Fix type of return value by data.find

[msawahara]

Hi.

I use usb-proxy to analyze USB devices and it is very useful.
However, it required minor fix to use injection feature in my environment.

Problem

In aarch64, a std::out_of_range exception is thrown if a injection rule doesn't match.

pi@raspberrypi:~/work/usb-proxy $ lsb_release -d
Description:    Debian GNU/Linux 11 (bullseye)
pi@raspberrypi:~/work/usb-proxy $ uname -a
Linux raspberrypi 5.15.56-v8+ #1575 SMP PREEMPT Fri Jul 22 20:31:26 BST 2022 aarch64 GNU/Linux
pi@raspberrypi:~/work/usb-proxy $ sudo ./usb-proxy --device=fe980000.usb --driver=fe980000.usb --vendor_id=0590 --product_id=001a --enable_injection
Device is: fe980000.usb
Driver is: fe980000.usb
vendor_id is: 1424
product_id is: 26
Injection enabled
Parsed injection file: injection.json
Device opened successfully
Setup USB config successfully
Start hotplug_monitor thread, thread id(32888)
Start for EP0, thread id(32886)
event: connect, length: 0
event: control, length: 8
  bRequestType: 0x80  (IN), bRequest: 0x06, wValue: 0x0100, wIndex: 0x0000, wLength: 8
  type = USB_TYPE_STANDARD
  req = USB_REQ_GET_DESCRIPTOR
  desc = USB_DT_DEVICE
terminate called after throwing an instance of 'std::out_of_range'
  what():  basic_string::replace: __pos (which is 4294967295) > this->size() (which is 8)
Aborted

std::basic_string::find returns std::string::npos if the pattern doesn't match.
std::string::npos is 18446744073709551615UL in aarch64, but when it is assigned to __u32, it overflows and becomes 4294967295.

Fix

Use std::string::size_type instead of __u32.
std::string::size_type is the correct return type for std::basic_string::find.

Alternatively, we can use the auto keyword without std::string::size_type explicitly.

[AristoChen]

Hi @msawahara

Sorry for reply so late, I joined a new company not long ago, so I spend most of my time to get myself more familiar with the onboard training.

Thank you for spending time playing around with this project! The PR looks good to me, will merge after I test it on the boards I have, hopefully I can find some time to test next week :)

[AristoChen]

Hi @msawahara ,

Appreciate for the PR!

[msawahara]

Thank you for the merging!