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Article contents:== taglib [[toc:]] === Introduction This egg provides a usable subset of bindings to the [[https://taglib.org/|taglib]] library. === Author Vasilij Schneidermann === Repository [[https://depp.brause.cc/taglib]] === Current state of the bindings The egg does intentionally not use taglib's C API as is due to incompatibilities with the CHICKEN FFI. For this reason the bindings are modeled after its C API with the following differences: * Only UTF-8 strings are supported, there is no flag to switch between UTF-8 and Latin-1 * Memory management immediately frees strings, there is no option to defer garbage collection of strings * The API exclusively operates on {{TagLib::File}} instances, represented as {{taglib-file}} records * The raw tag property API is supported in addition to the audio property and tag property API, it permits retrieving and setting more than the standard set of tag properties === Requirements Install the taglib library with your operating system's package manager. === API Note that due to pervasive use of {{and-let*}} all API calls will return {{#f}} if the {{FILE}} argument's resources have been freed. ==== File management ===== file-open <procedure>(file-open PATH)</procedure> Opens an audio file the {{PATH}} string points to. If successful, a {{taglib-file}} record is returned which is used in all subsequent API calls, otherwise {{#f}}. ===== file-valid? <procedure>(file-valid? FILE)</procedure> Returns {{#t}} if {{FILE}} is a {{taglib-file}} record and readable, otherwise {{#f}}. ===== file-save! <procedure>(file-save! FILE)</procedure> Stores changes made by the setter procedures to the file backing {{FILE}}. ===== file-free! <procedure>(file-free! FILE)</procedure> Frees the resources associated with {{FILE}} if any. This procedure is used as finalizer for {{taglib-file}} records, therefore it's not necessary to call it manually, but can be done anyway. ==== Audio properties ===== audio-property <procedure>(audio-property FILE KEY)</procedure> Returns an audio property for {{FILE}}, either a number or {{#f}} if it couldn't be detected. {{KEY}} must be one of the following symbols: ; {{length}} : Length in seconds with millisecond precision ; {{bitrate}} : Bit rate in kb/s ; {{samplerate}} : Sample rate in Hz ; {{channels}} : Number of channels ===== audio-properties <procedure>(audio-properties FILE)</procedure> Returns an alist of all audio properties for {{FILE}}. The keys are {{(length bitrate samplerate channels)}}, the values are the same as if obtained by using {{audio-property}}. ==== Tag properties ===== tag-property / tag-property-set! <procedure>(tag-property FILE KEY)</procedure> <procedure>(tag-property-set! FILE KEY VALUE)</procedure> <setter>(set! (tag-property FILE KEY) VALUE)</setter> Returns or sets a tag property for {{FILE}}. {{KEY}} must be one of the following symbols: ; {{title}} : Title (string) ; {{artist}} : Artist (string) ; {{album}} : Album (string) ; {{comment}} : Comment (string) ; {{genre}} : Genre (string) ; {{year}} : Year (number) ; {{track}} : Track (number) A return value of {{#f}} indicates an unset property. Likewise {{#f}} can be used as {{VALUE}} to clear a property. ===== tag-properties <procedure>(tag-properties FILE)</procedure> Returns an alist of all tag properties for {{FILE}}. The keys are {{(title artist album comment genre year track)}}, the values the same as if obtained by using {{tag-property}}. ==== Raw tag properties ===== raw-tag-property-exists? <procedure>(raw-tag-property-exists? FILE KEY)</procedure> Returns {{#t}} if {{FILE}} contains the raw tag property {{KEY}}, otherwise {{#f}}. {{KEY}} must be a string. ===== raw-tag-property / raw-tag-property-set! <procedure>(raw-tag-property FILE KEY)</procedure> <procedure>(raw-tag-property-set! FILE KEY VALUES)</procedure> <setter>(set! (raw-tag-property FILE KEY) VALUES)</setter> Returns or sets a list of string values in {{FILE}} for the raw tag property {{KEY}}. {{KEY}} must be a string. {{VALUES}} is a list of strings. An unset property is represented as the empty list. ===== raw-tag-property-clear! <procedure>(raw-tag-property-clear! FILE KEY)</procedure> Clears the raw tag property in {{FILE}} for {{KEY}}. {{KEY}} must be a string. ===== raw-tag-properties / raw-tag-properties-set! <procedure>(raw-tag-properties FILE)</procedure> <procedure>(raw-tag-properties-set! FILE PROPERTIES)</procedure> <setter>(set! (raw-tag-properties FILE) PROPERTIES)</setter> Returns or sets an alist of raw tag properties for {{FILE}}. {{PROPERTIES}} is an alist where each key is a string and each value a non-empty list of strings. === Examples <enscript highlight="scheme"> (import scheme) (import (chicken base)) (import (chicken pretty-print)) (import (chicken process-context)) (import (chicken string)) (import (prefix taglib taglib:)) (define (with-unit value unit) (if value (string-append (->string value) unit) "unknown")) (define (inexact arg) (and (number? arg) (exact->inexact arg))) (for-each (lambda (path) (let ((file (taglib:file-open path))) (when (and file (taglib:file-valid? file)) (print "Processing: " path "...") (print "Length: " (with-unit (inexact (taglib:audio-property file 'length)) "s")) (print "Bitrate: " (with-unit (taglib:audio-property file 'bitrate) "kb/s")) (print "Samplerate: " (with-unit (taglib:audio-property file 'samplerate) "Hz")) (print "Channels: " (or (taglib:audio-property file 'channels) "unknown")) (print "Title: " (or (taglib:tag-property file 'title) "unknown")) (print "Artist: " (or (taglib:tag-property file 'artist) "unknown")) (print "Album: " (or (taglib:tag-property file 'album) "unknown")) (print "Comment: " (or (taglib:tag-property file 'comment) "unknown")) (print "Genre: " (or (taglib:tag-property file 'genre) "unknown")) (print "Year: " (or (taglib:tag-property file 'year) "unknown")) (print "Track: " (or (taglib:tag-property file 'track) "unknown")) (for-each (lambda (property) (let ((key (car property)) (values (cdr property))) (print key ": " (string-intersperse values ",")))) (taglib:raw-tag-properties file))))) (command-line-arguments)) </enscript> Further examples can be found [[https://depp.brause.cc/taglib/examples|in the repository]]. === License Copyright 2019 Vasilij Schneidermann This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This library 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 Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with this library; if not, write to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA === Version history ==== 0.2.4 * Use {{taglib-config}} instead of {{pkg-config}} ==== 0.2.2 * Fix build warnings ==== 0.2.1 * Print build script call, abort on non-zero exit ==== 0.2 * Quote build script variables on Windows ==== 0.1 * Initial release Description of your changes:

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