make file format readers close fds early

we were using two fds per open image, now we just use one

jpg, magick, tiff, png

ChangeLog

@@ -8,6 +8,7 @@
 - add magicload_buffer() [mcuelenaere]
 - added test_foreign.py, plus more test images
 - rewritten tiff writer is about 3 - 4x faster at making pyramids
+- jpg, magick, png, tiff readers now use only 1 fd per input image
 
 6/2/15 started 7.42.3
 - bump version for back-compat ABI change

TODO

@@ -1,3 +1,4 @@
+
 - support orientation tag in tiff images
 
   see

libvips/foreign/jpeg2vips.c

@@ -64,6 +64,9 @@
  * 20/1/15
  * 	- don't call jpeg_finish_decompress(), all it does is read and check 
  * 	  the tail of the file
+ * 26/2/15
+ * 	- close the jpeg read down early for a header read ... this saves an
+ * 	  fd during jpg read, handy for large numbers of input images 
  */
 
 /*
@@ -166,6 +169,8 @@ typedef struct _ReadJpeg {
 	gboolean autorotate;
 } ReadJpeg;
 
+/* This can be called many times.
+ */
 static int
 readjpeg_free( ReadJpeg *jpeg )
 {
@@ -199,7 +204,7 @@ readjpeg_free( ReadJpeg *jpeg )
 	VIPS_FREE( jpeg->filename );
 	jpeg->eman.fp = NULL;
 
-	/* I don't think this can fail.
+	/* I don't think this can fail. It's harmless to call many times. 
 	 */
 	jpeg_destroy_decompress( &jpeg->cinfo );
 
@@ -1111,6 +1116,12 @@ vips__jpeg_read_file( const char *filename, VipsImage *out,
 	if( vips__jpeg_read( jpeg, out, header_only ) ) 
 		return( -1 );
 
+	/* We can kill off the decompress early if this is just a header read.
+	 * This saves an fd during read.
+	 */
+	if( header_only )
+		readjpeg_free( jpeg );
+
 	return( 0 );
 }
 

libvips/foreign/magick2vips.c

@@ -44,6 +44,9 @@
  * 	- add @density option 
  * 16/2/15 mcuelenaere
  * 	- add blob read
+ * 26/2/15
+ * 	- close the read down early for a header read ... this saves an
+ * 	  fd during file read, handy for large numbers of input images 
  */
 
 /*
@@ -127,11 +130,13 @@ typedef struct _Read {
 	GMutex *lock;
 } Read;
 
-static int
-read_destroy( VipsImage *im, Read *read )
+/* Can be called many times.
+ */
+static void
+read_free( Read *read )
 {
 #ifdef DEBUG
-	printf( "magick2vips: read_destroy: %s\n", read->filename );
+	printf( "magick2vips: read_free: %s\n", read->filename );
 #endif /*DEBUG*/
 
 	VIPS_FREE( read->filename );
@@ -140,6 +145,14 @@ read_destroy( VipsImage *im, Read *read )
 	VIPS_FREE( read->frames );
 	DestroyExceptionInfo( &read->exception );
 	VIPS_FREEF( vips_g_mutex_free, read->lock );
+}
+
+/* Can be called many times.
+ */
+static int
+read_close( VipsImage *im, Read *read )
+{
+	read_free( read ); 
 
 	return( 0 );
 }
@@ -173,7 +186,7 @@ read_new( const char *filename, VipsImage *im, gboolean all_frames,
 	read->frame_height = 0;
 	read->lock = vips_g_mutex_new();
 
-	g_signal_connect( im, "close", G_CALLBACK( read_destroy ), read );
+	g_signal_connect( im, "close", G_CALLBACK( read_close ), read );
 
 	if( !read->image_info ) 
 		return( NULL );
@@ -741,6 +754,10 @@ vips__magick_read_header( const char *filename, VipsImage *im,
 		return( -1 );
 	}
 
+	/* Just a header read: we can free the read early and save an fd.
+	 */
+	read_free( read );
+
 	return( 0 );
 }
 

libvips/foreign/tiff2vips.c

@@ -154,6 +154,9 @@
  * 	- read any XMP metadata
  * 19/1/15
  * 	- try to handle 8-bit colormaps
+ * 26/2/15
+ * 	- close the read down early for a header read ... this saves an
+ * 	  fd during file read, handy for large numbers of input images 
  */
 
 /*
@@ -1678,12 +1681,20 @@ read_stripwise( ReadTiff *rtiff, VipsImage *out )
 	return( 0 );
 }
 
+/* Can be called many times.
+ */
 static void
-readtiff_destroy( VipsObject *object, ReadTiff *rtiff )
+readtiff_free( ReadTiff *rtiff )
 {
 	VIPS_FREEF( TIFFClose, rtiff->tiff );
 }
 
+static void
+readtiff_close( VipsObject *object, ReadTiff *rtiff )
+{
+	readtiff_free( rtiff ); 
+}
+
 static ReadTiff *
 readtiff_new( VipsImage *out, int page, gboolean readbehind )
 {
@@ -1710,7 +1721,7 @@ readtiff_new( VipsImage *out, int page, gboolean readbehind )
 	rtiff->contig_buf = NULL;
 
 	g_signal_connect( out, "close", 
-		G_CALLBACK( readtiff_destroy ), rtiff ); 
+		G_CALLBACK( readtiff_close ), rtiff ); 
 
 	if( rtiff->page < 0 || rtiff->page > 1000000 ) {
 		vips_error( "tiff2vips", _( "bad page number %d" ),
@@ -1918,6 +1929,10 @@ vips__tiff_read_header( const char *filename, VipsImage *out, int page )
 	if( parse_header( rtiff, out ) )
 		return( -1 );
 
+	/* Just a header read: we can free the tiff read early and save an fd.
+	 */
+	readtiff_free( rtiff );
+
 	return( 0 );
 }
 

libvips/foreign/vipspng.c

@@ -52,6 +52,9 @@
  * 	- don't check profiles, helps with libpng >=1.6.11
  * 27/10/14 Lovell
  * 	- add @filter option 
+ * 26/2/15
+ * 	- close the read down early for a header read ... this saves an
+ * 	  fd during file read, handy for large numbers of input images 
  */
 
 /*
@@ -150,6 +153,8 @@ typedef struct {
 
 } Read;
 
+/* Can be called many times.
+ */
 static void
 read_destroy( Read *read )
 {
@@ -423,6 +428,10 @@ vips__png_header( const char *name, VipsImage *out )
 		png2vips_header( read, out ) ) 
 		return( -1 );
 
+	/* Just a header read: we can free the read early and save an fd.
+	 */
+	read_destroy( read );
+
 	return( 0 );
 }