Compressed resource data in 'dcmp' (1) format,
as stored in compressed resources with header type 8 and decompressor ID 1.
The 'dcmp' (1) decompressor resource is included in the System file of System 7.0 and later.
This compression format is used for a few compressed resources in System 7.0's files
(such as the Finder Help file).
This decompressor is also included with and used by some other Apple applications,
such as ResEdit.
(Note: ResEdit includes the 'dcmp' (1) resource,
but none of its resources actually use this decompressor.)
This compression format supports some basic general-purpose compression schemes, including backreferences to previous data and run-length encoding. It also includes some types of compression tailored specifically to Mac OS resources, including a set of single-byte codes that correspond to entries in a hard-coded lookup table.
The 'dcmp' (0) compression format (see dcmp_0.ksy) is very similar to this format,
with the main difference that it operates mostly on units of 2 or 4 bytes.
This makes the ``dcmp' (0)format more suitable for word-aligned data, such as executable code, bitmaps, sounds, etc. The'dcmp' (0)` format also appears to be generally preferred over `'dcmp' (1)`,
with the latter only being used in resource files that contain mostly unaligned data,
such as text.
This page hosts a formal specification of Compressed Macintosh resource data, Apple `'dcmp' (1)` format using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for Java generated by Kaitai Struct depends on the Java runtime library. You have to install it before you can parse data.
The Java runtime library is published in the Maven Central Repository. Refer to the artifact page for instructions how to add it into your project with the build tool that you use.
Parse a local file and get structure in memory:
Dcmp1 data = Dcmp1.fromFile("path/to/local/file.bin");
Or parse structure from a byte array:
byte[] someArray = new byte[] { ... };
Dcmp1 data = new Dcmp1(new ByteBufferKaitaiStream(someArray));
After that, one can get various attributes from the structure by invoking getter methods like:
data.chunks() // => The sequence of chunks that make up the compressed data.
// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
import io.kaitai.struct.ByteBufferKaitaiStream;
import io.kaitai.struct.KaitaiStruct;
import io.kaitai.struct.KaitaiStream;
import java.io.IOException;
import java.util.ArrayList;
import java.util.Map;
import java.util.HashMap;
import java.util.Arrays;
/**
* Compressed resource data in `'dcmp' (1)` format,
* as stored in compressed resources with header type `8` and decompressor ID `1`.
*
* The `'dcmp' (1)` decompressor resource is included in the System file of System 7.0 and later.
* This compression format is used for a few compressed resources in System 7.0's files
* (such as the Finder Help file).
* This decompressor is also included with and used by some other Apple applications,
* such as ResEdit.
* (Note: ResEdit includes the `'dcmp' (1)` resource,
* but none of its resources actually use this decompressor.)
*
* This compression format supports some basic general-purpose compression schemes,
* including backreferences to previous data and run-length encoding.
* It also includes some types of compression tailored specifically to Mac OS resources,
* including a set of single-byte codes that correspond to entries in a hard-coded lookup table.
*
* The `'dcmp' (0)` compression format (see dcmp_0.ksy) is very similar to this format,
* with the main difference that it operates mostly on units of 2 or 4 bytes.
* This makes the ``dcmp' (0)` format more suitable for word-aligned data,
* such as executable code, bitmaps, sounds, etc.
* The `'dcmp' (0)` format also appears to be generally preferred over `'dcmp' (1)`,
* with the latter only being used in resource files that contain mostly unaligned data,
* such as text.
* @see <a href="https://github.com/dgelessus/python-rsrcfork/blob/f891a6e/src/rsrcfork/compress/dcmp1.py">Source</a>
*/
public class Dcmp1 extends KaitaiStruct {
public static Dcmp1 fromFile(String fileName) throws IOException {
return new Dcmp1(new ByteBufferKaitaiStream(fileName));
}
public Dcmp1(KaitaiStream _io) {
this(_io, null, null);
}
public Dcmp1(KaitaiStream _io, KaitaiStruct _parent) {
this(_io, _parent, null);
}
public Dcmp1(KaitaiStream _io, KaitaiStruct _parent, Dcmp1 _root) {
super(_io);
this._parent = _parent;
this._root = _root == null ? this : _root;
_read();
}
private void _read() {
this.chunks = new ArrayList<Chunk>();
{
Chunk _it;
int i = 0;
do {
_it = new Chunk(this._io, this, _root);
this.chunks.add(_it);
i++;
} while (!(_it.tag() == 255));
}
}
/**
* A single chunk of compressed data.
* Each chunk in the compressed data expands to a sequence of bytes in the uncompressed data,
* except when `tag == 0xff`,
* which marks the end of the data and does not correspond to any bytes in the uncompressed data.
*
* Most chunks are stateless and always expand to the same data,
* regardless of where the chunk appears in the sequence.
* However,
* some chunks affect the behavior of future chunks,
* or expand to different data depending on which chunks came before them.
*/
public static class Chunk extends KaitaiStruct {
public static Chunk fromFile(String fileName) throws IOException {
return new Chunk(new ByteBufferKaitaiStream(fileName));
}
public enum TagKind {
INVALID(-1),
LITERAL(0),
BACKREFERENCE(1),
TABLE_LOOKUP(2),
EXTENDED(3),
END(4);
private final long id;
TagKind(long id) { this.id = id; }
public long id() { return id; }
private static final Map<Long, TagKind> byId = new HashMap<Long, TagKind>(6);
static {
for (TagKind e : TagKind.values())
byId.put(e.id(), e);
}
public static TagKind byId(long id) { return byId.get(id); }
}
public Chunk(KaitaiStream _io) {
this(_io, null, null);
}
public Chunk(KaitaiStream _io, Dcmp1 _parent) {
this(_io, _parent, null);
}
public Chunk(KaitaiStream _io, Dcmp1 _parent, Dcmp1 _root) {
super(_io);
this._parent = _parent;
this._root = _root;
_read();
}
private void _read() {
this.tag = this._io.readU1();
{
TagKind on = ( ((tag() >= 0) && (tag() <= 31)) ? TagKind.LITERAL : ( ((tag() >= 32) && (tag() <= 207)) ? TagKind.BACKREFERENCE : ( ((tag() >= 208) && (tag() <= 209)) ? TagKind.LITERAL : (tag() == 210 ? TagKind.BACKREFERENCE : ( ((tag() >= 213) && (tag() <= 253)) ? TagKind.TABLE_LOOKUP : (tag() == 254 ? TagKind.EXTENDED : (tag() == 255 ? TagKind.END : TagKind.INVALID)))))));
if (on != null) {
switch (( ((tag() >= 0) && (tag() <= 31)) ? TagKind.LITERAL : ( ((tag() >= 32) && (tag() <= 207)) ? TagKind.BACKREFERENCE : ( ((tag() >= 208) && (tag() <= 209)) ? TagKind.LITERAL : (tag() == 210 ? TagKind.BACKREFERENCE : ( ((tag() >= 213) && (tag() <= 253)) ? TagKind.TABLE_LOOKUP : (tag() == 254 ? TagKind.EXTENDED : (tag() == 255 ? TagKind.END : TagKind.INVALID)))))))) {
case EXTENDED: {
this.body = new ExtendedBody(this._io, this, _root);
break;
}
case LITERAL: {
this.body = new LiteralBody(this._io, this, _root, tag());
break;
}
case END: {
this.body = new EndBody(this._io, this, _root);
break;
}
case TABLE_LOOKUP: {
this.body = new TableLookupBody(this._io, this, _root, tag());
break;
}
case BACKREFERENCE: {
this.body = new BackreferenceBody(this._io, this, _root, tag());
break;
}
}
}
}
}
/**
* The body of a literal data chunk.
*
* The data that this chunk expands to is stored literally in the body (`literal`).
* Optionally,
* the literal data may also be stored for use by future backreference chunks (`do_store`).
*/
public static class LiteralBody extends KaitaiStruct {
public LiteralBody(KaitaiStream _io, int tag) {
this(_io, null, null, tag);
}
public LiteralBody(KaitaiStream _io, Dcmp1.Chunk _parent, int tag) {
this(_io, _parent, null, tag);
}
public LiteralBody(KaitaiStream _io, Dcmp1.Chunk _parent, Dcmp1 _root, int tag) {
super(_io);
this._parent = _parent;
this._root = _root;
this.tag = tag;
_read();
}
private void _read() {
if (isLenLiteralSeparate()) {
this.lenLiteralSeparate = this._io.readU1();
}
this.literal = this._io.readBytes(lenLiteral());
}
private Boolean doStore;
/**
* Whether this literal should be stored for use by future backreference chunks.
*
* See the documentation of the `backreference_body` type for details about backreference chunks.
*/
public Boolean doStore() {
if (this.doStore != null)
return this.doStore;
boolean _tmp = (boolean) ((isLenLiteralSeparate() ? tag() == 209 : (tag() & 16) != 0));
this.doStore = _tmp;
return this.doStore;
}
private Integer lenLiteralM1InTag;
/**
* The part of the tag byte that indicates the length of the literal data,
* in bytes,
* minus one.
*
* If the tag byte is 0xd0 or 0xd1,
* the length is stored in a separate byte after the tag byte and before the literal data.
*/
public Integer lenLiteralM1InTag() {
if (this.lenLiteralM1InTag != null)
return this.lenLiteralM1InTag;
if (!(isLenLiteralSeparate())) {
int _tmp = (int) ((tag() & 15));
this.lenLiteralM1InTag = _tmp;
}
return this.lenLiteralM1InTag;
}
private Boolean isLenLiteralSeparate;
/**
* Whether the length of the literal is stored separately from the tag.
*/
public Boolean isLenLiteralSeparate() {
if (this.isLenLiteralSeparate != null)
return this.isLenLiteralSeparate;
boolean _tmp = (boolean) (tag() >= 208);
this.isLenLiteralSeparate = _tmp;
return this.isLenLiteralSeparate;
}
private Integer lenLiteral;
/**
* The length of the literal data,
* in bytes.
*
* In practice,
* this value is always greater than zero,
* as there is no use in storing a zero-length literal.
*/
public Integer lenLiteral() {
if (this.lenLiteral != null)
return this.lenLiteral;
int _tmp = (int) ((isLenLiteralSeparate() ? lenLiteralSeparate() : (lenLiteralM1InTag() + 1)));
this.lenLiteral = _tmp;
return this.lenLiteral;
}
private Integer lenLiteralSeparate;
private byte[] literal;
private int tag;
private Dcmp1 _root;
private Dcmp1.Chunk _parent;
/**
* The length of the literal data,
* in bytes.
*
* This field is only present if the tag byte is 0xd0 or 0xd1.
* In practice,
* this only happens if the length is 0x11 or greater,
* because smaller lengths can be encoded into the tag byte.
*/
public Integer lenLiteralSeparate() { return lenLiteralSeparate; }
/**
* The literal data.
*/
public byte[] literal() { return literal; }
/**
* The tag byte preceding this chunk body.
*/
public int tag() { return tag; }
public Dcmp1 _root() { return _root; }
public Dcmp1.Chunk _parent() { return _parent; }
}
/**
* The body of a backreference chunk.
*
* This chunk expands to the data stored in a preceding literal chunk,
* indicated by an index number (`index`).
*/
public static class BackreferenceBody extends KaitaiStruct {
public BackreferenceBody(KaitaiStream _io, int tag) {
this(_io, null, null, tag);
}
public BackreferenceBody(KaitaiStream _io, Dcmp1.Chunk _parent, int tag) {
this(_io, _parent, null, tag);
}
public BackreferenceBody(KaitaiStream _io, Dcmp1.Chunk _parent, Dcmp1 _root, int tag) {
super(_io);
this._parent = _parent;
this._root = _root;
this.tag = tag;
_read();
}
private void _read() {
if (isIndexSeparate()) {
this.indexSeparateMinus = this._io.readU1();
}
}
private Boolean isIndexSeparate;
/**
* Whether the index is stored separately from the tag.
*/
public Boolean isIndexSeparate() {
if (this.isIndexSeparate != null)
return this.isIndexSeparate;
boolean _tmp = (boolean) (tag() == 210);
this.isIndexSeparate = _tmp;
return this.isIndexSeparate;
}
private Integer indexInTag;
/**
* The index of the referenced literal chunk,
* as stored in the tag byte.
*/
public Integer indexInTag() {
if (this.indexInTag != null)
return this.indexInTag;
int _tmp = (int) ((tag() - 32));
this.indexInTag = _tmp;
return this.indexInTag;
}
private Integer indexSeparate;
/**
* The index of the referenced literal chunk,
* as stored separately from the tag byte,
* with the implicit offset corrected for.
*/
public Integer indexSeparate() {
if (this.indexSeparate != null)
return this.indexSeparate;
if (isIndexSeparate()) {
int _tmp = (int) ((indexSeparateMinus() + 176));
this.indexSeparate = _tmp;
}
return this.indexSeparate;
}
private Integer index;
/**
* The index of the referenced literal chunk.
*
* Stored literals are assigned index numbers in the order in which they appear in the compressed data,
* starting at 0.
* Non-stored literals are not counted in the numbering and cannot be referenced using backreferences.
* Once an index is assigned to a stored literal,
* it is never changed or unassigned for the entire length of the compressed data.
*
* As the name indicates,
* a backreference can only reference stored literal chunks found *before* the backreference,
* not ones that come after it.
*/
public Integer index() {
if (this.index != null)
return this.index;
int _tmp = (int) ((isIndexSeparate() ? indexSeparate() : indexInTag()));
this.index = _tmp;
return this.index;
}
private Integer indexSeparateMinus;
private int tag;
private Dcmp1 _root;
private Dcmp1.Chunk _parent;
/**
* The index of the referenced literal chunk,
* stored separately from the tag.
* The value in this field is stored minus 0xb0.
*
* This field is only present if the tag byte is 0xd2.
* For other tag bytes,
* the index is encoded in the tag byte.
* Values smaller than 0xb0 cannot be stored in this field,
* they must always be encoded in the tag byte.
*/
public Integer indexSeparateMinus() { return indexSeparateMinus; }
/**
* The tag byte preceding this chunk body.
*/
public int tag() { return tag; }
public Dcmp1 _root() { return _root; }
public Dcmp1.Chunk _parent() { return _parent; }
}
/**
* The body of a table lookup chunk.
* This body is always empty.
*
* This chunk always expands to two bytes (`value`),
* determined from the tag byte using a fixed lookup table (`lookup_table`).
* This lookup table is hardcoded in the decompressor and always the same for all compressed data.
*/
public static class TableLookupBody extends KaitaiStruct {
public TableLookupBody(KaitaiStream _io, int tag) {
this(_io, null, null, tag);
}
public TableLookupBody(KaitaiStream _io, Dcmp1.Chunk _parent, int tag) {
this(_io, _parent, null, tag);
}
public TableLookupBody(KaitaiStream _io, Dcmp1.Chunk _parent, Dcmp1 _root, int tag) {
super(_io);
this._parent = _parent;
this._root = _root;
this.tag = tag;
_read();
}
private void _read() {
}
private ArrayList<byte[]> lookupTable;
/**
* Fixed lookup table that maps tag byte numbers to two bytes each.
*
* The entries in the lookup table are offset -
* index 0 stands for tag 0xd5, 1 for 0xd6, etc.
*/
public ArrayList<byte[]> lookupTable() {
if (this.lookupTable != null)
return this.lookupTable;
this.lookupTable = new ArrayList<byte[]>(Arrays.asList(new byte[] { 0, 0 }, new byte[] { 0, 1 }, new byte[] { 0, 2 }, new byte[] { 0, 3 }, new byte[] { 46, 1 }, new byte[] { 62, 1 }, new byte[] { 1, 1 }, new byte[] { 30, 1 }, new byte[] { -1, -1 }, new byte[] { 14, 1 }, new byte[] { 49, 0 }, new byte[] { 17, 18 }, new byte[] { 1, 7 }, new byte[] { 51, 50 }, new byte[] { 18, 57 }, new byte[] { -19, 16 }, new byte[] { 1, 39 }, new byte[] { 35, 34 }, new byte[] { 1, 55 }, new byte[] { 7, 6 }, new byte[] { 1, 23 }, new byte[] { 1, 35 }, new byte[] { 0, -1 }, new byte[] { 0, 47 }, new byte[] { 7, 14 }, new byte[] { -3, 60 }, new byte[] { 1, 53 }, new byte[] { 1, 21 }, new byte[] { 1, 2 }, new byte[] { 0, 7 }, new byte[] { 0, 62 }, new byte[] { 5, -43 }, new byte[] { 2, 1 }, new byte[] { 6, 7 }, new byte[] { 7, 8 }, new byte[] { 48, 1 }, new byte[] { 1, 51 }, new byte[] { 0, 16 }, new byte[] { 23, 22 }, new byte[] { 55, 62 }, new byte[] { 54, 55 }));
return this.lookupTable;
}
private byte[] value;
/**
* The two bytes that the tag byte expands to,
* based on the fixed lookup table.
*/
public byte[] value() {
if (this.value != null)
return this.value;
this.value = lookupTable().get((int) (tag() - 213));
return this.value;
}
private int tag;
private Dcmp1 _root;
private Dcmp1.Chunk _parent;
/**
* The tag byte preceding this chunk body.
*/
public int tag() { return tag; }
public Dcmp1 _root() { return _root; }
public Dcmp1.Chunk _parent() { return _parent; }
}
/**
* The body of an end chunk.
* This body is always empty.
*
* The last chunk in the compressed data must always be an end chunk.
* An end chunk cannot appear elsewhere in the compressed data.
*/
public static class EndBody extends KaitaiStruct {
public static EndBody fromFile(String fileName) throws IOException {
return new EndBody(new ByteBufferKaitaiStream(fileName));
}
public EndBody(KaitaiStream _io) {
this(_io, null, null);
}
public EndBody(KaitaiStream _io, Dcmp1.Chunk _parent) {
this(_io, _parent, null);
}
public EndBody(KaitaiStream _io, Dcmp1.Chunk _parent, Dcmp1 _root) {
super(_io);
this._parent = _parent;
this._root = _root;
_read();
}
private void _read() {
}
private Dcmp1 _root;
private Dcmp1.Chunk _parent;
public Dcmp1 _root() { return _root; }
public Dcmp1.Chunk _parent() { return _parent; }
}
/**
* The body of an extended chunk.
* The meaning of this chunk depends on the extended tag byte stored in the chunk data.
*/
public static class ExtendedBody extends KaitaiStruct {
public static ExtendedBody fromFile(String fileName) throws IOException {
return new ExtendedBody(new ByteBufferKaitaiStream(fileName));
}
public ExtendedBody(KaitaiStream _io) {
this(_io, null, null);
}
public ExtendedBody(KaitaiStream _io, Dcmp1.Chunk _parent) {
this(_io, _parent, null);
}
public ExtendedBody(KaitaiStream _io, Dcmp1.Chunk _parent, Dcmp1 _root) {
super(_io);
this._parent = _parent;
this._root = _root;
_read();
}
private void _read() {
this.tag = this._io.readU1();
switch (tag()) {
case 2: {
this.body = new RepeatBody(this._io, this, _root);
break;
}
}
}
/**
* The body of a repeat chunk.
*
* This chunk expands to the same byte repeated a number of times,
* i. e. it implements a form of run-length encoding.
*/
public static class RepeatBody extends KaitaiStruct {
public static RepeatBody fromFile(String fileName) throws IOException {
return new RepeatBody(new ByteBufferKaitaiStream(fileName));
}
public RepeatBody(KaitaiStream _io) {
this(_io, null, null);
}
public RepeatBody(KaitaiStream _io, Dcmp1.Chunk.ExtendedBody _parent) {
this(_io, _parent, null);
}
public RepeatBody(KaitaiStream _io, Dcmp1.Chunk.ExtendedBody _parent, Dcmp1 _root) {
super(_io);
this._parent = _parent;
this._root = _root;
_read();
}
private void _read() {
this.toRepeatRaw = new DcmpVariableLengthInteger(this._io);
this.repeatCountM1Raw = new DcmpVariableLengthInteger(this._io);
}
private Integer toRepeat;
/**
* The value to repeat.
*
* Although it is stored as a variable-length integer,
* this value must fit into an unsigned 8-bit integer.
*/
public Integer toRepeat() {
if (this.toRepeat != null)
return this.toRepeat;
int _tmp = (int) (toRepeatRaw().value());
this.toRepeat = _tmp;
return this.toRepeat;
}
private Integer repeatCountM1;
/**
* The number of times to repeat the value,
* minus one.
*
* This value must not be negative.
*/
public Integer repeatCountM1() {
if (this.repeatCountM1 != null)
return this.repeatCountM1;
int _tmp = (int) (repeatCountM1Raw().value());
this.repeatCountM1 = _tmp;
return this.repeatCountM1;
}
private Integer repeatCount;
/**
* The number of times to repeat the value.
*
* This value must be positive.
*/
public Integer repeatCount() {
if (this.repeatCount != null)
return this.repeatCount;
int _tmp = (int) ((repeatCountM1() + 1));
this.repeatCount = _tmp;
return this.repeatCount;
}
private DcmpVariableLengthInteger toRepeatRaw;
private DcmpVariableLengthInteger repeatCountM1Raw;
private Dcmp1 _root;
private Dcmp1.Chunk.ExtendedBody _parent;
/**
* Raw variable-length integer representation of `to_repeat`.
*/
public DcmpVariableLengthInteger toRepeatRaw() { return toRepeatRaw; }
/**
* Raw variable-length integer representation of `repeat_count_m1`.
*/
public DcmpVariableLengthInteger repeatCountM1Raw() { return repeatCountM1Raw; }
public Dcmp1 _root() { return _root; }
public Dcmp1.Chunk.ExtendedBody _parent() { return _parent; }
}
private int tag;
private RepeatBody body;
private Dcmp1 _root;
private Dcmp1.Chunk _parent;
/**
* The chunk's extended tag byte.
* This controls the structure of the body and the meaning of the chunk.
*/
public int tag() { return tag; }
/**
* The chunk's body.
*/
public RepeatBody body() { return body; }
public Dcmp1 _root() { return _root; }
public Dcmp1.Chunk _parent() { return _parent; }
}
private int tag;
private KaitaiStruct body;
private Dcmp1 _root;
private Dcmp1 _parent;
/**
* The chunk's tag byte.
* This controls the structure of the body and the meaning of the chunk.
*/
public int tag() { return tag; }
/**
* The chunk's body.
*
* Certain chunks do not have any data following the tag byte.
* In this case,
* the body is a zero-length structure.
*/
public KaitaiStruct body() { return body; }
public Dcmp1 _root() { return _root; }
public Dcmp1 _parent() { return _parent; }
}
private ArrayList<Chunk> chunks;
private Dcmp1 _root;
private KaitaiStruct _parent;
/**
* The sequence of chunks that make up the compressed data.
*/
public ArrayList<Chunk> chunks() { return chunks; }
public Dcmp1 _root() { return _root; }
public KaitaiStruct _parent() { return _parent; }
}