Allow opening device by Serial

hid_api.gemspec

@@ -22,6 +22,7 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   spec.add_dependency "ffi", "~> 1.9"
+  spec.add_dependency "ffi_wide_char", "~> 1.1"
 
   spec.add_development_dependency "bundler", "~> 1.8"
   spec.add_development_dependency "rake", "~> 10.0"

lib/hid_api.rb

@@ -19,7 +19,7 @@ class HidError < StandardError; end
   typedef Device, :device
   typedef :int, :vendor_id
   typedef :int, :product_id
-  typedef :int, :serial_number
+  typedef WideString, :serial_number
   typedef :int, :length
   typedef :int, :timeout
 
@@ -49,7 +49,7 @@ class << self
     alias enumerate hid_enumerate
     alias free_enumeration hid_free_enumeration
     def open(vendor_id, product_id, serial_number = nil)
-      device = hid_open(vendor_id, product_id, serial_number || 0)
+      device = hid_open(vendor_id, product_id, serial_number)
       if device.null?
         error = format(
           "Unable to open %s",
@@ -67,6 +67,3 @@ def open_path(path)
     end
   end
 end
-
-# Attempts to extend some core FFI classes with platform-aware string-handling
-FFI::AbstractMemory.include(HidApi::Util::WCHAR)

lib/hid_api/device.rb

@@ -38,15 +38,15 @@ def serial_number_string
     def read(length)
       buffer = clear_buffer length
       with_hid_error_handling do
-        HidApi.hid_read self, buffer, buffer.length
+        HidApi.hid_read self, buffer, buffer.size
       end
       buffer
     end
 
     def read_timeout(length, timeout)
       buffer = clear_buffer length
       with_hid_error_handling do
-        HidApi.hid_read_timeout self, buffer, buffer.length, timeout
+        HidApi.hid_read_timeout self, buffer, buffer.size, timeout
       end
       buffer
     end
@@ -59,7 +59,7 @@ def write(data)
       end
 
       with_hid_error_handling do
-        HidApi.hid_write self, buffer, buffer.length
+        HidApi.hid_write self, buffer, buffer.size
       end
     end
 
@@ -80,16 +80,13 @@ def error
     private
 
     def clear_buffer(length)
-      b = FFI::Buffer.new(1, length)
-      # FFI::Buffer doesn't clear the first byte if length < 8
-      b.put_char 0, 0
-      b
+      return FFI::MemoryPointer.new(:char, length)
     end
 
     def get_buffered_string(field)
       buffer = clear_buffer 255
-      HidApi.send "hid_get_#{field}_string", self, buffer, buffer.length
-      buffer.read_wchar_string
+      HidApi.send "hid_get_#{field}_string", self, buffer, buffer.size
+      WideString.from_native(buffer)
     end
 
     def with_hid_error_handling

lib/hid_api/device_info.rb

@@ -28,7 +28,7 @@ def self.release(pointer)
             :next,                DeviceInfo.auto_ptr # struct hid_device_info * next
 
     # Makes the struct members available as methods
-    layout.members.each do |f|
+    members.each do |f|
       define_method(f) do
         self[f]
       end

lib/hid_api/wide_string.rb

@@ -1,4 +1,5 @@
 require "ffi"
+require 'ffi_wide_char'
 
 module HidApi
   # An FFI data converter that marshalls data from specific device fields via
@@ -8,9 +9,13 @@ class WideString
     native_type FFI::Type::POINTER
 
     class << self
-      def from_native(value, _context)
+      def from_native(value, _ctx = nil)
         return nil if value.null?
-        value.read_wchar_string
+        FfiWideChar.read_wide_string(value).encode('utf-8')
+      end
+
+      def to_native(value, _ctx = nil)
+        FfiWideChar.to_wide_string value
       end
     end
   end