text: // Copyright 2014 The Chromium Authors. All rights reserved.
  // Use of this source code is governed by a BSD-style license that can be
  // found in the LICENSE file.
  
  #include "media/midi/usb_midi_descriptor_parser.h"
  
  #include <algorithm>
  
  #include "base/logging.h"
  
  namespace media {
  
  namespace {
  
  // The constants below are specified in USB spec, USB audio spec
  // and USB midi spec.
  
  enum DescriptorType {
    TYPE_DEVICE = 1,
    TYPE_CONFIGURATION = 2,
    TYPE_STRING = 3,
    TYPE_INTERFACE = 4,
    TYPE_ENDPOINT = 5,
    TYPE_DEVICE_QUALIFIER = 6,
    TYPE_OTHER_SPEED_CONFIGURATION = 7,
    TYPE_INTERFACE_POWER = 8,
  
    TYPE_CS_INTERFACE = 36,
    TYPE_CS_ENDPOINT = 37,
  };
  
  enum DescriptorSubType {
    SUBTYPE_MS_DESCRIPTOR_UNDEFINED = 0,
    SUBTYPE_MS_HEADER = 1,
    SUBTYPE_MIDI_IN_JACK = 2,
    SUBTYPE_MIDI_OUT_JACK = 3,
    SUBTYPE_ELEMENT = 4,
  };
  
  enum JackType {
    JACK_TYPE_UNDEFINED = 0,
    JACK_TYPE_EMBEDDED = 1,
    JACK_TYPE_EXTERNAL = 2,
  };
  
  const uint8 kAudioInterfaceClass = 1;
  const uint8 kAudioMidiInterfaceSubclass = 3;
  
  class JackMatcher {
   public:
    explicit JackMatcher(uint8 id) : id_(id) {}
  
    bool operator() (const UsbMidiJack& jack) const {
      return jack.jack_id == id_;
    }
  
   private:
    uint8 id_;
  };
  
  }  // namespace
  
  UsbMidiDescriptorParser::UsbMidiDescriptorParser()
      : is_parsing_usb_midi_interface_(false),
        current_endpoint_address_(0),
        current_cable_number_(0) {}
  
  UsbMidiDescriptorParser::~UsbMidiDescriptorParser() {}
  
  bool UsbMidiDescriptorParser::Parse(UsbMidiDevice* device,
                                      const uint8* data,
                                      size_t size,
                                      std::vector<UsbMidiJack>* jacks) {
    jacks->clear();
    bool result = ParseInternal(device, data, size, jacks);
    if (!result)
      jacks->clear();
    Clear();
    return result;
  }
  
  bool UsbMidiDescriptorParser::ParseInternal(UsbMidiDevice* device,
                                              const uint8* data,
                                              size_t size,
                                              std::vector<UsbMidiJack>* jacks) {
    for (const uint8* current = data;
         current < data + size;
         current += current[0]) {
      uint8 length = current[0];
      if (length < 2) {
        DVLOG(1) << "Descriptor Type is not accessible.";
        return false;
      }
      if (current + length > data + size) {
        DVLOG(1) << "The header size is incorrect.";
        return false;
      }
      DescriptorType descriptor_type = static_cast<DescriptorType>(current[1]);
      if (descriptor_type != TYPE_INTERFACE && !is_parsing_usb_midi_interface_)
        continue;
  
      switch (descriptor_type) {
        case TYPE_INTERFACE:
          if (!ParseInterface(current, length))
            return false;
          break;
        case TYPE_CS_INTERFACE:
          // We are assuming that the corresponding INTERFACE precedes
          // the CS_INTERFACE descriptor, as specified.
          if (!ParseCSInterface(device, current, length))
            return false;
          break;
        case TYPE_ENDPOINT:
          // We are assuming that endpoints are contained in an interface.
          if (!ParseEndpoint(current, length))
            return false;
          break;
        case TYPE_CS_ENDPOINT:
          // We are assuming that the corresponding ENDPOINT precedes
          // the CS_ENDPOINT descriptor, as specified.
          if (!ParseCSEndpoint(current, length, jacks))
            return false;
          break;
        default:
          // Ignore uninteresting types.
          break;
      }
    }
    return true;
  }
  
  bool UsbMidiDescriptorParser::ParseInterface(const uint8* data, size_t size) {
    if (size != 9) {
      DVLOG(1) << "INTERFACE header size is incorrect.";
      return false;
    }
    incomplete_jacks_.clear();
  
    uint8 interface_class = data[5];
    uint8 interface_subclass = data[6];
  
    // All descriptors of endpoints contained in this interface
    // precede the next INTERFACE descriptor.
    is_parsing_usb_midi_interface_ =
        interface_class == kAudioInterfaceClass &&
        interface_subclass == kAudioMidiInterfaceSubclass;
    return true;
  }
  
  bool UsbMidiDescriptorParser::ParseCSInterface(UsbMidiDevice* device,
                                                 const uint8* data,
                                                 size_t size) {
    // Descriptor Type and Descriptor Subtype should be accessible.
    if (size < 3) {
      DVLOG(1) << "CS_INTERFACE header size is incorrect.";
      return false;
    }
  
    DescriptorSubType subtype = static_cast<DescriptorSubType>(data[2]);
  
    if (subtype != SUBTYPE_MIDI_OUT_JACK &&
        subtype != SUBTYPE_MIDI_IN_JACK)
      return true;
  
    if (size < 6) {
      DVLOG(1) << "CS_INTERFACE (MIDI JACK) header size is incorrect.";
      return false;
    }
    uint8 jack_type = data[3];
    uint8 id = data[4];
    if (jack_type == JACK_TYPE_EMBEDDED) {
      // We can't determine the associated endpoint now.
      incomplete_jacks_.push_back(UsbMidiJack(device, id, 0, 0));
    }
    return true;
  }
  
  bool UsbMidiDescriptorParser::ParseEndpoint(const uint8* data, size_t size) {
    if (size < 4) {
      DVLOG(1) << "ENDPOINT header size is incorrect.";
      return false;
    }
    current_endpoint_address_ = data[2];
    current_cable_number_ = 0;
    return true;
  }
  
  bool UsbMidiDescriptorParser::ParseCSEndpoint(const uint8* data,
                                                size_t size,
                                                std::vector<UsbMidiJack>* jacks) {
    const size_t kSizeForEmptyJacks = 4;
    // CS_ENDPOINT must be of size 4 + n where n is the number of associated
    // jacks.
    if (size < kSizeForEmptyJacks) {
      DVLOG(1) << "CS_ENDPOINT header size is incorrect.";
      return false;
    }
    uint8 num_jacks = data[3];
    if (size != kSizeForEmptyJacks + num_jacks) {
      DVLOG(1) << "CS_ENDPOINT header size is incorrect.";
      return false;
    }
  
    for (size_t i = 0; i < num_jacks; ++i) {
      uint8 jack = data[kSizeForEmptyJacks + i];
      std::vector<UsbMidiJack>::iterator it =
          std::find_if(incomplete_jacks_.begin(),
                       incomplete_jacks_.end(),
                       JackMatcher(jack));
      if (it == incomplete_jacks_.end()) {
        DVLOG(1) << "A non-existing MIDI jack is associated.";
        return false;
      }
      if (current_cable_number_ > 0xf) {
        DVLOG(1) << "Cable number should range from 0x0 to 0xf.";
        return false;
      }
      // CS_ENDPOINT follows ENDPOINT and hence we can use the following
      // member variables.
      it->cable_number = current_cable_number_++;
      it->endpoint_address = current_endpoint_address_;
      jacks->push_back(*it);
      incomplete_jacks_.erase(it);
    }
    return true;
  }
  
  void UsbMidiDescriptorParser::Clear() {
    is_parsing_usb_midi_interface_ = false;
    current_endpoint_address_ = 0;
    current_cable_number_ = 0;
    incomplete_jacks_.clear();
  }
  
  }  // namespace media
  