(require 'mm-view)
(require 'mm-decode)
+(require 'json)
(eval-when-compile (require 'cl))
(defvar notmuch-command "notmuch"
(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:
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