Mostly "working". More so on the "Getting it work side" at the moment, needs cleaning up.

doldoc.py

#!/usr/bin/env python3
"""
Written by Kyler "Félix" Eastridge for the TempleOS community.

This is free and unencumbered software released into the public domain.

Anyone is free to copy, modify, publish, use, compile, sell, or
distribute this software, either in source code form or as a compiled
binary, for any purpose, commercial or non-commercial, and by any
means.

In jurisdictions that recognize copyright laws, the author or authors
of this software dedicate any and all copyright interest in the
software to the public domain. We make this dedication for the benefit
of the public at large and to the detriment of our heirs and
successors. We intend this dedication to be an overt act of
relinquishment in perpetuity of all present and future rights to this
software under copyright law.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

For more information, please refer to <https://unlicense.org>
"""

import struct
import io
import argparse

class DolDocError(BaseException):
    pass

class DolDocElement:
    def __init__(self, name, id):
        self.name = name
        self.id = id
    
    def __str__(self):
        return self.name
    
    def __repr__(self):
        return "<DolDocElement {}>".format(self)
    
    @classmethod
    def fromStream(cls, name, id, stream):
        self = cls(name, id)
        return self
    
    @classmethod
    def fromBytes(cls, name, id, data):
        buffer = io.BytesIO(data)
        buffer.seek(0)
        return cls.fromStream(name, id, buffer)

class DolDocElementEnd(DolDocElement):
    def __str__(self):
        return "END"

class DolDocElementColor(DolDocElement):
    colors = [
        "BLACK", "BLUE", "GREEN", "CYAN", "RED", "PURPLE",
        "BROWN", "LTGRAY", "DKGRAY", "LTBLUE", "LTGREEN",
        "LTCYAN", "LTRED", "LTPURPLE", "YELLOW", "WHITE"
    ]
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.color = 0
    
    def __str__(self):
        return "{} {}".format(self.name, self.colors[self.color])
    
    @classmethod
    def fromStream(cls, name, id, stream):
        self = cls(name, id)
        self.color = stream.read(1)[0]
        return self

class DolDocElementCircle(DolDocElement):
    #X, Y, Radius
    sCircle = struct.Struct("<iii")
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.x = 0
        self.y = 0
        self.radius = 0
    
    def __str__(self):
        return "{} ({}, {}):{}R".format(self.name, self.x, self.y, self.radius)
    
    @classmethod
    def fromStream(cls, name, id, stream):
        self = cls(name, id)
        self.x, self.y, self.radius = self.sCircle.unpack(
            stream.read(self.sCircle.size)
        )
        return self

class DolDocElementLine(DolDocElement):
    #X1, Y1, X2, Y2
    sLine = struct.Struct("<iiii")
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.x1 = 0
        self.y1 = 0
        self.x2 = 0
        self.y2 = 0
    
    def __str__(self):
        return "{} ({}, {}), ({}, {})".format(self.name, self.x1, self.y1, self.x2, self.y2)
    
    @classmethod
    def fromStream(cls, name, id, stream):
        self = cls(name, id)
        self.x1, self.y1, self.x2, self.y2 = \
            self.sLine.unpack(
                stream.read(self.sLine.size)
            )
        return self

class DolDocElementFloodFill(DolDocElement):
    #X, Y
    sFloodFill = struct.Struct("<ii")
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.x = 0
        self.y = 0
    
    def __str__(self):
        return "{} ({}, {})".format(self.name, self.x, self.y)
    
    @classmethod
    def fromStream(cls, name, id, stream):
        self = cls(name, id)
        self.x, self.y = self.sFloodFill.unpack(
            stream.read(self.sFloodFill.size)
        )
        return self

class DolDocElementThick(DolDocElement):
    sThickness = struct.Struct("<i")
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.thickness = 0
    
    def __str__(self):
        return "{} {}".format(self.name, self.thickness)
    
    @classmethod
    def fromStream(cls, name, id, stream):
        self = cls(name, id)
        self.thickness, = self.sThickness.unpack(
            stream.read(self.sThickness.size)
        )
        return self

class DolDocElementMesh(DolDocElement):
    #Vertice count, Triangle count
    sMeshHeader = struct.Struct("<ii")
    
    #X, Y, Z
    sVertex = struct.Struct("<iii")
    
    #Color, A, B, C
    sTriangle = struct.Struct("<iiii")
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.vertices = []
        self.triangles = []
    
    def __str__(self):
        return "{} {}V,{}T".format(self.name, len(self.vertices), len(self.triangles))
    
    @classmethod
    def fromStream(cls, name, id, stream):
        self = cls(name, id)
        vertex_cnt, tri_cnt = self.sMeshHeader.unpack(
            stream.read(self.sMeshHeader.size)
        )
        self.vertices = [None] * vertex_cnt
        for i in range(vertex_cnt):
            self.vertices[i] = self.sVertex.unpack(
                stream.read(self.sVertex.size)
            )
        
        self.triangles = [None] * tri_cnt
        for i in range(tri_cnt):
            self.triangles[i] = self.sTriangle.unpack(
                stream.read(self.sTriangle.size)
            )
        return self

class DolDocElementPoint(DolDocElement):
    #x, y, z(?)
    sPoint = struct.Struct("<iii")
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.x = 0
        self.y = 0
        self.z = 0
    
    def __str__(self):
        return "{} ({},{})".format(self.name, self.x, self.y)
    
    @classmethod
    def fromStream(cls, name, id, stream):
        self = cls(name, id)
        self.x, self.y, self.z = self.sPoint.unpack(
            stream.read(self.sPoint.size)
        )
        return self

class DolDocElementText(DolDocElement):
    sTextHeader = struct.Struct("<ii")
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.x = 0
        self.y = 0
        self.text = b""
    
    def __str__(self):
        return "{} {},{}:{}".format(self.name, self.x, self.y, self.text)
    
    @classmethod
    def fromStream(cls, name, id, stream):
        self = cls(name, id)
        self.x, self.y = self.sTextHeader.unpack(
            stream.read(self.sTextHeader.size)
        )
        self.text = b""
        while True:
            v = stream.read(1)
            if v == b"\0":
                break
            self.text += v
        
        return self


class DolDocElementBitMap(DolDocElement):
    sBitMapHeader = struct.Struct("<iiii")
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.x = 0
        self.y = 0
        self.width = 0
        self.height = 0
        self.data = []
    
    def __str__(self):
        return "{} ({},{}):{}W,{}H".format(self.name, self.x, self.y, self.width, self.height)
    
    @classmethod
    def fromStream(cls, name, id, stream):
        self = cls(name, id)
        self.x, self.y, self.width, self.height = self.sBitMapHeader.unpack(
            stream.read(self.sBitMapHeader.size)
        )
        
        #TODO: Unpack this further.
        #It should be a left = pixel >> 4, right = pixel & 0xF
        self.data = stream.read(self.width*self.height)
        return self


class DolDocElementArrow(DolDocElement):
    #X1, Y1, X2, Y2
    sArrow = struct.Struct("<iiii")
    
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        self.x1 = 0
        self.y1 = 0
        self.x2 = 0
        self.y2 = 0
    
    def __str__(self):
        return "{} ({}, {}), ({}, {})".format(self.name, self.x1, self.y1, self.x2, self.y2)
    
    @classmethod
    def fromStream(cls, name, id, stream):
        self = cls(name, id)
        self.x1, self.y1, self.x2, self.y2 = \
            self.sArrow.unpack(
                stream.read(self.sArrow.size)
            )
        return self

DolDocTypes = {
    "End": DolDocElementEnd,
    "Color": DolDocElementColor,
    "Thick": DolDocElementThick,
    #"PlanarSymmetry": DolDocPlanarSymmetry,
    #"Transform": DolDocTransform,
    #"Shift": DolDocShift,
    "Pt": DolDocElementPoint, #FIXME: VERIFY
    #"PolyPt": DolDocPolyPt,
    "Line": DolDocElementLine,
    #"PolyLine": DolDocElementPolyLine,
    #"Rect": DolDocRect,
    "Circle": DolDocElementCircle,
    #"Ellipse": DolDocEllipse,
    #"Polygon": DolDocPolygon,
    #"BSpline2": DolDocBSpline2,
    #"BSpline3": DolDocBSpline3,
    "FloodFill": DolDocElementFloodFill,
    "BitMap": DolDocElementBitMap,
    "Mesh": DolDocElementMesh,
    "Arrow": DolDocElementArrow,
    "Text": DolDocElementText,
    #"TextBox": DolDocTextBox
    #"TextDiamond": DolDocTextDiamond
}

DolDocMapping = [
    ('End', 'End'),
    ('Color', 'Color'),
    ('Dither Color', 'Color'),
    ('Thick', 'Thick'),
    ('Planar Symmetry', 'PlanarSymmetry'),
    ('Transform On', 'Transform'),
    ('Transform Off', 'Transform'),
    ('Shift', 'Shift'),
    ('Point', 'Pt'),
    ('PolyPoint', 'PolyPt'),
    ('Line', 'Line'),
    ('PolyLine', 'PolyLine'),
    ('Rect', 'Rect'),
    ('Rotated Rect', 'Rect'),
    ('Circle', 'Circle'),
    ('Ellipse', 'Ellipse'),
    ('Polygon', 'Polygon'),
    ('BSpline2', 'BSpline2'),
    ('BSpline2 Closed', 'BSpline2'),
    ('BSpline3', 'BSpline3'),
    ('BSpline3 Closed', 'BSpline3'),
    ('Flood Fill', 'FloodFill'),
    ('Flood Fill Not Color', 'FloodFill'),
    ('BitMap', 'BitMap'),
    ('Mesh', 'Mesh'),
    ('Shiftable Mesh', 'Mesh'),
    ('Arrow', 'Arrow'),
    ('Text', 'Text'),
    ('Text Box', 'TextBox'),
    ('Text Diamond', 'TextDiamond')
]

class DolDocEntry:
    def __init__(self):
        self.elements = []
    
    @classmethod
    def fromStream(cls, stream):
        self = cls()
        i = 0
        while True:
            try:
                etype = stream.read(1)[0]
            except IndexError:
                raise DolDocError("EOF reached before End marker!")
            
            if etype > len(DolDocMapping):
                raise DolDocError("Don't know what type {} at {} is!".format(etype, stream.tell()))
            
            name = DolDocMapping[etype][0]
            cls = DolDocMapping[etype][1]
            if cls not in DolDocTypes:
                raise DolDocError("Don't know how to decode {} at {}!".format(cls, stream.tell()))
            
            elm = DolDocTypes[cls].fromStream(name, etype, stream)
            
            self.elements.append(elm)
            print(elm)
            if elm.name == "End":
                break
        
        return self
    
    @classmethod
    def fromBytes(cls, data):
        buffer = io.BytesIO(data)
        buffer.seek(0)
        return cls.fromStream(buffer)

class DolDoc:
    sDolDocEntry = struct.Struct("<IIII")
    def __init__(self, text = "", chunks = None):
        self.text = text
        self.chunks = chunks or []
    
    @classmethod
    def load(cls, handle):
        self = cls()
        buffer = b""
        while True:
            c = handle.read(1)
            if not c or c == b"\0":
                break
            buffer += c
        
        self.text = buffer
        while True:
            data = handle.read(self.sDolDocEntry.size)
            if not data:
                break
            chunkId, flags, size, refCount \
                = self.sDolDocEntry.unpack(data)
            data = handle.read(size)
            self.chunks.append([
                chunkId,
                flags,
                size,
                refCount,
                DolDocEntry.fromBytes(data)
            ])
        return self

if __name__ == "__main__":
    # create the top-level parser
    parser = argparse.ArgumentParser()
    
    subparsers = parser.add_subparsers(help='sub-command help')

    # List
    parser_list = subparsers.add_parser("l", help='a help')
    parser_list.add_argument('file', nargs="+", type=argparse.FileType('rb'), help='Input file(s)')

    # Extract
    parser_extract = subparsers.add_parser("e", help='b help')
    parser_extract.add_argument('file', nargs="+", type=argparse.FileType('rb'), help='Input file(s)')
    parser_extract.add_argument('-o', '--output', nargs="+", type=argparse.FileType('rb'), help='Output directory')

    args = parser.parse_args()
    
    for file in args.file:
        print("# "+file.name)
        dd = DolDoc.load(file)
        file.close()