From: Mark Walters Date: Tue, 21 May 2013 15:20:43 +0000 (+0100) Subject: Re: [PATCH 4/5] emacs: Streaming S-expression parser X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=3ffbe0de1804021004e084155d76ec6d9b7b4c1a;p=notmuch-archives.git Re: [PATCH 4/5] emacs: Streaming S-expression parser --- diff --git a/d4/47ecb2cee71a61a1656607a9fe434a649b8f02 b/d4/47ecb2cee71a61a1656607a9fe434a649b8f02 new file mode 100644 index 000000000..eaf4e1a78 --- /dev/null +++ b/d4/47ecb2cee71a61a1656607a9fe434a649b8f02 @@ -0,0 +1,344 @@ +Return-Path: +X-Original-To: notmuch@notmuchmail.org +Delivered-To: notmuch@notmuchmail.org +Received: from localhost (localhost [127.0.0.1]) + by olra.theworths.org (Postfix) with ESMTP id 252E2431FC0 + for ; Tue, 21 May 2013 08:20:59 -0700 (PDT) +X-Virus-Scanned: Debian amavisd-new at olra.theworths.org +X-Spam-Flag: NO +X-Spam-Score: -1.098 +X-Spam-Level: +X-Spam-Status: No, score=-1.098 tagged_above=-999 required=5 + tests=[DKIM_ADSP_CUSTOM_MED=0.001, FREEMAIL_FROM=0.001, + NML_ADSP_CUSTOM_MED=1.2, RCVD_IN_DNSWL_MED=-2.3] autolearn=disabled +Received: from olra.theworths.org ([127.0.0.1]) + by localhost (olra.theworths.org [127.0.0.1]) (amavisd-new, port 10024) + with ESMTP id TmNBrcZJbhd7 for ; + Tue, 21 May 2013 08:20:49 -0700 (PDT) +Received: from mail2.qmul.ac.uk (mail2.qmul.ac.uk [138.37.6.6]) + (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) + (No client certificate requested) + by olra.theworths.org (Postfix) with ESMTPS id C3872431FB6 + for ; Tue, 21 May 2013 08:20:48 -0700 (PDT) +Received: from smtp.qmul.ac.uk ([138.37.6.40]) + by mail2.qmul.ac.uk with esmtp (Exim 4.71) + (envelope-from ) + id 1UeoMo-0006uE-Qb; Tue, 21 May 2013 16:20:47 +0100 +Received: from 93-97-24-31.zone5.bethere.co.uk ([93.97.24.31] helo=localhost) + by smtp.qmul.ac.uk with esmtpsa (TLSv1:AES128-SHA:128) (Exim 4.71) + (envelope-from ) + id 1UeoMo-000577-6x; Tue, 21 May 2013 16:20:46 +0100 +From: Mark Walters +To: Austin Clements , notmuch@notmuchmail.org +Subject: Re: [PATCH 4/5] emacs: Streaming S-expression parser +In-Reply-To: <1368851472-5382-5-git-send-email-amdragon@mit.edu> +References: <1368851472-5382-1-git-send-email-amdragon@mit.edu> + <1368851472-5382-5-git-send-email-amdragon@mit.edu> +User-Agent: Notmuch/0.14+255~gff3cc55 (http://notmuchmail.org) Emacs/23.4.1 + (x86_64-pc-linux-gnu) +Date: Tue, 21 May 2013 16:20:43 +0100 +Message-ID: <87fvxg2wc4.fsf@qmul.ac.uk> +MIME-Version: 1.0 +Content-Type: text/plain; charset=utf-8 +Content-Transfer-Encoding: quoted-printable +X-Sender-Host-Address: 93.97.24.31 +X-QM-SPAM-Info: Sender has good ham record. :) +X-QM-Body-MD5: f9436054f15c52f0a216976259eed7a2 (of first 20000 bytes) +X-SpamAssassin-Score: -0.2 +X-SpamAssassin-SpamBar: / +X-SpamAssassin-Report: The QM spam filters have analysed this message to + determine if it is + spam. We require at least 5.0 points to mark a message as spam. + This message scored -0.2 points. + Summary of the scoring: + * 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail + provider * (markwalters1009[at]gmail.com) + * -0.2 AWL AWL: From: address is in the auto white-list +X-QM-Scan-Virus: ClamAV says the message is clean +X-BeenThere: notmuch@notmuchmail.org +X-Mailman-Version: 2.1.13 +Precedence: list +List-Id: "Use and development of the notmuch mail system." + +List-Unsubscribe: , + +List-Archive: +List-Post: +List-Help: +List-Subscribe: , + +X-List-Received-Date: Tue, 21 May 2013 15:20:59 -0000 + + +Hi + +This patch looks good to me. Some minor comments below. + +Best wishes + +Mark + + +On Sat, 18 May 2013, Austin Clements wrote: +> This provides the same interface as the streaming JSON parser, but +> reads S-expressions incrementally. The only difference is that the +> `notmuch-sexp-parse-partial-list' helper does not handle interleaved +> error messages (since we now have the ability to separate these out at +> the invocation level), so it no longer takes an error function and +> does not need to do the horrible resynchronization that the JSON +> parser had to. +> +> Some implementation improvements have been made over the JSON parser. +> This uses a vector instead of a list for the parser data structure, +> since this allows faster access to elements (and modern versions of +> Emacs handle storage of small vectors efficiently). Private functions +> follow the "prefix--name" convention. And the implementation is much +> simpler overall because S-expressions are much easier to parse. +> --- +> emacs/Makefile.local | 1 + +> emacs/notmuch-parser.el | 212 +++++++++++++++++++++++++++++++++++++++++= +++++++ +> 2 files changed, 213 insertions(+) +> create mode 100644 emacs/notmuch-parser.el +> +> diff --git a/emacs/Makefile.local b/emacs/Makefile.local +> index 456700a..a910aff 100644 +> --- a/emacs/Makefile.local +> +++ b/emacs/Makefile.local +> @@ -3,6 +3,7 @@ +> dir :=3D emacs +> emacs_sources :=3D \ +> $(dir)/notmuch-lib.el \ +> + $(dir)/notmuch-parser.el \ +> $(dir)/notmuch.el \ +> $(dir)/notmuch-query.el \ +> $(dir)/notmuch-show.el \ +> diff --git a/emacs/notmuch-parser.el b/emacs/notmuch-parser.el +> new file mode 100644 +> index 0000000..1b7cf64 +> --- /dev/null +> +++ b/emacs/notmuch-parser.el +> @@ -0,0 +1,212 @@ +> +;; notmuch-parser.el --- streaming S-expression parser +> +;; +> +;; Copyright =C2=A9 Austin Clements +> +;; +> +;; This file is part of Notmuch. +> +;; +> +;; Notmuch is free software: you can redistribute it and/or modify it +> +;; under the terms of the GNU General Public License as published by +> +;; the Free Software Foundation, either version 3 of the License, or +> +;; (at your option) any later version. +> +;; +> +;; Notmuch 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 Notmuch. If not, see . +> +;; +> +;; Authors: Austin Clements +> + +> +(require 'cl) +> + +> +(defun notmuch-sexp-create-parser (buffer) +> + "Return a streaming S-expression parser that reads from BUFFER. +> + +> +This parser is designed to incrementally read an S-expression +> +whose structure is known to the caller. Like a typical +> +S-expression parsing interface, it provides a function to read a +> +complete S-expression from the input. However, it extends this +> +with an additional function that requires the next value in the +> +input to be a list and descends into it, allowing its elements to +> +be read one at a time or further descended into. Both functions +> +can return 'retry to indicate that not enough input is available. +> + +> +The parser always consumes input from BUFFER's point. Hence, the +> +caller is allowed to delete any data before point and may +> +resynchronize after an error by moving point." +> + +> + (vector 'notmuch-sexp-parser +> + buffer +> + ;; List depth +> + 0 +> + ;; Partial parse position marker +> + nil +> + ;; Partial parse state +> + nil)) +> + +> +(defmacro notmuch-sexp--buffer (sp) `(aref ,sp 1)) +> +(defmacro notmuch-sexp--depth (sp) `(aref ,sp 2)) +> +(defmacro notmuch-sexp--partial-pos (sp) `(aref ,sp 3)) +> +(defmacro notmuch-sexp--partial-state (sp) `(aref ,sp 4)) + +Why the double hyphen --? Is it a name-space or some convention? + + +> +(defun notmuch-sexp-read (sp) +> + "Consume and return the value at point in SP's buffer. +> + +> +Returns 'retry if there is insufficient input to parse a complete +> +value (though it may still move point over whitespace). If the +> +parser is currently inside a list and the next token ends the +> +list, this moves point just past the terminator and returns 'end. +> +Otherwise, this moves point to just past the end of the value and +> +returns the value." +> + +> + (with-current-buffer (notmuch-sexp--buffer sp) +> + (skip-chars-forward " \n\r\t") +> + (cond ((eobp) 'retry) +> + ((=3D (char-after) ?\)) +> + ;; We've reached the end of a list +> + (if (=3D (notmuch-sexp--depth sp) 0) +> + ;; .. but we weren't in a list. Let read signal the +> + ;; error. +> + (read (current-buffer)) + +Why is good for read to signal the error rather than us doing it? + +> + ;; Go up a level and return an end token +> + (decf (notmuch-sexp--depth sp)) +> + (forward-char) +> + 'end)) +> + ((=3D (char-after) ?\() +> + ;; We're at the beginning of a list. If we haven't started +> + ;; a partial parse yet, attempt to read the list in its +> + ;; entirety. If this fails, or we've started a partial +> + ;; parse, extend the partial parse to figure out when we +> + ;; have a complete list. +> + (catch 'return +> + (when (null (notmuch-sexp--partial-state sp)) +> + (let ((start (point))) +> + (condition-case nil +> + (throw 'return (read (current-buffer))) +> + (end-of-file (goto-char start))))) +> + ;; Extend the partial parse +> + (let (is-complete) +> + (save-excursion +> + (let* ((new-state (parse-partial-sexp +> + (or (notmuch-sexp--partial-pos sp) (point)) +> + (point-max) 0 nil +> + (notmuch-sexp--partial-state sp))) +> + ;; A complete value is available if we've +> + ;; reached depth 0. +> + (depth (first new-state))) +> + (assert (>=3D depth 0)) +> + (if (=3D depth 0) +> + ;; Reset partial parse state +> + (setf (notmuch-sexp--partial-state sp) nil +> + (notmuch-sexp--partial-pos sp) nil +> + is-complete t) +> + ;; Update partial parse state +> + (setf (notmuch-sexp--partial-state sp) new-state +> + (notmuch-sexp--partial-pos sp) (point-marker))))) +> + (if is-complete +> + (read (current-buffer)) +> + 'retry)))) +> + (t +> + ;; Attempt to read a non-compound value +> + (let ((start (point))) +> + (condition-case nil +> + (let ((val (read (current-buffer)))) +> + ;; We got what looks like a complete read, but if +> + ;; we reached the end of the buffer in the process, +> + ;; we may not actually have all of the input we +> + ;; need (unless it's a string, which is delimited). +> + (if (or (stringp val) (not (eobp))) +> + val +> + ;; We can't be sure the input was complete +> + (goto-char start) +> + 'retry)) +> + (end-of-file +> + (goto-char start) +> + 'retry))))))) +> + +> +(defun notmuch-sexp-begin-list (sp) +> + "Parse the beginning of a list value and enter the list. +> + +> +Returns 'retry if there is insufficient input to parse the +> +beginning of the list. If this is able to parse the beginning of +> +a list, it moves point past the token that opens the list and +> +returns t. Later calls to `notmuch-sexp-read' will return the +> +elements inside the list. If the input in buffer is not the +> +beginning of a list, throw invalid-read-syntax." +> + +> + (with-current-buffer (notmuch-sexp--buffer sp) +> + (skip-chars-forward " \n\r\t") +> + (cond ((eobp) 'retry) +> + ((=3D (char-after) ?\() +> + (forward-char) +> + (incf (notmuch-sexp--depth sp)) +> + t) +> + (t +> + ;; Skip over the bad character like `read' does +> + (forward-char) +> + (signal 'invalid-read-syntax (list (string (char-before)))))))) +> + +> +(defun notmuch-sexp-eof (sp) +> + "Signal an error if there is more data in SP's buffer. +> + +> +Moves point to the beginning of any trailing data or to the end +> +of the buffer if there is only trailing whitespace." +> + +> + (with-current-buffer (notmuch-sexp--buffer sp) +> + (skip-chars-forward " \n\r\t") +> + (unless (eobp) +> + (error "Trailing garbage following expression")))) +> + +> +(defvar notmuch-sexp--parser nil +> + "The buffer-local notmuch-sexp-parser instance. +> + +> +Used by `notmuch-sexp-parse-partial-list'.") +> + +> +(defvar notmuch-sexp--state nil +> + "The buffer-local `notmuch-sexp-parse-partial-list' state.") +> + +> +(defun notmuch-sexp-parse-partial-list (result-function result-buffer) +> + "Incrementally parse an S-expression list from the current buffer. +> + +> +This function consume an S-expression list from the current + +consumes + +> +buffer, applying RESULT-FUNCTION in RESULT-BUFFER to each +> +complete value in the list. It operates incrementally and should +> +be called whenever the input buffer has been extended with +> +additional data. The caller just needs to ensure it does not +> +move point in the input buffer." +> + +> + ;; Set up the initial state +> + (unless (local-variable-p 'notmuch-sexp--parser) +> + (set (make-local-variable 'notmuch-sexp--parser) +> + (notmuch-sexp-create-parser (current-buffer))) +> + (set (make-local-variable 'notmuch-sexp--state) 'begin)) +> + (let (done) +> + (while (not done) +> + (case notmuch-sexp--state +> + (begin +> + ;; Enter the list +> + (if (eq (notmuch-sexp-begin-list notmuch-sexp--parser) 'retry) +> + (setq done t) +> + (setq notmuch-sexp--state 'result))) +> + (result +> + ;; Parse a result +> + (let ((result (notmuch-sexp-read notmuch-sexp--parser))) +> + (case result +> + (retry (setq done t)) +> + (end (setq notmuch-sexp--state 'end)) +> + (t (with-current-buffer result-buffer +> + (funcall result-function result)))))) +> + (end +> + ;; Any trailing data is unexpected +> + (notmuch-sexp-eof notmuch-sexp--parser) +> + (setq done t))))) +> + ;; Clear out what we've parsed +> + (delete-region (point-min) (point))) +> + +> +(provide 'notmuch-parser) +> + +> +;; Local Variables: +> +;; byte-compile-warnings: (not cl-functions) +> +;; End: +> --=20 +> 1.7.10.4