Added wiping free space capability

- new Dirtable.wipefreespace member to zero unallocated clusters
- new wipe tool
- ability to optimize virtual disk containers combining wipe with imgclone tool
- fixed a small help-bug in mkvdisk.py

FATtools/FAT.py

@@ -630,7 +630,6 @@ def free(self, start, runs=None):
             if self.last <= next <= self.last+7: break
 
 
-
 class Chain(object):
     "Opens a cluster chain or run like a plain file"
     def __init__ (self, boot, fat, cluster, size=0, nofat=0, end=0):
@@ -1392,6 +1391,18 @@ def getdiskspace(self):
         free_bytes = self.fat.free_clusters * self.boot.cluster
         return (self.fat.free_clusters, free_bytes)
 
+    def wipefreespace(self):
+        "Zeroes free clusters"
+        buf = (4<<20) * b'\x00'
+        fourmegs = (4<<20)//self.boot.cluster
+        for start, length in self.fat.free_clusters_map.items():
+            if DEBUG&4: log("Wiping %d clusters from cluster #%d", length, start)
+            self.boot.stream.seek(self.boot.cl2offset(start))
+            while length:
+                q = min(length, fourmegs)
+                self.boot.stream.write(buf[:q*self.boot.cluster])
+                length -= q
+
     def open(self, name):
         "Opens the chain corresponding to an existing file name"
         self._checkopen()

FATtools/exFAT.py

@@ -838,6 +838,18 @@ def getdiskspace(self):
         free_bytes = self.boot.bitmap.free_clusters * self.boot.cluster
         return (self.boot.bitmap.free_clusters, free_bytes)
 
+    def wipefreespace(self):
+        "Zeroes free clusters"
+        buf = (4<<20) * b'\x00'
+        fourmegs = (4<<20)//self.boot.cluster
+        for start, length in self.boot.bitmap.free_clusters_map.items():
+            if DEBUG&4: log("Wiping %d clusters from cluster #%d", length, start)
+            self.boot.stream.seek(self.boot.cl2offset(start))
+            while length:
+                q = min(length, fourmegs)
+                self.boot.stream.write(buf[:q*self.boot.cluster])
+                length -= q
+
     def open(self, name):
         "Opens the slot corresponding to an existing file name"
         self._checkopen()

FATtools/scripts/main.py

@@ -2,7 +2,7 @@
 
 
 def main():
-    scripts=["cat","cp","imgclone","ls","mkfat","mkvdisk","rm","reordergui"]
+    scripts=["cat","cp","imgclone","ls","mkfat","mkvdisk","rm","reordergui","wipe"]
     help_s="Usage: fattools " + ''.join( ['%s|'%s for s in scripts])[:-1]
 
     if len(sys.argv) < 2:

FATtools/scripts/mkvdisk.py

@@ -33,7 +33,6 @@ def call(args):
 
     if not args.image_size:
         print("mkvdisk error: you must specify a virtual disk image size!")
-        par.print_help()
         sys.exit(1)
 
     u = args.image_size[-1].lower()

FATtools/scripts/wipe.py

@@ -0,0 +1,40 @@
+# -*- coding: utf-8 -*-
+import sys, os, argparse, logging
+from FATtools import Volume
+
+DEBUG = 0
+from FATtools.debug import log
+
+#~ logging.basicConfig(level=logging.DEBUG, filename='wipe.log', filemode='w')
+
+class Arguments:
+    pass
+
+
+def wipe(img):
+    v = Volume.vopen(img,'r+b')
+    if not hasattr(v, 'wipefreespace'):
+        print("Couldn't open a FAT/exFAT filesystem inside '%s'"%img)
+        sys.exit(1)
+    print('Wiping %d free clusters (%d bytes) . . .' % v.getdiskspace())
+    v.wipefreespace()
+    print('Done.')
+
+def create_parser(parser_create_fn=argparse.ArgumentParser,parser_create_args=None):
+    help_s = """
+    fattools wipe IMAGE_FILE
+    """
+    par = parser_create_fn(*parser_create_args,usage=help_s,
+    formatter_class=argparse.RawDescriptionHelpFormatter,
+    description="Wipes the free space in an (ex)FAT formatted disk, zeroing all free clusters.",
+    epilog="Combined with imgclone tool, it permits to optimize a virtual disk image size.\n")
+    par.add_argument('image_file', nargs=1)
+    return par
+
+def call(args):
+    wipe(args.image_file[0])
+
+if __name__ == '__main__':
+    par=create_parser()
+    args = par.parse_args()
+    call(args)

FATtools/version.py

@@ -1 +1 @@
-__version__ = '1.0.28'
+__version__ = '1.0.29'

README.MD

@@ -21,7 +21,7 @@ Following features are implemented (mostly in Python, with a few ctypes calls to
 - MBR and GPT partitions handling
 - Long File Name and Unicode support
 - tools to open, create, rename, list and delete files and directories, and to partition disks
-- facilities to sort, clean and shrink directory tables
+- facilities to sort, clean and shrink directory tables and to wipe (zero) free space
 - file fragmentation calculator
 - mkfat tool to properly (partition and) apply a FAT12/16/32 or exFAT filesystem to a block device (file or disk) and let CHKDSK be happy with it (included exFAT compressed Up-Case table generator)
 
@@ -57,10 +57,16 @@ fattools mkfat -t exfat -p gpt image.vhdx
 fattools mkvdisk -b image.vdi delta.vdi
 ```
 
+- to wipe free space in an (ex)FAT formatted disk, zeroing all free clusters:
+```
+fattools wipe image.vhd
+```
+
 - to convert a RAW disk image into a Dynamic VHD (so implicitly virtualizing zeroed data blocks):
 ```
 fattools imgclone image.raw image.vhd
 ```
+Please note that resulting image size can be reduced if the free space in image.raw has been wiped (zeroed) before.
 
 - to list contents in a disk image, copy items to/from it, display and erase them:
 ```