Module prolog 

Object types by prolog and the size walk over nibbles.

Prologs, type names and the rules for finding an object’s end: wiki: protocols/hp-object-format (RPLMAN chapter 3; the 49G types from the Conn4x sources; DOEXT0-4 from the 48 entry list). The names are those the calculator’s G D directory listing prints.

Structs

Record

One variable record of a directory body (wiki: hardware/hp48-system-ram “Directories”): a 5-nibble offset from this field back to the previous record’s name length field (0 for the first record), the name’s length n in 2 nibbles, its characters, n again (absent when n = 0), the object. Records lie oldest first; the directory’s offset field points at the newest.

Enums

ObjectType

Object types by prolog.

Constants

MAX_DEPTH

Deepest nesting the walks follow.

SEMI

SEMI, the end marker of composites (lists, programs, algebraics, units).

Functions

element_size

Size of an embedded object (composite element, tagged payload, directory variable): an object with a known prolog, else a 5-nibble ROM pointer.

object_size

Size in nibbles of the object at nibble at. Fails on an unknown prolog, a truncated object or nesting deeper than MAX_DEPTH.

read_field

The width-nibble field at at, low nibble first; None past the end or for fields wider than 8 nibbles.

records

The records of the directory body whose last-variable offset field is at offset_at (records follow it), in memory order (oldest first).