buffer_sequence.h

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/*
  Copyright (c) 2021, 2024, Oracle and/or its affiliates.
 
  This program is free software; you can redistribute it and/or modify
  it under the terms of the GNU General Public License, version 2.0,
  as published by the Free Software Foundation.
 
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  but not limited to OpenSSL) that is licensed under separate terms,
  as designated in a particular file or component or in included license
  documentation.  The authors of MySQL hereby grant you an additional
  permission to link the program and your derivative works with the
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  the program or referenced in the documentation.
 
  This program is distributed in the hope that it will be useful,
  but WITHOUT ANY WARRANTY; without even the implied warranty of
  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  GNU General Public License for more details.
 
  You should have received a copy of the GNU General Public License
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  Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/
 
#ifndef ROUTER_SRC_HTTP_SRC_HTTP_CNO_BUFFER_SEQUENCE_H_
#define ROUTER_SRC_HTTP_SRC_HTTP_CNO_BUFFER_SEQUENCE_H_
 
#include <iterator>
#include <vector>
 
#include "cno/core.h"
#include "mysql/harness/net_ts/buffer.h"
 
namespace http {
namespace cno {
 
template <typename ResultType = net::const_buffer>
class Sequence {
 public:
  Sequence(const ResultType *begin, size_t size) : begin_{begin}, size_{size} {}
 
  const ResultType *begin() const { return begin_; }
  const ResultType *end() const { return begin_ + size_; }
 
 private:
  const ResultType *begin_;
  size_t size_;
};
 
template <typename SourceType = cno_buffer_t,
          typename ResultType = net::const_buffer>
class BufferSequence {
 public:
  class Iterator {
   public:
    using iterator_category = std::input_iterator_tag;
    using value_type = ResultType;
    using difference_type = void;
    using pointer = ResultType *;
    using reference = ResultType &;
 
   public:
    Iterator(const BufferSequence *parent, size_t index)
        : parent_{parent}, index_{index} {
      make_result();
    }
 
    void operator++() {
      ++index_;
      make_result();
    }
 
    bool operator!=(const Iterator &it) const { return result_ != it.result_; }
    bool operator==(const Iterator &it) const { return result_ == it.result_; }
    reference operator*() { return *result_; }
    Iterator operator+(const int value) const {
      return {parent_, index_ + value};
    }
    pointer operator->() { return result_; }
 
    operator value_type() { return result_; }
 
    size_t left() { return parent_->source_count_ - index_; }
    const SourceType *get_buffer() { return parent_->source_ + index_; }
 
   private:
    void make_result() {
      while (parent_->destination_initialized_count_ <= index_) {
        if (index_ >= parent_->source_count_) break;
 
        auto &src = parent_->source_[index_];
        parent_->destination_[index_] = {src.data, src.size};
 
        ++parent_->destination_initialized_count_;
      }
 
      result_ = &parent_->destination_[0] + index_;
    }
 
    const BufferSequence *parent_;
    size_t index_;
    pointer result_{nullptr};
  };
 
  BufferSequence(const SourceType *source, size_t source_count)
      : source_{source}, source_count_{source_count} {
    destination_.resize(source_count_);
  }
 
  const Iterator begin() const { return Iterator(this, 0); }
  const Iterator end() const { return Iterator(this, source_count_); }
 
  const SourceType *source_;
  size_t source_count_{0};
  mutable std::vector<ResultType> destination_;
  mutable size_t destination_initialized_count_{0};
};
 
}  // namespace cno
}  // namespace http
 
#endif  // ROUTER_SRC_HTTP_SRC_HTTP_CNO_BUFFER_SEQUENCE_H_