From: Austin Clements Date: Mon, 9 Jul 2012 21:42:40 +0000 (+2000) Subject: [PATCH v3 7/9] emacs: Implement an incremental JSON parser X-Git-Url: http://git.tremily.us/gitweb.cgi?a=commitdiff_plain;h=4be7ac8647756aa7c8f2fc9a75f76a009b3a889d;p=notmuch-archives.git [PATCH v3 7/9] emacs: Implement an incremental JSON parser --- diff --git a/d1/0b3c0c402b289cedea209d5d948a680b949cbd b/d1/0b3c0c402b289cedea209d5d948a680b949cbd new file mode 100644 index 000000000..7580eeb1f --- /dev/null +++ b/d1/0b3c0c402b289cedea209d5d948a680b949cbd @@ -0,0 +1,314 @@ +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 BB6AE429E48 + for ; Mon, 9 Jul 2012 14:42:53 -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 Hsy1uAofA-a9 for ; + Mon, 9 Jul 2012 14:42:51 -0700 (PDT) +Received: from dmz-mailsec-scanner-7.mit.edu (DMZ-MAILSEC-SCANNER-7.MIT.EDU + [18.7.68.36]) + by olra.theworths.org (Postfix) with ESMTP id 01BBF429E26 + for ; Mon, 9 Jul 2012 14:42:49 -0700 (PDT) +X-AuditID: 12074424-b7f2a6d0000008bf-c9-4ffb5058443f +Received: from mailhub-auth-2.mit.edu ( [18.7.62.36]) + by dmz-mailsec-scanner-7.mit.edu (Symantec Messaging Gateway) with SMTP + id 58.72.02239.8505BFF4; Mon, 9 Jul 2012 17:42:48 -0400 (EDT) +Received: from outgoing.mit.edu (OUTGOING-AUTH.MIT.EDU [18.7.22.103]) + by mailhub-auth-2.mit.edu (8.13.8/8.9.2) with ESMTP id q69LgmAq003851; + Mon, 9 Jul 2012 17:42:48 -0400 +Received: from drake.dyndns.org (26-4-176.dynamic.csail.mit.edu [18.26.4.176]) + (authenticated bits=0) + (User authenticated as amdragon@ATHENA.MIT.EDU) + by outgoing.mit.edu (8.13.6/8.12.4) with ESMTP id q69LgikB022689 + (version=TLSv1/SSLv3 cipher=AES256-SHA bits=256 verify=NOT); + Mon, 9 Jul 2012 17:42:47 -0400 (EDT) +Received: from amthrax by drake.dyndns.org with local (Exim 4.77) + (envelope-from ) + id 1SoLjA-0004g6-2C; Mon, 09 Jul 2012 17:42:44 -0400 +From: Austin Clements +To: notmuch@notmuchmail.org +Subject: [PATCH v3 7/9] emacs: Implement an incremental JSON parser +Date: Mon, 9 Jul 2012 17:42:40 -0400 +Message-Id: <1341870162-17782-8-git-send-email-amdragon@mit.edu> +X-Mailer: git-send-email 1.7.10 +In-Reply-To: <1341870162-17782-1-git-send-email-amdragon@mit.edu> +References: <1341354059-29396-1-git-send-email-amdragon@mit.edu> + <1341870162-17782-1-git-send-email-amdragon@mit.edu> +X-Brightmail-Tracker: + H4sIAAAAAAAAA+NgFjrKIsWRmVeSWpSXmKPExsUixG6nohsR8Nvf4MtxPYvVc3ksrt+cyWzx + ZuU8Vgdmj52z7rJ7HP66kMXj2apbzAHMUVw2Kak5mWWpRfp2CVwZh3d9ZyxY5Vlx5lFqA+MH + yy5GTg4JAROJB5MWsUHYYhIX7q0Hsrk4hAT2MUpMOfScHcJZzyhx6dxdJpAqIYGTTBLzlmhA + JOYySlzY9ZUVJMEmoCGxbf9yRhBbREBaYufd2WBxZoE4iS1T/oPFhQWcJXa17ABbxyKgKrHs + /h1mEJtXwEFi7tbbLBBnyEs8vd8HVsMp4Cgx5+YORojF5RKfb/xjnsDIv4CRYRWjbEpulW5u + YmZOcWqybnFyYl5eapGuuV5uZoleakrpJkZwaLmo7GBsPqR0iFGAg1GJh3cjy29/IdbEsuLK + 3EOMkhxMSqK8eZ5AIb6k/JTKjMTijPii0pzU4kOMEhzMSiK8t1yBcrwpiZVVqUX5MClpDhYl + cd7rKTf9hQTSE0tSs1NTC1KLYLIyHBxKEryX/YEaBYtS01Mr0jJzShDSTBycIMN5gIafA6nh + LS5IzC3OTIfIn2JUlAIaDZIQAElklObB9cJi/xWjONArwrw7QKp4gGkDrvsV0GAmoMHtPb9A + BpckIqSkGhi3auf1xMxO/Lj5iP8cic6oE7reH5rUFz+fKVW+6ljDnaPfZRSeGPy1qn4j6l3r + ea9h5fKwA5F6i188spg60+hLZ4ZAyWxTk/n1VYePc3ySe19afypipatz/1Ius0ve5zp/vbl2 + qcpg8pu3e9VtCqZWVYcrdN4JEFVZs8LtxeMrj1xqejPZ31QosRRnJBpqMRcVJwIATWt0XdgC AAA= +Cc: tomi.ollila@iki.fi +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, 09 Jul 2012 21:42:54 -0000 + +This parser is designed to read streaming JSON whose structure is +known to the caller. Like a typical JSON parsing interface, it +provides a function to read a complete JSON value from the input. +However, it extends this with an additional function that +requires the next value in the input to be a compound value 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 supports efficient partial parsing, so there's no need to +frame the input for correctness or performance. + +The bulk of the parsing is still done by Emacs' json.el, so any +improvements or optimizations to that will benefit the incremental +parser as well. + +Currently only descending into JSON lists is supported because that's +all we need, but support for descending into JSON objects can be added +in the future. +--- + emacs/notmuch-lib.el | 197 ++++++++++++++++++++++++++++++++++++++++++++++++++ + 1 file changed, 197 insertions(+) + +diff --git a/emacs/notmuch-lib.el b/emacs/notmuch-lib.el +index c829df3..aa25513 100644 +--- a/emacs/notmuch-lib.el ++++ b/emacs/notmuch-lib.el +@@ -23,6 +23,7 @@ + + (require 'mm-view) + (require 'mm-decode) ++(require 'json) + (eval-when-compile (require 'cl)) + + (defvar notmuch-command "notmuch" +@@ -296,6 +297,202 @@ was called." + (defvar notmuch-show-process-crypto nil) + (make-variable-buffer-local 'notmuch-show-process-crypto) + ++;; Incremental JSON parsing ++ ++(defun notmuch-json-create-parser (buffer) ++ "Return a streaming JSON parser that consumes input from BUFFER. ++ ++This parser is designed to read streaming JSON whose structure is ++known to the caller. Like a typical JSON parsing interface, it ++provides a function to read a complete JSON value from the input. ++However, it extends this with an additional function that ++requires the next value in the input to be a compound value 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 and data before point and may ++resynchronize after an error by moving point." ++ ++ (list buffer ++ ;; Terminator stack: a stack of characters that indicate the ++ ;; end of the compound values enclosing point ++ '() ++ ;; Next: One of ++ ;; * 'expect-value if the next token must be a value, but a ++ ;; value has not yet been reached ++ ;; * 'value if point is at the beginning of a value ++ ;; * 'expect-comma if the next token must be a comma ++ 'expect-value ++ ;; Allow terminator: non-nil if the next token may be a ++ ;; terminator ++ nil ++ ;; Partial parse position: If state is 'value, a marker for ++ ;; the position of the partial parser or nil if no partial ++ ;; parsing has happened yet ++ nil ++ ;; Partial parse state: If state is 'value, the current ++ ;; `parse-partial-sexp' state ++ nil)) ++ ++(defmacro notmuch-json-buffer (jp) `(first ,jp)) ++(defmacro notmuch-json-term-stack (jp) `(second ,jp)) ++(defmacro notmuch-json-next (jp) `(third ,jp)) ++(defmacro notmuch-json-allow-term (jp) `(fourth ,jp)) ++(defmacro notmuch-json-partial-pos (jp) `(fifth ,jp)) ++(defmacro notmuch-json-partial-state (jp) `(sixth ,jp)) ++ ++(defvar notmuch-json-syntax-table ++ (let ((table (make-syntax-table))) ++ ;; The standard syntax table is what we need except that "." needs ++ ;; to have word syntax instead of punctuation syntax. ++ (modify-syntax-entry ?. "w" table) ++ table) ++ "Syntax table used for incremental JSON parsing.") ++ ++(defun notmuch-json-scan-to-value (jp) ++ ;; Helper function that consumes separators, terminators, and ++ ;; whitespace from point. Returns nil if it successfully reached ++ ;; the beginning of a value, 'end if it consumed a terminator, or ++ ;; 'retry if not enough input was available to reach a value. Upon ++ ;; nil return, (notmuch-json-next jp) is always 'value. ++ ++ (if (eq (notmuch-json-next jp) 'value) ++ ;; We're already at a value ++ nil ++ ;; Drive the state toward 'expect-value ++ (skip-chars-forward " \t\r\n") ++ (or (when (eobp) 'retry) ++ ;; Test for the terminator for the current compound ++ (when (and (notmuch-json-allow-term jp) ++ (eq (char-after) (car (notmuch-json-term-stack jp)))) ++ ;; Consume it and expect a comma or terminator next ++ (forward-char) ++ (setf (notmuch-json-term-stack jp) (cdr (notmuch-json-term-stack jp)) ++ (notmuch-json-next jp) 'expect-comma ++ (notmuch-json-allow-term jp) t) ++ 'end) ++ ;; Test for a separator ++ (when (eq (notmuch-json-next jp) 'expect-comma) ++ (when (/= (char-after) ?,) ++ (signal 'json-readtable-error (list "expected ','"))) ++ ;; Consume it, switch to 'expect-value, and disallow a ++ ;; terminator ++ (forward-char) ++ (skip-chars-forward " \t\r\n") ++ (setf (notmuch-json-next jp) 'expect-value ++ (notmuch-json-allow-term jp) nil) ++ ;; We moved point, so test for eobp again and fall through ++ ;; to the next test if there's more input ++ (when (eobp) 'retry)) ++ ;; Next must be 'expect-value and we know this isn't ++ ;; whitespace, EOB, or a terminator, so point must be on a ++ ;; value ++ (progn ++ (assert (eq (notmuch-json-next jp) 'expect-value)) ++ (setf (notmuch-json-next jp) 'value) ++ nil)))) ++ ++(defun notmuch-json-begin-compound (jp) ++ "Parse the beginning of a compound value and traverse inside it. ++ ++Returns 'retry if there is insufficient input to parse the ++beginning of the compound. If this is able to parse the ++beginning of a compound, it moves point past the token that opens ++the compound and returns t. Later calls to `notmuch-json-read' ++will return the compound's elements. ++ ++Entering JSON objects is currently unimplemented." ++ ++ (with-current-buffer (notmuch-json-buffer jp) ++ ;; Disallow terminators ++ (setf (notmuch-json-allow-term jp) nil) ++ (or (notmuch-json-scan-to-value jp) ++ (if (/= (char-after) ?\[) ++ (signal 'json-readtable-error (list "expected '['")) ++ (forward-char) ++ (push ?\] (notmuch-json-term-stack jp)) ++ ;; Expect a value or terminator next ++ (setf (notmuch-json-next jp) 'expect-value ++ (notmuch-json-allow-term jp) t) ++ t)))) ++ ++(defun notmuch-json-read (jp) ++ "Parse the value at point in JP's buffer. ++ ++Returns 'retry if there is insufficient input to parse a complete ++JSON value (though it may still move point over separators or ++whitespace). If the parser is currently inside a compound value ++and the next token ends the list or object, 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-json-buffer jp) ++ (or ++ ;; Get to a value state ++ (notmuch-json-scan-to-value jp) ++ ++ ;; Can we parse a complete value? ++ (let ((complete ++ (if (looking-at "[-+0-9tfn]") ++ ;; This is a number or a keyword, so the partial ++ ;; parser isn't going to help us because a truncated ++ ;; number or keyword looks like a complete symbol to ++ ;; it. Look for something that clearly ends it. ++ (save-excursion ++ (skip-chars-forward "^]},: \t\r\n") ++ (not (eobp))) ++ ++ ;; We're looking at a string, object, or array, which we ++ ;; can partial parse. If we just reached the value, set ++ ;; up the partial parser. ++ (when (null (notmuch-json-partial-state jp)) ++ (setf (notmuch-json-partial-pos jp) (point-marker))) ++ ++ ;; Extend the partial parse until we either reach EOB or ++ ;; get the whole value ++ (save-excursion ++ (let ((pstate ++ (with-syntax-table notmuch-json-syntax-table ++ (parse-partial-sexp ++ (notmuch-json-partial-pos jp) (point-max) 0 nil ++ (notmuch-json-partial-state jp))))) ++ ;; A complete value is available if we've reached ++ ;; depth 0 or less and encountered a complete ++ ;; subexpression. ++ (if (and (<= (first pstate) 0) (third pstate)) ++ t ++ ;; Not complete. Update the partial parser state ++ (setf (notmuch-json-partial-pos jp) (point-marker) ++ (notmuch-json-partial-state jp) pstate) ++ nil)))))) ++ ++ (if (not complete) ++ 'retry ++ ;; We have a value. Reset the partial parse state and expect ++ ;; a comma or terminator after the value. ++ (setf (notmuch-json-next jp) 'expect-comma ++ (notmuch-json-allow-term jp) t ++ (notmuch-json-partial-pos jp) nil ++ (notmuch-json-partial-state jp) nil) ++ ;; Parse the value ++ (let ((json-object-type 'plist) ++ (json-array-type 'list) ++ (json-false nil)) ++ (json-read))))))) ++ ++(defun notmuch-json-eof (jp) ++ "Signal a json-error if there is more data in JP'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-json-buffer jp) ++ (skip-chars-forward " \t\r\n") ++ (unless (eobp) ++ (signal 'json-error (list "Trailing garbage following JSON data"))))) ++ + (provide 'notmuch-lib) + + ;; Local Variables: +-- +1.7.10 +