mirror of
https://github.com/cc65/cc65.git
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550 lines
15 KiB
ArmAsm
550 lines
15 KiB
ArmAsm
;
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; 2017-11-07, Piotr Fusik
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;
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; unsigned __fastcall__ inflatemem (char* dest, const char* source);
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;
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; NOTE: Be extremely careful with modifications, because this code is heavily
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; optimized for size (for example assumes certain register and flag values
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; when its internal routines return). Test with the gunzip65 sample.
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;
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.export _inflatemem
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.import incsp2
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.importzp sp, sreg, ptr1, ptr2, ptr3, ptr4
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; --------------------------------------------------------------------------
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;
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; Constants
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;
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; Argument values for getBits.
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GET_1_BIT = $81
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GET_2_BITS = $82
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GET_3_BITS = $84
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GET_4_BITS = $88
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GET_5_BITS = $90
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GET_6_BITS = $a0
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GET_7_BITS = $c0
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; Huffman trees.
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TREE_SIZE = 16
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PRIMARY_TREE = 0
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DISTANCE_TREE = TREE_SIZE
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; Alphabet.
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LENGTH_SYMBOLS = 1+29+2 ; EOF, 29 length symbols, two unused symbols
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DISTANCE_SYMBOLS = 30
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CONTROL_SYMBOLS = LENGTH_SYMBOLS+DISTANCE_SYMBOLS
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; --------------------------------------------------------------------------
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;
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; Page zero
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;
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; Pointer to the compressed data.
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inputPointer := ptr1 ; 2 bytes
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; Pointer to the uncompressed data.
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outputPointer := ptr2 ; 2 bytes
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; Local variables.
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; As far as there is no conflict, same memory locations are used
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; for different variables.
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inflateStored_pageCounter := ptr3 ; 1 byte
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inflateDynamic_symbol := ptr3 ; 1 byte
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inflateDynamic_lastLength := ptr3+1 ; 1 byte
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.assert ptr4 = ptr3 + 2, error, "Need three bytes for inflateDynamic_tempCodes"
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inflateDynamic_tempCodes := ptr3+1 ; 3 bytes
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inflateDynamic_allCodes := inflateDynamic_tempCodes+1 ; 1 byte
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inflateDynamic_primaryCodes := inflateDynamic_tempCodes+2 ; 1 byte
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inflateCodes_sourcePointer := ptr3 ; 2 bytes
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inflateCodes_lengthMinus2 := ptr4 ; 1 byte
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getBits_base := sreg ; 1 byte
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getBit_buffer := sreg+1 ; 1 byte
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; --------------------------------------------------------------------------
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;
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; Code
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;
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_inflatemem:
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; inputPointer = source
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sta inputPointer
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stx inputPointer+1
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; outputPointer = dest
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ldy #1
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lda (sp),y
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sta outputPointer+1
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dey
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lda (sp),y
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sta outputPointer
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; ldy #0
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sty getBit_buffer
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inflate_blockLoop:
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; Get a bit of EOF and two bits of block type
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; ldy #0
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sty getBits_base
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lda #GET_3_BITS
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jsr getBits
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lsr a
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; A and Z contain block type, C contains EOF flag
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; Save EOF flag
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php
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bne inflateCompressed
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; Decompress a 'stored' data block.
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; ldy #0
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sty getBit_buffer ; ignore bits until byte boundary
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jsr getWord ; skip the length we don't need
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jsr getWord ; get the one's complement length
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sta inflateStored_pageCounter
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bcs inflateStored_firstByte ; jmp
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inflateStored_copyByte:
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jsr getByte
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; sec
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inflateStoreByte:
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jsr storeByte
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bcc inflateCodes_loop
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inflateStored_firstByte:
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inx
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bne inflateStored_copyByte
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inc inflateStored_pageCounter
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bne inflateStored_copyByte
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; Block decompressed.
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inflate_nextBlock:
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plp
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bcc inflate_blockLoop
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; Decompression complete.
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; return outputPointer - dest
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lda outputPointer
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; ldy #0
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; sec
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sbc (sp),y
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iny
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pha
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lda outputPointer+1
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sbc (sp),y
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tax
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pla
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; pop dest
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jmp incsp2
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inflateCompressed:
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; Decompress a Huffman-coded data block
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; A=1: fixed block, initialize with fixed codes
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; A=2: dynamic block, start by clearing all code lengths
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; A=3: invalid compressed data, not handled in this routine
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eor #2
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; ldy #0
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inflateCompressed_setCodeLengths:
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tax
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beq inflateCompressed_setLiteralCodeLength
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; fixed Huffman literal codes:
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; 144 8-bit codes
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; 112 9-bit codes
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lda #4
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cpy #144
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rol a
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inflateCompressed_setLiteralCodeLength:
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sta literalSymbolCodeLength,y
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beq inflateCompressed_setControlCodeLength
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; fixed Huffman control codes:
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; 24 7-bit codes
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; 6 8-bit codes
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; 2 meaningless 8-bit codes
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; 30 5-bit distance codes
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lda #5+DISTANCE_TREE
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cpy #LENGTH_SYMBOLS
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bcs inflateCompressed_setControlCodeLength
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cpy #24
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adc #$100+2-DISTANCE_TREE
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inflateCompressed_setControlCodeLength:
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cpy #CONTROL_SYMBOLS
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bcs inflateCompressed_noControlSymbol
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sta controlSymbolCodeLength,y
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inflateCompressed_noControlSymbol:
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iny
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bne inflateCompressed_setCodeLengths
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tax
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beq inflateDynamic
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; Decompress a block
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inflateCodes:
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jsr buildHuffmanTree
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inflateCodes_loop:
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jsr fetchPrimaryCode
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bcc inflateStoreByte
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beq inflate_nextBlock
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; Copy sequence from look-behind buffer
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; ldy #0
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sty getBits_base
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cmp #9
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bcc inflateCodes_setSequenceLength
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tya
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; lda #0
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cpx #1+28
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bcs inflateCodes_setSequenceLength
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dex
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txa
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lsr a
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ror getBits_base
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inc getBits_base
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lsr a
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rol getBits_base
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jsr getAMinus1BitsMax8
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; sec
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adc #0
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inflateCodes_setSequenceLength:
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sta inflateCodes_lengthMinus2
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ldx #DISTANCE_TREE
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jsr fetchCode
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cmp #4
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bcc inflateCodes_setOffsetLowByte
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inc getBits_base
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lsr a
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jsr getAMinus1BitsMax8
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inflateCodes_setOffsetLowByte:
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eor #$ff
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sta inflateCodes_sourcePointer
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lda getBits_base
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cpx #10
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bcc inflateCodes_setOffsetHighByte
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lda getNPlus1Bits_mask-10,x
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jsr getBits
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clc
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inflateCodes_setOffsetHighByte:
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eor #$ff
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; clc
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adc outputPointer+1
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sta inflateCodes_sourcePointer+1
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jsr copyByte
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jsr copyByte
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inflateCodes_copyByte:
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jsr copyByte
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dec inflateCodes_lengthMinus2
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bne inflateCodes_copyByte
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beq inflateCodes_loop ; jmp
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inflateDynamic:
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; Decompress a block reading Huffman trees first
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; ldy #0
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; numberOfPrimaryCodes = 257 + getBits(5)
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; numberOfDistanceCodes = 1 + getBits(5)
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; numberOfTemporaryCodes = 4 + getBits(4)
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ldx #3
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inflateDynamic_getHeader:
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lda inflateDynamic_headerBits-1,x
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jsr getBits
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; sec
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adc inflateDynamic_headerBase-1,x
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sta inflateDynamic_tempCodes-1,x
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dex
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bne inflateDynamic_getHeader
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; Get lengths of temporary codes in the order stored in inflateDynamic_tempSymbols
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; ldx #0
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inflateDynamic_getTempCodeLengths:
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lda #GET_3_BITS
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jsr getBits
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ldy inflateDynamic_tempSymbols,x
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sta literalSymbolCodeLength,y
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ldy #0
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inx
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cpx inflateDynamic_tempCodes
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bcc inflateDynamic_getTempCodeLengths
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; Build the tree for temporary codes
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jsr buildHuffmanTree
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; Use temporary codes to get lengths of literal/length and distance codes
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; ldx #0
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; sec
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inflateDynamic_decodeLength:
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; C=1: literal codes
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; C=0: control codes
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stx inflateDynamic_symbol
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php
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; Fetch a temporary code
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jsr fetchPrimaryCode
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; Temporary code 0..15: put this length
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bpl inflateDynamic_storeLengths
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; Temporary code 16: repeat last length 3 + getBits(2) times
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; Temporary code 17: put zero length 3 + getBits(3) times
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; Temporary code 18: put zero length 11 + getBits(7) times
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tax
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jsr getBits
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cpx #GET_3_BITS
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bcc inflateDynamic_code16
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beq inflateDynamic_code17
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; sec
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adc #7
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inflateDynamic_code17:
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; ldy #0
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sty inflateDynamic_lastLength
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inflateDynamic_code16:
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tay
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lda inflateDynamic_lastLength
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iny
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iny
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inflateDynamic_storeLengths:
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iny
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plp
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ldx inflateDynamic_symbol
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inflateDynamic_storeLength:
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bcc inflateDynamic_controlSymbolCodeLength
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sta literalSymbolCodeLength,x
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inx
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cpx #1
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inflateDynamic_storeNext:
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dey
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bne inflateDynamic_storeLength
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sta inflateDynamic_lastLength
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beq inflateDynamic_decodeLength ; jmp
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inflateDynamic_controlSymbolCodeLength:
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cpx inflateDynamic_primaryCodes
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bcc inflateDynamic_storeControl
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; the code lengths we skip here were zero-initialized
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; in inflateCompressed_setControlCodeLength
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bne inflateDynamic_noStartDistanceTree
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ldx #LENGTH_SYMBOLS
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inflateDynamic_noStartDistanceTree:
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ora #DISTANCE_TREE
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inflateDynamic_storeControl:
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sta controlSymbolCodeLength,x
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inx
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cpx inflateDynamic_allCodes
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bcc inflateDynamic_storeNext
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dey
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; ldy #0
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jmp inflateCodes
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; Build Huffman trees basing on code lengths (in bits)
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; stored in the *SymbolCodeLength arrays
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buildHuffmanTree:
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; Clear nBitCode_literalCount, nBitCode_controlCount
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tya
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; lda #0
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buildHuffmanTree_clear:
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sta nBitCode_clearFrom,y
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iny
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bne buildHuffmanTree_clear
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; Count number of codes of each length
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; ldy #0
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buildHuffmanTree_countCodeLengths:
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ldx literalSymbolCodeLength,y
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inc nBitCode_literalCount,x
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bne buildHuffmanTree_notAllLiterals
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stx allLiteralsCodeLength
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buildHuffmanTree_notAllLiterals:
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cpy #CONTROL_SYMBOLS
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bcs buildHuffmanTree_noControlSymbol
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ldx controlSymbolCodeLength,y
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inc nBitCode_controlCount,x
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buildHuffmanTree_noControlSymbol:
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iny
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bne buildHuffmanTree_countCodeLengths
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; Calculate offsets of symbols sorted by code length
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; lda #0
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ldx #$100-4*TREE_SIZE
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buildHuffmanTree_calculateOffsets:
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sta nBitCode_literalOffset+4*TREE_SIZE-$100,x
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clc
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adc nBitCode_literalCount+4*TREE_SIZE-$100,x
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inx
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bne buildHuffmanTree_calculateOffsets
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; Put symbols in their place in the sorted array
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; ldy #0
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buildHuffmanTree_assignCode:
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tya
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ldx literalSymbolCodeLength,y
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ldy nBitCode_literalOffset,x
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inc nBitCode_literalOffset,x
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sta codeToLiteralSymbol,y
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tay
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cpy #CONTROL_SYMBOLS
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bcs buildHuffmanTree_noControlSymbol2
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ldx controlSymbolCodeLength,y
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ldy nBitCode_controlOffset,x
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inc nBitCode_controlOffset,x
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sta codeToControlSymbol,y
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tay
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buildHuffmanTree_noControlSymbol2:
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iny
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bne buildHuffmanTree_assignCode
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rts
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; Read Huffman code using the primary tree
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fetchPrimaryCode:
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ldx #PRIMARY_TREE
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; Read a code from input using the tree specified in X.
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; Return low byte of this code in A.
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; Return C flag reset for literal code, set for length code.
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fetchCode:
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; ldy #0
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tya
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fetchCode_nextBit:
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jsr getBit
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rol a
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inx
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bcs fetchCode_ge256
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; are all 256 literal codes of this length?
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cpx allLiteralsCodeLength
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beq fetchCode_allLiterals
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; is it literal code of length X?
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sec
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sbc nBitCode_literalCount,x
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bcs fetchCode_notLiteral
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; literal code
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; clc
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adc nBitCode_literalOffset,x
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tax
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lda codeToLiteralSymbol,x
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fetchCode_allLiterals:
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clc
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rts
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; code >= 256, must be control
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fetchCode_ge256:
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; sec
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sbc nBitCode_literalCount,x
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sec
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; is it control code of length X?
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fetchCode_notLiteral:
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; sec
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sbc nBitCode_controlCount,x
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bcs fetchCode_nextBit
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; control code
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; clc
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adc nBitCode_controlOffset,x
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tax
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lda codeToControlSymbol,x
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and #$1f ; make distance symbols zero-based
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tax
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; sec
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rts
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; Read A minus 1 bits, but no more than 8
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getAMinus1BitsMax8:
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rol getBits_base
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tax
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cmp #9
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bcs getByte
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lda getNPlus1Bits_mask-2,x
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getBits:
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jsr getBits_loop
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getBits_normalizeLoop:
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lsr getBits_base
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ror a
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bcc getBits_normalizeLoop
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rts
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; Read 16 bits
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getWord:
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jsr getByte
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tax
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; Read 8 bits
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getByte:
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lda #$80
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getBits_loop:
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jsr getBit
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ror a
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bcc getBits_loop
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rts
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; Read one bit, return in the C flag
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getBit:
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lsr getBit_buffer
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bne getBit_return
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pha
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; ldy #0
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lda (inputPointer),y
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inc inputPointer
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bne getBit_samePage
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inc inputPointer+1
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getBit_samePage:
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sec
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ror a
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sta getBit_buffer
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pla
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getBit_return:
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rts
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; Copy a previously written byte
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copyByte:
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ldy outputPointer
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lda (inflateCodes_sourcePointer),y
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ldy #0
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; Write a byte
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storeByte:
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; ldy #0
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sta (outputPointer),y
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inc outputPointer
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bne storeByte_return
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inc outputPointer+1
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inc inflateCodes_sourcePointer+1
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storeByte_return:
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rts
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; --------------------------------------------------------------------------
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;
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; Constant data
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;
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.rodata
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getNPlus1Bits_mask:
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.byte GET_1_BIT,GET_2_BITS,GET_3_BITS,GET_4_BITS,GET_5_BITS,GET_6_BITS,GET_7_BITS
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inflateDynamic_tempSymbols:
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.byte GET_2_BITS,GET_3_BITS,GET_7_BITS,0,8,7,9,6,10,5,11,4,12,3,13,2,14,1,15
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inflateDynamic_headerBits:
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.byte GET_4_BITS,GET_5_BITS,GET_5_BITS
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inflateDynamic_headerBase:
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.byte 3,LENGTH_SYMBOLS,0
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; --------------------------------------------------------------------------
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;
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; Uninitialised data
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;
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.bss
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; Data for building trees.
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literalSymbolCodeLength:
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.res 256
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controlSymbolCodeLength:
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.res CONTROL_SYMBOLS
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; Huffman trees.
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nBitCode_clearFrom:
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nBitCode_literalCount:
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.res 2*TREE_SIZE
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nBitCode_controlCount:
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.res 2*TREE_SIZE
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nBitCode_literalOffset:
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.res 2*TREE_SIZE
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nBitCode_controlOffset:
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.res 2*TREE_SIZE
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allLiteralsCodeLength:
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.res 1
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codeToLiteralSymbol:
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.res 256
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codeToControlSymbol:
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.res CONTROL_SYMBOLS
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