hidapi/libusb: maintain in-memory cache of vendor/product strings

libusb/hid.c

@@ -433,6 +433,111 @@ static wchar_t *get_usb_string(libusb_device_handle *dev, uint8_t idx)
  return str;
 }
 
+struct usb_string_cache_entry {
+ uint16_t vid;
+ uint16_t pid;
+ wchar_t *vendor;
+ wchar_t *product;
+};
+
+static struct usb_string_cache_entry *usb_string_cache = NULL;
+static size_t usb_string_cache_size = 0;
+static size_t usb_string_cache_insert_pos = 0;
+
+static int usb_string_cache_grow()
+{
+ struct usb_string_cache_entry *new_cache;
+ size_t allocSize;
+ size_t new_cache_size;
+
+ new_cache_size = usb_string_cache_size + 8;
+ allocSize = sizeof(struct usb_string_cache_entry) * new_cache_size;
+ new_cache = (struct usb_string_cache_entry *)realloc(usb_string_cache, allocSize);
+ if (!new_cache)
+ return -1;
+
+ usb_string_cache = new_cache;
+ usb_string_cache_size = new_cache_size;
+
+ return 0;
+}
+
+static void usb_string_cache_destroy()
+{
+ size_t i;
+ for (i = 0; i < usb_string_cache_insert_pos; i++) {
+ free(usb_string_cache[i].vendor);
+ free(usb_string_cache[i].product);
+ }
+ free(usb_string_cache);
+
+ usb_string_cache = NULL;
+ usb_string_cache_size = 0;
+ usb_string_cache_insert_pos = 0;
+}
+
+static struct usb_string_cache_entry *usb_string_cache_insert()
+{
+ struct usb_string_cache_entry *new_entry = NULL;
+ if (usb_string_cache_insert_pos >= usb_string_cache_size) {
+ if (usb_string_cache_grow() < 0)
+ return NULL;
+ }
+ new_entry = &usb_string_cache[usb_string_cache_insert_pos];
+ usb_string_cache_insert_pos++;
+ return new_entry;
+}
+
+static int usb_string_can_cache(uint16_t vid, uint16_t pid)
+{
+ if (!vid || !pid) {
+ /* We can't cache these, they aren't unique */
+ return 0;
+ }
+
+ if (vid == 0x0f0d && pid == 0x00dc) {
+ /* HORI reuses this VID/PID for many different products */
+ return 0;
+ }
+
+ /* We can cache these strings */
+ return 1;
+}
+
+static const struct usb_string_cache_entry *usb_string_cache_find(struct libusb_device_descriptor *desc, struct libusb_device_handle *handle)
+{
+ struct usb_string_cache_entry *entry = NULL;
+ size_t i;
+
+ /* Search for existing string cache entry */
+ for (i = 0; i < usb_string_cache_insert_pos; i++) {
+ entry = &usb_string_cache[i];
+ if (entry->vid != desc->idVendor)
+ continue;
+ if (entry->pid != desc->idProduct)
+ continue;
+ return entry;
+ }
+
+ /* Not found, create one. */
+ entry = usb_string_cache_insert();
+ if (!entry)
+ return NULL;
+
+ entry->vid = desc->idVendor;
+ entry->pid = desc->idProduct;
+ if (desc->iManufacturer > 0)
+ entry->vendor = get_usb_string(handle, desc->iManufacturer);
+ else
+ entry->vendor = NULL;
+ if (desc->iProduct > 0)
+ entry->product = get_usb_string(handle, desc->iProduct);
+ else
+ entry->product = NULL;
+
+ return entry;
+}
+
 /**
  Max length of the result: "000-000.000.000.000.000.000.000:000.000" (39 chars).
  64 is used for simplicity/alignment.
@@ -500,6 +605,8 @@ int HID_API_EXPORT hid_init(void)
 
 int HID_API_EXPORT hid_exit(void)
 {
+ usb_string_cache_destroy();
+
  if (usb_context) {
  libusb_exit(usb_context);
  usb_context = NULL;
@@ -622,10 +729,21 @@ static struct hid_device_info * create_device_info_for_device(libusb_device *dev
  cur_dev->serial_number = get_usb_string(handle, desc->iSerialNumber);
 
  /* Manufacturer and Product strings */
- if (desc->iManufacturer > 0)
- cur_dev->manufacturer_string = get_usb_string(handle, desc->iManufacturer);
- if (desc->iProduct > 0)
- cur_dev->product_string = get_usb_string(handle, desc->iProduct);
+ const struct usb_string_cache_entry *string_cache;
+ if (usb_string_can_cache(desc->idVendor, desc->idProduct) &&
+ (string_cache = usb_string_cache_find(desc, handle)) != NULL) {
+ if (string_cache->vendor) {
+ cur_dev->manufacturer_string = wcsdup(string_cache->vendor);
+ }
+ if (string_cache->product) {
+ cur_dev->product_string = wcsdup(string_cache->product);
+ }
+ } else {
+ if (desc->iManufacturer > 0)
+ cur_dev->manufacturer_string = get_usb_string(handle, desc->iManufacturer);
+ if (desc->iProduct > 0)
+ cur_dev->product_string = get_usb_string(handle, desc->iProduct);
+ }
 
  return cur_dev;
 }