tiffsave: ensure large file support (>2GB) on MSVC

On MSVC, `off_t` and `lseek()` are limited to signed 32-bit offsets,
which limits their capability to handle files larger than 2GB.

To support saving TIFF files that exceed this size, replace their use
with `gint64` and `vips__seek()`, where the latter uses `_lseeki64()`
internally.

See: conan-io/conan#15578.

ChangeLog

@@ -7,6 +7,7 @@ date-tbd 8.15.2
 - ppmload: ensure multi-line comments are skipped [lovell]
 - fix arrayjoin with some pipelines [TheEssem]
 - fix high Q mono JPEG TIFF write with mozjpeg [cavenel]
+- tiffsave: ensure large file support (>2GB) on MSVC [kleisauke]
 
 18/12/23 8.15.1
 

libvips/include/vips/connection.h

@@ -428,8 +428,11 @@ struct _VipsTarget {
 	int write_point;
 
 	/* Write position in memory_buffer.
+	 *
+	 * off_t can be 32 bits on some platforms, so make sure we have a
+	 * full 64.
 	 */
-	off_t position;
+	gint64 position;
 
 	/* Temp targets on the filesystem need deleting, sometimes.
 	 */
@@ -466,8 +469,11 @@ typedef struct _VipsTargetClass {
 	gint64 (*read)(VipsTarget *, void *, size_t);
 
 	/* Seek output. Args exactly as lseek(2).
+	 *
+	 * We have to use int64 rather than off_t, since we must work on
+	 * Windows, where off_t can be 32-bits.
 	 */
-	off_t (*seek)(VipsTarget *, off_t offset, int whence);
+	gint64 (*seek)(VipsTarget *, gint64 offset, int whence);
 
 	/* Output has been generated, so do any clearing up,
 	 * eg. copy the bytes we saved in memory to the target blob.
@@ -492,7 +498,7 @@ int vips_target_write(VipsTarget *target, const void *data, size_t length);
 VIPS_API
 gint64 vips_target_read(VipsTarget *target, void *buffer, size_t length);
 VIPS_API
-off_t vips_target_seek(VipsTarget *target, off_t offset, int whence);
+gint64 vips_target_seek(VipsTarget *target, gint64 offset, int whence);
 VIPS_API
 int vips_target_end(VipsTarget *target);
 VIPS_DEPRECATED_FOR(vips_target_end)

libvips/iofuncs/target.c

@@ -175,15 +175,17 @@ vips_target_write_real(VipsTarget *target, const void *data, size_t length)
 	return result;
 }
 
-static off_t
-vips_target_seek_real(VipsTarget *target, off_t offset, int whence)
+static gint64
+vips_target_seek_real(VipsTarget *target, gint64 offset, int whence)
 {
 	VipsConnection *connection = VIPS_CONNECTION(target);
 	const char *nick = vips_connection_nick(connection);
 
-	off_t new_position;
+	gint64 new_position;
 
-	VIPS_DEBUG_MSG("vips_target_seek_real: offset = %ld, whence = %d\n",
+	VIPS_DEBUG_MSG(
+		"vips_target_seek_real: offset = %" G_GINT64_FORMAT
+		", whence = %d\n",
 		offset, whence);
 
 	if (target->memory_buffer) {
@@ -212,7 +214,11 @@ vips_target_seek_real(VipsTarget *target, off_t offset, int whence)
 		target->position = new_position;
 	}
 	else
-		new_position = lseek(connection->descriptor, offset, whence);
+		/* We need to use the vips__seek() wrapper so we can seek long
+		 * files on Windows.
+		 */
+		new_position = vips__seek_no_error(connection->descriptor,
+			offset, whence);
 
 	return new_position;
 }
@@ -539,7 +545,7 @@ vips_target_write(VipsTarget *target, const void *buffer, size_t length)
  *
  * Arguments exactly as read(2).
  *
- * Reading froma  target sounds weird, but libtiff needs this for
+ * Reading from a target sounds weird, but libtiff needs this for
  * multi-page writes. This method will fail for targets like pipes.
  *
  * Returns: the number of bytes read, 0 on end of file, -1 on error.
@@ -570,22 +576,25 @@ vips_target_read(VipsTarget *target, void *buffer, size_t length)
  *
  * Returns: the new seek position, -1 on error.
  */
-off_t
-vips_target_seek(VipsTarget *target, off_t position, int whence)
+gint64
+vips_target_seek(VipsTarget *target, gint64 position, int whence)
 {
 	VipsTargetClass *class = VIPS_TARGET_GET_CLASS(target);
 
-	off_t new_position;
+	gint64 new_position;
 
-	VIPS_DEBUG_MSG("vips_target_seek: pos = %ld, whence = %d\n",
+	VIPS_DEBUG_MSG(
+		"vips_target_seek: pos = %" G_GINT64_FORMAT
+		", whence = %d\n",
 		position, whence);
 
 	if (vips_target_flush(target))
 		return -1;
 
 	new_position = class->seek(target, position, whence);
 
-	VIPS_DEBUG_MSG("vips_target_seek: new_position = %ld\n",
+	VIPS_DEBUG_MSG(
+		"vips_target_seek: new_position = %" G_GINT64_FORMAT "\n",
 		new_position);
 
 	return new_position;