Simplify TokenFilter interface

Expose Pl_QPDFTokenizer, and have it do more of the work of managing the token filter's pipeline.

Simplify TokenFilter interface
Expose Pl_QPDFTokenizer, and have it do more of the work of managing the token filter's pipeline.
Jay Berkenbilt
1 parent 1fdd86a0
Showing 10 changed files with 44 additions and 67 deletions
examples/pdf-count-strings.cc
examples/pdf-filter-tokens.cc
include/qpdf/Pl_QPDFTokenizer.hh
include/qpdf/QPDFObjectHandle.hh
libqpdf/ContentNormalizer.cc
libqpdf/Pl_QPDFTokenizer.cc
libqpdf/QPDFObjectHandle.cc
libqpdf/QPDF_Stream.cc
libqpdf/qpdf/ContentNormalizer.hh
qpdf/test_driver.cc
@@ -62,8 +62,6 @@ StringCounter::handleEOF()
     // can enhance the output if we want.
     write("\n% strings found: ");
     write(QUtil::int_to_string(this->count));
-    // If you override handleEOF, you must always remember to call finish().
-    finish();
 }
  
 int
@@ -184,12 +184,6 @@ ColorToGray::handleEOF()
         writeToken(this->all_stack.at(0));
         this->all_stack.pop_front();
     }
-    // Remember to call finish(). If you override handleEOF, it is
-    // essential that you call finish() or else you are likely to lose
-    // some data in buffers of downstream pipelines that are not
-    // flushed out. This is also mentioned in comments in
-    // QPDFObjectHandle.hh.
-    finish();
 }
  
 int main(int argc, char* argv[])
@@ -41,8 +41,12 @@
 class Pl_QPDFTokenizer: public Pipeline
 {
   public:
+    // Whatever pipeline is provided as "next" will be set as the
+    // pipeline that the token filter writes to. If next is not
+    // provided, any output written by the filter will be discarded.
     Pl_QPDFTokenizer(char const* identifier,
-                     QPDFObjectHandle::TokenFilter* filter);
+                     QPDFObjectHandle::TokenFilter* filter,
+                     Pipeline* next = 0);
     virtual ~Pl_QPDFTokenizer();
     virtual void write(unsigned char* buf, size_t len);
     virtual void finish();
@@ -45,6 +45,7 @@ class QPDF_Dictionary;
 class QPDF_Array;
 class QPDFTokenizer;
 class QPDFExc;
+class Pl_QPDFTokenizer;
  
 class QPDFObjectHandle
 {
@@ -81,18 +82,13 @@ class QPDFObjectHandle
     // in a lexically aware fashion. TokenFilters can be attached to
     // streams using the addTokenFilter or addContentTokenFilter
     // methods or can be applied on the spot by filterPageContents.
+    // You may also use Pl_QPDFTokenizer directly if you need full
+    // control.
+    //
     // The handleToken method is called for each token, including the
     // eof token, and then handleEOF is called at the very end.
     // Handlers may call write (or writeToken) to pass data
-    // downstream. The finish() method must be called exactly one time
-    // to ensure that any written data is flushed out. The default
-    // handleEOF calls finish. If you override handleEOF, you must
-    // ensure that finish() is called either there or in response to
-    // whatever event causes you to terminate creation of output.
-    // Failure to call finish() may result in some of the data you
-    // have written being lost. You should not rely on a destructor
-    // for calling finish() since the destructor call may occur later
-    // than you expect. Please see examples/pdf-filter-tokens.cc and
+    // downstream. Please see examples/pdf-filter-tokens.cc and
     // examples/pdf-count-strings.cc for examples of using
     // TokenFilters.
     //
@@ -115,15 +111,17 @@ class QPDFObjectHandle
         {
         }
         virtual void handleToken(QPDFTokenizer::Token const&) = 0;
-        virtual void handleEOF()
-        {
-            // If you override handleEOF, you must be sure to call
-            // finish().
-            finish();
-        }
+        virtual void handleEOF();
  
-        // This is called internally by the qpdf library.
-        void setPipeline(Pipeline*);
+        class PipelineAccessor
+        {
+            friend class Pl_QPDFTokenizer;
+          private:
+            static void setPipeline(TokenFilter* f, Pipeline* p)
+            {
+                f->setPipeline(p);
+            }
+        };
  
       protected:
         QPDF_DLL
@@ -132,10 +130,10 @@ class QPDFObjectHandle
         void write(std::string const& str);
         QPDF_DLL
         void writeToken(QPDFTokenizer::Token const&);
-        QPDF_DLL
-        void finish();
  
       private:
+        void setPipeline(Pipeline*);
+
         Pipeline* pipeline;
     };
  
@@ -82,12 +82,6 @@ ContentNormalizer::handleToken(QPDFTokenizer::Token const&amp; token)
     }
 }
  
-void
-ContentNormalizer::handleEOF()
-{
-    finish();
-}
-
 bool
 ContentNormalizer::anyBadTokens() const
 {
@@ -15,14 +15,15 @@ Pl_QPDFTokenizer::Members::~Members()
 {
 }
  
-Pl_QPDFTokenizer::Pl_QPDFTokenizer(
-    char const* identifier,
-    QPDFObjectHandle::TokenFilter* filter)
-    :
-    Pipeline(identifier, 0),
+Pl_QPDFTokenizer::Pl_QPDFTokenizer(char const* identifier,
+                                   QPDFObjectHandle::TokenFilter* filter,
+                                   Pipeline* next) :
+    Pipeline(identifier, next),
     m(new Members)
 {
     m->filter = filter;
+    QPDFObjectHandle::TokenFilter::PipelineAccessor::setPipeline(
+        m->filter, next);
     m->tokenizer.allowEOF();
     m->tokenizer.includeIgnorable();
 }
@@ -88,4 +89,11 @@ Pl_QPDFTokenizer::finish()
     }
  
     this->m->filter->handleEOF();
+    QPDFObjectHandle::TokenFilter::PipelineAccessor::setPipeline(
+        m->filter, 0);
+    Pipeline* next = this->getNext(true);
+    if (next)
+    {
+        next->finish();
+    }
 }
@@ -16,7 +16,6 @@
 #include <qpdf/Pl_Buffer.hh>
 #include <qpdf/Pl_Concatenate.hh>
 #include <qpdf/Pl_QPDFTokenizer.hh>
-#include <qpdf/Pl_Discard.hh>
 #include <qpdf/BufferInputSource.hh>
 #include <qpdf/QPDFExc.hh>
  
@@ -65,6 +64,11 @@ CoalesceProvider::provideStreamData(int, int, Pipeline* p)
 }
  
 void
+QPDFObjectHandle::TokenFilter::handleEOF()
+{
+}
+
+void
 QPDFObjectHandle::TokenFilter::setPipeline(Pipeline* p)
 {
     this->pipeline = p;
@@ -75,8 +79,7 @@ QPDFObjectHandle::TokenFilter::write(char const* data, size_t len)
 {
     if (! this->pipeline)
     {
-        throw std::logic_error(
-            "TokenFilter::write called before setPipeline");
+        return;
     }
     if (len)
     {
@@ -98,17 +101,6 @@ QPDFObjectHandle::TokenFilter::writeToken(QPDFTokenizer::Token const&amp; token)
 }
  
 void
-QPDFObjectHandle::TokenFilter::finish()
-{
-    if (! this->pipeline)
-    {
-        throw std::logic_error(
-            "TokenFilter::finish called before setPipeline");
-    }
-    this->pipeline->finish();
-}
-
-void
 QPDFObjectHandle::ParserCallbacks::terminateParsing()
 {
     throw TerminateParsing();
@@ -1007,14 +999,7 @@ QPDFObjectHandle::filterPageContents(TokenFilter* filter, Pipeline* next)
     std::string description = "token filter for page object " +
         QUtil::int_to_string(this->objid) + " " +
         QUtil::int_to_string(this->generation);
-    Pl_QPDFTokenizer token_pipeline(description.c_str(), filter);
-    PointerHolder<Pipeline> next_p;
-    if (next == 0)
-    {
-        next_p = new Pl_Discard();
-        next = next_p.getPointer();
-    }
-    filter->setPipeline(next);
+    Pl_QPDFTokenizer token_pipeline(description.c_str(), filter, next);
     this->pipePageContents(&token_pipeline);
 }
  
@@ -459,9 +459,8 @@ QPDF_Stream::pipeStreamData(Pipeline* pipeline,
 	if (encode_flags & qpdf_ef_normalize)
 	{
             normalizer = new ContentNormalizer();
-            normalizer->setPipeline(pipeline);
 	    pipeline = new Pl_QPDFTokenizer(
-                "normalizer", normalizer.getPointer());
+                "normalizer", normalizer.getPointer(), pipeline);
 	    to_delete.push_back(pipeline);
 	}
  
@@ -470,9 +469,8 @@ QPDF_Stream::pipeStreamData(Pipeline* pipeline,
                  this->token_filters.rbegin();
              iter != this->token_filters.rend(); ++iter)
         {
-            (*iter)->setPipeline(pipeline);
             pipeline = new Pl_QPDFTokenizer(
-                "token filter", (*iter).getPointer());
+                "token filter", (*iter).getPointer(), pipeline);
             to_delete.push_back(pipeline);
         }
  
@@ -9,7 +9,6 @@ class ContentNormalizer: public QPDFObjectHandle::TokenFilter
     ContentNormalizer();
     virtual ~ContentNormalizer();
     virtual void handleToken(QPDFTokenizer::Token const&);
-    virtual void handleEOF();
  
     bool anyBadTokens() const;
     bool lastTokenWasBad() const;
@@ -123,7 +123,6 @@ class TokenFilter: public QPDFObjectHandle::TokenFilter
     {
         writeToken(QPDFTokenizer::Token(QPDFTokenizer::tt_name, "/bye"));
         write("\n");
-        finish();
     }
 };