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Orange
06f9a8c9ee
Implements a pattern scanning feature that allows searching for byte patterns within a byte range. Adds `scan_for_pattern` method to `PatternScanner` to locate a pattern within a byte span. Adds corner case tests to verify functionality and handle invalid inputs.
80 lines
2.6 KiB
C++
80 lines
2.6 KiB
C++
//
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// Created by Vlad on 10/4/2025.
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//
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#include "omath/utility/pattern_scan.hpp"
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#include <charconv>
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namespace omath
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{
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std::optional<std::span<std::byte>::const_iterator>
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PatternScanner::scan_for_pattern(const std::string_view& pattern, const std::span<std::byte>& range)
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{
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const auto parsed_pattern = parse_pattern(pattern);
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if (!parsed_pattern)
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return std::nullopt;
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const std::ptrdiff_t scan_size =
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static_cast<std::ptrdiff_t>(range.size()) - static_cast<std::ptrdiff_t>(pattern.size());
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for (std::ptrdiff_t i = 0; i < scan_size; i++)
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{
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bool found = true;
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for (std::ptrdiff_t j = 0; j < static_cast<std::ptrdiff_t>(pattern.size()); j++)
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{
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found = parsed_pattern->at(j) == std::nullopt || parsed_pattern->at(j) == *(range.data() + i + j);
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if (!found)
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break;
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}
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if (found)
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return range.begin() + i;
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}
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return std::nullopt;
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}
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std::expected<std::vector<std::optional<std::byte>>, PatternScanError>
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PatternScanner::parse_pattern(const std::string_view& pattern_string)
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{
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std::vector<std::optional<std::byte>> pattern;
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auto start = pattern_string.cbegin();
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while (start != pattern_string.cend())
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{
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const auto end = std::find(start, pattern_string.cend(), ' ');
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const auto sting_view_start = std::distance(pattern_string.cbegin(), start);
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const auto sting_view_end = std::distance(start, end);
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const std::string_view byte_str = pattern_string.substr(sting_view_start, sting_view_end);
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if (byte_str.empty())
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{
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start = end != pattern_string.end() ? std::next(end) : end;
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continue;
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}
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if (byte_str == "?" || byte_str == "??")
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{
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pattern.emplace_back(std::nullopt);
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start = end != pattern_string.end() ? std::next(end) : end;
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continue;
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}
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std::uint8_t value = 0;
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// ReSharper disable once CppTooWideScopeInitStatement
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const auto [_, error_code] = std::from_chars(byte_str.data(), byte_str.data() + byte_str.size(), value, 16);
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if (error_code != std::errc{})
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return std::unexpected(PatternScanError::INVALID_PATTERN_STRING);
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pattern.emplace_back(static_cast<std::byte>(value));
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start = end != pattern_string.end() ? std::next(end) : end;
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}
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return pattern;
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}
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} // namespace omath
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