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Phase 37 datatypes plan

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Simon Dick edited this page Jun 20, 2026 · 1 revision

Phase 37 — amiga.datatypes (planned, low priority)

Part of the Amiga port design log.

Status: planned, low priority. Not yet started — this page is the scope sketch, to be expanded into a step plan when the phase is picked up.

Wrap datatypes.library (V39+) for universal file recognition. datatypes.library is AmigaOS's plug-in registry of file-format handlers (.datatype modules in SYS:Classes/DataTypes/); any running system knows about every datatype that's been installed on it.

from amiga import datatypes

# "What is this file?" — works for everything the system has a
# datatype for: PNG/JPEG/GIF/IFF ILBM, 8SVX/AIFF/WAV, ASCII/IFF FTXT,
# anim, etc.
info = datatypes.recognize("Work:Photos/holiday.jpg")
# {'group': 'picture', 'type': 'jpeg', 'name': 'JPEG (JFIF)'}

# Slightly more: full DTA_* attribute dump.
attrs = datatypes.info("Work:Photos/holiday.jpg")
# {'BaseName': 'JPEG', 'GroupID': 'pict', 'Width': 1280, 'Height': 720, ...}

Scope

  • amiga.datatypes.recognize(path) → dict with group, type, name. Uses ObtainDataTypeA(DTST_FILE, lock, NULL) then GetDTAttrs(DTA_BaseName, DTA_GroupID, DTA_Name), releases via ReleaseDataType.
  • amiga.datatypes.info(path) → dict. Same as recognize but also queries common attrs (DTA_NominalHoriz / _NominalVert for pictures, DTA_Duration / _SampleLength for sound, etc.) so callers can do quick metadata reads without NewDTObject.
  • amiga.datatypes.groups() → list of installed group IDs (one of "sound" / "picture" / "text" / "anim" / "system" / "document"). Iterates the dtl_* chain in DataTypesList.

Out of scope

  • NewDTObjectA / DoDTMethodA(DTM_DRAW) rendering — requires a RastPort and a target BitMap, plus colour-map handling for CLUT formats. That's a much larger surface (graphics.library BitMap wrappers + intuition Screen/Window plumbing) and the payoff for a MicroPython workload is narrow.
  • Save-as-other-format (DTM_WRITE) — same render-pipeline problem in reverse.
  • Audio playback (DTM_TRIGGER on sound datatypes) — needs AHI on modern hosts.
  • BOOPSI object exposure — NewDTObject returns an Object * that callers normally drive via SetDTAttrs / GetDTAttrs/DoDTMethod. Surfacing that as a Python type is a whole separate phase (one BOOPSI superclass per Python class).

Dependencies

  • datatypes.library v39+. Lazy open. The library is V39+ (OS 3.0) baseline — earlier Kickstarts simply skip the import (we already require V37 for things like lib_call, so V39 is a small bump but worth a clean OSError(MP_ENOSYS) if missing).

Files

ports/amiga/moddatatypes.c              — C module
ports/amiga/modules/amiga.py            — adds `import _datatypes as datatypes`
tests/ports/amiga/test_datatypes_smoke.py     — vamos arg-shape smoke

Variants: all three. ~2 KB text per variant.

Why "low priority"

recognize / info is genuinely useful but rarely on the critical path for a MicroPython script — file-type sniffing is more often done by reading the first few bytes (b"\x89PNG", b"\xff\xd8"). The big win is universal sniffing across formats the system has been taught about (third-party PNG / JPEG / WebP .datatypes), and that lives or dies by which datatypes are installed on the target host. Land Phase 35 / 36 first; pick up Phase 37 if a real caller shows up.

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