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+ id 1UeoMo-000577-6x; Tue, 21 May 2013 16:20:46 +0100\r
+From: Mark Walters <markwalters1009@gmail.com>\r
+To: Austin Clements <amdragon@MIT.EDU>, notmuch@notmuchmail.org\r
+Subject: Re: [PATCH 4/5] emacs: Streaming S-expression parser\r
+In-Reply-To: <1368851472-5382-5-git-send-email-amdragon@mit.edu>\r
+References: <1368851472-5382-1-git-send-email-amdragon@mit.edu>\r
+ <1368851472-5382-5-git-send-email-amdragon@mit.edu>\r
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+Date: Tue, 21 May 2013 16:20:43 +0100\r
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+\r
+\r
+Hi\r
+\r
+This patch looks good to me. Some minor comments below.\r
+\r
+Best wishes\r
+\r
+Mark\r
+\r
+\r
+On Sat, 18 May 2013, Austin Clements <amdragon@MIT.EDU> wrote:\r
+> This provides the same interface as the streaming JSON parser, but\r
+> reads S-expressions incrementally. The only difference is that the\r
+> `notmuch-sexp-parse-partial-list' helper does not handle interleaved\r
+> error messages (since we now have the ability to separate these out at\r
+> the invocation level), so it no longer takes an error function and\r
+> does not need to do the horrible resynchronization that the JSON\r
+> parser had to.\r
+>\r
+> Some implementation improvements have been made over the JSON parser.\r
+> This uses a vector instead of a list for the parser data structure,\r
+> since this allows faster access to elements (and modern versions of\r
+> Emacs handle storage of small vectors efficiently). Private functions\r
+> follow the "prefix--name" convention. And the implementation is much\r
+> simpler overall because S-expressions are much easier to parse.\r
+> ---\r
+> emacs/Makefile.local | 1 +\r
+> emacs/notmuch-parser.el | 212 +++++++++++++++++++++++++++++++++++++++++=\r
+++++++\r
+> 2 files changed, 213 insertions(+)\r
+> create mode 100644 emacs/notmuch-parser.el\r
+>\r
+> diff --git a/emacs/Makefile.local b/emacs/Makefile.local\r
+> index 456700a..a910aff 100644\r
+> --- a/emacs/Makefile.local\r
+> +++ b/emacs/Makefile.local\r
+> @@ -3,6 +3,7 @@\r
+> dir :=3D emacs\r
+> emacs_sources :=3D \\r
+> $(dir)/notmuch-lib.el \\r
+> + $(dir)/notmuch-parser.el \\r
+> $(dir)/notmuch.el \\r
+> $(dir)/notmuch-query.el \\r
+> $(dir)/notmuch-show.el \\r
+> diff --git a/emacs/notmuch-parser.el b/emacs/notmuch-parser.el\r
+> new file mode 100644\r
+> index 0000000..1b7cf64\r
+> --- /dev/null\r
+> +++ b/emacs/notmuch-parser.el\r
+> @@ -0,0 +1,212 @@\r
+> +;; notmuch-parser.el --- streaming S-expression parser\r
+> +;;\r
+> +;; Copyright =C2=A9 Austin Clements\r
+> +;;\r
+> +;; This file is part of Notmuch.\r
+> +;;\r
+> +;; Notmuch is free software: you can redistribute it and/or modify it\r
+> +;; under the terms of the GNU General Public License as published by\r
+> +;; the Free Software Foundation, either version 3 of the License, or\r
+> +;; (at your option) any later version.\r
+> +;;\r
+> +;; Notmuch is distributed in the hope that it will be useful, but\r
+> +;; WITHOUT ANY WARRANTY; without even the implied warranty of\r
+> +;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU\r
+> +;; General Public License for more details.\r
+> +;;\r
+> +;; You should have received a copy of the GNU General Public License\r
+> +;; along with Notmuch. If not, see <http://www.gnu.org/licenses/>.\r
+> +;;\r
+> +;; Authors: Austin Clements <aclements@csail.mit.edu>\r
+> +\r
+> +(require 'cl)\r
+> +\r
+> +(defun notmuch-sexp-create-parser (buffer)\r
+> + "Return a streaming S-expression parser that reads from BUFFER.\r
+> +\r
+> +This parser is designed to incrementally read an S-expression\r
+> +whose structure is known to the caller. Like a typical\r
+> +S-expression parsing interface, it provides a function to read a\r
+> +complete S-expression from the input. However, it extends this\r
+> +with an additional function that requires the next value in the\r
+> +input to be a list and descends into it, allowing its elements to\r
+> +be read one at a time or further descended into. Both functions\r
+> +can return 'retry to indicate that not enough input is available.\r
+> +\r
+> +The parser always consumes input from BUFFER's point. Hence, the\r
+> +caller is allowed to delete any data before point and may\r
+> +resynchronize after an error by moving point."\r
+> +\r
+> + (vector 'notmuch-sexp-parser\r
+> + buffer\r
+> + ;; List depth\r
+> + 0\r
+> + ;; Partial parse position marker\r
+> + nil\r
+> + ;; Partial parse state\r
+> + nil))\r
+> +\r
+> +(defmacro notmuch-sexp--buffer (sp) `(aref ,sp 1))\r
+> +(defmacro notmuch-sexp--depth (sp) `(aref ,sp 2))\r
+> +(defmacro notmuch-sexp--partial-pos (sp) `(aref ,sp 3))\r
+> +(defmacro notmuch-sexp--partial-state (sp) `(aref ,sp 4))\r
+\r
+Why the double hyphen --? Is it a name-space or some convention?\r
+\r
+\r
+> +(defun notmuch-sexp-read (sp)\r
+> + "Consume and return the value at point in SP's buffer.\r
+> +\r
+> +Returns 'retry if there is insufficient input to parse a complete\r
+> +value (though it may still move point over whitespace). If the\r
+> +parser is currently inside a list and the next token ends the\r
+> +list, this moves point just past the terminator and returns 'end.\r
+> +Otherwise, this moves point to just past the end of the value and\r
+> +returns the value."\r
+> +\r
+> + (with-current-buffer (notmuch-sexp--buffer sp)\r
+> + (skip-chars-forward " \n\r\t")\r
+> + (cond ((eobp) 'retry)\r
+> + ((=3D (char-after) ?\))\r
+> + ;; We've reached the end of a list\r
+> + (if (=3D (notmuch-sexp--depth sp) 0)\r
+> + ;; .. but we weren't in a list. Let read signal the\r
+> + ;; error.\r
+> + (read (current-buffer))\r
+\r
+Why is good for read to signal the error rather than us doing it?\r
+\r
+> + ;; Go up a level and return an end token\r
+> + (decf (notmuch-sexp--depth sp))\r
+> + (forward-char)\r
+> + 'end))\r
+> + ((=3D (char-after) ?\()\r
+> + ;; We're at the beginning of a list. If we haven't started\r
+> + ;; a partial parse yet, attempt to read the list in its\r
+> + ;; entirety. If this fails, or we've started a partial\r
+> + ;; parse, extend the partial parse to figure out when we\r
+> + ;; have a complete list.\r
+> + (catch 'return\r
+> + (when (null (notmuch-sexp--partial-state sp))\r
+> + (let ((start (point)))\r
+> + (condition-case nil\r
+> + (throw 'return (read (current-buffer)))\r
+> + (end-of-file (goto-char start)))))\r
+> + ;; Extend the partial parse\r
+> + (let (is-complete)\r
+> + (save-excursion\r
+> + (let* ((new-state (parse-partial-sexp\r
+> + (or (notmuch-sexp--partial-pos sp) (point))\r
+> + (point-max) 0 nil\r
+> + (notmuch-sexp--partial-state sp)))\r
+> + ;; A complete value is available if we've\r
+> + ;; reached depth 0.\r
+> + (depth (first new-state)))\r
+> + (assert (>=3D depth 0))\r
+> + (if (=3D depth 0)\r
+> + ;; Reset partial parse state\r
+> + (setf (notmuch-sexp--partial-state sp) nil\r
+> + (notmuch-sexp--partial-pos sp) nil\r
+> + is-complete t)\r
+> + ;; Update partial parse state\r
+> + (setf (notmuch-sexp--partial-state sp) new-state\r
+> + (notmuch-sexp--partial-pos sp) (point-marker)))))\r
+> + (if is-complete\r
+> + (read (current-buffer))\r
+> + 'retry))))\r
+> + (t\r
+> + ;; Attempt to read a non-compound value\r
+> + (let ((start (point)))\r
+> + (condition-case nil\r
+> + (let ((val (read (current-buffer))))\r
+> + ;; We got what looks like a complete read, but if\r
+> + ;; we reached the end of the buffer in the process,\r
+> + ;; we may not actually have all of the input we\r
+> + ;; need (unless it's a string, which is delimited).\r
+> + (if (or (stringp val) (not (eobp)))\r
+> + val\r
+> + ;; We can't be sure the input was complete\r
+> + (goto-char start)\r
+> + 'retry))\r
+> + (end-of-file\r
+> + (goto-char start)\r
+> + 'retry)))))))\r
+> +\r
+> +(defun notmuch-sexp-begin-list (sp)\r
+> + "Parse the beginning of a list value and enter the list.\r
+> +\r
+> +Returns 'retry if there is insufficient input to parse the\r
+> +beginning of the list. If this is able to parse the beginning of\r
+> +a list, it moves point past the token that opens the list and\r
+> +returns t. Later calls to `notmuch-sexp-read' will return the\r
+> +elements inside the list. If the input in buffer is not the\r
+> +beginning of a list, throw invalid-read-syntax."\r
+> +\r
+> + (with-current-buffer (notmuch-sexp--buffer sp)\r
+> + (skip-chars-forward " \n\r\t")\r
+> + (cond ((eobp) 'retry)\r
+> + ((=3D (char-after) ?\()\r
+> + (forward-char)\r
+> + (incf (notmuch-sexp--depth sp))\r
+> + t)\r
+> + (t\r
+> + ;; Skip over the bad character like `read' does\r
+> + (forward-char)\r
+> + (signal 'invalid-read-syntax (list (string (char-before))))))))\r
+> +\r
+> +(defun notmuch-sexp-eof (sp)\r
+> + "Signal an error if there is more data in SP's buffer.\r
+> +\r
+> +Moves point to the beginning of any trailing data or to the end\r
+> +of the buffer if there is only trailing whitespace."\r
+> +\r
+> + (with-current-buffer (notmuch-sexp--buffer sp)\r
+> + (skip-chars-forward " \n\r\t")\r
+> + (unless (eobp)\r
+> + (error "Trailing garbage following expression"))))\r
+> +\r
+> +(defvar notmuch-sexp--parser nil\r
+> + "The buffer-local notmuch-sexp-parser instance.\r
+> +\r
+> +Used by `notmuch-sexp-parse-partial-list'.")\r
+> +\r
+> +(defvar notmuch-sexp--state nil\r
+> + "The buffer-local `notmuch-sexp-parse-partial-list' state.")\r
+> +\r
+> +(defun notmuch-sexp-parse-partial-list (result-function result-buffer)\r
+> + "Incrementally parse an S-expression list from the current buffer.\r
+> +\r
+> +This function consume an S-expression list from the current\r
+\r
+consumes\r
+\r
+> +buffer, applying RESULT-FUNCTION in RESULT-BUFFER to each\r
+> +complete value in the list. It operates incrementally and should\r
+> +be called whenever the input buffer has been extended with\r
+> +additional data. The caller just needs to ensure it does not\r
+> +move point in the input buffer."\r
+> +\r
+> + ;; Set up the initial state\r
+> + (unless (local-variable-p 'notmuch-sexp--parser)\r
+> + (set (make-local-variable 'notmuch-sexp--parser)\r
+> + (notmuch-sexp-create-parser (current-buffer)))\r
+> + (set (make-local-variable 'notmuch-sexp--state) 'begin))\r
+> + (let (done)\r
+> + (while (not done)\r
+> + (case notmuch-sexp--state\r
+> + (begin\r
+> + ;; Enter the list\r
+> + (if (eq (notmuch-sexp-begin-list notmuch-sexp--parser) 'retry)\r
+> + (setq done t)\r
+> + (setq notmuch-sexp--state 'result)))\r
+> + (result\r
+> + ;; Parse a result\r
+> + (let ((result (notmuch-sexp-read notmuch-sexp--parser)))\r
+> + (case result\r
+> + (retry (setq done t))\r
+> + (end (setq notmuch-sexp--state 'end))\r
+> + (t (with-current-buffer result-buffer\r
+> + (funcall result-function result))))))\r
+> + (end\r
+> + ;; Any trailing data is unexpected\r
+> + (notmuch-sexp-eof notmuch-sexp--parser)\r
+> + (setq done t)))))\r
+> + ;; Clear out what we've parsed\r
+> + (delete-region (point-min) (point)))\r
+> +\r
+> +(provide 'notmuch-parser)\r
+> +\r
+> +;; Local Variables:\r
+> +;; byte-compile-warnings: (not cl-functions)\r
+> +;; End:\r
+> --=20\r
+> 1.7.10.4\r
projects / notmuch-archives.git / commitdiff