source/modules/water/files/TemporaryFile.h

   1 /*
   2   ==============================================================================
   3
   4    This file is part of the Water library.
   5    Copyright (c) 2016 ROLI Ltd.
   6    Copyright (C) 2017-2022 Filipe Coelho <falktx@falktx.com>
   7
   8    Permission is granted to use this software under the terms of the ISC license
   9    http://www.isc.org/downloads/software-support-policy/isc-license/
  10
  11    Permission to use, copy, modify, and/or distribute this software for any
  12    purpose with or without fee is hereby granted, provided that the above
  13    copyright notice and this permission notice appear in all copies.
  14
  15    THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH REGARD
  16    TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND
  17    FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT,
  18    OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
  19    USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
  20    TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
  21    OF THIS SOFTWARE.
  22
  23   ==============================================================================
  24 */
  25
  26 #ifndef WATER_TEMPORARYFILE_H_INCLUDED
  27 #define WATER_TEMPORARYFILE_H_INCLUDED
  28
  29 #include "TemporaryFile.h"
  30 #include "File.h"
  31
  32 namespace water {
  33
  34 //==============================================================================
  35 /**
  36     Manages a temporary file, which will be deleted when this object is deleted.
  37
  38     This object is intended to be used as a stack based object, using its scope
  39     to make sure the temporary file isn't left lying around.
  40
  41     For example:
  42
  43     @code
  44     {
  45         File myTargetFile ("~/myfile.txt");
  46
  47         // this will choose a file called something like "~/myfile_temp239348.txt"
  48         // which definitely doesn't exist at the time the constructor is called.
  49         TemporaryFile temp (myTargetFile);
  50
  51         // create a stream to the temporary file, and write some data to it...
  52         ScopedPointer<FileOutputStream> out (temp.getFile().createOutputStream());
  53
  54         if (out != nullptr)
  55         {
  56             out->write ( ...etc )
  57             out = nullptr; // (deletes the stream)
  58
  59             // ..now we've finished writing, this will rename the temp file to
  60             // make it replace the target file we specified above.
  61             bool succeeded = temp.overwriteTargetFileWithTemporary();
  62         }
  63
  64         // ..and even if something went wrong and our overwrite failed,
  65         // as the TemporaryFile object goes out of scope here, it'll make sure
  66         // that the temp file gets deleted.
  67     }
  68     @endcode
  69
  70     @see File, FileOutputStream
  71 */
  72 class TemporaryFile
  73 {
  74 public:
  75     //==============================================================================
  76     enum OptionFlags
  77     {
  78         useHiddenFile = 1,          /**< Indicates that the temporary file should be hidden -
  79                                          i.e. its name should start with a dot. */
  80         putNumbersInBrackets = 2    /**< Indicates that when numbers are appended to make sure
  81                                          the file is unique, they should go in brackets rather
  82                                          than just being appended (see File::getNonexistentSibling() )*/
  83     };
  84
  85     //==============================================================================
  86     /** Creates a randomly-named temporary file in the default temp directory.
  87
  88         @param suffix       a file suffix to use for the file
  89         @param optionFlags  a combination of the values listed in the OptionFlags enum
  90         The file will not be created until you write to it. And remember that when
  91         this object is deleted, the file will also be deleted!
  92     */
  93     TemporaryFile (const String& suffix = String(),
  94                    int optionFlags = 0);
  95
  96     /** Creates a temporary file in the same directory as a specified file.
  97
  98         This is useful if you have a file that you want to overwrite, but don't
  99         want to harm the original file if the write operation fails. You can
 100         use this to create a temporary file next to the target file, then
 101         write to the temporary file, and finally use overwriteTargetFileWithTemporary()
 102         to replace the target file with the one you've just written.
 103
 104         This class won't create any files until you actually write to them. And remember
 105         that when this object is deleted, the temporary file will also be deleted!
 106
 107         @param targetFile   the file that you intend to overwrite - the temporary
 108                             file will be created in the same directory as this
 109         @param optionFlags  a combination of the values listed in the OptionFlags enum
 110     */
 111     TemporaryFile (const File& targetFile,
 112                    int optionFlags = 0);
 113
 114     /** Creates a temporary file using an explicit filename.
 115         The other constructors are a better choice than this one, unless for some reason
 116         you need to explicitly specify the temporary file you want to use.
 117
 118         @param targetFile    the file that you intend to overwrite
 119         @param temporaryFile the temporary file to be used
 120     */
 121     TemporaryFile (const File& targetFile,
 122                    const File& temporaryFile);
 123
 124     /** Destructor.
 125
 126         When this object is deleted it will make sure that its temporary file is
 127         also deleted! If the operation fails, it'll throw an assertion in debug
 128         mode.
 129     */
 130     ~TemporaryFile();
 131
 132     //==============================================================================
 133     /** Returns the temporary file. */
 134     const File& getFile() const noexcept                { return temporaryFile; }
 135
 136     /** Returns the target file that was specified in the constructor. */
 137     const File& getTargetFile() const noexcept          { return targetFile; }
 138
 139     /** Tries to move the temporary file to overwrite the target file that was
 140         specified in the constructor.
 141
 142         If you used the constructor that specified a target file, this will attempt
 143         to replace that file with the temporary one.
 144
 145         Before calling this, make sure:
 146         - that you've actually written to the temporary file
 147         - that you've closed any open streams that you were using to write to it
 148         - and that you don't have any streams open to the target file, which would
 149           prevent it being overwritten
 150
 151         If the file move succeeds, this returns false, and the temporary file will
 152         have disappeared. If it fails, the temporary file will probably still exist,
 153         but will be deleted when this object is destroyed.
 154     */
 155     bool overwriteTargetFileWithTemporary() const;
 156
 157     /** Attempts to delete the temporary file, if it exists.
 158         @returns true if the file is successfully deleted (or if it didn't exist).
 159     */
 160     bool deleteTemporaryFile() const;
 161
 162
 163 private:
 164     //==============================================================================
 165     const File temporaryFile, targetFile;
 166
 167     CARLA_DECLARE_NON_COPYABLE (TemporaryFile)
 168 };
 169
 170 }
 171
 172 #endif // WATER_TEMPORARYFILE_H_INCLUDED