File size: 6,050 Bytes
43203b4 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 | (cl:in-package :cl-flow)
(defvar *current-context* nil)
(defvar *continue* nil)
(defvar *parent-context* nil)
(define-constant +min-stack-extension+ 3)
(defstruct flow-context
(native-dispatcher nil
:type (or null function)
:read-only t)
(dispatcher nil
:type (or null function))
(value nil
:type t)
(function nil
:type (or null function))
(stack (make-array +min-stack-extension+ :element-type 'list :initial-element nil
:fill-pointer 0 :adjustable t)
:type array
:read-only t)
(parent nil
:type (or null flow-context)
:read-only t))
(defun dispatch (context task invariant &rest args &key &allow-other-keys)
(setf (flow-context-function context) task)
(apply (flow-context-dispatcher context) invariant args))
(defun dispatch-rest (context)
(declare (type flow-context context)
#.+optimize-form+)
(cond
((eq *current-context* context) (setf *continue* t))
((eq *parent-context* context)
;; see catch in #'%dispatch-rest:
;; this is to unwind a stack
;; to avoid overflowing it
;; in case of single-threaded dispatch
(throw *parent-context* t))
(t (%dispatch-rest context))))
(defun make-child-flow-context (parent-context)
(init-context-dispatcher
(make-flow-context :native-dispatcher (flow-context-native-dispatcher parent-context)
:value (flow-context-value parent-context)
:parent parent-context)))
(defun %dispatch-rest (flow-context)
(declare (type flow-context flow-context)
#.+optimize-form+)
(let ((*parent-context* *current-context*)
(*current-context* flow-context)
(*continue* nil))
(loop for block = (chop-head flow-context)
do (setf *continue* nil)
(when block
(if (listp block)
(progn
(push-flow-stack flow-context block)
(setf *continue* t))
(when (catch *current-context*
(funcall block flow-context)
nil)
(setf *continue* t))))
while *continue*)))
(defun capture-flow-value (context value)
(setf (flow-context-value context) value))
(defun push-flow-stack (context flow)
(vector-push-extend flow (flow-context-stack context) +min-stack-extension+))
(defun chop-head (context)
(let ((stack (flow-context-stack context)))
(symbol-macrolet ((current (aref stack (1- (length stack)))))
(flet ((%chop-head ()
(let ((top current))
(if (listp top)
(let ((head (first top))
(tail (rest top)))
(prog1 head
(if tail
(setf current tail)
(vector-pop stack))))
(vector-pop stack)))))
(loop while (> (length stack) 0)
thereis (%chop-head))))))
;;;
;;; RESTARTS
;;;
(defun try-restart (restart-name &optional (arg nil provided-p))
(if provided-p
(invoke-restart restart-name arg)
(invoke-restart restart-name)))
(defun rerun-flow-block ()
(try-restart 'rerun-flow-block))
(defun skip-flow-block ()
(try-restart 'skip-flow-block))
(defun inject-flow (flow)
(try-restart 'inject-flow flow))
(defun use-flow-block-value (value)
(try-restart 'use-flow-block-value value))
(defun %%rerun-invoke ()
(throw 'begin (values nil t nil)))
(defun %%rerun-invoke-text (stream)
(format stream "Rerun current flow block"))
(defun %%skip-invoke ()
(throw 'begin (values nil nil nil)))
(defun %%skip-invoke-text (stream)
(format stream "Skip flow block returning nil"))
(defun %%use-invoke (value)
(throw 'begin (values value nil nil)))
(defun %%use-invoke-text (stream)
(format stream "Skip flow block returning provided value"))
(defun %%inject-invoke (flow)
(throw 'begin (values nil nil flow)))
(defun %%inject-invoke-text (stream)
(format stream "Inject flow to run instead of current block"))
(defun %invoke-with-restarts (fu arg)
(declare (type (function (t) *) fu)
#.+optimize-form+)
;; catch+restart-bind insead of tagbody+restart-case to avoid any consing
(catch 'begin
(restart-bind ((rerun-flow-block #'%%rerun-invoke
:report-function #'%%rerun-invoke-text)
(skip-flow-block #'%%skip-invoke
:report-function #'%%skip-invoke-text)
(use-flow-block-value #'%%use-invoke
:report-function #'%%use-invoke-text)
(inject-flow #'%%inject-invoke
:report-function #'%%inject-invoke-text))
(values (funcall fu arg) nil nil))))
(defun invoke-with-restarts (flow-context fu arg)
(declare (type (function (t) *) fu)
#.+optimize-form+)
;; loop instead tagbody to avoid any consing
(loop do (multiple-value-bind (result looping-p flow)
(%invoke-with-restarts fu arg)
(cond
(flow (push-flow-stack flow-context flow)
(dispatch-rest flow-context)
(return))
((not looping-p) (return result))))))
(defun invoke-flow-function (context)
(capture-flow-value context (invoke-with-restarts context
(flow-context-function context)
(flow-context-value context)))
(dispatch-rest context))
(defun init-context-dispatcher (context)
(let ((dispatcher (flow-context-native-dispatcher context)))
(labels ((%invoke ()
(invoke-flow-function context))
(%dispatcher (invariant &rest args &key &allow-other-keys)
(apply dispatcher #'%invoke invariant args)))
(setf (flow-context-dispatcher context) #'%dispatcher)))
context)
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