Add ability to set zlib compression level globally

ChangeLog

@@ -1,3 +1,8 @@
+2019-08-23  Jay Berkenbilt  <ejb@ql.org>
+
+	* Add option Pl_Flate::setCompressionLevel to globally set the
+	zlib compression level used by all Pl_Flate pipelines.
+
 2019-08-22  Jay Berkenbilt  <ejb@ql.org>
 
 	* In QPDFObjectHandle::ParserCallbacks, in addition to

include/qpdf/Pl_Flate.hh

@@ -28,6 +28,7 @@ class Pl_Flate: public Pipeline
 {
   public:
     static unsigned int const def_bufsize = 65536;
+    static int compression_level;
 
     enum action_e { a_inflate, a_deflate };
 
@@ -42,6 +43,15 @@ class Pl_Flate: public Pipeline
     QPDF_DLL
     virtual void finish();
 
+    // Globally set compression level from 1 (fastest, least
+    // compression) to 9 (slowest, most compression). Use -1 to set
+    // the default compression level. This is passed directly to zlib.
+    // This method returns a pointer to the current Pl_Flate object so
+    // you can create a pipeline with
+    // Pl_Flate(...)->setCompressionLevel(...)
+    QPDF_DLL
+    static void setCompressionLevel(int);
+
   private:
     void handleData(unsigned char* data, size_t len, int flush);
     void checkError(char const* prefix, int error_code);

libqpdf/Pl_Flate.cc

@@ -6,6 +6,8 @@
 #include <qpdf/QUtil.hh>
 #include <qpdf/QIntC.hh>
 
+int Pl_Flate::compression_level = Z_DEFAULT_COMPRESSION;
+
 Pl_Flate::Members::Members(size_t out_bufsize,
                            action_e action) :
     out_bufsize(out_bufsize),
@@ -120,7 +122,7 @@ Pl_Flate::handleData(unsigned char* data, size_t len, int flush)
 #endif
 	if (this->m->action == a_deflate)
 	{
-	    err = deflateInit(&zstream, Z_DEFAULT_COMPRESSION);
+	    err = deflateInit(&zstream, compression_level);
 	}
 	else
 	{
@@ -235,6 +237,12 @@ Pl_Flate::finish()
     this->getNext()->finish();
 }
 
+void
+Pl_Flate::setCompressionLevel(int level)
+{
+    compression_level = level;
+}
+
 void
 Pl_Flate::checkError(char const* prefix, int error_code)
 {

zlib-flate/qtest/zf.test

@@ -7,15 +7,21 @@ require TestDriver;
 
 my $td = new TestDriver('zlib-flate');
 
-$td->runtest("compress",
-	     {$td->COMMAND => "zlib-flate -compress < 1.uncompressed"},
-	     {$td->FILE => "1.compressed",
-	      $td->EXIT_STATUS => 0});
+foreach my $level ('', '=1', '=9')
+{
+    my $f = $level;
+    $f =~ s/=/-/;
+    $td->runtest("compress",
+                 {$td->COMMAND =>
+                      "zlib-flate -compress$level < 1.uncompressed"},
+                 {$td->FILE => "1.compressed$f",
+                      $td->EXIT_STATUS => 0});
 
-$td->runtest("uncompress",
-	     {$td->COMMAND => "zlib-flate -uncompress < 1.compressed"},
-	     {$td->FILE => "1.uncompressed",
-	      $td->EXIT_STATUS => 0});
+    $td->runtest("uncompress",
+                 {$td->COMMAND => "zlib-flate -uncompress < 1.compressed"},
+                 {$td->FILE => "1.uncompressed",
+                      $td->EXIT_STATUS => 0});
+}
 
 $td->runtest("error",
 	     {$td->COMMAND => "zlib-flate -uncompress < 1.uncompressed"},
@@ -23,4 +29,4 @@ $td->runtest("error",
 	      $td->EXIT_STATUS => 2},
 	     $td->NORMALIZE_NEWLINES);
 
-$td->report(3);
+$td->report(7);

zlib-flate/zlib-flate.cc

@@ -12,8 +12,14 @@ static char const* whoami = 0;
 
 void usage()
 {
-    std::cerr << "Usage: " << whoami << " { -uncompress | -compress }"
-	      << std::endl;
+    std::cerr << "Usage: " << whoami << " { -uncompress | -compress[=n] }"
+	      << std::endl
+              << "If n is specified with -compress, it is a"
+              << " zlib compression level from" << std::endl
+              << "1 to 9 where lower numbers are faster and"
+              << " less compressed and higher" << std::endl
+              << "numbers are slower and more compresed"
+              << std::endl;
     exit(2);
 }
 
@@ -43,6 +49,7 @@ int main(int argc, char* argv[])
     {
 	usage();
     }
+    // QXXXQ level
 
     Pl_Flate::action_e action = Pl_Flate::a_inflate;
 
@@ -54,6 +61,12 @@ int main(int argc, char* argv[])
     {
 	action = Pl_Flate::a_deflate;
     }
+    else if ((strncmp(argv[1], "-compress=", 10) == 0))
+    {
+	action = Pl_Flate::a_deflate;
+        int level = QUtil::string_to_int(argv[1] + 10);
+        Pl_Flate::setCompressionLevel(level);
+    }
     else
     {
 	usage();