Context

type Context = { view: DataView; index: number; }

A Context is used to keep record of the input being parsed and the current parsing position within that input.

The view is the actual input, transformed into an array of bytes wrapped in a DataView. Kessel deals in UTF-8 characters, which may be anywhere between one and four bytes per character, and using an array of bytes to represent the input lets Kessel deal with the variable-length characters in the most flexible manner.

The index is a byte-based index (as opposed to the output of error messages, which is character-based). Kessel ensures that, as long as the byte array is properly formed (i.e., that someone didn't pass in bytes that don't actually represent real characters), it will always have index pointing at the first byte of the next character.

Contexts should be created using the functions okReply, failReply, and fatalReplybecause they ensure that no older contexts are overwritten (which can become important in nested and compound errors, which keep multiple contexts).

Properties

• view: A DataView representing the input text. This view is created by the parsing functions parse and run from any of the legal types of input.
• index: A pointer that marks the current location in the view. The next byte read by a parser will be the byte at that location.

See Also

• Reply
• failReply
• fatalReply
• okReply
• parse
• run