src/gromacs/utility/textstream.h

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  35 /*! \libinternal \file
  36  * \brief
  37  * Declares interfaces for simple input/output streams.
  38  *
  39  * \author Teemu Murtola <teemu.murtola@gmail.com>
  40  * \inlibraryapi
  41  * \ingroup module_utility
  42  */
  43 #ifndef GMX_UTILITY_TEXTSTREAM_H
  44 #define GMX_UTILITY_TEXTSTREAM_H
  45
  46 #include <memory>
  47
  48 namespace gmx
  49 {
  50
  51 /*! \libinternal \brief
  52  * Interface for reading text.
  53  *
  54  * Concrete implementations can read the text from, e.g., a file or an in-memory
  55  * string.  The main use is to allow unit tests to inject in-memory buffers
  56  * instead of writing files to be read by the code under test, but there are
  57  * also use cases outside the tests where it is useful to abstract out whether
  58  * the input is from a real file or something else.
  59  *
  60  * To use more advanced formatting than reading raw lines, use TextReader.
  61  *
  62  * Both methods in the interface can throw std::bad_alloc or other exceptions
  63  * that indicate failures to read from the stream.
  64  *
  65  * \inlibraryapi
  66  * \ingroup module_utility
  67  */
  68 class TextInputStream
  69 {
  70     public:
  71         virtual ~TextInputStream() {}
  72
  73         /*! \brief
  74          * Reads a line (with newline included) from the stream.
  75          *
  76          * \param[out] line    String to receive the line.
  77          * \returns    `false` if nothing was read because the stream ended.
  78          *
  79          * On error or when `false` is returned, \p line will be empty.
  80          */
  81         virtual bool readLine(std::string *line) = 0;
  82         /*! \brief
  83          * Closes the stream.
  84          *
  85          * It is not allowed to read from a stream after it has been closed.
  86          * See TextOutputStream::close() for rationale for a close() method
  87          * separate from the destructor.  For input, failures during close
  88          * should be rare, but it is clearer to keep the interface symmetric.
  89          */
  90         virtual void close() = 0;
  91 };
  92
  93 /*! \libinternal \brief
  94  * Interface for writing text.
  95  *
  96  * Concrete implementations can write the text to, e.g., a file or an in-memory
  97  * string.  The main use is to allow unit tests to inject in-memory buffers
  98  * instead of reading in files produced by the code under test, but there are
  99  * also use cases outside the tests where it is useful to abstract out whether
 100  * the output is into a real file or something else.
 101  *
 102  * To use more advanced formatting than writing plain strings, use TextWriter.
 103  *
 104  * The current implementation assumes text-only output in several places, but
 105  * this interface could possibly be generalized also for binary files.
 106  * However, since all binary files currently written by \Gromacs are either
 107  * XDR- or TNG-based, they may require a different approach.  Also, it is worth
 108  * keeping the distinction between text and binary files clear, since Windows
 109  * does transparent `LF`-`CRLF` newline translation for text files, so mixing
 110  * modes when reading and/or writing the same file can cause subtle issues.
 111  *
 112  * Both methods in the interface can throw std::bad_alloc or other exceptions
 113  * that indicate failures to write to the stream.
 114  *
 115  * \inlibraryapi
 116  * \ingroup module_utility
 117  */
 118 class TextOutputStream
 119 {
 120     public:
 121         virtual ~TextOutputStream() {}
 122
 123         /*! \brief
 124          * Writes a given string to the stream.
 125          */
 126         virtual void write(const char *text) = 0;
 127         /*! \brief
 128          * Closes the stream.
 129          *
 130          * It is not allowed to write to a stream after it has been closed.
 131          * A method separate from the destructor is provided such that errors
 132          * that occur while closing the stream (e.g., when closing the file)
 133          * can be handled using exceptions.
 134          * The destructor is not allowed to throw, so code that wants to
 135          * observe such errors needs to call close() after it has finished
 136          * writing to the stream.
 137          */
 138         virtual void close() = 0;
 139 };
 140
 141 //! Shorthand for a smart pointer to a TextInputStream.
 142 typedef std::shared_ptr<TextInputStream> TextInputStreamPointer;
 143 //! Shorthand for a smart pointer to a TextOutputStream.
 144 typedef std::shared_ptr<TextOutputStream> TextOutputStreamPointer;
 145
 146 } // namespace gmx
 147
 148 #endif