Windows: enumerate a specific list of vendor/product ids

[pedroos]

This additional function (enumerate_m()) works the same as enumerate(), but enables a set of specific vendor ids and product ids to be specified. This avoids manual filtering of results when more than one vendor id/product id combination needs to be enumerated.

[Youw]

Please see: #373.

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As a maintainer of libusb/hidapi I vote against this PR for a number of reasons:

• you add a new API for Windows only, which is not convenient - there is nothing Windows specific in this implementation;
• you specify the size of input arrays at all; as a matter if fact, size_t vendor_id_length = sizeof(vendor_ids) / sizeof(vendor_ids[0]); (almost) always evaluates to 2; see here: https://stackoverflow.com/questions/17590226/finding-length-of-array-inside-a-function
• it is a 99% copy-paste of hid_enumerate;
• there is no real need for such an API;

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Why don't just use simple hid_enumerate ?

It will give you same result, for all supported platforms:

bool device_matches(struct hid_device_info *dev) {
    unsigned short vendor_ids[] = ...;
    unsigned short product_ids[] = ...;
    int products_size = 2;

    for (int i = 0; i < products_size; i++) {
        if (dev->vendor_id == vendor_ids[i] && dev->product_id == product_ids[i])
            return true;
    }
    return false;
}

// use your device here, or save it somewhere for later
bool use_dev(struct hid_device_info *dev);

struct hid_device_info *devs, *cur_dev;
devs = hid_enumerate(0x0, 0x0);
cur_dev = devs; 
while (cur_dev) {
    if (device_matches(cur_dev)) {
        use_dev(cur_dev);
    }
    cur_dev = cur_dev->next;
}
hid_free_enumeration(devs);

[pedroos]

Yeah, I hadn't seen the 0x0 option. Thanks for pointing that out.