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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>
This commit is contained in:
Steven Noonan 2021-04-22 15:44:01 -07:00 committed by Sam Lantinga
parent 4535d65491
commit 17d8479d98
1 changed files with 105 additions and 6 deletions
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111
src/hidapi/libusb/hid.c
View File

@ -440,6 +440,94 @@ err:
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
{