| // Copyright 2020 The Pigweed Authors |
| // |
| // 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 |
| // |
| // https://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. |
| |
| #include "pw_tokenizer/encode_args.h" |
| |
| #include <algorithm> |
| #include <cstring> |
| |
| #include "pw_preprocessor/compiler.h" |
| #include "pw_varint/varint.h" |
| |
| namespace pw { |
| namespace tokenizer { |
| namespace { |
| |
| // Declare the types as an enum for convenience. |
| enum class ArgType : uint8_t { |
| kInt = PW_TOKENIZER_ARG_TYPE_INT, |
| kInt64 = PW_TOKENIZER_ARG_TYPE_INT64, |
| kDouble = PW_TOKENIZER_ARG_TYPE_DOUBLE, |
| kString = PW_TOKENIZER_ARG_TYPE_STRING, |
| }; |
| |
| size_t EncodeInt(int value, const std::span<std::byte>& output) { |
| return varint::Encode(value, std::as_writable_bytes(output)); |
| } |
| |
| size_t EncodeInt64(int64_t value, const std::span<std::byte>& output) { |
| return varint::Encode(value, std::as_writable_bytes(output)); |
| } |
| |
| size_t EncodeFloat(float value, const std::span<std::byte>& output) { |
| if (output.size() < sizeof(value)) { |
| return 0; |
| } |
| std::memcpy(output.data(), &value, sizeof(value)); |
| return sizeof(value); |
| } |
| |
| size_t EncodeString(const char* string, const std::span<std::byte>& output) { |
| // The top bit of the status byte indicates if the string was truncated. |
| static constexpr size_t kMaxStringLength = 0x7Fu; |
| |
| if (output.empty()) { // At least one byte is needed for the status/size. |
| return 0; |
| } |
| |
| if (string == nullptr) { |
| string = "NULL"; |
| } |
| |
| // Subtract 1 to save room for the status byte. |
| const size_t max_bytes = |
| std::min(static_cast<size_t>(output.size()), kMaxStringLength) - 1; |
| |
| // Scan the string to find out how many bytes to copy. |
| size_t bytes_to_copy = 0; |
| std::byte overflow_bit = std::byte(0); |
| |
| while (string[bytes_to_copy] != '\0') { |
| if (bytes_to_copy == max_bytes) { |
| overflow_bit = std::byte('\x80'); |
| break; |
| } |
| bytes_to_copy += 1; |
| } |
| |
| output[0] = static_cast<std::byte>(bytes_to_copy) | overflow_bit; |
| std::memcpy(output.data() + 1, string, bytes_to_copy); |
| |
| return bytes_to_copy + 1; // include the status byte in the total |
| } |
| |
| } // namespace |
| |
| size_t EncodeArgs(pw_tokenizer_ArgTypes types, |
| va_list args, |
| std::span<std::byte> output) { |
| size_t arg_count = types & PW_TOKENIZER_TYPE_COUNT_MASK; |
| types >>= PW_TOKENIZER_TYPE_COUNT_SIZE_BITS; |
| |
| size_t encoded_bytes = 0; |
| while (arg_count != 0u) { |
| // How many bytes were encoded; 0 indicates that there wasn't enough space. |
| size_t argument_bytes = 0; |
| |
| switch (static_cast<ArgType>(types & 0b11u)) { |
| case ArgType::kInt: |
| argument_bytes = EncodeInt(va_arg(args, int), output); |
| break; |
| case ArgType::kInt64: |
| argument_bytes = EncodeInt64(va_arg(args, int64_t), output); |
| break; |
| case ArgType::kDouble: |
| argument_bytes = |
| EncodeFloat(static_cast<float>(va_arg(args, double)), output); |
| break; |
| case ArgType::kString: |
| argument_bytes = EncodeString(va_arg(args, const char*), output); |
| break; |
| } |
| |
| // If zero bytes were encoded, the encoding buffer is full. |
| if (argument_bytes == 0u) { |
| break; |
| } |
| |
| output = output.subspan(argument_bytes); |
| encoded_bytes += argument_bytes; |
| |
| arg_count -= 1; |
| types >>= 2; // each argument type is encoded in two bits |
| } |
| |
| return encoded_bytes; |
| } |
| |
| } // namespace tokenizer |
| } // namespace pw |