checkers.cpp

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#include "ada/checkers.h"
#include <algorithm>
 
namespace ada::checkers {
 
ada_really_inline ada_constexpr bool is_ipv4(std::string_view view) noexcept {
  // The string is not empty and does not contain upper case ASCII characters.
  //
  // Optimization. To be considered as a possible ipv4, the string must end
  // with 'x' or a lowercase hex character.
  // Most of the time, this will be false so this simple check will save a lot
  // of effort.
  char last_char = view.back();
  // If the address ends with a dot, we need to prune it (special case).
  if (last_char == '.') {
    view.remove_suffix(1);
    if (view.empty()) {
      return false;
    }
    last_char = view.back();
  }
  bool possible_ipv4 = (last_char >= '0' && last_char <= '9') ||
                       (last_char >= 'a' && last_char <= 'f') ||
                       last_char == 'x';
  if (!possible_ipv4) {
    return false;
  }
  // From the last character, find the last dot.
  size_t last_dot = view.rfind('.');
  if (last_dot != std::string_view::npos) {
    // We have at least one dot.
    view = view.substr(last_dot + 1);
  }
  if (std::all_of(view.begin(), view.end(), ada::checkers::is_digit)) {
    return true;
  }
  // It could be hex (0x), but not if there is a single character.
  if (view.size() == 1) {
    return false;
  }
  // It must start with 0x.
  if (!std::equal(view.begin(), view.begin() + 2, "0x")) {
    return false;
  }
  // We must allow "0x".
  if (view.size() == 2) {
    return true;
  }
  // We have 0x followed by some characters, we need to check that they are
  // hexadecimals.
  return std::all_of(view.begin() + 2, view.end(),
                     ada::unicode::is_lowercase_hex);
}
 
// for use with path_signature, we include all characters that need percent
// encoding.
static constexpr std::array<uint8_t, 256> path_signature_table =
    []() constexpr {
      std::array<uint8_t, 256> result{};
      for (size_t i = 0; i < 256; i++) {
        if (i <= 0x20 || i == 0x22 || i == 0x23 || i == 0x3c || i == 0x3e ||
            i == 0x3f || i == 0x60 || i == 0x7b || i == 0x7b || i == 0x7d ||
            i > 0x7e) {
          result[i] = 1;
        } else if (i == 0x25) {
          result[i] = 8;
        } else if (i == 0x2e) {
          result[i] = 4;
        } else if (i == 0x5c) {
          result[i] = 2;
        } else {
          result[i] = 0;
        }
      }
      return result;
    }();
 
ada_really_inline constexpr uint8_t path_signature(
    std::string_view input) noexcept {
  // The path percent-encode set is the query percent-encode set and U+003F (?),
  // U+0060 (`), U+007B ({), and U+007D (}). The query percent-encode set is the
  // C0 control percent-encode set and U+0020 SPACE, U+0022 ("), U+0023 (#),
  // U+003C (<), and U+003E (>). The C0 control percent-encode set are the C0
  // controls and all code points greater than U+007E (~).
  size_t i = 0;
  uint8_t accumulator{};
  for (; i + 7 < input.size(); i += 8) {
    accumulator |= uint8_t(path_signature_table[uint8_t(input[i])] |
                           path_signature_table[uint8_t(input[i + 1])] |
                           path_signature_table[uint8_t(input[i + 2])] |
                           path_signature_table[uint8_t(input[i + 3])] |
                           path_signature_table[uint8_t(input[i + 4])] |
                           path_signature_table[uint8_t(input[i + 5])] |
                           path_signature_table[uint8_t(input[i + 6])] |
                           path_signature_table[uint8_t(input[i + 7])]);
  }
  for (; i < input.size(); i++) {
    accumulator |= uint8_t(path_signature_table[uint8_t(input[i])]);
  }
  return accumulator;
}
 
ada_really_inline constexpr bool verify_dns_length(
    std::string_view input) noexcept {
  if (input.back() == '.') {
    if (input.size() > 254) return false;
  } else if (input.size() > 253)
    return false;
 
  size_t start = 0;
  while (start < input.size()) {
    auto dot_location = input.find('.', start);
    // If not found, it's likely the end of the domain
    if (dot_location == std::string_view::npos) dot_location = input.size();
 
    auto label_size = dot_location - start;
    if (label_size > 63 || label_size == 0) return false;
 
    start = dot_location + 1;
  }
 
  return true;
}
}  // namespace ada::checkers