bms-js

BMS Parser for JavaScript

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A Be-Music Source file-format parser. It is made primarily for usage in Bemuse.

Usage

Documentation has been lacking. For now, please see issue 26 for preliminary usage notes.

BMS Parsing Stages

BMS will be parsed in three stages:

1. Use bms.Reader to turn a Buffer with BMS file content into a String.
   • Performs character set detection. Since BMS file encoding varies.
     • This part is done by bemusepack to convert BMS file into UTF-8.
2. Use bms.Compiler to compile the String into a BMSChart.
   • Syntax-level processing is done here, such as:
     • #RANDOM
     • #SETRANDOM
     • #SWITCH
   • Results in three primary data structures:
     • headers contains all BMS headers
     • objects contains all BMS objects on the timeline.
     • timeSignature contains the time signature information.
       • also allows converting from measure+fraction to beat
3. BMSChart contains all information needed to further process the song. These modules can then be used to extract information from BMSChart.
   • SongInfo allows looking up title, subtitle, artist, maker, and genre.
     • Implicit/multiplex subtitles taken into account here.
   • Timing allows conversion from beat to seconds.
     • BPM, BPM changes, STOP objects, and STP commands taken into account here.
   • Positioning allows conversion from beat to in-game position.
     • SPEED and SCROLL commands (BEMUSE's BMS extensions) taken into account here.
   • Notes parses the notechart, resulting in in-game notes.
     • Channel mapping is taken into consideration here.
     • Normal notes and long notes taken into account here.
     • Also emits list of notes to autoplay.

Other Utility Classes

• Speedcore allows calculation of position and velocity over a linear graph.