Added #contiguous method to make block mapping more efficient, and

renamed #mapblock -> #map_block for consistency.

diff --git a/lib/diskimage.mli b/lib/diskimage.mli
index 9247551..b926193 100644 (file)
--- a/lib/diskimage.mli
+++ b/lib/diskimage.mli
@@ -34,6 +34,7 @@ class virtual device :
   object
     method virtual name : string
       (** Return some printable name for the device. *)
+
     method virtual size : Int63.t
       (** Return the size of the device in bytes.
 
@@ -44,15 +45,16 @@ class virtual device :
       (** [read offset len] reads len bytes starting at offset.
 
          Note: A default implementation is provided for [read],
-         but it is fairly inefficient because it uses {!mapblock} to
+         but it is fairly inefficient because it uses {!map_block} to
          map each block in the request. *)
     method read_bitstring : Int63.t -> Int63.t -> Bitmatch.bitstring
       (** [read_bitstring] is the same as [read] but returns
          a pa_bitmatch-style bitstring. *)
+
     method virtual blocksize : Int63.t
       (** [blocksize] returns the natural block size of the device. *)
-    method virtual mapblock : Int63.t -> (device * Int63.t) list
-      (** [mapblock] describes how a block in this device is
+    method virtual map_block : Int63.t -> (device * Int63.t) list
+      (** [map_block] describes how a block in this device is
          mapped down to any underlying device(s).
 
          Returns [[]] (empty list) if there is no underlying
@@ -62,13 +64,24 @@ class virtual device :
          Normally the returned list has length 1, but in cases
          such as mirroring you can have the same block mapped
          to several underlying devices. *)
+
+    method virtual contiguous : Int63.t -> Int63.t
+      (** [contiguous offset] returns the number of contiguous
+         {i bytes} starting at byte [offset] on this device,
+         before (eg.) end of device or some discontinuity in
+         the mapping table occurs.
+
+         This method and {!map_block} allow callers to determine how
+         high level blocks map to low level disk images efficiently
+         (complex striping and interleaving patterns can make the
+         process much less efficient however). *)
   end
   (**
      A virtual (or physical!) device, encapsulating any translation
      that has to be done to access the device.  eg. For partitions
      there is a simple offset, but for LVM you may need complicated
      table lookups.
-    
+     
      Note this very rare use of OOP in OCaml!
   *)
 
@@ -79,7 +92,8 @@ class block_device : string -> Int63.t ->
     method read : Int63.t -> Int63.t -> string
     method read_bitstring : Int63.t -> Int63.t -> Bitmatch.bitstring
     method blocksize : Int63.t
-    method mapblock : Int63.t -> (device * Int63.t) list
+    method map_block : Int63.t -> (device * Int63.t) list
+    method contiguous : Int63.t -> Int63.t
     method close : unit -> unit
       (** Close the device, freeing up the file descriptor. *)
   end
@@ -96,7 +110,8 @@ class offset_device : string -> Int63.t -> Int63.t -> Int63.t -> device ->
     method read : Int63.t -> Int63.t -> string
     method read_bitstring : Int63.t -> Int63.t -> Bitmatch.bitstring
     method blocksize : Int63.t
-    method mapblock : Int63.t -> (device * Int63.t) list
+    method map_block : Int63.t -> (device * Int63.t) list
+    method contiguous : Int63.t -> Int63.t
   end
     (** A concrete device which maps a linear part of an underlying device.
 
@@ -115,7 +130,8 @@ class blocksize_overlay : Int63.t -> device ->
     method read : Int63.t -> Int63.t -> string
     method read_bitstring : Int63.t -> Int63.t -> Bitmatch.bitstring
     method blocksize : Int63.t
-    method mapblock : Int63.t -> (device * Int63.t) list
+    method contiguous : Int63.t -> Int63.t
+    method map_block : Int63.t -> (device * Int63.t) list
   end
     (** Change the blocksize of an existing device. *)
 

diff --git a/lib/diskimage_lvm2.ml b/lib/diskimage_lvm2.ml
index ea127cb..4432e90 100644 (file)
--- a/lib/diskimage_lvm2.ml
+++ b/lib/diskimage_lvm2.ml
@@ -64,22 +64,39 @@ object (self)
    *)
   method blocksize = extent_size
 
-  (* Map block (extent) i to the underlying device. *)
-  method mapblock i =
+  method private map i =
     if i < ~^0 || i >= size_in_extents then
       invalid_arg "linear_map_device: read outside device";
 
     let rec loop = function
       | [] ->
-         []
+         None
       | (start_extent, end_extent, dev, pvoffset) :: rest ->
-         if start_extent <= i && i < end_extent then
-           [dev, (pvoffset +^ i) *^ extent_size]
-         else
+         if start_extent <= i && i < end_extent then (
+           let dev_offset = (pvoffset +^ i) *^ extent_size in
+           Some (start_extent, end_extent, dev, dev_offset, pvoffset)
+         ) else
            loop rest
     in
     loop segments
 
+  (* Map block (extent) i to the underlying device. *)
+  method map_block i =
+    match self#map i with
+    | Some (_, _, dev, dev_offset, _) -> [dev, dev_offset]
+    | None -> []
+
+  (* Continguous span. *)
+  method contiguous offset =
+    let offset_in_extents = offset /^ extent_size in
+
+    (* Get the segment that this offset lies in. *)
+    match self#map offset_in_extents with
+    | Some (_, end_extent, dev, dev_offset, _) ->
+       (* Contiguous bytes up to the end of this extent. *)
+       end_extent *^ extent_size -^ offset
+    | None -> ~^0
+
   (* NB. Use the superclass #read method. *)
 end
 

diff --git a/lib/diskimage_utils.ml b/lib/diskimage_utils.ml
index 4ad508d..80a7e3a 100644 (file)
--- a/lib/diskimage_utils.ml
+++ b/lib/diskimage_utils.ml
@@ -29,7 +29,8 @@ object (self)
   method virtual size : int63
   method virtual name : string
   method virtual blocksize : int63
-  method virtual mapblock : int63 -> (device * int63) list
+  method virtual map_block : int63 -> (device * int63) list
+  method virtual contiguous : Int63.t -> Int63.t
 
   (* Block-based read.  Inefficient so normally overridden in subclasses. *)
   method read offset len =
@@ -51,7 +52,7 @@ object (self)
     let not_mapped_error () = invalid_arg "device: read: block not mapped" in
 
     (* Copy the first block (partial). *)
-    (match self#mapblock first_blk with
+    (match self#map_block first_blk with
      | [] -> not_mapped_error ()
      | (dev, base) :: _ ->
         let len =
@@ -63,7 +64,7 @@ object (self)
     (* Copy the middle blocks. *)
     let rec loop blk =
       if blk < last_blk then (
-       (match self#mapblock blk with
+       (match self#map_block blk with
         | [] -> not_mapped_error ()
         | (dev, base) :: _ ->
             let str = dev#read ~^0 self#blocksize in
@@ -76,7 +77,7 @@ object (self)
 
     (* Copy the last block (partial). *)
     if first_blk < last_blk then (
-      match self#mapblock last_blk with
+      match self#map_block last_blk with
       | [] -> not_mapped_error ()
       | (dev, base) :: _ ->
          let len = (offset +^ len) -^ last_blk *^ blocksize in
@@ -109,7 +110,9 @@ object (self)
   method size = size
   method name = filename
   method blocksize = blocksize
-  method mapblock _ = []
+  method map_block _ = []
+  method contiguous offset =
+    size -^ offset
   method close () = close fd
 end
 
@@ -128,7 +131,9 @@ object
       );
     dev#read (start+^offset) len
   method blocksize = blocksize
-  method mapblock i = [dev, i *^ blocksize +^ start]
+  method map_block i = [dev, i *^ blocksize +^ start]
+  method contiguous offset =
+    size -^ offset
 end
 
 (* A device with just a modified block size. *)
@@ -137,11 +142,12 @@ object
   inherit device
   method name = dev#name
   method size = dev#size
-  method read offset len = dev#read offset len
+  method read = dev#read
   method blocksize = new_blocksize
-  method mapblock new_blk =
+  method map_block new_blk =
     let orig_blk = new_blk *^ new_blocksize /^ dev#blocksize in
-    dev#mapblock orig_blk
+    dev#map_block orig_blk
+  method contiguous offset = dev#size -^ offset
 end
 
 (* The null device.  Any attempt to read generates an error. *)
@@ -152,7 +158,8 @@ object
   method size = ~^0
   method name = "null"
   method blocksize = ~^1
-  method mapblock _ = assert false
+  method map_block _ = assert false
+  method contiguous _ = ~^0
 end
 
 type machine = {

diff --git a/lib/diskimage_utils.mli b/lib/diskimage_utils.mli
index 5e91520..641483d 100644 (file)
--- a/lib/diskimage_utils.mli
+++ b/lib/diskimage_utils.mli
@@ -29,7 +29,8 @@ class virtual device :
     method read : Int63.t -> Int63.t -> string
     method read_bitstring : Int63.t -> Int63.t -> Bitmatch.bitstring
     method virtual blocksize : Int63.t
-    method virtual mapblock : Int63.t -> (device * Int63.t) list
+    method virtual map_block : Int63.t -> (device * Int63.t) list
+    method virtual contiguous : Int63.t -> Int63.t
   end
 
 class block_device : string -> Int63.t ->
@@ -39,7 +40,8 @@ class block_device : string -> Int63.t ->
     method read : Int63.t -> Int63.t -> string
     method read_bitstring : Int63.t -> Int63.t -> Bitmatch.bitstring
     method blocksize : Int63.t
-    method mapblock : Int63.t -> (device * Int63.t) list
+    method map_block : Int63.t -> (device * Int63.t) list
+    method contiguous : Int63.t -> Int63.t
     method close : unit -> unit
   end
 
@@ -50,7 +52,8 @@ class offset_device : string -> Int63.t -> Int63.t -> Int63.t -> device ->
     method read : Int63.t -> Int63.t -> string
     method read_bitstring : Int63.t -> Int63.t -> Bitmatch.bitstring
     method blocksize : Int63.t
-    method mapblock : Int63.t -> (device * Int63.t) list
+    method map_block : Int63.t -> (device * Int63.t) list
+    method contiguous : Int63.t -> Int63.t
   end
 
 class blocksize_overlay : Int63.t -> device ->
@@ -60,7 +63,8 @@ class blocksize_overlay : Int63.t -> device ->
     method read : Int63.t -> Int63.t -> string
     method read_bitstring : Int63.t -> Int63.t -> Bitmatch.bitstring
     method blocksize : Int63.t
-    method mapblock : Int63.t -> (device * Int63.t) list
+    method map_block : Int63.t -> (device * Int63.t) list
+    method contiguous : Int63.t -> Int63.t
   end
 
 val null_device : device