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439 lines
12 KiB
Plaintext
439 lines
12 KiB
Plaintext
;
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; File: DeCompressDefProc1.a
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; By Donn Denman
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;
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; Contains: parts of the decompress defprocs that are common to all.
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;
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; Copyright: © 1990 by Apple Computer, Inc., all rights reserved.
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;
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; Change History (most recent first):
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;
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; <4> 8/14/90 DD Changed variable lookup at FetchData and assignment at
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; RememberData to use unsigned word offsets.
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; <3> 7/24/90 gbm Fix branches to next instruction, but don't break debug mode...
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; :)
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; <2> 4/18/90 DD Added RunLength Encoding and Delta Encoding variations.
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; <1> 4/12/90 DD first checked in today
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; BBS versions above:
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;___________________________________________________________________________________________________
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********************************************************************************************
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*
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* Procedure UnPackData(SourcePtr, DestPtr, VarTable: ptr; VarTableSize: Longint);
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*
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* Description: Unpack the data from the source pointer to the dest pointer.
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* The unpacking is automatically terminated when the end token is reached.
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*
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*
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********************************************************************************************
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UnPackFrame Record {A6Link},Decr
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SourcePtr DS.L 1
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DestPtr DS.L 1
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VarTablePtr DS.L 1
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VarTableSize DS.L 1
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ReturnAddress DS.L 1
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A6Link DS.L 1
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LocalSize DS.L 0
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EndR
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With UnpackFrame
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UnPackData
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Link A6,#LocalSize ;do the unpack from ptr A0 into pointer in A1.
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MoveM.L D0-D3/A0-A4,-(SP)
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; Set up the registers, for fast handling.
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Move.L SourcePtr(A6),A4 ;input stream.
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Move.L DestPtr(A6),A1 ;output stream.
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Lea CodeDispatchTable,A2 ;dispatch table.
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Move.L VarTablePtr(A6),A3 ;variable table.
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Move.L VarTableSize(A6),D0 ; table size.
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Bsr InitRemember ;init the var table.
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Bra UnpackLoop ; now go to the unpack loop.
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ExitUnpack
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MoveM.L (SP)+,D0-D3/A0-A4
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UnLk A6
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Move.L (SP)+,A0
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Add #SourcePtr-ReturnAddress,SP
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Jmp (A0)
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EndWith
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********************************************************************************************
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*
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* GetEncodedValue
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*
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* Description: gets the value pointed to by A4 into D0.L. The values are encoded:
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*
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* Tag Range computation method
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* --- ----- ------------------
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* 0..127 0,127 Tag[0]
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* 128..254 -16384,16127 (Tag[0]-$C0)*$100+Tag[1]
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* 255 same as Long Tag[1]<<24 + Tag[2]<<16 + Tag[3]<<8 + Tag[4]
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*
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* Input: A4: pointer to tags.
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*
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* Output: A0: points past tags.
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* D0: value long.
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*
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*
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********************************************************************************************
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GetEncodedValue Head
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; try byte encoding, cuz it is so easy.
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MoveQ #0,D0
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Move.B (A4)+,D0
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Bpl.S @HaveValue ;got the result already.
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; is it long encoded?
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Cmp.B #FourByteValue,D0 ;long?
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Beq.S @FetchLong ;yep, that's fairly easy too.
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; word encoded value.
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Sub.W #TwoByteValue*3/2,D0 ;cut back the range, toggle the psuedo sign bit.
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Asl.W #8,D0 ;shift by a byte (*256).
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Asl.W #1,D0 ;shift away the top bit.
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ASR.W #1,D0 ;sign extend the top bit.
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Move.B (A4)+,D0 ;get the next byte.
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Ext.L D0 ;sign extend to a long value.
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Bra.S @HaveValue
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; long encoding
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@FetchLong
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Move.B (A4)+,D0 ;add in the next byte.
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Asl.W #8,D0 ;shift by a byte (*256).
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Move.B (A4)+,D0 ;add in the next byte.
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Asl.L #8,D0 ;shift by a byte (*256).
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Move.B (A4)+,D0 ;add in the next byte.
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Asl.L #8,D0 ;shift by a byte (*256).
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Move.B (A4)+,D0 ;add in the next byte.
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@HaveValue
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Tail
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;
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; CopyWithLength - copy the data following an encoded length.
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;
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CopyWithLength
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Bsr GetEncodedValue ;get the value into D0.
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IF delta=2 THEN
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Add.W D0,D0 ;double the value if we are processing word chucks.
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EndIF
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;BRA.S CopyData ;fall through
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;
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; CopyData - copy the data already knowing the word length.
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;
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CopyData
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Bra.S @Sub1FirstTime
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@CopyData
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Move.B (A4)+,(A1)+ ;copy a byte.
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@Sub1FirstTime
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DBRA D0,@CopyData
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Rts
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;
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; RememberLiteral - copy the data already knowing the word length.
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; Also add this literal to the Var Table.
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;
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RememberLiteral
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Bsr.S RememberData ;stuff the data pointed to by A4, for length D0 into the var table.
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; fall through to CopyLiteralAndLoop
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;
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; CopyLiteralAndLoop - copy the data pointed to by the input into the output and loop.
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;
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CopyLiteralAndLoop
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Bsr.S CopyData
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Bra UnpackLoop
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;
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; RememberWithLength - copy the data preceeded by a byte length.
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; Also add this literal to the Var Table.
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;
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RememberWithLength
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Bsr GetEncodedValue ;get the value into D0.
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IF delta=2 THEN
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Add.W D0,D0 ;double the value if we are processing word chucks.
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EndIF
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Bsr.S RememberData ;stuff the data pointed to by A4, for length D0 into the var table.
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Bra.S CopyData
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;
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; InitRemember - Init the var table.
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; Entry: A3 - Var Table.
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; D0 - Table size.
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;
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InitRemember
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Move.W D0,VarsList(A3) ;first entry points to the end of the table.
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Move.W #2+VarsList,NextVarIndex(A3) ;point to the next var entry.
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Rts
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;
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; RememberData - stuff the data pointed to by A4, for length D0 into the var table.
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;
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; Entry: A4 - Pointer to the data.
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; D0 - length of the data.
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; A3 - Var Table.
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;
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; Exit: A1,D0 - preserved.
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; A0,D1 Trashed.
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;
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RememberData
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MoveM.L D0/A1,-(SP)
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MoveQ #0,D1
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Move.W NextVarIndex(A3),D1 ;get the index into the next var.
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AddQ.W #2,NextVarIndex(A3) ;bump the index.
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Lea -2(A3,D1.L),A0 ;point to the previous data offset.
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Move.W (A0)+,D1 ;it defines where my new string must end.
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Sub.W D0,D1 ;compute my new offset.
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Move.W D1,(A0) ;put my offset in place.
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; Debugging
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IF DoDebug > 0 THEN
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Lea 0(A3,D1.L),A1 ;point to my data loc.
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Cmp.L A0,A1
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BGT.S @NoOverFlow
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BreakError 'Variable Table Over Flow!'
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@NoOverFlow
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ENDIF
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; Debugging
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Lea 0(A3,D1.L),A0 ;point to my data loc.
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Move.L A4,A1
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Bsr.S BlockMoveBytes
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MoveM.L (SP)+,D0/A1
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Rts
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;
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; BlockMoveBytes - block moves bytes from (A1)+ to (A0)+ for D0.W.
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;
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BlockMoveBytes
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Bra.S @Sub1FirstTime
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@CopyData
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Move.B (A1)+,(A0)+ ;copy a byte.
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@Sub1FirstTime
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DBRA D0,@CopyData
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Rts
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;
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; ReuseByte2Length - Reuse the data indexed by the following byte, to add 256 to.
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;
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ReuseByte2Length
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MoveQ #0,D0
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Move.B (A4)+,D0 ;get the length from the input stream
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Add.W #Max1ByteReuse+256,D0 ;bump by the number of vars we can ref in one byte.
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Bra.S FetchData ;call FetchData.
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;
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; ReuseWordLength - copy the data following a word length.
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;
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ReuseWordLength
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MoveQ #0,D0
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Move.B (A4)+,D0 ;get the length from the input stream
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Asl.W #8,D0 ;shift into high byte.
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Bra.S ReuseLowByte
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;
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; ReuseByteLength - Reuse the data indexed by the following byte.
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;
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ReuseByteLength
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MoveQ #0,D0
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ReuseLowByte
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Move.B (A4)+,D0 ;get the length from the input stream
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Add.W #Max1ByteReuse,D0 ;bump by the number of vars we can ref in one byte.
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;Bra.S FetchData ;call FetchData.
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;
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; FetchData - retrieve the data from index D0 of the var table.
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;
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; Entry: A1 - Pointer to the output stream.
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; D0 - index the data.
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; A3 - Var Table.
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;
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; Exit: A0,D0,D1 Trashed.
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;
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FetchData
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Add.W D0,D0 ;make the index into an offset.
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; Debugging
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IF DoDebug > 0 THEN
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Cmp.W NextVarIndex(A3),D0 ;are we indexing too far into the table?
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BLo.S @NoProblem
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BreakError 'Error - Index beyond end of vars list'
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@NoProblem
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ENDIF
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; Debugging
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Lea VarsList(A3,D0),A0 ;point to the previous entry (end of this string).
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Move.W (A0)+,D0 ;get the data offset of the previous entry.
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MoveQ #0,D1 ;clear high word, so unsigned offsets will work.
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Move.W (A0),D1 ;get the offset of this entry.
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Sub.W D1,D0 ;compute the length of this entry.
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Lea 0(A3,D1.L),A0 ;point to the string.
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Exg A0,A1 ;point A1 to the string, A0 to the output Stream.
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Bsr.S BlockMoveBytes
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Move.L A0,A1 ;get output ptr back.
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Rts
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;
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; ReuseData - Reuse the data indexed by the encoded byte.
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;
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ReuseData
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Bsr.S FetchData ;fetch the data from the var table.
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Bra UnpackLoop ; go back to the main loop.
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HandleExtensions
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Move.B (A4)+,D0 ;get the extension opCode.
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Beq.S @JumpTableTrans
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SubQ.B #RunLengthByteTransCode,D0 ; runlength encoding by bytes?
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Blo.S @EntryVectorTrans ; is it an entry vector trans?
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Beq RunLengthByteTrans
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SubQ.B #DiffWordTransCode-RunLengthByteTransCode,D0 ;peel off the next two cases.
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Blo RunLengthWordTrans
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Beq DiffWordTrans
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SubQ.B #DiffEncLongTransCode-DiffWordTransCode,D0 ;peel off the next two cases.
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Blo DiffEncWordTrans
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Beq DiffEncLongTrans
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BreakError 'got an undefined Extension op-code'
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Bra @Return
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; EntryVector transformation
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; Format is as follows:
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; BranchOffset Delta NumEntries Offset0 < Offset1 Offset2 ... OffsetN >
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; where each item is an encoded value.
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; Offset1...OffsetN is an optional words list that is
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; present only if Delta==0. If Delta != 0 then
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; the Delta is added to Offset0 to create Offset1 etc.
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;
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@EntryVectorTrans
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MoveM.L D2-D7,-(SP)
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Move.W #$6100,D3
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Move.W #$4EED,D5
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Bsr.S GoGetEncodedValue ;get the initial branch offset.
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Move.W D0,D4
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Bsr.S GoGetEncodedValue ;get the Delta amount.
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Move.W D0,D2
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Bsr.S GoGetEncodedValue ;get the number of entries.
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Move.W D0,D7
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Bsr.S GoGetEncodedValue ;get the inital offset.
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Move.W D0,D6
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Bra.S @HaveOffset
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@ExpandEntryVector
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SubQ #8,D4 ;compute the next branch offset.
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Tst D2 ;is there an offset list?
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Beq.S @GetNextOffset ;if the delta is constant (non-zero) then
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Add.W D2,D6 ; compute next offset.
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Bra.S @HaveOffset
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@GetNextOffset
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Bsr.S GoGetEncodedValue ;get the next offset.
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Move.W D0,D6
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@HaveOffset
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MoveM.W D3-D6,(A1) ;output the next entry vector.
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AddQ #8,A1 ;move the output pointer past the entry.
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DBRA D7,@ExpandEntryVector ;until all entries are done.
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MoveM.L (SP)+,D2-D7
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Bra.S @Return
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; JumpTable transformation
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; Format is as follows:
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; Seg# NumEntries Delta0 Delta1 Delta2
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; where each value is encoded.
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;
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@JumpTableTrans
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MoveM.L D3-D7,-(SP)
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Move.W #$3F3C,D3
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Move.W #$A9F0,D5
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Move.W #6,D6 ;init the offset to our bias.
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Bsr.S GoGetEncodedValue ;get the segment number
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Move.W D0,D4 ;remember seg
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Bsr.S GoGetEncodedValue ;get the number of entries.
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Move.W D0,D7
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Bra.S @skipLastOffset
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@StuffLoop
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Bsr.S GoGetEncodedValue ;get the delta plus bias of 6.
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SubQ #6,D0 ;adjust the delta by my bias (allows some small negs to be a byte).
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Add.W D0,D6 ;add the delta to the last offset.
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MoveM.W D3-D6,(A1) ;output the next jump table entry.
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AddQ #8,A1
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@skipLastOffset
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DBRA D7,@StuffLoop ;until all entries are done.
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MoveM.W D3-D5,(A1) ;output the next jump table entry.
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AddQ #6,A1
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MoveM.L (SP)+,D3-D7
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@Return
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Rts
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GoGetEncodedValue
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Bra GetEncodedValue ;get the value
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RunLengthByteTrans Head
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Bsr.S GoGetEncodedValue ;get the value
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Move.W D0,D1 ;remember value.
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Bsr.S GoGetEncodedValue ;get the rep count.
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@RunLengthByte
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Move.B D1,(A1)+ ;output the value.
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DBRA D0,@RunLengthByte ;loop till all done.
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Tail
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RunLengthWordTrans Head
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Bsr.S GoGetEncodedValue ;get the value
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Move.W D0,D1 ;remember value.
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Bsr.S GoGetEncodedValue ;get the rep count.
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@RunLengthWord
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Move.W D1,(A1)+ ;output the value.
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DBRA D0,@RunLengthWord ;loop till all done.
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Tail
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DiffWordTrans Head
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Bsr.S GoGetEncodedValue ;get the initial value
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Move.L D0,D2 ;remember value.
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Bsr.S GoGetEncodedValue ;get the rep count.
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Move.L D0,D1
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Bra.S @FirstTime
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@DiffWord
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Move.B (A4)+,D0 ;get the delta
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Ext.W D0
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Add.W D0,D2 ;add in the signed delta
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@FirstTime
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Move.W D2,(A1)+ ;output the value.
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DBRA D1,@DiffWord ;loop till all done.
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Tail
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DiffEncWordTrans Head
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Bsr.S GoGetEncodedValue ;get the initial value
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Move.L D0,D2 ;remember value.
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Bsr.S GoGetEncodedValue ;get the rep count.
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Move.L D0,D1
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Bra.S @FirstTime
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@DiffWord
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Bsr.S GoGetEncodedValue ;get the delta.
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Add.L D0,D2 ;add in the signed delta
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@FirstTime
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Move.W D2,(A1)+ ;output the value.
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DBRA D1,@DiffWord ;loop till all done.
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Tail
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DiffEncLongTrans Head
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Bsr.S GoGetEncodedValue ;get the initial value
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Move.L D0,D2 ;remember value.
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Bsr.S GoGetEncodedValue ;get the rep count.
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Move.L D0,D1
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Bra.S @FirstTime
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@DiffLong
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Bsr.S GoGetEncodedValue ;get the delta.
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Add.L D0,D2 ;add in the signed delta
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@FirstTime
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Move.L D2,(A1)+ ;output the value.
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DBRA D1,@DiffLong ;loop till all done.
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Tail
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