src/connectivity/bluetooth/core/bt-host/transport/sco_data_packet.cc

// Copyright 2021 The Fuchsia 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 "sco_data_packet.h"

#include <endian.h>

#include "slab_allocators.h"
#include "src/connectivity/bluetooth/core/bt-host/common/log.h"

namespace bt::hci {

namespace slab_allocators {

// Slab-allocator traits for SCO data packets.
using MaxScoTraits =
    PacketTraits<hci_spec::SynchronousDataHeader, kMaxScoDataPacketSize, kNumMaxScoDataPackets>;

using MaxScoAllocator = fbl::SlabAllocator<MaxScoTraits>;

}  // namespace slab_allocators

// Type containing both a fixed packet storage buffer and a ScoDataPacket interface to the buffer.
// Does not deallocate from a slab buffer when destroyed (unlike SlabPacket).
using MaxScoDataPacket =
    slab_allocators::internal::FixedSizePacket<hci_spec::SynchronousDataHeader,
                                               slab_allocators::kMaxScoDataPacketSize>;

std::unique_ptr<ScoDataPacket> ScoDataPacket::New(uint8_t payload_size) {
  std::unique_ptr<ScoDataPacket> packet = slab_allocators::MaxScoAllocator::New(payload_size);
  if (!packet) {
    bt_log(INFO, "hci", "ScoDataPacket slab allocators capacity exhausted");
    return std::make_unique<MaxScoDataPacket>(payload_size);
  }
  return packet;
}

std::unique_ptr<ScoDataPacket> ScoDataPacket::New(hci_spec::ConnectionHandle connection_handle,
                                                  uint8_t payload_size) {
  std::unique_ptr<ScoDataPacket> packet = ScoDataPacket::New(payload_size);
  packet->WriteHeader(connection_handle);
  return packet;
}

hci_spec::ConnectionHandle ScoDataPacket::connection_handle() const {
  // Return the lower 12-bits of the first two octets.
  return le16toh(view().header().handle_and_flags) & 0x0FFF;
}
hci_spec::SynchronousDataPacketStatusFlag ScoDataPacket::packet_status_flag() const {
  // Return bits 4-5 in the higher octet of |handle_and_flags|, i.e. 0b00xx000000000000.
  return static_cast<hci_spec::SynchronousDataPacketStatusFlag>(
      (le16toh(view().header().handle_and_flags) >> 12) & 0x0003);
}

void ScoDataPacket::InitializeFromBuffer() {
  mutable_view()->Resize(/*payload_size=*/le16toh(view().header().data_total_length));
}

void ScoDataPacket::WriteHeader(hci_spec::ConnectionHandle connection_handle) {
  // Handle must fit inside 12-bits.
  ZX_ASSERT(connection_handle <= 0x0FFF);
  // This sets the Packet Status Flag (upper bits of handle_and_flags) to 0, which is required for
  // Host->Controller SCO packets.
  mutable_view()->mutable_header()->handle_and_flags = htole16(connection_handle);
  mutable_view()->mutable_header()->data_total_length = static_cast<uint8_t>(view().payload_size());
}

}  // namespace bt::hci

DECLARE_STATIC_SLAB_ALLOCATOR_STORAGE(bt::hci::slab_allocators::MaxScoTraits,
                                      bt::hci::slab_allocators::kMaxNumSlabs,
                                      /*alloc_initial=*/true);