From: Austin Clements Date: Mon, 27 May 2013 19:04:36 +0000 (+2000) Subject: Re: [PATCH 4/5] emacs: Streaming S-expression parser X-Git-Url: http://git.tremily.us/?a=commitdiff_plain;h=3730c36519973e6ad1add3164508a801dfc91693;p=notmuch-archives.git Re: [PATCH 4/5] emacs: Streaming S-expression parser --- diff --git a/e6/e0f5ccbd9971408925337bf9f473b2a13f349c b/e6/e0f5ccbd9971408925337bf9f473b2a13f349c new file mode 100644 index 000000000..e1b7e2821 --- /dev/null +++ b/e6/e0f5ccbd9971408925337bf9f473b2a13f349c @@ -0,0 +1,409 @@ +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 07049431FAF + for ; Mon, 27 May 2013 12:04:55 -0700 (PDT) +X-Virus-Scanned: Debian amavisd-new at olra.theworths.org +X-Spam-Flag: NO +X-Spam-Score: -0.7 +X-Spam-Level: +X-Spam-Status: No, score=-0.7 tagged_above=-999 required=5 + tests=[RCVD_IN_DNSWL_LOW=-0.7] 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 4uuybgHLJgkT for ; + Mon, 27 May 2013 12:04:45 -0700 (PDT) +Received: from dmz-mailsec-scanner-4.mit.edu (DMZ-MAILSEC-SCANNER-4.MIT.EDU + [18.9.25.15]) + by olra.theworths.org (Postfix) with ESMTP id 4565E431FAE + for ; Mon, 27 May 2013 12:04:45 -0700 (PDT) +X-AuditID: 1209190f-b7f256d000005616-05-51a3ae491c90 +Received: from mailhub-auth-3.mit.edu ( [18.9.21.43]) + by dmz-mailsec-scanner-4.mit.edu (Symantec Messaging Gateway) with SMTP + id 4C.05.22038.94EA3A15; Mon, 27 May 2013 15:04:41 -0400 (EDT) +Received: from outgoing.mit.edu (OUTGOING-AUTH-1.MIT.EDU [18.9.28.11]) + by mailhub-auth-3.mit.edu (8.13.8/8.9.2) with ESMTP id r4RJ4ewa024942; + Mon, 27 May 2013 15:04:41 -0400 +Received: from awakening.csail.mit.edu (awakening.csail.mit.edu [18.26.4.91]) + (authenticated bits=0) + (User authenticated as amdragon@ATHENA.MIT.EDU) + by outgoing.mit.edu (8.13.8/8.12.4) with ESMTP id r4RJ4bg4029612 + (version=TLSv1/SSLv3 cipher=DHE-RSA-AES128-SHA bits=128 verify=NOT); + Mon, 27 May 2013 15:04:38 -0400 +Received: from amthrax by awakening.csail.mit.edu with local (Exim 4.80) + (envelope-from ) + id 1Uh2ii-0008EC-PM; Mon, 27 May 2013 15:04:36 -0400 +Date: Mon, 27 May 2013 15:04:36 -0400 +From: Austin Clements +To: Mark Walters +Subject: Re: [PATCH 4/5] emacs: Streaming S-expression parser +Message-ID: <20130527190436.GS5999@mit.edu> +References: <1368851472-5382-1-git-send-email-amdragon@mit.edu> + <1368851472-5382-5-git-send-email-amdragon@mit.edu> + <87fvxg2wc4.fsf@qmul.ac.uk> + <87ip2b3moz.fsf@awakening.csail.mit.edu> + <8761y7ph8v.fsf@qmul.ac.uk> +MIME-Version: 1.0 +Content-Type: text/plain; charset=iso-8859-1 +Content-Disposition: inline +Content-Transfer-Encoding: 8bit +In-Reply-To: <8761y7ph8v.fsf@qmul.ac.uk> +User-Agent: Mutt/1.5.21 (2010-09-15) +X-Brightmail-Tracker: + H4sIAAAAAAAAA+NgFlrLKsWRmVeSWpSXmKPExsUixCmqreu5bnGgwcstYhar5/JYXL85k9mB + yWPnrLvsHs9W3WIOYIrisklJzcksSy3St0vgyth1bTljwbf8iu6bk1kaGI+FdTFyckgImEg0 + H5nPBmGLSVy4tx7I5uIQEtjHKLH0ynVmCGcjo8TKb9OgnNNMEo3dC9khnCWMEtPWLGIC6WcR + UJVo7/nBCGKzCWhIbNu/HMwWEdCRuH1oATuIzSwgLfHtdzNQPQeHsICtxKL9YKt5BbQl9i35 + wwox8w6jxJe+lUwQCUGJkzOfsED06kjs3HqHDaQXZM7yfxwQYXmJ5q2zmUFsTqC1E161g80U + FVCRmHJyG9sERuFZSCbNQjJpFsKkWUgmLWBkWcUom5JbpZubmJlTnJqsW5ycmJeXWqRropeb + WaKXmlK6iREcB5L8Oxi/HVQ6xCjAwajEwzshe3GgEGtiWXFl7iFGSQ4mJVHe0yuAQnxJ+SmV + GYnFGfFFpTmpxYcYJTiYlUR4t4PkeFMSK6tSi/JhUtIcLErivFdTbvoLCaQnlqRmp6YWpBbB + ZGU4OJQkeP3XAjUKFqWmp1akZeaUIKSZODhBhvMADdcAqeEtLkjMLc5Mh8ifYjTm2Hx+8jtG + jravQFKIJS8/L1VKnNcJpFQApDSjNA9uGiyVvWIUB3pOmNcepIoHmAbh5r0CWsUEtEqcGWxV + SSJCSqqBUeNA6of0Pk3vGeqBq//naWTxVC67FPLsQOUdycY10e1B9ds7/lccCbbb9r+h/9nB + 6wtqLTvVfZlMbn44Hrl/X9fe+Q5vXk5bbpD2hTnqfemuHZvnMS7o1g20PGJWffnr4etdxbfN + WBmTDt3ycZy9dpZcqhnnKRVvsczuT+5LFf8/UFB737oyS4mlOCPRUIu5qDgRAMQVG6RAAwAA +Cc: notmuch@notmuchmail.org +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: Mon, 27 May 2013 19:04:55 -0000 + +Quoth Mark Walters on May 25 at 9:59 am: +> +> Hi +> +> On Wed, 22 May 2013, Austin Clements wrote: +> > On Tue, 21 May 2013, Mark Walters wrote: +> >> Hi +> >> +> >> This patch looks good to me. Some minor comments below. +> > +> > Some minor replies below. +> > +> > In building some other code on top of this, I found an interesting (but +> > easy to fix) interface bug. Currently, the interface is designed as if +> > it doesn't matter what buffer these functions are called from, however, +> > because they move point and expect this point motion to persist, it's +> > actually not safe to call this interface unless the caller is in the +> > right buffer anyway. For example, if the buffer is selected in a +> > window, the with-current-buffer in the parser functions will actually +> > move a *temporary* point, meaning that the only way the caller can +> > discover the new point is to first select the buffer for itself. I can +> > think of two solutions: 1) maintain our own mark for the parser's +> > current position or 2) tweak the doc strings and code so that it reads +> > from the current buffer. 1 keeps the interface the way it's currently +> > documented, but complicates the parser implementation and interface and +> > doesn't simplify the caller. 2 simplifies the parser and it turns out +> > all callers already satisfy the requirement. +> +> I am confused by this: the docs strings for json/sexp-parse-partial-list +> both say something like "Parse a partial JSON list from current buffer"? +> Or do you mean the with-current-buffer in notmuch-search-process-filter? + +I was referring to the lower level parser, which effectively has the +same requirement but isn't documented to and has code that pointlessly +tries to track the parsing buffer (I consider +json/sexp-parse-partial-list to be a helper). In fact, one reason the +lower level parser didn't choke is because right now we only use it +through json/sexp-parse-partial-list, which requires that it be called +from the right buffer. + +> >> 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 := emacs +> >>> emacs_sources := \ +> >>> $(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 © 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? +> > +> > More specifically, this seems to be the most common Elisp convention for +> > indicating private symbols. +> +> Ok. If we are keeping the json parser it might be worth making it follow +> the same convention but as it is purely internal it's probably not worth +> bothering. + +Yeah, it is purely internal. Also, I was planning to remove the JSON +parser (or maybe move it somewhere else? I feel bad deleting that +much perfectly functional code, though of course git will keep it in +perpetuity). + +> >>> +(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) +> >>> + ((= (char-after) ?\)) +> >>> + ;; We've reached the end of a list +> >>> + (if (= (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? +> > +> > This ensures the syntax error handling and signal behavior of +> > notmuch-sexp-read is identical in every way to a regular read call. +> > Maybe the comment should read "Let read signal the error like we do in +> > all other code paths."? +> +> Yes that would be good: or perhaps "like it does in all other code +> paths". + +Sure. + +> Best wishes +> +> Mark +> +> > +> >>> + ;; Go up a level and return an end token +> >>> + (decf (notmuch-sexp--depth sp)) +> >>> + (forward-char) +> >>> + 'end)) +> >>> + ((= (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 (>= depth 0)) +> >>> + (if (= 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) +> >>> + ((= (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 +> > +> > Oops, yes. +> > +> >>> +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: