# HG changeset patch
# User David Scott <dave.scott@xxxxxxxxxxxxx>
# Date 1282565809 -3600
# Node ID 9de4d96802c250f68519c26b7c021c41beda995b
# Parent 4aeb389f3b5a2e88c87228094217b7d092ed22ca
CA-43021: Small refactorings of the new sparse_dd code.
Split the 'Stream' signature into two since we don't have to be reading and
writing to the same kind of data.
Add a convenient 'substring' record type rather than passing around multiple
arguments all the time.
Signed-off-by: David Scott <dave.scott@xxxxxxxxxxxxx>
diff -r 4aeb389f3b5a -r 9de4d96802c2 ocaml/xapi/sparse_dd.ml
--- a/ocaml/xapi/sparse_dd.ml Mon Aug 23 13:09:56 2010 +0100
+++ b/ocaml/xapi/sparse_dd.ml Mon Aug 23 13:16:49 2010 +0100
@@ -23,13 +23,20 @@
let quantum = 16384 in
((x + quantum + quantum - 1) / quantum) * quantum
-(** The copying routine can operate on anything which looks like a
file-descriptor/Stream *)
-module type Stream = sig
- type stream
- val read: stream -> int64 -> string -> int -> int -> unit
- val write: stream -> int64 -> string -> int -> int -> int
+(** Represents a substring without making a copy *)
+type substring = {
+ buf: string;
+ offset: int;
+ len: int;
+}
+
+(** The copying routine has inputs and outputs which both look like a
+ Unix file-descriptor *)
+module type IO = sig
+ type t
+ val op: t -> int64 -> substring -> unit
end
-
+
(* [fold_over_blocks (s, len) skip f initial] applies contiguous (start,
length) pairs to
[f] starting at [s] up to maximum length [len] where each pair is as large
as possible
up to [skip]. *)
@@ -51,22 +58,21 @@
}
(** Perform the data duplication ("DD") *)
-module DD(S : Stream) = struct
+module DD(Input : IO)(Output : IO) = struct
(** [copy progress_cb bat sparse src dst size] copies blocks of data
from [src] to [dst]
where [bat] represents the allocated / dirty blocks in [src];
where if sparse is None it means don't scan for and skip over
blocks of zeroes in [src]
where if sparse is (Some c) it means do scan for and skip over
blocks of 'c' in [src]
while calling [progress_cb] frequently to report the fraction
complete
*)
- let copy progress_cb bat sparse (src: S.stream) (dst: S.stream) size =
+ let copy progress_cb bat sparse (src: Input.t) (dst: Output.t) size =
let buf = String.create (Int64.to_int blocksize) in
let do_block stats (offset, this_chunk) : stats =
progress_cb ((Int64.to_float offset) /. (Int64.to_float
size));
- S.read src offset buf 0 (Int64.to_int this_chunk);
+ Input.op src offset { buf = buf; offset = 0; len =
Int64.to_int this_chunk };
let write_extent stats (s, e) =
- let n = S.write dst (offset +* (Int64.of_int
s)) buf s e in
- if n < e then raise (ShortWrite(s, e, n));
- { stats with writes = stats.writes + 1; bytes =
stats.bytes +* (Int64.of_int n) }
+ Output.op dst (offset +* (Int64.of_int s)) {
buf = buf; offset = s; len = e };
+ { stats with writes = stats.writes + 1; bytes =
stats.bytes +* (Int64.of_int e) }
in
begin match sparse with
| Some zero -> Zerocheck.fold_over_nonzeros buf
(Int64.to_int this_chunk) roundup write_extent stats
@@ -77,54 +83,57 @@
end
(* Helper function to always return a block of zeroes, like /dev/null *)
-let read_zeroes _ _ buf offset len =
- for i = 0 to len - 1 do
- buf.[offset + i] <- '\000'
- done
+module Zero_reader = struct
+ type t = unit
+ let op _ _ { buf = buf; offset = offset; len = len } =
+ for i = 0 to len - 1 do
+ buf.[offset + i] <- '\000'
+ done
+end
-(** A Stream interface implemented over strings, useful for testing *)
-module String_stream = struct
- type stream = string
- let blit src srcoff dst dstoff len =
- (* Printf.printf "[%s](%d) -> [%s](%d) %d\n" "?" srcoff "?"
dstoff len; *)
- String.blit src srcoff dst dstoff len
- let read str stream_offset buf offset len =
+let blit src srcoff dst dstoff len =
+ (* Printf.printf "[%s](%d) -> [%s](%d) %d\n" "?" srcoff "?" dstoff len;
*)
+ String.blit src srcoff dst dstoff len
+
+module String_reader = struct
+ type t = string
+ let op str stream_offset { buf = buf; offset = offset; len = len } =
blit str (Int64.to_int stream_offset) buf offset len
- let write str stream_offset buf offset len =
- blit buf offset str (Int64.to_int stream_offset) len;
- len
+end
+module String_writer = struct
+ type t = string
+ let op str stream_offset { buf = buf; offset = offset; len = len } =
+ blit buf offset str (Int64.to_int stream_offset) len
end
(** A File interface implemented over open Unix files *)
-module File_stream = struct
- type stream = Unix.file_descr
-
- let read stream stream_offset buf offset len =
+module File_reader = struct
+ type t = Unix.file_descr
+ let op stream stream_offset { buf = buf; offset = offset; len = len } =
Unix.LargeFile.lseek stream stream_offset Unix.SEEK_SET;
Unixext.really_read stream buf offset len
- let write stream stream_offset buf offset len =
+end
+module File_writer = struct
+ type t = Unix.file_descr
+ let op stream stream_offset { buf = buf; offset = offset; len = len } =
let newoff = Unix.LargeFile.lseek stream stream_offset
Unix.SEEK_SET in
(* Printf.printf "Unix.write buf len %d; offset %d; len %d\n"
(String.length buf) offset len; *)
- Unix.write stream buf offset len
+ let n = Unix.write stream buf offset len in
+ if n < len
+ then raise (ShortWrite(offset, len, n))
end
(** An implementation of the DD algorithm over strings *)
-module String_copy = DD(String_stream)
+module String_copy = DD(String_reader)(String_writer)
(** An implementatino of the DD algorithm which copies zeroes into strings *)
-module String_write_zero = DD(struct
- include String_stream
- let read = read_zeroes
-end)
+module String_write_zero = DD(Zero_reader)(String_writer)
(** An implementatino of the DD algorithm over Unix files *)
-module File_copy = DD(File_stream)
+module File_copy = DD(File_reader)(File_writer)
(** An implementatin of the DD algorithm which copies zeroes into files *)
-module File_write_zero = DD(struct
- include File_stream
- let read = read_zeroes
-end)
+module File_write_zero = DD(Zero_reader)(File_writer)
(** [file_dd ?progress_cb ?size ?bat prezeroed src dst]
If [size] is not given, will assume a plain file and will use st_size from
Unix.stat.
@@ -154,7 +163,7 @@
(fun fraction -> progress_cb (0.5 *. fraction)),
(fun fraction -> progress_cb (0.5 *. fraction +. 0.5)) in
Printf.printf "Wiping\n";
- File_write_zero.copy progress_cb_zero bat' None ifd ofd size;
+ File_write_zero.copy progress_cb_zero bat' None () ofd size;
Printf.printf "Copying\n";
File_copy.copy progress_cb_copy bat (if prezeroed then Some '\000' else
None) ifd ofd size
@@ -199,7 +208,7 @@
let bat' = if prezeroed
then empty_bat
else Bat.difference full_bat bat in
- String_write_zero.copy (fun _ -> ()) bat' None input output
(Int64.of_int size);
+ String_write_zero.copy (fun _ -> ()) bat' None () output
(Int64.of_int size);
let stats = String_copy.copy (fun _ -> ()) bat (if prezeroed
then Some zero else None) input output (Int64.of_int size) in
assert (String.compare input output = 0);
stats
ocaml/xapi/sparse_dd.ml | 97 ++++++++++++++++++++++++++----------------------
1 files changed, 53 insertions(+), 44 deletions(-)
xen-api.hg-1.patch
Description: Text Data
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