HashStream.cpp

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/*
 * HashStream.cpp
 *
 * Copyright (C) 2011 IBR, TU Braunschweig
 *
 * Written-by: Johannes Morgenroth <morgenroth@ibr.cs.tu-bs.de>
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 */

#include "HashStream.h"
#include <sstream>

namespace ibrcommon
{
        HashStream::HashStream(const unsigned int hash, const size_t buffer)
         : iostream(this), data_buf_(buffer), data_size_(buffer), hash_buf_(hash), hash_size_(hash), final_(false)
        {
                // Initialize get pointer.  This should be zero so that underflow is called upon first read.
                setg(0, 0, 0);
                setp(&data_buf_[0], &data_buf_[0] + data_size_ - 1);
        }

        HashStream::~HashStream()
        {
        }

        std::string HashStream::extract(std::istream &stream)
        {
                std::stringstream buf;
                buf << stream.rdbuf();
                return buf.str();
        }

        int HashStream::sync()
        {
                int ret = std::char_traits<char>::eq_int_type(this->overflow(
                                std::char_traits<char>::eof()), std::char_traits<char>::eof()) ? -1
                                : 0;

                return ret;
        }

        std::char_traits<char>::int_type HashStream::overflow(std::char_traits<char>::int_type c)
        {
                char *ibegin = &data_buf_[0];
                char *iend = pptr();

                // mark the buffer as free
                setp(&data_buf_[0], &data_buf_[0] + data_size_ - 1);

                if (!std::char_traits<char>::eq_int_type(c, std::char_traits<char>::eof()))
                {
                        *iend++ = std::char_traits<char>::to_char_type(c);
                }

                // if there is nothing to send, just return
                if ((iend - ibegin) == 0)
                {
                        return std::char_traits<char>::not_eof(c);
                }

                // hashing
                update(&data_buf_[0], (iend - ibegin));

                return std::char_traits<char>::not_eof(c);
        }

        std::char_traits<char>::int_type HashStream::underflow()
        {
                // TODO: add seek mechanisms to reset the istream

                if (!final_)
                {
                        finalize(&hash_buf_[0], hash_size_);
                        final_ = true;

                        // Since the input buffer content is now valid (or is new)
                        // the get pointer should be initialized (or reset).
                        setg(&hash_buf_[0], &hash_buf_[0], &hash_buf_[0] + hash_size_);

                        return std::char_traits<char>::not_eof(hash_buf_[0]);
                }

                return std::char_traits<char>::eof();
        }
}