Split inferWriterDriver into two

Similar to #340, the 2-argument infer{Reader|Writer}Driver might try to
do too much by both modifying options and finding the correct driver.
This patch splits the inferWriterDriver into two pieces. The
inferWriterDriver part does just that, while a new method,
inferWriterOptionsChanges, modifies an options object based upon a given
filename.

include/pdal/StageFactory.hpp

@@ -93,10 +93,12 @@ class PDAL_DLL StageFactory
 
     // infer the driver to use based on filename extension
     // returns "" if no driver found
-    // 
-    // this may also add on an option to pass to the driver, such as the filename
-    // (or something inferred from the extension, such as .laz means we need to use compress=true)
-    static std::string inferWriterDriver(const std::string& filename, pdal::Options& options);
+    static std::string inferWriterDriver(const std::string& filename);
+
+    // modify options based upon expectations implicit in a given filename
+    // e.g. output files ending in .laz should be compressed
+    static void inferWriterOptionsChanges(const std::string& filename,
+                                          pdal::Options& options);
 
     Reader* createReader(const std::string& type, const Options& options);
     Filter* createFilter(const std::string& type, Stage& prevStage, const Options& options);

src/StageFactory.cpp

@@ -201,24 +201,13 @@ std::string StageFactory::inferReaderDriver(const std::string& filename, pdal::O
     return driver; // will be "" if not found
 }
 
-std::string StageFactory::inferWriterDriver(const std::string& filename, pdal::Options& options)
+
+std::string StageFactory::inferWriterDriver(const std::string& filename)
 {
     std::string ext = boost::filesystem::extension(filename);
 
     boost::to_lower(ext);
 
-    if (boost::algorithm::iequals(ext,".laz"))
-    {
-        options.add("compression", true);
-    }
-
-    if (boost::algorithm::iequals(ext,".pcd"))
-    {
-        options.add("format","PCD");
-    }
-
-    options.add<std::string>("filename", filename);
-
     std::map<std::string, std::string> drivers;
     drivers["las"] = "drivers.las.writer";
     drivers["laz"] = "drivers.las.writer";
@@ -241,6 +230,26 @@ std::string StageFactory::inferWriterDriver(const std::string& filename, pdal::O
     return driver; // will be "" if not found
 }
 
+
+void StageFactory::inferWriterOptionsChanges(const std::string& filename, pdal::Options& options)
+{
+    std::string ext = boost::filesystem::extension(filename);
+    boost::to_lower(ext);
+
+    if (boost::algorithm::iequals(ext,".laz"))
+    {
+        options.add("compression", true);
+    }
+
+    if (boost::algorithm::iequals(ext,".pcd"))
+    {
+        options.add("format","PCD");
+    }
+
+    options.add<std::string>("filename", filename);
+}
+
+
 Reader* StageFactory::createReader(const std::string& type, const Options& options)
 {
     ReaderCreator* f = getReaderCreator(type);

src/kernel/Support.cpp

@@ -101,11 +101,12 @@ pdal::Writer* AppSupport::makeWriter(pdal::Options& options, pdal::Stage& stage)
     const std::string outputFile = options.getValueOrThrow<std::string>("filename");
 
     pdal::StageFactory factory;
-    std::string driver = factory.inferWriterDriver(outputFile, options);
+    std::string driver = factory.inferWriterDriver(outputFile);
     if (driver == "")
     {
         throw app_runtime_error("Cannot determine output file type of " + outputFile);
     }
+    factory.inferWriterOptionsChanges(outputFile, options);
 
     pdal::Writer* writer = factory.createWriter(driver, stage, options);
     if (!writer)
@@ -220,4 +221,4 @@ void HeartbeatCallback::callback()
     return;
 }
 
-}} // pdal::kernel
+}} // pdal::kernel