276 lines
8.6 KiB
C++
276 lines
8.6 KiB
C++
/*
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Copyright 2016 Amebis
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This file is part of stdex.
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stdex is free software: you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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stdex is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with stdex. If not, see <http://www.gnu.org/licenses/>.
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*/
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#pragma once
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#include "common.h"
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#include <ios>
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#include <istream>
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#include <ostream>
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namespace stdex {
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namespace idrec {
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///
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/// Skips current record data
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///
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/// \param[in] stream Input stream
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///
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/// \returns
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/// - true when successful
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/// - false otherwise
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///
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template <class T_SIZE, unsigned int ALIGN>
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inline bool ignore(_In_ std::istream& stream)
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{
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// Read record size.
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T_SIZE size;
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stream.read((char*)&size, sizeof(size));
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if (!stream.good()) return false;
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// Skip the record data.
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size += (T_SIZE)(ALIGN - size) % ALIGN;
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stream.ignore(size);
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if (!stream.good()) return false;
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return true;
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}
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///
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/// Finds record data
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///
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/// \param[in] stream Input stream
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/// \param[in] id Record ID
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/// \param[in] end Position limit. Default is -1 (no limit).
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///
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/// \returns
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/// - true when found
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/// - false otherwise
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///
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template <class T_ID, class T_SIZE, unsigned int ALIGN>
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inline bool find(_In_ std::istream& stream, _In_ T_ID id, _In_opt_ std::streamoff end = (std::streamoff)-1)
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{
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T_ID _id;
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while (end == (std::streamoff)-1 || stream.tellg() < end) {
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stream.read((char*)&_id, sizeof(_id));
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if (!stream.good()) return false;
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if (_id == id) {
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// The record was found.
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return true;
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} else
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ignore<T_SIZE, ALIGN>(stream);
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}
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return false;
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}
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///
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/// Writes record header
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///
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/// \param[in] stream Output stream
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/// \param[in] id Record ID
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///
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/// \returns Position of the record header start in \p stream. Save for later \c close call.
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///
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template <class T_ID, class T_SIZE>
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inline std::streamoff open(_In_ std::ostream& stream, _In_ T_ID id)
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{
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std::streamoff start = stream.tellp();
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// Write ID.
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if (stream.fail()) return (std::streamoff)-1;
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stream.write((const char*)&id, sizeof(id));
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// Write 0 as a placeholder for data size.
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if (stream.fail()) return (std::streamoff)-1;
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T_SIZE size = 0;
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stream.write((const char*)&size, sizeof(size));
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return start;
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}
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///
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/// Updates record header
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///
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/// \param[in] stream Output stream
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/// \param[in] start Start position of the record in \p stream
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///
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/// \returns Position of the record end in \p stream
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///
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template <class T_ID, class T_SIZE, unsigned int ALIGN>
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inline std::streamoff close(_In_ std::ostream& stream, _In_ std::streamoff start)
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{
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std::streamoff end = stream.tellp();
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T_SIZE
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size = (T_SIZE)(end - start - sizeof(T_ID) - sizeof(T_SIZE)),
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remainder = (T_SIZE)(ALIGN - size) % ALIGN; // Number of bytes we need to add, to keep the data integral number of ALIGN blocks long
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if (remainder) {
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// Append padding.
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static const char padding[ALIGN] = {};
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stream.write(padding, remainder);
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end += remainder;
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}
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// Update the data size.
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if (stream.fail()) return (std::streamoff)-1;
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stream.seekp(start + sizeof(T_ID));
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stream.write((const char*)&size, sizeof(size));
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stream.seekp(end);
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return end;
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}
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///
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/// Helper class for read/write of records to/from memory
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///
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template <class T, class T_ID, class T_SIZE, unsigned int ALIGN>
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class record
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{
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public:
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///
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/// Constructs the class
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///
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/// \param[in] d Reference to record data
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///
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inline record(_In_ T &d) : data( d) {}
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inline record(_In_ const T &d) : data((T&)d) {}
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///
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/// Assignment operator
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///
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/// \param[in] r Source record
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///
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/// \returns A const reference to this struct
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///
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inline const record<T, T_ID, T_SIZE, ALIGN>& operator =(_In_ const record<T, T_ID, T_SIZE, ALIGN> &r)
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{
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data = r.data;
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return *this;
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}
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///
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/// Writes record header
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///
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/// \param[in] stream Output stream
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///
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/// \returns Position of the record header start in \p stream. Save for later \c close call.
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///
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static inline std::streamoff open(_In_ std::ostream& stream)
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{
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return stdex::idrec::open<T_ID, T_SIZE>(stream, id);
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}
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///
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/// Updates record header
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///
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/// \param[in] stream Output stream
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/// \param[in] start Start position of the record in \p stream
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///
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/// \returns Position of the record end in \p stream
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///
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static inline std::streamoff close(_In_ std::ostream& stream, _In_ std::streamoff start)
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{
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return stdex::idrec::close<T_ID, T_SIZE, ALIGN>(stream, start);
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}
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///
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/// Finds record data
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///
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/// \param[in] stream Input stream
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/// \param[in] end Position limit. Default is -1 (no limit).
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///
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/// \returns
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/// - true when found
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/// - false otherwise
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///
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static inline bool find(_In_ std::istream& stream, _In_opt_ std::streamoff end = (std::streamoff)-1)
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{
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return stdex::idrec::find<T_ID, T_SIZE, ALIGN>(stream, id, end);
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}
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static const T_ID id; ///< Record id
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T &data; ///< Record data reference
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};
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};
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};
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///
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/// Writes record to a stream
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///
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/// \param[in] stream Output stream
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/// \param[in] r Record
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///
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/// \returns The stream \p stream
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///
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template <class T, class T_ID, class T_SIZE, unsigned int ALIGN>
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inline std::ostream& operator <<(_In_ std::ostream& stream, _In_ const stdex::idrec::record<T, T_ID, T_SIZE, ALIGN> r)
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{
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// Parameter r does not need to be passed by reference. It has only one field (data), which is a reference itself already. The id field is static anyway.
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std::streamoff start = r.open(stream);
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if (stream.fail()) return stream;
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stream << r.data;
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r.close(stream, start);
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return stream;
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}
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///
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/// Reads record from a stream
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///
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/// \param[in] stream Input stream
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/// \param[out] r Record
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///
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/// \returns The stream \p stream
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///
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template <class T, class T_ID, class T_SIZE, unsigned int ALIGN>
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inline std::istream& operator >>(_In_ std::istream& stream, _Out_ stdex::idrec::record<T, T_ID, T_SIZE, ALIGN> r)
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{
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// Parameter r does not need to be passed by reference. It has only one field (data), which is a reference itself already. The id field is static anyway.
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// Read data size.
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T_SIZE size;
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stream.read((char*)&size, sizeof(size));
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if (!stream.good()) return stream;
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// Read data.
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std::streamoff start = stream.tellg();
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stream >> r.data; // TODO: operator >> should not read past the record data! Make a size limited stream and read from it instead.
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size += (T_SIZE)(ALIGN - size) % ALIGN;
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stream.seekg(start + size);
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return stream;
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}
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