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| -rw-r--r-- | emacs/notmuch-lib.el | 197 |
1 files changed, 197 insertions, 0 deletions
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: |