internal.hpp

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#pragma once

#include "types.hpp"
#include <cstring>

// Do not compile on systems with non-8-bit bytes
static_assert(std::numeric_limits<unsigned char>::digits == 8);

namespace mcap {

namespace internal {

constexpr uint64_t MinHeaderLength = /* magic bytes */ sizeof(Magic) +
                                     /* opcode */ 1 +
                                     /* record length */ 8 +
                                     /* profile length */ 4 +
                                     /* library length */ 4;
constexpr uint64_t FooterLength = /* opcode */ 1 +
                                  /* record length */ 8 +
                                  /* summary start */ 8 +
                                  /* summary offset start */ 8 +
                                  /* summary crc */ 4 +
                                  /* magic bytes */ sizeof(Magic);

inline std::string ToHex(uint8_t byte) {
  std::string result{2, '\0'};
  result[0] = "0123456789ABCDEF"[(uint8_t(byte) >> 4) & 0x0F];
  result[1] = "0123456789ABCDEF"[uint8_t(byte) & 0x0F];
  return result;
}
inline std::string ToHex(std::byte byte) {
  return ToHex(uint8_t(byte));
}

inline std::string to_string(const std::string& arg) {
  return arg;
}
inline std::string to_string(std::string_view arg) {
  return std::string(arg);
}
inline std::string to_string(const char* arg) {
  return std::string(arg);
}
template <typename... T>
[[nodiscard]] inline std::string StrCat(T&&... args) {
  using mcap::internal::to_string;
  using std::to_string;
  return ("" + ... + to_string(std::forward<T>(args)));
}

inline uint32_t KeyValueMapSize(const KeyValueMap& map) {
  uint32_t size = 0;
  for (const auto& [key, value] : map) {
    size += 4 + key.size() + 4 + value.size();
  }
  return size;
}

inline const std::string CompressionString(Compression compression) {
  switch (compression) {
    case Compression::None:
    default:
      return std::string{};
    case Compression::Lz4:
      return "lz4";
    case Compression::Zstd:
      return "zstd";
  }
}

inline uint16_t ParseUint16(const std::byte* data) {
  return uint16_t(data[0]) | (uint16_t(data[1]) << 8);
}

inline uint32_t ParseUint32(const std::byte* data) {
  return uint32_t(data[0]) | (uint32_t(data[1]) << 8) | (uint32_t(data[2]) << 16) |
         (uint32_t(data[3]) << 24);
}

inline Status ParseUint32(const std::byte* data, uint64_t maxSize, uint32_t* output) {
  if (maxSize < 4) {
    const auto msg = StrCat("cannot read uint32 from ", maxSize, " bytes");
    return Status{StatusCode::InvalidRecord, msg};
  }
  *output = ParseUint32(data);
  return StatusCode::Success;
}

inline uint64_t ParseUint64(const std::byte* data) {
  return uint64_t(data[0]) | (uint64_t(data[1]) << 8) | (uint64_t(data[2]) << 16) |
         (uint64_t(data[3]) << 24) | (uint64_t(data[4]) << 32) | (uint64_t(data[5]) << 40) |
         (uint64_t(data[6]) << 48) | (uint64_t(data[7]) << 56);
}

inline Status ParseUint64(const std::byte* data, uint64_t maxSize, uint64_t* output) {
  if (maxSize < 8) {
    const auto msg = StrCat("cannot read uint64 from ", maxSize, " bytes");
    return Status{StatusCode::InvalidRecord, msg};
  }
  *output = ParseUint64(data);
  return StatusCode::Success;
}

inline Status ParseStringView(const std::byte* data, uint64_t maxSize, std::string_view* output) {
  uint32_t size = 0;
  if (auto status = ParseUint32(data, maxSize, &size); !status.ok()) {
    const auto msg = StrCat("cannot read string size: ", status.message);
    return Status{StatusCode::InvalidRecord, msg};
  }
  if (uint64_t(size) > (maxSize - 4)) {
    const auto msg = StrCat("string size ", size, " exceeds remaining bytes ", (maxSize - 4));
    return Status(StatusCode::InvalidRecord, msg);
  }
  *output = std::string_view(reinterpret_cast<const char*>(data + 4), size);
  return StatusCode::Success;
}

inline Status ParseString(const std::byte* data, uint64_t maxSize, std::string* output) {
  uint32_t size = 0;
  if (auto status = ParseUint32(data, maxSize, &size); !status.ok()) {
    return status;
  }
  if (uint64_t(size) > (maxSize - 4)) {
    const auto msg = StrCat("string size ", size, " exceeds remaining bytes ", (maxSize - 4));
    return Status(StatusCode::InvalidRecord, msg);
  }
  *output = std::string(reinterpret_cast<const char*>(data + 4), size);
  return StatusCode::Success;
}

inline Status ParseByteArray(const std::byte* data, uint64_t maxSize, ByteArray* output) {
  uint32_t size = 0;
  if (auto status = ParseUint32(data, maxSize, &size); !status.ok()) {
    return status;
  }
  if (uint64_t(size) > (maxSize - 4)) {
    const auto msg = StrCat("byte array size ", size, " exceeds remaining bytes ", (maxSize - 4));
    return Status(StatusCode::InvalidRecord, msg);
  }
  output->resize(size);
  std::memcpy(output->data(), data + 4, size);
  return StatusCode::Success;
}

inline Status ParseKeyValueMap(const std::byte* data, uint64_t maxSize, KeyValueMap* output) {
  uint32_t sizeInBytes = 0;
  if (auto status = ParseUint32(data, maxSize, &sizeInBytes); !status.ok()) {
    return status;
  }
  if (sizeInBytes > (maxSize - 4)) {
    const auto msg =
      StrCat("key-value map size ", sizeInBytes, " exceeds remaining bytes ", (maxSize - 4));
    return Status(StatusCode::InvalidRecord, msg);
  }

  // Account for the byte size prefix in sizeInBytes to make the bounds checking
  // below simpler
  sizeInBytes += 4;

  output->clear();
  uint64_t pos = 4;
  while (pos < sizeInBytes) {
    std::string_view key;
    if (auto status = ParseStringView(data + pos, sizeInBytes - pos, &key); !status.ok()) {
      const auto msg = StrCat("cannot read key-value map key at pos ", pos, ": ", status.message);
      return Status{StatusCode::InvalidRecord, msg};
    }
    pos += 4 + key.size();
    std::string_view value;
    if (auto status = ParseStringView(data + pos, sizeInBytes - pos, &value); !status.ok()) {
      const auto msg = StrCat("cannot read key-value map value for key \"", key, "\" at pos ", pos,
                              ": ", status.message);
      return Status{StatusCode::InvalidRecord, msg};
    }
    pos += 4 + value.size();
    output->emplace(key, value);
  }
  return StatusCode::Success;
}

inline std::string MagicToHex(const std::byte* data) {
  return internal::ToHex(data[0]) + internal::ToHex(data[1]) + internal::ToHex(data[2]) +
         internal::ToHex(data[3]) + internal::ToHex(data[4]) + internal::ToHex(data[5]) +
         internal::ToHex(data[6]) + internal::ToHex(data[7]);
}

}  // namespace internal

}  // namespace mcap