--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/libuwrap/find_matchspec.c	Thu Sep 07 04:00:56 2023 +0000
@@ -0,0 +1,92 @@
+/*
+ * In this module we implement the function that locates a USB device
+ * by matchspec structure: looking for specific VID/PID, possibly qualified
+ * by strings and/or index.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <usb.h>
+#include "find_dev.h"
+#include "prelim_init.h"
+
+static void
+get_string(usb_dev_handle *usbh, int index, char *buf, size_t buflen)
+{
+	int rc;
+
+	rc = usb_get_string_simple(usbh, index, buf, buflen);
+	if (rc <= 0) {
+		fprintf(stderr, "error: USB string retrieval failed\n");
+		exit(1);
+	}
+}
+
+static int
+is_match(struct usb_device *dev, const struct usbdev_matchspec *match)
+{
+	struct usb_device_descriptor *desc = &dev->descriptor;
+	usb_dev_handle *usbh;
+	char strbuf[1024];
+
+	if (desc->idVendor != match->usb_vid)
+		return 0;
+	if (desc->idProduct != match->usb_pid)
+		return 0;
+	if (match->manuf_string || match->product_string || match->serial) {
+		usbh = usb_open(dev);
+		if (!usbh) {
+			fprintf(stderr, "error: usb_open() failed\n");
+			exit(1);
+		}
+		if (match->manuf_string) {
+			get_string(usbh, desc->iManufacturer,
+				   strbuf, sizeof strbuf);
+			if (strncmp(match->manuf_string,
+				    strbuf, sizeof strbuf)) {
+				usb_close(usbh);
+				return 0;
+			}
+		}
+		if (match->product_string) {
+			get_string(usbh, desc->iProduct, strbuf, sizeof strbuf);
+			if (strncmp(match->product_string,
+				    strbuf, sizeof strbuf)) {
+				usb_close(usbh);
+				return 0;
+			}
+		}
+		if (match->serial) {
+			get_string(usbh, desc->iSerialNumber,
+				   strbuf, sizeof strbuf);
+			if (strncmp(match->serial, strbuf, sizeof strbuf)) {
+				usb_close(usbh);
+				return 0;
+			}
+		}
+		usb_close(usbh);
+	}
+	return 1;
+}
+
+struct usb_device *
+find_usbdev_by_matchspec(const struct usbdev_matchspec *match)
+{
+	struct usb_bus *bus;
+	struct usb_device *dev;
+	unsigned index = match->index;
+
+	libusb_prelim_init();
+	for (bus = usb_get_busses(); bus; bus = bus->next) {
+		for (dev = bus->devices; dev; dev = dev->next) {
+			if (is_match(dev, match)) {
+				if (!index)
+					return dev;
+				index--;
+			}
+		}
+	}
+	return 0;
+}