http_etag.h

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// Copyright (c) Microsoft Corporation. All rights reserved.
// Licensed under the Apache 2.0 License.
#pragma once
 
#define FMT_HEADER_ONLY
#include <regex>
#include <set>
#include <string>
 
namespace ccf
{
  namespace http
  {
    class Matcher
    {
    private:
      bool any_value = false;
      std::set<std::string> if_etags;
 
    public:
      Matcher(const std::string& match_header)
      {
        if (match_header == "*")
        {
          any_value = true;
          return;
        }
 
        std::regex etag_rx("\\\"([0-9a-f]+)\\\",?\\s*");
        auto etags_begin = std::sregex_iterator(
          match_header.begin(), match_header.end(), etag_rx);
        auto etags_end = std::sregex_iterator();
        ssize_t last_matched = 0;
 
        for (std::sregex_iterator i = etags_begin; i != etags_end; ++i)
        {
          if (i->position() != last_matched)
          {
            throw std::runtime_error("Invalid If-Match header");
          }
          std::smatch match = *i;
          if_etags.insert(match[1].str());
          last_matched = match.position() + match.length();
        }
 
        ssize_t last_index_in_header = match_header.size();
 
        if (last_matched != last_index_in_header || if_etags.empty())
        {
          throw std::runtime_error("Invalid If-Match header");
        }
      }
 
      bool matches(const std::string& etag) const
      {
        return any_value || if_etags.contains(etag);
      }
 
      bool is_any() const
      {
        return any_value;
      }
    };
  }
}