compactos.cc

   1 //
   2 // compactos.cc
   3 //
   4 // Copyright (C) 2021 Christian Franke
   5 //
   6 // SPDX-License-Identifier: MIT
   7 //
   8
   9 #include "compactos.h"
  10
  11 /* Not yet provided by w32api headers. */
  12 #ifndef FSCTL_SET_EXTERNAL_BACKING
  13 #define FSCTL_SET_EXTERNAL_BACKING \
  14   CTL_CODE(FILE_DEVICE_FILE_SYSTEM, 195, METHOD_BUFFERED, FILE_SPECIAL_ACCESS)
  15 #endif
  16
  17 #ifndef WOF_CURRENT_VERSION
  18 #define WOF_CURRENT_VERSION 1
  19
  20 typedef struct _WOF_EXTERNAL_INFO {
  21   DWORD Version;
  22   DWORD Provider;
  23 } WOF_EXTERNAL_INFO;
  24
  25 #endif
  26
  27 #ifndef WOF_PROVIDER_FILE
  28 #define WOF_PROVIDER_FILE 2
  29 #define FILE_PROVIDER_CURRENT_VERSION 1
  30
  31 typedef struct _FILE_PROVIDER_EXTERNAL_INFO_V1 {
  32   DWORD Version;
  33   DWORD Algorithm;
  34   DWORD Flags;
  35 } FILE_PROVIDER_EXTERNAL_INFO_V1;
  36
  37 #endif
  38
  39 #ifndef ERROR_COMPRESSION_NOT_BENEFICIAL
  40 #define ERROR_COMPRESSION_NOT_BENEFICIAL 344
  41 #endif
  42
  43 int CompactOsCompressFile(HANDLE h, DWORD algorithm)
  44 {
  45   struct {
  46     WOF_EXTERNAL_INFO Wof;
  47     FILE_PROVIDER_EXTERNAL_INFO_V1 FileProvider;
  48   } wfp;
  49   wfp.Wof.Version = WOF_CURRENT_VERSION;
  50   wfp.Wof.Provider = WOF_PROVIDER_FILE;
  51   wfp.FileProvider.Version = FILE_PROVIDER_CURRENT_VERSION;
  52   wfp.FileProvider.Algorithm = algorithm;
  53   wfp.FileProvider.Flags = 0;
  54
  55   if (!DeviceIoControl(h, FSCTL_SET_EXTERNAL_BACKING, &wfp, sizeof(wfp), 0, 0, 0, 0))
  56     {
  57       if (GetLastError() != ERROR_COMPRESSION_NOT_BENEFICIAL)
  58         return -1;
  59       return 0;
  60     }
  61
  62   return 1;
  63 }