1 0 obj
+<<
+  /Pages 6 0 R
+  /Type /Catalog
+>>
+endobj
+
+%% Original object ID: 7 0
+2 0 obj
+<<
+  /Length 3 0 R
+>>
+stream
+potato
+endstream
+endobj
+
+%QDF: ignore_newline
+3 0 obj
+6
+endobj
+
+%% Original object ID: 8 0
+4 0 obj
+<<
+  /Length 5 0 R
+>>
+stream
+salad
+endstream
+endobj
+
+%QDF: ignore_newline
+5 0 obj
+5
+endobj
+
+%% Original object ID: 2 0
+6 0 obj
+<<
+  /Count 1
+  /Kids [
+    7 0 R
+  ]
+  /Type /Pages
+>>
+endobj
+
+%% Page 1
+%% Original object ID: 3 0
+7 0 obj
+<<
+  /Contents 8 0 R
+  /MediaBox [
+    0
+    0
+    612
+    792
+  ]
+  /Parent 6 0 R
+  /Resources <<
+    /Font <<
+      /F1 10 0 R
+    >>
+    /ProcSet 11 0 R
+  >>
+  /Type /Page
+>>
+endobj
+
+%% Contents for page 1
+%% Original object ID: 4 0
+8 0 obj
+<<
+  /Length 9 0 R
+>>
+stream
+BT
+  /F1 24 Tf
+  72 720 Td
+  (Potato) Tj
+ET
+endstream
+endobj
+
+9 0 obj
+44
+endobj
+
+%% Original object ID: 6 0
+10 0 obj
+<<
+  /BaseFont /Helvetica
+  /Encoding /WinAnsiEncoding
+  /Name /F1
+  /Subtype /Type1
+  /Type /Font
+>>
+endobj
+
+%% Original object ID: 5 0
+11 0 obj
+[
+  /PDF
+  /Text
+]
+endobj
+
+xref
+0 12
+0000000000 65535 f 
+0000000052 00000 n 
+0000000133 00000 n 
+0000000216 00000 n 
+0000000261 00000 n 
+0000000343 00000 n 
+0000000388 00000 n 
+0000000497 00000 n 
+0000000741 00000 n 
+0000000840 00000 n 
+0000000886 00000 n 
+0000001032 00000 n 
+trailer <<
+  /Root 1 0 R
+  /Size 12
+  /Streams [
+    2 0 R
+    4 0 R
+  ]
+  /ID [<31415926535897932384626433832795><31415926535897932384626433832795>]
+>>
+startxref
+1068
+%%EOF

qpdf/test_driver.cc

@@ -16,6 +16,7 @@
 #include <qpdf/Pl_StdioFile.hh>
 #include <qpdf/Pl_Buffer.hh>
 #include <qpdf/Pl_Flate.hh>
+#include <qpdf/Pl_Discard.hh>
 #include <qpdf/QPDFWriter.hh>
 #include <qpdf/QPDFSystemError.hh>
 #include <qpdf/QIntC.hh>
@@ -2798,6 +2799,48 @@ void runtest(int n, char const* filename1, char const* arg2)
         w.setQDFMode(true);
         w.write();
     }
+    else if (n == 78)
+    {
+        // Test functional versions of replaceStreamData()
+
+        auto f1 = [](Pipeline* p) {
+            p->write(QUtil::unsigned_char_pointer("potato"), 6);
+            p->finish();
+        };
+        auto f2 = [](Pipeline* p, bool suppress_warnings, bool will_retry) {
+            std::cerr << "f2" << std::endl;
+            if (will_retry)
+            {
+                std::cerr << "failing" << std::endl;
+                return false;
+            }
+            if (! suppress_warnings)
+            {
+                std::cerr << "warning" << std::endl;
+            }
+            p->write(QUtil::unsigned_char_pointer("salad"), 5);
+            p->finish();
+            std::cerr << "f2 done" << std::endl;
+            return true;
+        };
+
+        auto null = QPDFObjectHandle::newNull();
+        auto s1 = QPDFObjectHandle::newStream(&pdf);
+        s1.replaceStreamData(f1, null, null);
+        auto s2 = QPDFObjectHandle::newStream(&pdf);
+        s2.replaceStreamData(f2, null, null);
+        pdf.getTrailer().replaceKey(
+            "/Streams", QPDFObjectHandle::newArray({s1, s2}));
+        std::cout << "piping with warning suppression" << std::endl;
+        Pl_Discard d;
+        s2.pipeStreamData(&d, nullptr, 0, qpdf_dl_all, true, false);
+
+        std::cout << "writing" << std::endl;
+        QPDFWriter w(pdf, "a.pdf");
+        w.setStaticID(true);
+        w.setQDFMode(true);
+        w.write();
+    }
     else
     {
 	throw std::runtime_error(std::string("invalid test ") +