Add 'usbstorage' iostream

This ends up being just a file interface for dive computers that expose
their data as a filesystem that can be mounted.

Right now that's only the Garmin Descent Mk1, although technically the
Uemis Zurich also did that (but oddly, and the backend was never merged
into libdivecomputer).

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

examples/common.c

@@ -99,6 +99,7 @@ static const transport_table_t g_transports[] = {
 	{"irda",      DC_TRANSPORT_IRDA},
 	{"bluetooth", DC_TRANSPORT_BLUETOOTH},
 	{"ble",       DC_TRANSPORT_BLE},
+	{"usbstorage",DC_TRANSPORT_USBSTORAGE},
 };
 
 const char *
@@ -537,6 +538,8 @@ dctool_iostream_open (dc_iostream_t **iostream, dc_context_t *context, dc_descri
 		return dctool_irda_open (iostream, context, descriptor, devname);
 	case DC_TRANSPORT_BLUETOOTH:
 		return dctool_bluetooth_open (iostream, context, descriptor, devname);
+	case DC_TRANSPORT_USBSTORAGE:
+		return dc_usb_storage_open (iostream, context, devname);
 	default:
 		return DC_STATUS_UNSUPPORTED;
 	}

include/libdivecomputer/common.h

@@ -48,9 +48,13 @@ typedef enum dc_transport_t {
 	DC_TRANSPORT_USBHID    = (1 << 2),
 	DC_TRANSPORT_IRDA      = (1 << 3),
 	DC_TRANSPORT_BLUETOOTH = (1 << 4),
-	DC_TRANSPORT_BLE       = (1 << 5)
+	DC_TRANSPORT_BLE       = (1 << 5),
+	DC_TRANSPORT_USBSTORAGE= (1 << 6),
 } dc_transport_t;
 
+// Idiotic enums can't be queried
+#define DC_TRANSPORT_USBSTORAGE DC_TRANSPORT_USBSTORAGE
+
 typedef enum dc_family_t {
 	DC_FAMILY_NULL = 0,
 	/* Suunto */

include/libdivecomputer/iostream.h

@@ -310,6 +310,9 @@ dc_iostream_sleep (dc_iostream_t *iostream, unsigned int milliseconds);
 dc_status_t
 dc_iostream_close (dc_iostream_t *iostream);
 
+dc_status_t
+dc_usb_storage_open (dc_iostream_t **out, dc_context_t *context, const char *name);
+
 #ifdef __cplusplus
 }
 #endif /* __cplusplus */

src/Makefile.am

@@ -77,6 +77,7 @@ libdivecomputer_la_SOURCES = \
 	irda.c \
 	usbhid.c \
 	bluetooth.c \
+	usb_storage.c \
 	custom.c
 
 if OS_WIN32

src/context.c

@@ -334,6 +334,7 @@ dc_context_get_transports (dc_context_t *context)
 #elif defined(HAVE_LIBUSB) && !defined(__APPLE__)
 		| DC_TRANSPORT_USBHID
 #endif
+		| DC_TRANSPORT_USBSTORAGE
 #ifdef _WIN32
 #ifdef HAVE_AF_IRDA_H
 		| DC_TRANSPORT_IRDA

src/libdivecomputer.symbols

@@ -76,6 +76,8 @@ dc_usbhid_device_free
 dc_usbhid_iterator_new
 dc_usbhid_open
 
+dc_usb_storage_open
+
 dc_custom_open
 
 dc_parser_new

src/usb_storage.c

@@ -0,0 +1,109 @@
+/*
+ * Dummy "stream" operations for USB storage
+ *
+ * Copyright (C) 2018 Linus Torvalds
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
+ * MA 02110-1301 USA
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include <limits.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+
+#include "common-private.h"
+#include "context-private.h"
+#include "iostream-private.h"
+#include "iterator-private.h"
+#include "descriptor-private.h"
+#include "timer.h"
+
+// Fake "device" that just contains the directory name that
+// you can read out of the iostream. All the actual IO is
+// up to you.
+typedef struct dc_usbstorage_t {
+	dc_iostream_t base;
+	char pathname[PATH_MAX];
+} dc_usbstorage_t;
+
+static dc_status_t
+dc_usb_storage_read (dc_iostream_t *iostream, void *data, size_t size, size_t *actual);
+
+static const dc_iostream_vtable_t dc_usbstorage_vtable = {
+	sizeof(dc_usbstorage_t),
+	NULL, /* set_timeout */
+	NULL, /* set_latency */
+	NULL, /* set_break */
+	NULL, /* set_dtr */
+	NULL, /* set_rts */
+	NULL, /* get_lines */
+	NULL, /* get_available */
+	NULL, /* configure */
+	dc_usb_storage_read, /* read */
+	NULL, /* write */
+	NULL, /* flush */
+	NULL, /* purge */
+	NULL, /* sleep */
+	NULL, /* close */
+};
+
+dc_status_t
+dc_usb_storage_open (dc_iostream_t **out, dc_context_t *context, const char *name)
+{
+	dc_usbstorage_t *device = NULL;
+	struct stat st;
+
+	if (out == NULL || name == NULL)
+		return DC_STATUS_INVALIDARGS;
+
+	INFO (context, "Open: name=%s", name);
+	if (stat(name, &st) < 0 || !S_ISDIR(st.st_mode))
+		return DC_STATUS_NODEVICE;
+
+	// Allocate memory.
+	device = (dc_usbstorage_t *) dc_iostream_allocate (context, &dc_usbstorage_vtable, DC_TRANSPORT_USBSTORAGE);
+	if (device == NULL) {
+		SYSERROR (context, ENOMEM);
+		return DC_STATUS_NOMEMORY;
+	}
+
+	strncpy(device->pathname, name, PATH_MAX);
+	device->pathname[PATH_MAX-1] = 0;
+
+	*out = (dc_iostream_t *) device;
+	return DC_STATUS_SUCCESS;
+}
+
+static dc_status_t
+dc_usb_storage_read (dc_iostream_t *iostream, void *data, size_t size, size_t *actual)
+{
+	dc_usbstorage_t *device = (dc_usbstorage_t *) iostream;
+	size_t len = strlen(device->pathname);
+
+	if (size <= len)
+		return DC_STATUS_IO;
+	memcpy(data, device->pathname, len+1);
+	if (actual)
+		*actual = len;
+	return DC_STATUS_SUCCESS;
+}