| /****************************************************************************** |
| * |
| * Copyright (C) 2017 The Android Open Source Project |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at: |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| ******************************************************************************/ |
| |
| #pragma once |
| |
| #include <array> |
| #include <vector> |
| |
| // Scan Response data from Traxxas |
| static constexpr std::array<uint8_t, 18> trx_quirk{ |
| {0x14, 0x09, 0x54, 0xFF, 0xFF, 0x20, 0x42, 0x4C, 0x45, 0x05, 0x12, 0xFF, |
| 0x00, 0xE8, 0x03, 0x02, 0x0A, 0x00}}; |
| |
| class AdvertiseDataParser { |
| // Return true if the packet is malformed, but should be considered valid for |
| // compatibility with already existing devices |
| static bool MalformedPacketQuirk(const std::vector<uint8_t>& ad, |
| size_t position) { |
| auto data_start = ad.begin() + position; |
| |
| // Traxxas - bad name length |
| if (std::equal(data_start, data_start + 3, trx_quirk.begin()) && |
| std::equal(data_start + 5, data_start + 11, trx_quirk.begin() + 5) && |
| std::equal(data_start + 12, data_start + 18, trx_quirk.begin() + 12)) { |
| return true; |
| } |
| |
| return false; |
| } |
| |
| public: |
| static void RemoveTrailingZeros(std::vector<uint8_t>& ad) { |
| size_t position = 0; |
| |
| size_t ad_len = ad.size(); |
| while (position != ad_len) { |
| uint8_t len = ad[position]; |
| |
| // A field length of 0 would be invalid as it should at least contain the |
| // EIR field type. However, some existing devices send zero padding at the |
| // end of advertisement. If this is the case, cut the zero padding from |
| // end of the packet. Otherwise i.e. gluing scan response to advertise |
| // data will result in data with zero padding in the middle. |
| if (len == 0) { |
| size_t zeros_start = position; |
| for (size_t i = position + 1; i < ad_len; i++) { |
| if (ad[i] != 0) return; |
| } |
| |
| ad.erase(ad.begin() + zeros_start, ad.end()); |
| return; |
| } |
| |
| if (position + len >= ad_len) { |
| return; |
| } |
| |
| position += len + 1; |
| } |
| } |
| |
| /** |
| * Return true if this |ad| represent properly formatted advertising data. |
| */ |
| static bool IsValid(const std::vector<uint8_t>& ad) { |
| size_t position = 0; |
| |
| size_t ad_len = ad.size(); |
| while (position != ad_len) { |
| uint8_t len = ad[position]; |
| |
| // A field length of 0 would be invalid as it should at least contain the |
| // EIR field type. However, some existing devices send zero padding at the |
| // end of advertisement. If this is the case, treat the packet as valid. |
| if (len == 0) { |
| for (size_t i = position + 1; i < ad_len; i++) { |
| if (ad[i] != 0) return false; |
| } |
| return true; |
| } |
| |
| // If the length of the current field would exceed the total data length, |
| // then the data is badly formatted. |
| if (position + len >= ad_len) { |
| if (MalformedPacketQuirk(ad, position)) return true; |
| |
| return false; |
| } |
| |
| position += len + 1; |
| } |
| |
| return true; |
| } |
| |
| /** |
| * This function returns a pointer inside the |ad| array of length |ad_len| |
| * where a field of |type| is located, together with its length in |p_length| |
| */ |
| static const uint8_t* GetFieldByType(const uint8_t* ad, size_t ad_len, |
| uint8_t type, uint8_t* p_length) { |
| size_t position = 0; |
| |
| while (position != ad_len) { |
| uint8_t len = ad[position]; |
| |
| if (len == 0) break; |
| if (position + len >= ad_len) break; |
| |
| uint8_t adv_type = ad[position + 1]; |
| |
| if (adv_type == type) { |
| /* length doesn't include itself */ |
| *p_length = len - 1; /* minus the length of type */ |
| return ad + position + 2; |
| } |
| |
| position += len + 1; /* skip the length of data */ |
| } |
| |
| *p_length = 0; |
| return NULL; |
| } |
| |
| /** |
| * This function returns a pointer inside the |adv| where a field of |type| is |
| * located, together with it' length in |p_length| |
| */ |
| static const uint8_t* GetFieldByType(std::vector<uint8_t> const& ad, |
| uint8_t type, uint8_t* p_length) { |
| return GetFieldByType(ad.data(), ad.size(), type, p_length); |
| } |
| }; |