From 17d8479d980ebd37707c03e4d9e86aa0438f0ab9 Mon Sep 17 00:00:00 2001
From: Steven Noonan <[EMAIL REDACTED]>
Date: Thu, 22 Apr 2021 15:44:01 -0700
Subject: [PATCH] hidapi/libusb: maintain in-memory cache of vendor/product
strings
The get_usb_string call is rather expensive on some USB devices, so we
cache the vendor/product strings for future lookups (e.g. when
hid_enumerate is invoked again later).
This way, we only need to ask libusb for strings for devices we haven't
seen since before we started.
Signed-off-by: Steven Noonan <steven@valvesoftware.com>
Signed-off-by: Sam Lantinga <slouken@libsdl.org>
---
src/hidapi/libusb/hid.c | 111 +++++++++++++++++++++++++++++++++++++---
1 file changed, 105 insertions(+), 6 deletions(-)
diff --git a/src/hidapi/libusb/hid.c b/src/hidapi/libusb/hid.c
index 3fd95e061..1175da99c 100644
--- a/src/hidapi/libusb/hid.c
+++ b/src/hidapi/libusb/hid.c
@@ -440,6 +440,94 @@ 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;
+}
+
+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 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;
+}
+
static char *make_path(libusb_device *dev, int interface_number)
{
char str[64];
@@ -473,6 +561,8 @@ 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;
@@ -617,6 +707,7 @@ struct hid_device_info HID_API_EXPORT *hid_enumerate(unsigned short vendor_id,
if (res >= 0) {
struct hid_device_info *tmp;
+ const struct usb_string_cache_entry *string_cache;
/* VID/PID match. Create the record. */
tmp = (struct hid_device_info*) calloc(1, sizeof(struct hid_device_info));
@@ -638,12 +729,20 @@ struct hid_device_info HID_API_EXPORT *hid_enumerate(unsigned short vendor_id,
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);
+ if (dev_vid && dev_pid) {
+ string_cache = usb_string_cache_find(&desc, handle);
+ if (string_cache) {
+ cur_dev->manufacturer_string = wcsdup(string_cache->vendor);
+ 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);
+ }
#ifdef INVASIVE_GET_USAGE
{