Allow reading from InputSource and writing to Pipeline

Allowing users to subclass InputSource and Pipeline to read and write
from/to arbitrary sources provides the maximum flexibility for users
who want to read and write from other than files or memory.

ChangeLog

@@ -1,3 +1,10 @@
+2012-09-23  Jay Berkenbilt  <ejb@ql.org>
+
+	* Add public methods QPDF::processInputSource and
+	QPDFWriter::setOutputPipeline to allow users to read from custom
+	input sources and to write to custom pipelines.  This allows the
+	maximum flexibility in sources for reading and writing PDF files.
+
 2012-09-06  Jay Berkenbilt  <ejb@ql.org>
 
 	* 3.0.2: release

include/qpdf/QPDF.hh

@@ -72,6 +72,13 @@ class QPDF
 			   char const* buf, size_t length,
 			   char const* password = 0);
 
+    // Parse a PDF file loaded from a custom InputSource.  If you have
+    // your own method of retrieving a PDF file, you can subclass
+    // InputSource and use this method.
+    QPDF_DLL
+    void processInputSource(PointerHolder<InputSource>,
+                            char const* password = 0);
+
     // Create a QPDF object for an empty PDF.  This PDF has no pages
     // or objects other than a minimal trailer, a document catalog,
     // and a /Pages tree containing zero pages.  Pages and other

include/qpdf/QPDFWriter.hh

@@ -95,6 +95,15 @@ class QPDFWriter
     QPDF_DLL
     Buffer* getBuffer();
 
+    // Supply your own pipeline object.  Output will be written to
+    // this pipeline, and QPDFWriter will call finish() on the
+    // pipeline.  It is the caller's responsibility to manage the
+    // memory for the pipeline.  The pipeline is never deleted by
+    // QPDFWriter, which makes it possible for you to call additional
+    // methods on the pipeline after the writing is finished.
+    QPDF_DLL
+    void setOutputPipeline(Pipeline*);
+
     // Setting Parameters
 
     // Set the value of object stream mode.  In disable mode, we never

libqpdf/QPDF.cc

@@ -138,9 +138,8 @@ void
 QPDF::processFile(char const* filename, char const* password)
 {
     FileInputSource* fi = new FileInputSource();
-    this->file = fi;
     fi->setFilename(filename);
-    parse(password);
+    processInputSource(fi, password);
 }
 
 void
@@ -148,9 +147,8 @@ QPDF::processFile(char const* description, FILE* filep,
                   bool close_file, char const* password)
 {
     FileInputSource* fi = new FileInputSource();
-    this->file = fi;
     fi->setFile(description, filep, close_file);
-    parse(password);
+    processInputSource(fi, password);
 }
 
 void
@@ -158,10 +156,18 @@ QPDF::processMemoryFile(char const* description,
 			char const* buf, size_t length,
 			char const* password)
 {
-    this->file =
+    processInputSource(
 	new BufferInputSource(description,
 			      new Buffer((unsigned char*)buf, length),
-			      true);
+			      true),
+        password);
+}
+
+void
+QPDF::processInputSource(PointerHolder<InputSource> source,
+                         char const* password)
+{
+    this->file = source;
     parse(password);
 }
 

libqpdf/QPDFWriter.cc

@@ -134,6 +134,13 @@ QPDFWriter::getBuffer()
     return result;
 }
 
+void
+QPDFWriter::setOutputPipeline(Pipeline* p)
+{
+    this->filename = "custom pipeline";
+    initializePipelineStack(p);
+}
+
 void
 QPDFWriter::setObjectStreamMode(qpdf_object_stream_e mode)
 {

qpdf/qtest/qpdf.test

@@ -149,7 +149,7 @@ $td->runtest("remove page we don't have",
 	     $td->NORMALIZE_NEWLINES);
 # ----------
 $td->notify("--- Miscellaneous Tests ---");
-$n_tests += 53;
+$n_tests += 55;
 
 $td->runtest("qpdf version",
 	     {$td->COMMAND => "qpdf --version"},
@@ -403,6 +403,13 @@ $td->runtest("check output",
 $td->runtest("check output",
              {$td->FILE => "d.pdf"},
              {$td->FILE => "extra-header-lin-newline.pdf"});
+$td->runtest("output to custom pipeline",
+             {$td->COMMAND => "test_driver 33 minimal.pdf"},
+             {$td->STRING => "test 33 done\n", $td->EXIT_STATUS => 0},
+             $td->NORMALIZE_NEWLINES);
+$td->runtest("check output",
+             {$td->FILE => "a.pdf"},
+             {$td->FILE => "custom-pipeline.pdf"});
 
 show_ntests();
 # ----------

qpdf/test_driver.cc

@@ -1112,6 +1112,20 @@ void runtest(int n, char const* filename1, char const* filename2)
             w.write();
         }
     }
+    else if (n == 33)
+    {
+        // Test writing to a custom pipeline
+        Pl_Buffer p("buffer");
+        QPDFWriter w(pdf);
+        w.setStaticID(true);
+        w.setOutputPipeline(&p);
+        w.write();
+        PointerHolder<Buffer> b = p.getBuffer();
+        FILE* f = QUtil::fopen_wrapper("open a.pdf",
+                                       fopen("a.pdf", "wb"));
+        fwrite(b->getBuffer(), b->getSize(), 1, f);
+        fclose(f);
+    }
     else
     {
 	throw std::runtime_error(std::string("invalid test ") +