Add parallel decoder.

1 files changed, 136 insertions, 0 deletions

diff --git a/src/parallel-decoder.lisp b/src/parallel-decoder.lisp
new file mode 100644
index 0000000..9af1ceb
--- /dev/null
+++ b/src/parallel-decoder.lisp
@@ -0,0 +1,136 @@
+;; This file is part of eris-cl.
+;; Copyright (C) 2022 Piotr Szarmański
+
+;; eris-cl is free software: you can redistribute it and/or modify it under the
+;; terms of the GNU Lesser General Public License as published by the Free
+;; Software Foundation, either version 3 of the License, or (at your option) any
+;; later versqion.
+
+;; eris-cl is distributed in the hope that it will be useful, but WITHOUT ANY
+;; WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+;; A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+
+;; You should have received a copy of the GNU General Public License along with
+;; eris-cl. If not, see <https://www.gnu.org/licenses/>.
+
+(in-package :eris)
+
+(defun split-list-equally (list parts)
+  (let* ((len (length list))
+         (mod (mod len parts))
+         (base (/ (- len mod) parts)))
+    (if (< len parts)
+        (map 'list #'list list)
+        (loop with pos = 0
+              for i from (1- parts) downto 0
+              collecting (subseq
+                          list
+                          pos
+                          (if (<= mod i)
+                              (setf pos (+ pos base))
+                              (setf pos (+ pos base 1))))))))
+
+(defun mem-write-vector (vector ptr &optional (offset 0) (count (length vector)))
+  (declare (type (simple-array (unsigned-byte 8)) vector)
+           (type fixnum offset count))
+  (declare (optimize ;; (speed 3) (safety 0) (space 0)
+                     (debug 3)))
+  (loop for i below count
+        for off from offset
+        do (setf (cffi:mem-ref ptr :unsigned-char off) (aref vector i))))
+
+(defclass reference-pair+ (reference-pair)
+  ((index :initarg :index :accessor index :type (integer 0 32768))))
+
+(defun map-over-key-references (function block)
+  (loop for i from 0 to (1- (/ (length block) 64))
+        for key-ref = (octets-to-reference-pair (subseq-shared block (* 64 i)))
+        until (key-reference-null? key-ref)
+        do (funcall function key-ref i)))
+
+(defun decode-blocks (reference-pair-list level block-capacity fetch-function output-file cache-capacity last-block)
+  (lambda ()
+    (mmap:with-mmap (addr fd size output-file :open :write :protection :write :mmap :shared)
+      (let ((get-block (cached-lambda (:cache-class 'lru-cache 
+                                       :capacity cache-capacity
+                                       :table (make-hash-table :size (1+ cache-capacity) :test #'equalp))
+                           (reference key &optional nonce)
+                         (let* ((block (execute-fetch-function fetch-function reference)))
+                           (unless block (error 'missing-block :reference reference))
+                           (hash-check block reference)
+                           (decrypt-block block key nonce))))
+            (nonce-array (initialize-nonce-array level)))
+        (labels ((descend (level reference-pair block-id)
+                   (let ((block (funcall get-block (reference reference-pair) (key reference-pair) (aref nonce-array level))))
+                     (if (zerop level)
+                         (if (= last-block block-id)
+                             (mem-write-vector block addr (* 64 block-capacity block-id) (unpad-block block))
+                             (mem-write-vector block addr (* 64 block-capacity block-id)))
+                         ;; (bordeaux-threads:with-lock-held (lock)
+                         ;;   (file-position stream (* 64 block-capacity block-id))
+                         ;;   (write-sequence block stream))
+                         (map-over-key-references
+                          (lambda (key-ref i)
+                            (descend (1- level) key-ref (+ i (* block-capacity block-id))))
+                          block)))))
+          (mapc (lambda (key-ref)
+                  (descend level key-ref (index key-ref)))
+                reference-pair-list))))))
+
+(defun eris-decode-parallel (read-capability fetch-function output-file
+                             &key (cache-capacity 4096) (threads 4) (initial-bindings bordeaux-threads:*default-special-bindings*))
+  "Decode an ERIS READ-CAPABILITY in parallel using THREADS threads into a file
+designated by OUTPUT-FILE.
+
+Fetch-function must be a function with one argument, the reference octet, which
+returns a (simple-array (unsigned-byte 8)) containing the block. The block will
+be destructively modified, so you MUST provide a fresh array every time. In
+addition, the function MUST be thread-safe.
+
+CACHE-CAPACITY indicates the total amount of blocks stored for all threads. Each
+thread has its own cache."
+  (declare (type read-capability read-capability)
+           (type function fetch-function)
+           (type integer cache-capacity))
+  (with-slots (level block-size root-reference-pair) read-capability
+    (let ((root (decrypt-block (execute-fetch-function fetch-function (reference root-reference-pair))
+                               (key root-reference-pair)
+                               (make-nonce level))))
+      (when (> level 0) (hash-check root (key root-reference-pair)))
+      (case level
+        (0 (with-open-file (file output-file :direction :output :element-type '(unsigned-byte 8))
+             (write-sequence root file :end (unpad-block root))))
+        (t (let* ((initial-list
+                    (loop for i from 0 to (/ block-size 64)
+                          for key-ref = (octets-to-reference-pair (subseq-shared root (* 64 i)))
+                          until (key-reference-null? key-ref)
+                          collect key-ref))
+                  (list (split-list-equally
+                         (loop for i from 0 to (1- (length initial-list))
+                               collecting (change-class (elt initial-list i) 'reference-pair+ :index i))
+                         threads))
+                  ;; (lock (bordeaux-threads:make-lock "stream-lock"))
+                  (eof (find-eof root
+                                 (lambda (reference key nonce)
+                                   (let* ((block (execute-fetch-function fetch-function reference)))
+                                     (unless block (error 'missing-block :reference reference))
+                                     (hash-check block reference)
+                                     (decrypt-block block key nonce)))
+                                 block-size
+                                 level)))
+             (let ((fd (osicat-posix:creat output-file #o666)))
+               (osicat-posix:posix-fallocate fd 0 eof)
+               (osicat-posix:close fd))
+             (map 'nil #'bordeaux-threads:join-thread
+                  (map 'list (lambda (reference-pairs)
+                               (bordeaux-threads:make-thread
+                                (decode-blocks reference-pairs
+                                               (1- level)
+                                               (/ block-size 64)
+                                               fetch-function
+                                               output-file
+                                               (truncate (/ cache-capacity threads))
+                                               (truncate (/ eof block-size)))
+                                :initial-bindings initial-bindings))
+                       list))))))))
+