Add hid_get_device_info (libusb#432)

- new API function: `struct hid_device_info * hid_get_device_info(hid_device *dev);` to get `hid_device_info` after the device already opened;
- reused existing implementation on Windows and macOS from enumeration routines to have the implementation;
- refactored libusb implementation to have a shared routine for `hid_enumerate` and `hid_get_device_info`;
- refactored hidraw implementation to have a shared routine for `hid_enumerate` and `hid_get_device_info`;

Resolves: libusb#431
Closes: libusb#164
Closes: libusb#163

hidapi/hidapi.h

@@ -470,6 +470,21 @@ extern "C" {
 		*/
 		int HID_API_EXPORT_CALL hid_get_serial_number_string(hid_device *dev, wchar_t *string, size_t maxlen);
 
+		/** @brief Get The struct #hid_device_info from a HID device.
+
+			@ingroup API
+			@param dev A device handle returned from hid_open().
+
+			@returns
+				This function returns a pointer to the struct #hid_device_info
+				for this hid_device, or NULL in the case of failure.
+				Call hid_error(dev) to get the failure reason.
+				This struct is valid until the device is closed with hid_close().
+
+			@note The returned object is owned by the @p dev, and SHOULD NOT be freed by the user.
+		*/
+		HID_API_EXPORT struct hid_device_info * HID_API_CALL hid_get_device_info(hid_device *dev);
+
 		/** @brief Get a string from a HID device, based on its string index.
 
 			@ingroup API

hidtest/test.c

@@ -51,6 +51,24 @@
 #endif
 //
 
+void print_device(struct hid_device_info *cur_dev) {
+	printf("Device Found\n  type: %04hx %04hx\n  path: %s\n  serial_number: %ls", cur_dev->vendor_id, cur_dev->product_id, cur_dev->path, cur_dev->serial_number);
+	printf("\n");
+	printf("  Manufacturer: %ls\n", cur_dev->manufacturer_string);
+	printf("  Product:      %ls\n", cur_dev->product_string);
+	printf("  Release:      %hx\n", cur_dev->release_number);
+	printf("  Interface:    %d\n",  cur_dev->interface_number);
+	printf("  Usage (page): 0x%hx (0x%hx)\n", cur_dev->usage, cur_dev->usage_page);
+	printf("\n");
+}
+
+void print_devices(struct hid_device_info *cur_dev) {
+	while (cur_dev) {
+		print_device(cur_dev);
+		cur_dev = cur_dev->next;
+	}
+}
+
 int main(int argc, char* argv[])
 {
 	(void)argc;
@@ -63,7 +81,7 @@ int main(int argc, char* argv[])
 	hid_device *handle;
 	int i;
 
-	struct hid_device_info *devs, *cur_dev;
+	struct hid_device_info *devs;
 
 	printf("hidapi test/example tool. Compiled with hidapi version %s, runtime version %s.\n", HID_API_VERSION_STR, hid_version_str());
 	if (HID_API_VERSION == HID_API_MAKE_VERSION(hid_version()->major, hid_version()->minor, hid_version()->patch)) {
@@ -83,18 +101,7 @@ int main(int argc, char* argv[])
 #endif
 
 	devs = hid_enumerate(0x0, 0x0);
-	cur_dev = devs;
-	while (cur_dev) {
-		printf("Device Found\n  type: %04hx %04hx\n  path: %s\n  serial_number: %ls", cur_dev->vendor_id, cur_dev->product_id, cur_dev->path, cur_dev->serial_number);
-		printf("\n");
-		printf("  Manufacturer: %ls\n", cur_dev->manufacturer_string);
-		printf("  Product:      %ls\n", cur_dev->product_string);
-		printf("  Release:      %hx\n", cur_dev->release_number);
-		printf("  Interface:    %d\n",  cur_dev->interface_number);
-		printf("  Usage (page): 0x%hx (0x%hx)\n", cur_dev->usage, cur_dev->usage_page);
-		printf("\n");
-		cur_dev = cur_dev->next;
-	}
+	print_devices(devs);
 	hid_free_enumeration(devs);
 
 	// Set up the command buffer.
@@ -134,6 +141,13 @@ int main(int argc, char* argv[])
 	printf("Serial Number String: (%d) %ls", wstr[0], wstr);
 	printf("\n");
 
+	struct hid_device_info* info = hid_get_device_info(handle);
+	if (info == NULL) {
+		printf("Unable to get device info\n");
+	} else {
+		print_devices(info);
+	}
+
 	// Read Indexed String 1
 	wstr[0] = 0x0000;
 	res = hid_get_indexed_string(handle, 1, wstr, MAX_STR);