src/gromacs/utility/fileredirector.h

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  35 /*! \libinternal \file
  36  * \brief
  37  * Declares gmx::IFileOutputRedirector.
  38  *
  39  * \author Teemu Murtola <teemu.murtola@gmail.com>
  40  * \inlibraryapi
  41  * \ingroup module_utility
  42  */
  43 #ifndef GMX_UTILITY_FILEREDIRECTOR_H
  44 #define GMX_UTILITY_FILEREDIRECTOR_H
  45
  46 #include <string>
  47
  48 #include "gromacs/utility/path.h"
  49 #include "gromacs/utility/textstream.h"
  50
  51 namespace gmx
  52 {
  53
  54 /*! \libinternal \brief
  55  * Allows overriding file existence checks from code that supports it.
  56  *
  57  * The calling code should take in this interface and use the methods in it
  58  * all file system operations that need to support this redirection.
  59  *
  60  * This allows tests to override the file existence checks without actually
  61  * using the file system.  See IFileOutputRedirector for notes on
  62  * a typical usage pattern.
  63  *
  64  * With some further refactoring of the File class, this could also support
  65  * redirecting input files from in-memory buffers as well, but for now the
  66  * current capabilities are sufficient.
  67  *
  68  * \inlibraryapi
  69  * \ingroup module_utility
  70  */
  71 class IFileInputRedirector
  72 {
  73     public:
  74         virtual ~IFileInputRedirector();
  75
  76         /*! \brief
  77          * Checks whether the provided path exists (and is a file).
  78          *
  79          * The \p onNotFound can be used to influence the behavior on error
  80          * conditions.  Functions to pass as this parameter are provided as
  81          * members of gmx::File.
  82          */
  83         virtual bool fileExists(const char            *filename,
  84                                 File::NotFoundHandler  onNotFound) const = 0;
  85
  86         //! Convenience method to check file existence using an std::string path.
  87         bool fileExists(const std::string     &filename,
  88                         File::NotFoundHandler  onNotFound) const
  89         {
  90             return fileExists(filename.c_str(), onNotFound);
  91         }
  92 };
  93
  94 /*! \libinternal \brief
  95  * Allows capturing `stdout` and file output from code that supports it.
  96  *
  97  * The calling code should take in this interface and use the stream objects
  98  * it returns for all output that needs to support this redirection.
  99  *
 100  * Currently, the (nearly) only purpose for this interface is for unit tests to
 101  * capture the file output without duplicating the knowledge of which files are
 102  * actually produced.  The tests can also replace actual files with in-memory
 103  * streams (e.g., a StringOutputStream), and test the output without actually
 104  * accessing the file system and managing actual files.
 105  *
 106  * As the main user for non-default implementation of this interface is tests,
 107  * code using this interface generally uses a pattern where the redirector is
 108  * initialized to defaultFileOutputRedirector(), and a separate setter is
 109  * provided for tests to change the default.  This allows code outside the
 110  * tests (and outside the code actually calling the redirector) to be written
 111  * as if this interface did not exist (i.e., they do not need to pass the
 112  * default instance).
 113  *
 114  * Also, the interface only supports text files, but can be generalized if/when
 115  * there is a need for binary streams (see also TextOutputStream).
 116  *
 117  * \inlibraryapi
 118  * \ingroup module_utility
 119  */
 120 class IFileOutputRedirector
 121 {
 122     public:
 123         virtual ~IFileOutputRedirector();
 124
 125         /*! \brief
 126          * Returns a stream to use for `stdout` output.
 127          */
 128         virtual TextOutputStream &standardOutput() = 0;
 129         /*! \brief
 130          * Returns a stream to use for output to a file at a given path.
 131          *
 132          * \param[in] filename  Requested file name.
 133          */
 134         virtual TextOutputStreamPointer openTextOutputFile(const char *filename) = 0;
 135
 136         //! Convenience method to open a stream using an std::string path.
 137         TextOutputStreamPointer openTextOutputFile(const std::string &filename)
 138         {
 139             return openTextOutputFile(filename.c_str());
 140         }
 141 };
 142
 143 //! \cond libapi
 144 /*! \brief
 145  * Returns default implementation for IFileInputRedirector.
 146  *
 147  * The returned implementation does not redirect anything, but just uses the
 148  * file system normally.
 149  *
 150  * Does not throw.
 151  *
 152  * \ingroup module_utility
 153  */
 154 IFileInputRedirector &defaultFileInputRedirector();
 155 /*! \brief
 156  * Returns default implementation for IFileOutputRedirector.
 157  *
 158  * The returned implementation does not redirect anything, but just opens the
 159  * files at requested locations.
 160  *
 161  * Does not throw.
 162  *
 163  * \ingroup module_utility
 164  */
 165 IFileOutputRedirector &defaultFileOutputRedirector();
 166 //! \endcond
 167
 168 } // namespace gmx
 169
 170 #endif