diff options
| -rw-r--r-- | emms-info-native.el | 145 |
1 files changed, 86 insertions, 59 deletions
diff --git a/emms-info-native.el b/emms-info-native.el index 9f0ed2d..97c1917 100644 --- a/emms-info-native.el +++ b/emms-info-native.el @@ -557,7 +557,8 @@ outside itself.") ("TRK" . "tracknumber") ("TRCK" . "tracknumber") ("TYE" . "year") - ("TYER" . "year")) + ("TYER" . "year") + ("TXXX" . user-defined)) "Mapping from id3v2 frame identifiers to EMMS info fields. Sources: @@ -572,6 +573,38 @@ Sources: (3 . utf-8)) "id3v2 text encodings.") +(defun emms-info-native--valid-id3v2-frame-id-p (id) + "Return t if ID is a proper id3v2 frame identifier, nil otherwise." + (if (= emms-info-native--id3v2-version 2) + (string-match "[A-Z0-9]\\{3\\}" id) + (string-match "[A-Z0-9]\\{4\\}" id))) + +(defun emms-info-native--checked-id3v2-size (elt bytes) + "Calculate id3v2 element ELT size from BYTES. +ELT must be either 'tag or 'frame. + +Return the size. Signal an error if the size is zero." + (let ((size (cond ((eq elt 'tag) + (emms-info-native--decode-id3v2-size bytes t)) + ((eq elt 'frame) + (if (= emms-info-native--id3v2-version 4) + (emms-info-native--decode-id3v2-size bytes t) + (emms-info-native--decode-id3v2-size bytes nil)))))) + (if (zerop size) + (error "id3v2 tag/frame size is zero") + size))) + +(defun emms-info-native--decode-id3v2-size (bytes syncsafe) + "Decode id3v2 element size from BYTES. +Depending on SYNCSAFE, BYTES are interpreted as 7- or 8-bit +bytes, MSB first. + +Return the decoded size." + (let ((num-bits (if syncsafe 7 8))) + (apply '+ (seq-map-indexed (lambda (elt idx) + (* (expt 2 (* num-bits idx)) elt)) + (reverse bytes))))) + (defun emms-info-native--decode-id3v2 (filename) "Read and decode id3v2 metadata from FILENAME. Return metadata in a list of (FIELD . VALUE) cons cells, or nil @@ -611,37 +644,10 @@ Return the size. Signal an error if the size is zero." (insert-file-contents-literally filename nil 10 14) (emms-info-native--checked-id3v2-size 'frame (buffer-string)))) -(defun emms-info-native--checked-id3v2-size (elt bytes) - "Calculate id3v2 element ELT size from BYTES. -ELT must be either 'tag or 'frame. - -Return the size. Signal an error if the size is zero." - (let ((size (cond ((eq elt 'tag) - (emms-info-native--decode-id3v2-size bytes t)) - ((eq elt 'frame) - (if (= emms-info-native--id3v2-version 4) - (emms-info-native--decode-id3v2-size bytes t) - (emms-info-native--decode-id3v2-size bytes nil)))))) - (if (zerop size) - (error "id3v2 tag/frame size is zero") - size))) - -(defun emms-info-native--decode-id3v2-size (bytes syncsafe) - "Decode id3v2 element size from BYTES. -Depending on SYNCSAFE, BYTES are interpreted as 7- or 8-bit -bytes, MSB first. - -Return the decoded size." - (let ((num-bits (if syncsafe 7 8))) - (apply '+ (seq-map-indexed (lambda (elt idx) - (* (expt 2 (* num-bits idx)) elt)) - (reverse bytes))))) - (defun emms-info-native--decode-id3v2-frames (filename begin end unsync) "Read and decode id3v2 text frames from FILENAME. -BEGIN should be the offset of first byte after id3v2 header and -extended header (if any), and END should be the offset after the -complete id3v2 tag. +BEGIN should be the offset of first byte of the first frame, and +END should be the offset after the complete id3v2 tag. If UNSYNC is t, the frames are assumed to have gone through unsynchronization and decoded as such. @@ -652,25 +658,13 @@ Return metadata in a list of (FIELD . VALUE) cons cells." comments) (condition-case nil (while (< offset limit) - (let* ((header (emms-info-native--decode-id3v2-frame-header filename - offset)) - (info-id (emms-info-native--id3v2-frame-info-id header)) - (decoded-size (bindat-get-field (cdr header) 'size))) - (setq offset (car header)) ;advance to frame data begin - (if (or unsync info-id) - ;; Note that if unsync is t, we have to always read a - ;; frame to gets its true size so that we can adjust - ;; offset correctly. - (let ((data (emms-info-native--read-id3v2-frame-data filename - offset - decoded-size - unsync))) - (setq offset (car data)) - (when info-id - (let ((value (emms-info-native--decode-id3v2-string (cdr data)))) - (push (cons info-id value) comments)))) - ;; Skip the frame. - (cl-incf offset decoded-size)))) + (let* ((frame-data (emms-info-native--decode-id3v2-frame filename + offset + unsync)) + (next-frame-offset (car frame-data)) + (comment (cdr frame-data))) + (when comment (push comment comments)) + (setq offset next-frame-offset))) (error nil)) comments)) @@ -678,11 +672,25 @@ Return metadata in a list of (FIELD . VALUE) cons cells." "Return the last decoded header size in bytes." (if (= emms-info-native--id3v2-version 2) 6 10)) -(defun emms-info-native--valid-id3v2-frame-id-p (id) - "Return t if ID is a proper id3v2 frame identifier, nil otherwise." - (if (= emms-info-native--id3v2-version 2) - (string-match "[A-Z0-9]\\{3\\}" id) - (string-match "[A-Z0-9]\\{4\\}" id))) +(defun emms-info-native--decode-id3v2-frame (filename offset unsync) + (let* ((header (emms-info-native--decode-id3v2-frame-header filename + offset)) + (info-id (emms-info-native--id3v2-frame-info-id header)) + (data-offset (car header)) + (size (bindat-get-field (cdr header) 'size))) + (if (or info-id unsync) + ;; Note that if unsync is t, we have to always read the frame + ;; to determine next-frame-offset. + (let* ((data (emms-info-native--read-id3v2-frame-data filename + data-offset + size + unsync)) + (next-frame-offset (car data)) + (value (emms-info-native--decode-id3v2-frame-data (cdr data) + info-id))) + (cons next-frame-offset value)) + ;; Skip the frame. + (cons (+ data-offset size) nil)))) (defun emms-info-native--decode-id3v2-frame-header (filename begin) "Read and decode id3v2 frame header from FILENAME. @@ -697,6 +705,12 @@ offset after the frame header, and FRAME is the decoded frame." (cons end (bindat-unpack emms-info-native--id3v2-frame-header-bindat-spec (buffer-string)))))) +(defun emms-info-native--id3v2-frame-info-id (frame) + "Return the emms-info identifier for FRAME. +If there is no such identifier, return nil." + (cdr (assoc (bindat-get-field frame 'id) + emms-info-native--id3v2-frame-to-info))) + (defun emms-info-native--read-id3v2-frame-data (filename begin num-bytes @@ -728,11 +742,24 @@ data." (insert-file-contents-literally filename nil begin end) (cons end (buffer-string)))))) -(defun emms-info-native--id3v2-frame-info-id (frame) - "Return the emms-info identifier for FRAME. -If there is no such identifier, return nil." - (cdr (assoc (bindat-get-field frame 'id) - emms-info-native--id3v2-frame-to-info))) +(defun emms-info-native--decode-id3v2-frame-data (data info-id) + "Decode id3v2 text frame data DATA. +If INFO-ID is `user-defined', assume that DATA is a TXXX frame +with key/value-pair. Extract the key and, if it is a mapped +element in `emms-info-native--id3v2-frame-to-info', use it as +INFO-ID. + +Return a cons cell (INFO-ID . VALUE) where VALUE is the decoded +string." + (when info-id + (let ((str (emms-info-native--decode-id3v2-string data))) + (cond ((stringp info-id) (cons info-id str)) + ((eq info-id 'user-defined) + (let* ((key-val (split-string str (string 0))) + (key (downcase (car key-val))) + (val (cadr key-val))) + (when (rassoc key emms-info-native--id3v2-frame-to-info) + (cons key val)))))))) (defun emms-info-native--decode-id3v2-string (bytes) "Decode id3v2 text information from BYTES. |