From 28daeb1a8a5f2ead77765769c5ce51289b20f0bb Mon Sep 17 00:00:00 2001
From: John Cupitt <jcupitt@gmail.com>
Date: Tue, 15 Oct 2019 10:09:24 +0100
Subject: [PATCH] start adding mmap input to stream

---
 libvips/include/vips/internal.h |  1 +
 libvips/include/vips/stream.h   | 10 ++++++
 libvips/iofuncs/mapfile.c       | 53 +++++++++++++++++++++++++++++++
 libvips/iofuncs/stream.c        | 55 ++++++++++++++++++++++++++++++++-
 4 files changed, 118 insertions(+), 1 deletion(-)

diff --git a/libvips/include/vips/internal.h b/libvips/include/vips/internal.h
index 3ecd3f1c..37e7ff60 100644
--- a/libvips/include/vips/internal.h
+++ b/libvips/include/vips/internal.h
@@ -136,6 +136,7 @@ void *vips__link_map( VipsImage *image, gboolean upstream,
 char *vips__b64_encode( const unsigned char *data, size_t data_length );
 unsigned char *vips__b64_decode( const char *buffer, size_t *data_length );
 
+gboolean vips__mmap_supported( int fd );
 void *vips__mmap( int fd, int writeable, size_t length, gint64 offset );
 int vips__munmap( const void *start, size_t length );
 int vips_mapfile( VipsImage * );
diff --git a/libvips/include/vips/stream.h b/libvips/include/vips/stream.h
index d81ea575..8cb2d911 100644
--- a/libvips/include/vips/stream.h
+++ b/libvips/include/vips/stream.h
@@ -129,6 +129,11 @@ typedef struct _VipsStreamInput {
 	 */
 	gboolean seekable;
 
+	/* TRUE is this descriptor supports mmap(). If not, then we have to
+	 * read() the whole thing.
+	 */
+	gboolean mapable;
+
 	/*< private >*/
 
 	/* The current read point.
@@ -148,6 +153,11 @@ typedef struct _VipsStreamInput {
 	 */
 	VipsBlob *blob;
 
+	/* If we've mmaped the file, the base and length.
+	 */
+	const void *baseaddr;
+	size_t length;
+
 } VipsStreamInput;
 
 typedef struct _VipsStreamInputClass {
diff --git a/libvips/iofuncs/mapfile.c b/libvips/iofuncs/mapfile.c
index 33911aac..9b4b74d7 100644
--- a/libvips/iofuncs/mapfile.c
+++ b/libvips/iofuncs/mapfile.c
@@ -90,6 +90,59 @@
 #include <io.h>
 #endif /*OS_WIN32*/
 
+/* Does this fd support mmap. Pipes won't, for example.
+ */
+gboolean
+vips__mmap_supported( int fd )
+{
+	void *baseaddr;
+	size_t length = 4096;
+	off_t offset = 0;
+
+#ifdef OS_WIN32
+{
+	HANDLE hFile = (HANDLE) _get_osfhandle( fd );
+
+	DWORD flProtect;
+        HANDLE hMMFile;
+
+	DWORD dwDesiredAccess;
+	ULARGE_INTEGER quad;
+	DWORD dwFileOffsetHigh;
+	DWORD dwFileOffsetLow;
+
+	flProtect = PAGE_READONLY;
+        if( !(hMMFile = CreateFileMapping( hFile,
+		NULL, flProtect, 0, 0, NULL )) ) 
+                return( FALSE );
+
+	dwDesiredAccess = FILE_MAP_READ;
+	quad.QuadPart = offset;
+	dwFileOffsetLow = quad.LowPart;
+	dwFileOffsetHigh = quad.HighPart;
+        if( !(baseaddr = (char *)MapViewOfFile( hMMFile, dwDesiredAccess, 
+		dwFileOffsetHigh, dwFileOffsetLow, length )) ) {
+		CloseHandle( hMMFile );
+                return( FALSE );
+        }
+	CloseHandle( hMMFile );
+	UnmapViewOfFile( baseaddr );
+}
+#else /*!OS_WIN32*/
+{
+	int prot = PROT_READ;
+	int flags = MAP_SHARED;
+
+	baseaddr = mmap( 0, length, prot, flags, fd, (off_t) offset );
+	if( baseaddr == MAP_FAILED ) 
+		return( FALSE ); 
+	munmap( baseaddr, length );
+}
+#endif /*OS_WIN32*/
+
+	return( TRUE );
+}
+
 void *
 vips__mmap( int fd, int writeable, size_t length, gint64 offset )
 {
diff --git a/libvips/iofuncs/stream.c b/libvips/iofuncs/stream.c
index f8c008fe..8f2f5066 100644
--- a/libvips/iofuncs/stream.c
+++ b/libvips/iofuncs/stream.c
@@ -63,6 +63,7 @@
 #include <unistd.h>
 
 #include <vips/vips.h>
+#include <vips/internal.h>
 #include <vips/debug.h>
 
 /* Try to make an O_BINARY ... sometimes need the leading '_'.
@@ -270,6 +271,9 @@ vips_stream_input_build( VipsObject *object )
 		 */
 		if( lseek( stream->descriptor, 0, SEEK_CUR ) != -1 )
 			input->seekable = TRUE;
+
+		if( vips__mmap_supported( stream->descriptor ) ) 
+			input->mapable = TRUE;
 	}
 
 	if( vips_object_argument_isset( object, "blob" ) )
@@ -396,6 +400,7 @@ vips_stream_input_class_init( VipsStreamInputClass *class )
 static void
 vips_stream_input_init( VipsStreamInput *input )
 {
+	input->length = -1;
 }
 
 /**
@@ -606,9 +611,57 @@ vips_stream_input_read( VipsStreamInput *input,
 	return( bytes_read );
 }
 
-unsigned char *
+static const void *
+vips_stream_input_try_map( VipsStreamInput *input, size_t *length )
+{
+	VipsStream *stream = VIPS_STREAM( input );
+
+	if( input->length < 0 )
+		input->length = vips_file_length( stream->descriptor );
+	if( input->length < 0 )
+		return( NULL );
+
+	if( !input->baseaddr ) {
+		input->baseaddr = vips__mmap( stream->descriptor, 
+			FALSE, input->length, 0 );
+		if( !input->baseaddr )
+			return( NULL );
+	}
+		
+	if( length )
+		*length = input->length;
+
+	return( input->baseaddr );
+}
+
+const void *
 vips_stream_input_map( VipsStreamInput *input, size_t *length )
 {
+	/* Memory source ... easy!
+	 */
+	if( input->blob )
+		return( vips_blob_get( input->blob, length ) );
+
+	/* An input that supports mmap.
+	 */
+	if( input->mapable ) {
+		if( !input->baseaddr ) {
+			input->baseaddr = vips_stream_input_try_map( input, 
+				&input->length );
+			if( !input->baseaddr )
+				return( NULL );
+		}
+
+		if( length )
+			*length = input->length;
+
+		return( input->baseaddr );
+	}
+
+	/* Have to read() the whole thing.
+	 */
+
+	return( NULL );
 }
 
 int