Example app crashed on Windows

[fpagliughi]

Tried running the list_devices example on Windows 7. It got the first four devices OK, then on the fifth one it crashed:

Bus 003 Device 005 ID 046d:c52f   12 Mbps
Device Descriptor:
  bcdUSB              2.00
  bDeviceClass        0x00
  bDeviceSubClass     0x00
  bDeviceProtocol     0x00
  bMaxPacketSize0        8
  idVendor          0x046d
  idProduct         0xc52f
  bcdDevice          30.00
thread 'main' panicked at 'index out of bounds: the len is 1 but the index is 1', C:\Temp\rusb\src\device_handle.rs:587:58
stack backtrace:
   0: std::sys_common::backtrace::_print::{{impl}}::fmt
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libstd\sys_common\backtrace.rs:61
   1: core::fmt::write
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libcore\fmt\mod.rs:1025
   2: std::io::Write::write_fmt<std::sys::windows::stdio::Stderr>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libstd\io\mod.rs:1427
   3: std::panicking::default_hook::{{closure}}
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libstd\panicking.rs:193
   4: std::panicking::default_hook
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libstd\panicking.rs:212
   5: std::panicking::rust_panic_with_hook
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libstd\panicking.rs:471
   6: std::panicking::begin_panic_handler
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libstd\panicking.rs:375
   7: core::panicking::panic_fmt
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libcore\panicking.rs:84
   8: core::panicking::panic_bounds_check
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libcore\panicking.rs:62
   9: rusb::device_handle::{{impl}}::read_string_descriptor::{{closure}}<rusb::context::GlobalContext>
             at .\src\device_handle.rs:587
  10: core::ops::function::impls::{{impl}}::call_once<(slice<u8>*),closure-0>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\src\libcore\ops\function.rs:285
  11: core::option::Option<slice<u8>*>::map<slice<u8>*,u16,mut closure-0*>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\src\libcore\option.rs:450
  12: core::iter::adapters::{{impl}}::next<u16,core::iter::adapters::Skip<core::slice::Chunks<u8>>,closure-0>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\src\libcore\iter\adapters\mod.rs:720
  13: alloc::vec::Vec<u16>::extend_desugared<u16,core::iter::adapters::Map<core::iter::adapters::Skip<core::slice::Chunks<u8>>, closure-0>>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\src\liballoc\vec.rs:2118
  14: alloc::vec::{{impl}}::spec_extend<u16,core::iter::adapters::Map<core::iter::adapters::Skip<core::slice::Chunks<u8>>, closure-0>>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\src\liballoc\vec.rs:2016
  15: alloc::vec::{{impl}}::from_iter<u16,core::iter::adapters::Map<core::iter::adapters::Skip<core::slice::Chunks<u8>>, closure-0>>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\src\liballoc\vec.rs:2010
  16: alloc::vec::{{impl}}::from_iter<u16,core::iter::adapters::Map<core::iter::adapters::Skip<core::slice::Chunks<u8>>, closure-0>>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\src\liballoc\vec.rs:1912
  17: core::iter::traits::iterator::Iterator::collect<core::iter::adapters::Map<core::iter::adapters::Skip<core::slice::Chunks<u8>>, closure-0>,alloc::vec::Vec<u16>>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\src\libcore\iter\traits\iterator.rs:1495
  18: rusb::device_handle::DeviceHandle<rusb::context::GlobalContext>::read_string_descriptor<rusb::context::GlobalContext>
             at .\src\device_handle.rs:590
  19: rusb::device_handle::DeviceHandle<rusb::context::GlobalContext>::read_manufacturer_string<rusb::context::GlobalContext>
             at .\src\device_handle.rs:611
  20: list_devices::print_device::{{closure}}<rusb::context::GlobalContext>
             at .\examples\list_devices.rs:108
  21: core::option::Option<mut list_devices::UsbDevice<rusb::context::GlobalContext>*>::map_or<mut list_devices::UsbDevice<rusb::context::GlobalContext>*,alloc::string::String,closure-0>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\src\libcore\option.rs:471
  22: list_devices::print_device<rusb::context::GlobalContext>
             at .\examples\list_devices.rs:105
  23: list_devices::list_devices
             at .\examples\list_devices.rs:54
  24: list_devices::main
             at .\examples\list_devices.rs:14
  25: std::rt::lang_start::{{closure}}<()>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\src\libstd\rt.rs:67
  26: std::panicking::try::do_call<closure-0,i32>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libstd\panicking.rs:292
  27: panic_unwind::__rust_maybe_catch_panic
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libpanic_unwind\lib.rs:78
  28: std::rt::lang_start_internal
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\/src\libstd\rt.rs:51
  29: std::rt::lang_start<()>
             at /rustc/5e1a799842ba6ed4a57e91f7ab9435947482f7d8\src\libstd\rt.rs:67
  30: main
  31: __scrt_common_main_seh
             at d:\agent\_work\3\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288
  32: BaseThreadInitThunk
  33: RtlUserThreadStart
note: Some details are omitted, run with `RUST_BACKTRACE=full` for a verbose backtrace.

[a1ien]

This is more like a broken device. Which returns the wrong string.
Try replace read_manufacturer_string call on line 107 to read_manufacturer_string_ascii

[fpagliughi]

Ah, OK. But I think the library should not panic on a bad string descriptor. We should at least test that the length of the descriptor is an even number, greater than 2 before trying to parse the string.

For a string descriptor, should the number of bytes read also be the length in the descriptor (byte 0)? If so, we could verify that as well.

I will have a look and send a PR if I think I can fix it.