Merge branch 'master' into master

asm/6502/decompress_v1.asm

@@ -7,6 +7,18 @@
 ;
 ; out:
 ; * LZSA_DST_LO and LZSA_DST_HI contain the last decompressed byte address, +1
+;
+; -----------------------------------------------------------------------------
+; Backward decompression is also supported, use lzsa -r -b <original_file> <compressed_file>
+; To use it, also define BACKWARD_DECOMPRESS=1 before including this code!
+;
+; in:
+; * LZSA_SRC_LO/LZSA_SRC_HI must contain the address of the last byte of compressed data
+; * LZSA_DST_LO/LZSA_DST_HI must contain the address of the last byte of the destination buffer
+;
+; out:
+; * LZSA_DST_LO/LZSA_DST_HI contain the last decompressed byte address, -1
+;
 ; -----------------------------------------------------------------------------
 ;
 ;  Copyright (C) 2019 Emmanuel Marty
@@ -37,10 +49,10 @@ DECODE_TOKEN
 
    AND #$70                             ; isolate literals count
    BEQ NO_LITERALS                      ; skip if no literals to copy
-   LSR A                                ; shift literals count into place
+   LSR                                  ; shift literals count into place
-   LSR A
+   LSR
-   LSR A
+   LSR
-   LSR A
+   LSR
    CMP #$07                             ; LITERALS_RUN_LEN?
    BCC PREPARE_COPY_LITERALS            ; if not, count is directly embedded in token
 
@@ -59,7 +71,8 @@ LARGE_VARLEN_LITERALS                   ; handle 16 bits literals count
                                         ; literals count = directly these 16 bits
    JSR GETLARGESRC                      ; grab low 8 bits in X, high 8 bits in A
    TAY                                  ; put high 8 bits in Y
-   BYTE $A9                             ; mask TAX (faster than BCS)
+   TXA
+
 PREPARE_COPY_LITERALS
    TAX
    BEQ COPY_LITERALS
@@ -79,7 +92,7 @@ NO_LITERALS
 
    JSR GETSRC                           ; get 8 bit offset from stream in A
    TAX                                  ; save for later
-   LDA #$0FF                            ; high 8 bits
+   LDA #$FF                             ; high 8 bits
    BNE GOT_OFFSET                       ; go prepare match
                                         ; (*like JMP GOT_OFFSET but shorter)
 
@@ -96,11 +109,29 @@ PREPARE_COPY_MATCH_Y
 
 COPY_MATCH_LOOP
    LDA $AAAA                            ; get one byte of backreference
+   JSR PUTDST                           ; copy to destination
+
+!ifdef BACKWARD_DECOMPRESS {
+
+   ; Backward decompression -- put backreference bytes backward
+
+   LDA COPY_MATCH_LOOP+1
+   BNE GETMATCH_DONE
+   DEC COPY_MATCH_LOOP+2
+GETMATCH_DONE
+   DEC COPY_MATCH_LOOP+1
+
+} else {
+
+   ; Forward decompression -- put backreference bytes forward
+
    INC COPY_MATCH_LOOP+1
    BNE GETMATCH_DONE
    INC COPY_MATCH_LOOP+2
 GETMATCH_DONE
-   JSR PUTDST                           ; copy to destination
+
+}
+
    DEX
    BNE COPY_MATCH_LOOP
    DEY
@@ -111,6 +142,29 @@ GET_LONG_OFFSET                         ; handle 16 bit offset:
    JSR GETLARGESRC                      ; grab low 8 bits in X, high 8 bits in A
 
 GOT_OFFSET
+
+!ifdef BACKWARD_DECOMPRESS {
+
+   ; Backward decompression - substract match offset
+
+   STA OFFSHI                           ; store high 8 bits of offset
+   STX OFFSLO
+
+   SEC                                  ; substract dest - match offset
+   LDA PUTDST+1
+OFFSLO = *+1
+   SBC #$AA                             ; low 8 bits
+   STA COPY_MATCH_LOOP+1                ; store back reference address
+   LDA PUTDST+2
+OFFSHI = *+1
+   SBC #$AA                             ; high 8 bits
+   STA COPY_MATCH_LOOP+2                ; store high 8 bits of address
+   SEC
+
+} else {
+
+   ; Forward decompression - add match offset
+
    STA OFFSHI                           ; store high 8 bits of offset
    TXA
 
@@ -123,6 +177,8 @@ OFFSHI = *+1
    ADC PUTDST+2
    STA COPY_MATCH_LOOP+2                ; store high 8 bits of address
    
+}
+
    PLA                                  ; retrieve token from stack again
    AND #$0F                             ; isolate match len (MMMM)
    ADC #$02                             ; plus carry which is always set by the high ADC
@@ -145,6 +201,45 @@ OFFSHI = *+1
 DECOMPRESSION_DONE
    RTS
 
+!ifdef BACKWARD_DECOMPRESS {
+
+   ; Backward decompression -- get and put bytes backward
+
+GETPUT
+   JSR GETSRC
+PUTDST
+LZSA_DST_LO = *+1
+LZSA_DST_HI = *+2
+   STA $AAAA
+   LDA PUTDST+1
+   BNE PUTDST_DONE
+   DEC PUTDST+2
+PUTDST_DONE
+   DEC PUTDST+1
+   RTS
+
+GETLARGESRC
+   JSR GETSRC                           ; grab low 8 bits
+   TAX                                  ; move to X
+                                        ; fall through grab high 8 bits
+
+GETSRC
+LZSA_SRC_LO = *+1
+LZSA_SRC_HI = *+2
+   LDA $AAAA
+   PHA
+   LDA GETSRC+1
+   BNE GETSRC_DONE
+   DEC GETSRC+2
+GETSRC_DONE
+   DEC GETSRC+1
+   PLA
+   RTS
+
+} else {
+
+   ; Forward decompression -- get and put bytes forward
+
 GETPUT
    JSR GETSRC
 PUTDST
@@ -171,3 +266,5 @@ LZSA_SRC_HI = *+2
    INC GETSRC+2
 GETSRC_DONE
    RTS
+
+}

asm/6502/decompress_v2.asm

@@ -8,6 +8,18 @@
 ;
 ; out:
 ; * LZSA_DST_LO and LZSA_DST_HI contain the last decompressed byte address, +1
+;
+; -----------------------------------------------------------------------------
+; Backward decompression is also supported, use lzsa -r -b -f2 <original_file> <compressed_file>
+; To use it, also define BACKWARD_DECOMPRESS=1 before including this code!
+;
+; in:
+; * LZSA_SRC_LO/LZSA_SRC_HI must contain the address of the last byte of compressed data
+; * LZSA_DST_LO/LZSA_DST_HI must contain the address of the last byte of the destination buffer
+;
+; out:
+; * LZSA_DST_LO/LZSA_DST_HI contain the last decompressed byte address, -1
+;
 ; -----------------------------------------------------------------------------
 ;
 ;  Copyright (C) 2019 Emmanuel Marty
@@ -41,9 +53,9 @@ DECODE_TOKEN
 
    AND #$18                             ; isolate literals count (LL)
    BEQ NO_LITERALS                      ; skip if no literals to copy
-   LSR A                                ; shift literals count into place
+   LSR                                  ; shift literals count into place
-   LSR A
+   LSR
-   LSR A
+   LSR
    CMP #$03                             ; LITERALS_RUN_LEN_V2?
    BCC PREPARE_COPY_LITERALS            ; if less, count is directly embedded in token
 
@@ -90,7 +102,7 @@ NO_LITERALS
     
                                         ; 00Z: 5 bit offset
 
-   LDX #$0FF                            ; set offset bits 15-8 to 1
+   LDX #$FF                             ; set offset bits 15-8 to 1
 
    JSR GETCOMBINEDBITS                  ; rotate Z bit into bit 0, read nibble for bits 4-1
    ORA #$E0                             ; set bits 7-5 to 1
@@ -130,6 +142,25 @@ GOT_OFFSET_LO
    STX OFFSHI                           ; store high byte of match offset
 
 REP_MATCH
+!ifdef BACKWARD_DECOMPRESS {
+
+   ; Backward decompression - substract match offset
+
+   SEC                                  ; add dest + match offset
+   LDA PUTDST+1                         ; low 8 bits
+OFFSLO = *+1
+   SBC #$AA
+   STA COPY_MATCH_LOOP+1                ; store back reference address
+   LDA PUTDST+2
+OFFSHI = *+1
+   SBC #$AA                             ; high 8 bits
+   STA COPY_MATCH_LOOP+2                ; store high 8 bits of address
+   SEC
+
+} else {
+
+   ; Forward decompression - add match offset
+
    CLC                                  ; add dest + match offset
    LDA PUTDST+1                         ; low 8 bits
 OFFSLO = *+1
@@ -140,6 +171,8 @@ OFFSHI = *+1
    ADC PUTDST+2
    STA COPY_MATCH_LOOP+2                ; store high 8 bits of address
    
+}
+   
    PLA                                  ; retrieve token from stack again
    AND #$07                             ; isolate match len (MMM)
    ADC #$01                             ; add MIN_MATCH_SIZE_V2 and carry
@@ -173,11 +206,29 @@ PREPARE_COPY_MATCH_Y
 
 COPY_MATCH_LOOP
    LDA $AAAA                            ; get one byte of backreference
+   JSR PUTDST                           ; copy to destination
+
+!ifdef BACKWARD_DECOMPRESS {
+
+   ; Backward decompression -- put backreference bytes backward
+
+   LDA COPY_MATCH_LOOP+1
+   BNE GETMATCH_DONE
+   DEC COPY_MATCH_LOOP+2
+GETMATCH_DONE
+   DEC COPY_MATCH_LOOP+1
+
+} else {
+
+   ; Forward decompression -- put backreference bytes forward
+
    INC COPY_MATCH_LOOP+1
    BNE GETMATCH_DONE
    INC COPY_MATCH_LOOP+2
 GETMATCH_DONE
-   JSR PUTDST                           ; copy to destination
+
+}
+
    DEX
    BNE COPY_MATCH_LOOP
    DEY
@@ -215,6 +266,45 @@ HAS_NIBBLES
    AND #$0F                             ; isolate low 4 bits of nibble
    RTS
 
+!ifdef BACKWARD_DECOMPRESS {
+
+   ; Backward decompression -- get and put bytes backward
+
+GETPUT
+   JSR GETSRC
+PUTDST
+LZSA_DST_LO = *+1
+LZSA_DST_HI = *+2
+   STA $AAAA
+   LDA PUTDST+1
+   BNE PUTDST_DONE
+   DEC PUTDST+2
+PUTDST_DONE
+   DEC PUTDST+1
+   RTS
+
+GETLARGESRC
+   JSR GETSRC                           ; grab low 8 bits
+   TAX                                  ; move to X
+                                        ; fall through grab high 8 bits
+
+GETSRC
+LZSA_SRC_LO = *+1
+LZSA_SRC_HI = *+2
+   LDA $AAAA
+   PHA
+   LDA GETSRC+1
+   BNE GETSRC_DONE
+   DEC GETSRC+2
+GETSRC_DONE
+   DEC GETSRC+1
+   PLA
+   RTS
+
+} else {
+
+   ; Forward decompression -- get and put bytes forward
+
 GETPUT
    JSR GETSRC
 PUTDST
@@ -241,3 +331,6 @@ LZSA_SRC_HI = *+2
    INC GETSRC+2
 GETSRC_DONE
    RTS
+
+}
+

asm/z80/unlzsa2_fast_v1.asm

@@ -1,5 +1,5 @@
 ;
-;  Speed-optimized LZSA2 decompressor by spke (v.1 02-07/06/2019, 218 bytes)
+;  Speed-optimized LZSA2 decompressor by spke (v.1 02-07/06/2019 +patch1-30/07/2019, 213/211(hd64180) bytes)
 ;
 ;  The data must be compressed using the command line compressor by Emmanuel Marty
 ;  The compression is done as follows:
@@ -56,7 +56,7 @@
 		ENDM
 
 		MACRO ADD_OFFSET
-		or a : sbc hl,de
+		push hl : or a : sbc hl,de : pop de
 		ENDM
 
 		MACRO BLOCKCOPY
@@ -70,7 +70,7 @@
 		ENDM
 
 		MACRO ADD_OFFSET
-		add hl,de
+		ex de,hl : add hl,de
 		ENDM
 
 		MACRO BLOCKCOPY
@@ -79,16 +79,32 @@
 
 	ENDIF
 
+	IFDEF	HD64180
+		MACRO LD_IX_DE
+		push de : pop ix
+		ENDM
+		MACRO LD_DE_IX
+		push ix : pop de
+		ENDM
+	ELSE
+		MACRO LD_IX_DE
+		ld ixl,e : ld ixh,d
+		ENDM
+		MACRO LD_DE_IX
+		ld e,ixl : ld d,ixh
+		ENDM
+	ENDIF
+
 @DecompressLZSA2:
 		; A' stores next nibble as %1111.... or assumed to contain trash
 		; B is assumed to be 0
-		xor a : ld b,a : exa : jr ReadToken
+		xor a : ld b,a : scf : exa : jr ReadToken
 
 
 
 
 
-LongerMatch:	exa : jp m,.noUpdate
+LongerMatch:	scf : exa : jr nc,.noUpdate
 
 			ld a,(hl) : or #F0 : exa
 			ld a,(hl) : NEXT_HL : or #0F
@@ -110,14 +126,14 @@ LongMatch:	;ld a,24 :
 ManyLiterals:	ld a,18 : 
 		add (hl) : NEXT_HL : jr nc,CopyLiterals
 		ld c,(hl) : NEXT_HL
-		ld a,b : ld b,(hl) : NEXT_HL
+		ld a,b : ld b,(hl)
-		jr CopyLiterals.useBC
+		jr ReadToken.useBC
 
 
 
 
 MoreLiterals:	ld b,(hl) : NEXT_HL
-		exa : jp m,.noUpdate
+		scf : exa : jr nc,.noUpdate
 
 			ld a,(hl) : or #F0 : exa
 			ld a,(hl) : NEXT_HL : or #0F
@@ -148,13 +164,13 @@ CASE01x:	cp %01100000 : rl d
 
 ReadOffsetE:	ld e,(hl) : NEXT_HL
 
-SaveOffset:	ld ixl,e : ld ixh,d
+SaveOffset:	LD_IX_DE
 
 MatchLen:	inc a : and %00000111 : jr z,LongerMatch : inc a
 
 CopyMatch:	ld c,a
-.useC		ex (sp),hl : push hl					; BC = len, DE = offset, HL = dest, SP ->[dest,src]
+.useC		ex (sp),hl						; BC = len, DE = offset, HL = dest, SP ->[src]
-		ADD_OFFSET : pop de					; BC = len, DE = dest, HL = dest-offset, SP->[src]
+		ADD_OFFSET						; BC = len, DE = dest, HL = dest-offset, SP->[src]
 		BLOCKCOPY : pop hl
 
 		; compressed data stream contains records
@@ -164,7 +180,8 @@ ReadToken:	ld a,(hl) : and %00011000 : jr z,NoLiterals
 		jp pe,MoreLiterals					; 00 has already been processed; this identifies the case of 11
 		rrca : rrca : rrca
 
-		ld c,a : ld a,(hl) : NEXT_HL				; token is re-read for further processing
+		ld c,a : ld a,(hl)					; token is re-read for further processing
+.useBC		NEXT_HL
 		BLOCKCOPY
 
 		; the token and literals are followed by the offset
@@ -173,8 +190,8 @@ ReadToken:	ld a,(hl) : and %00011000 : jr z,NoLiterals
 CASE1xx		cp %11000000 : jr nc,CASE11x
 
 		; "10x": the case of the 5-bit offset
-CASE10x:	ld c,a : xor a
+CASE10x:	ld c,a
-		exa : jp m,.noUpdate
+		exa : jr nc,.noUpdate
 
 			ld a,(hl) : or #F0 : exa
 			ld a,(hl) : NEXT_HL : or #0F
@@ -185,8 +202,8 @@ CASE10x:	ld c,a : xor a
 		dec d : dec d : jr ReadOffsetE
 
 		; "00x": the case of the 5-bit offset
-CASE00x:	ld c,a : xor a
+CASE00x:	ld c,a
-		exa : jp m,.noUpdate
+		exa : jr nc,.noUpdate
 
 			ld a,(hl) : or #F0 : exa
 			ld a,(hl) : NEXT_HL : or #0F
@@ -199,7 +216,7 @@ CASE00x:	ld c,a : xor a
 CASE11x		cp %11100000 : jr c,CASE110
 
 		; "111": repeated offset
-CASE111:	ld e,ixl : ld d,ixh : jr MatchLen
+CASE111:	LD_DE_IX : jr MatchLen
 
 		; "110": 16-bit offset
 CASE110:	ld d,(hl) : NEXT_HL : jr ReadOffsetE

asm/z80/unlzsa2_small_v1.asm

@@ -1,5 +1,5 @@
 ;
-;  Size-optimized LZSA2 decompressor by spke (v.1 02-09/06/2019, 145 bytes)
+;  Size-optimized LZSA2 decompressor by spke (v.1 02-09/06/2019 +patch1-30/07/2019, 144 bytes)
 ;
 ;  The data must be compressed using the command line compressor by Emmanuel Marty
 ;  The compression is done as follows:
@@ -57,7 +57,7 @@
 		ENDM
 
 		MACRO ADD_OFFSET
-		or a : sbc hl,de
+		push hl : or a : sbc hl,de : pop de
 		ENDM
 
 		MACRO BLOCKCOPY
@@ -71,7 +71,7 @@
 		ENDM
 
 		MACRO ADD_OFFSET
-		add hl,de
+		ex de,hl : add hl,de
 		ENDM
 
 		MACRO BLOCKCOPY
@@ -80,6 +80,37 @@
 
 	ENDIF
 
+	IFDEF	HD64180
+		MACRO LD_IY_DE
+		push de : pop iy
+		ENDM
+		MACRO LD_DE_IY
+		push iy : pop de
+		ENDM
+		MACRO LD_IXL_A
+		exx : ld l,a : exx
+		ENDM
+		MACRO LD_A_IXL
+		exx : ld a,l : exx
+		ENDM
+	ELSE
+		MACRO LD_IY_DE
+		;push de : pop iy
+		ld iyl,e : ld iyh,d
+		ENDM
+		MACRO LD_DE_IY
+		;push iy : pop de
+		ld e,iyl : ld d,iyh
+		ENDM
+		MACRO LD_IXL_A
+		ld ixl,a
+		ENDM
+		MACRO LD_A_IXL
+		ld a,ixl
+		ENDM
+	ENDIF
+
+
 @DecompressLZSA2:
 		xor a : ld b,a : exa : jr ReadToken
 
@@ -89,16 +120,16 @@ CASE01x:	cp %01100000 : rl d
 
 OffsetReadE:	ld e,(hl) : NEXT_HL
 
-SaveOffset:	ld iyl,e : ld iyh,d
+SaveOffset:	LD_IY_DE
 
 MatchLen:	and %00000111 : add 2 : cp 9 : call z,ExtendedCode
 
 CopyMatch:	ld c,a
-		ex (sp),hl : push hl						; BC = len, DE = offset, HL = dest, SP ->[dest,src]
+		ex (sp),hl							; BC = len, DE = offset, HL = dest, SP ->[src]
-		ADD_OFFSET : pop de						; BC = len, DE = dest, HL = dest-offset, SP->[src]
+		ADD_OFFSET							; BC = len, DE = dest, HL = dest-offset, SP->[src]
 		BLOCKCOPY : pop hl
 
-ReadToken:	ld a,(hl) : ld ixl,a : NEXT_HL
+ReadToken:	ld a,(hl) : LD_IXL_A : NEXT_HL
 		and %00011000 : jr z,NoLiterals
 
 		rrca : rrca : rrca
@@ -107,7 +138,7 @@ ReadToken:	ld a,(hl) : ld ixl,a : NEXT_HL
 		ld c,a
 		BLOCKCOPY
 
-NoLiterals:	push de : ld a,ixl
+NoLiterals:	push de : LD_A_IXL
 		or a : jp p,CASE0xx
 
 CASE1xx		cp %11000000 : jr nc,CASE11x
@@ -123,7 +154,7 @@ CASE00x:	call ReadNibble
 
 CASE11x		cp %11100000 : jr c,CASE110
 
-CASE111:	ld e,iyl : ld d,iyh : jr MatchLen
+CASE111:	LD_DE_IY : jr MatchLen
 
 CASE110:	ld d,(hl) : NEXT_HL : jr OffsetReadE
 

src/expand_context.c

@@ -35,6 +35,7 @@
 #include "expand_context.h"
 #include "expand_block_v1.h"
 #include "expand_block_v2.h"
+#include "lib.h"
 
 /**
  * Decompress one data block
@@ -45,14 +46,31 @@
  * @param nOutDataOffset starting index of where to store decompressed bytes in output buffer (and size of previously decompressed bytes)
  * @param nBlockMaxSize total size of output decompression buffer, in bytes
  * @param nFormatVersion version of format to use (1-2)
+ * @param nFlags compression flags (LZSA_FLAG_xxx)
  *
  * @return size of decompressed data in bytes, or -1 for error
  */
-int lzsa_decompressor_expand_block(const unsigned char *pInBlock, int nBlockSize, unsigned char *pOutData, int nOutDataOffset, int nBlockMaxSize, const int nFormatVersion) {
+int lzsa_decompressor_expand_block(unsigned char *pInBlock, int nBlockSize, unsigned char *pOutData, int nOutDataOffset, int nBlockMaxSize, const int nFormatVersion, const int nFlags) {
+   int nDecompressedSize;
+
+   if (nFlags & LZSA_FLAG_RAW_BACKWARD) {
+      lzsa_reverse_buffer(pInBlock, nBlockSize);
+   }
+
    if (nFormatVersion == 1)
-      return lzsa_decompressor_expand_block_v1(pInBlock, nBlockSize, pOutData, nOutDataOffset, nBlockMaxSize);
+      nDecompressedSize = lzsa_decompressor_expand_block_v1(pInBlock, nBlockSize, pOutData, nOutDataOffset, nBlockMaxSize);
    else if (nFormatVersion == 2)
-      return lzsa_decompressor_expand_block_v2(pInBlock, nBlockSize, pOutData, nOutDataOffset, nBlockMaxSize);
+      nDecompressedSize = lzsa_decompressor_expand_block_v2(pInBlock, nBlockSize, pOutData, nOutDataOffset, nBlockMaxSize);
    else
-      return -1;
+      nDecompressedSize = -1;
+
+   if (nDecompressedSize != -1 && (nFlags & LZSA_FLAG_RAW_BACKWARD)) {
+      lzsa_reverse_buffer(pOutData + nOutDataOffset, nDecompressedSize);
+   }
+
+   if (nFlags & LZSA_FLAG_RAW_BACKWARD) {
+      lzsa_reverse_buffer(pInBlock, nBlockSize);
+   }
+
+   return nDecompressedSize;
 }

src/expand_context.h

@@ -48,10 +48,11 @@ extern "C" {
  * @param nOutDataOffset starting index of where to store decompressed bytes in output buffer (and size of previously decompressed bytes)
  * @param nBlockMaxSize total size of output decompression buffer, in bytes
  * @param nFormatVersion version of format to use (1-2)
+ * @param nFlags compression flags (LZSA_FLAG_xxx)
  *
  * @return size of decompressed data in bytes, or -1 for error
  */
-int lzsa_decompressor_expand_block(const unsigned char *pInBlock, int nBlockSize, unsigned char *pOutData, int nOutDataOffset, int nBlockMaxSize, const int nFormatVersion);
+int lzsa_decompressor_expand_block(unsigned char *pInBlock, int nBlockSize, unsigned char *pOutData, int nOutDataOffset, int nBlockMaxSize, const int nFormatVersion, const int nFlags);
 
 #ifdef __cplusplus
 }

src/expand_inmem.c

@@ -98,8 +98,8 @@ size_t lzsa_get_max_decompressed_size_inmem(const unsigned char *pFileData, size
  *
  * @return actual decompressed size, or -1 for error
  */
-size_t lzsa_decompress_inmem(const unsigned char *pFileData, unsigned char *pOutBuffer, size_t nFileSize, size_t nMaxOutBufferSize, const unsigned int nFlags, int *pFormatVersion) {
+size_t lzsa_decompress_inmem(unsigned char *pFileData, unsigned char *pOutBuffer, size_t nFileSize, size_t nMaxOutBufferSize, const unsigned int nFlags, int *pFormatVersion) {
-   const unsigned char *pCurFileData = pFileData;
+   unsigned char *pCurFileData = pFileData;
    const unsigned char *pEndFileData = pCurFileData + nFileSize;
    unsigned char *pCurOutBuffer = pOutBuffer;
    const unsigned char *pEndOutBuffer = pCurOutBuffer + nMaxOutBufferSize;
@@ -107,7 +107,7 @@ size_t lzsa_decompress_inmem(const unsigned char *pFileData, unsigned char *pOut
    const int nHeaderSize = lzsa_get_header_size();
 
    if (nFlags & LZSA_FLAG_RAW_BLOCK) {
-      return (size_t)lzsa_decompressor_expand_block(pFileData, (int)nFileSize, pOutBuffer, 0, (int)nMaxOutBufferSize, *pFormatVersion);
+      return (size_t)lzsa_decompressor_expand_block(pFileData, (int)nFileSize, pOutBuffer, 0, (int)nMaxOutBufferSize, *pFormatVersion, nFlags);
    }
 
    /* Check header */
@@ -139,7 +139,7 @@ size_t lzsa_decompress_inmem(const unsigned char *pFileData, unsigned char *pOut
          if ((pCurFileData + nBlockDataSize) > pEndFileData)
             return -1;
 
-         nDecompressedSize = lzsa_decompressor_expand_block(pCurFileData, nBlockDataSize, pCurOutBuffer - nPreviousBlockSize, nPreviousBlockSize, (int)(pEndOutBuffer - pCurOutBuffer + nPreviousBlockSize), *pFormatVersion);
+         nDecompressedSize = lzsa_decompressor_expand_block(pCurFileData, nBlockDataSize, pCurOutBuffer - nPreviousBlockSize, nPreviousBlockSize, (int)(pEndOutBuffer - pCurOutBuffer + nPreviousBlockSize), *pFormatVersion, nFlags);
          if (nDecompressedSize < 0)
             return -1;
 

src/expand_inmem.h

@@ -61,7 +61,7 @@ size_t lzsa_get_max_decompressed_size_inmem(const unsigned char *pFileData, size
  *
  * @return actual decompressed size, or -1 for error
  */
-size_t lzsa_decompress_inmem(const unsigned char *pFileData, unsigned char *pOutBuffer, size_t nFileSize, size_t nMaxOutBufferSize, const unsigned int nFlags, int *pFormatVersion);
+size_t lzsa_decompress_inmem(unsigned char *pFileData, unsigned char *pOutBuffer, size_t nFileSize, size_t nMaxOutBufferSize, const unsigned int nFlags, int *pFormatVersion);
 
 #ifdef __cplusplus
 }

src/expand_streaming.c

@@ -196,7 +196,7 @@ lzsa_status_t lzsa_decompress_stream(lzsa_stream_t *pInStream, lzsa_stream_t *pO
                nDecompressedSize = nBlockSize;
             }
             else {
-               nDecompressedSize = lzsa_decompressor_expand_block(pInBlock, nBlockSize, pOutData, BLOCK_SIZE, BLOCK_SIZE, nFormatVersion);
+               nDecompressedSize = lzsa_decompressor_expand_block(pInBlock, nBlockSize, pOutData, BLOCK_SIZE, BLOCK_SIZE, nFormatVersion, nFlags);
                if (nDecompressedSize < 0) {
                   nDecompressionError = LZSA_ERROR_DECOMPRESSION;
                   break;

src/lib.h

@@ -69,6 +69,24 @@ typedef enum _lzsa_status_t {
 /* Compression flags */
 #define LZSA_FLAG_FAVOR_RATIO    (1<<0)      /**< 1 to compress with the best ratio, 0 to trade some compression ratio for extra decompression speed */
 #define LZSA_FLAG_RAW_BLOCK      (1<<1)      /**< 1 to emit raw block */
+#define LZSA_FLAG_RAW_BACKWARD   (1<<2)      /**< 1 to compress or decompress raw block backward */
+
+/**
+ * Reverse bytes in the specified buffer
+ *
+ * @param pBuffer pointer to buffer whose contents are to be reversed
+ * @param nBufferSize size of buffer in bytes
+ */
+static inline void lzsa_reverse_buffer(unsigned char *pBuffer, const int nBufferSize) {
+   int nMidPoint = nBufferSize / 2;
+   int i, j;
+
+   for (i = 0, j = nBufferSize - 1; i < nMidPoint; i++, j--) {
+      unsigned char c = pBuffer[i];
+      pBuffer[i] = pBuffer[j];
+      pBuffer[j] = c;
+   }
+}
 
 #ifdef __cplusplus
 }

src/lzsa.c

@@ -42,11 +42,12 @@
 #endif
 #include "lib.h"
 
-#define OPT_VERBOSE     1
+#define OPT_VERBOSE        1
-#define OPT_RAW         2
+#define OPT_RAW            2
-#define OPT_FAVOR_RATIO 4
+#define OPT_FAVOR_RATIO    4
+#define OPT_RAW_BACKWARD   8
 
-#define TOOL_VERSION "1.0.4"
+#define TOOL_VERSION "1.0.6"
 
 /*---------------------------------------------------------------------------*/
 
@@ -109,6 +110,8 @@ static int do_compress(const char *pszInFilename, const char *pszOutFilename, co
       nFlags |= LZSA_FLAG_FAVOR_RATIO;
    if (nOptions & OPT_RAW)
       nFlags |= LZSA_FLAG_RAW_BLOCK;
+   if (nOptions & OPT_RAW_BACKWARD)
+      nFlags |= LZSA_FLAG_RAW_BACKWARD;
 
    if (nOptions & OPT_VERBOSE) {
       nStartTime = do_get_time();
@@ -160,6 +163,8 @@ static int do_decompress(const char *pszInFilename, const char *pszOutFilename,
    nFlags = 0;
    if (nOptions & OPT_RAW)
       nFlags |= LZSA_FLAG_RAW_BLOCK;
+   if (nOptions & OPT_RAW_BACKWARD)
+      nFlags |= LZSA_FLAG_RAW_BACKWARD;
 
    if (nOptions & OPT_VERBOSE) {
       nStartTime = do_get_time();
@@ -308,6 +313,8 @@ static int do_compare(const char *pszInFilename, const char *pszOutFilename, con
    nFlags = 0;
    if (nOptions & OPT_RAW)
       nFlags |= LZSA_FLAG_RAW_BLOCK;
+   if (nOptions & OPT_RAW_BACKWARD)
+      nFlags |= LZSA_FLAG_RAW_BACKWARD;
 
    if (nOptions & OPT_VERBOSE) {
       nStartTime = do_get_time();
@@ -419,6 +426,8 @@ static int do_self_test(const unsigned int nOptions, const int nMinMatchSize, in
       nFlags |= LZSA_FLAG_FAVOR_RATIO;
    if (nOptions & OPT_RAW)
       nFlags |= LZSA_FLAG_RAW_BLOCK;
+   if (nOptions & OPT_RAW_BACKWARD)
+      nFlags |= LZSA_FLAG_RAW_BACKWARD;
 
    pGeneratedData = (unsigned char*)malloc(4 * BLOCK_SIZE);
    if (!pGeneratedData) {
@@ -477,7 +486,7 @@ static int do_self_test(const unsigned int nOptions, const int nMinMatchSize, in
       float fMatchProbability;
 
       fprintf(stdout, "size %zd", nGeneratedDataSize);
-      for (fMatchProbability = ((nOptions & OPT_RAW) ? 0.5f : 0); fMatchProbability <= 0.995f; fMatchProbability += fProbabilitySizeStep) {
+      for (fMatchProbability = 0; fMatchProbability <= 0.995f; fMatchProbability += fProbabilitySizeStep) {
          int nNumLiteralValues[12] = { 1, 2, 3, 15, 30, 56, 96, 137, 178, 191, 255, 256 };
          float fXorProbability;
 
@@ -590,6 +599,8 @@ static int do_compr_benchmark(const char *pszInFilename, const char *pszOutFilen
       nFlags |= LZSA_FLAG_FAVOR_RATIO;
    if (nOptions & OPT_RAW)
       nFlags |= LZSA_FLAG_RAW_BLOCK;
+   if (nOptions & OPT_RAW_BACKWARD)
+      nFlags |= LZSA_FLAG_RAW_BACKWARD;
 
    if (pszDictionaryFilename) {
       fprintf(stderr, "in-memory benchmarking does not support dictionaries\n");
@@ -720,6 +731,8 @@ static int do_dec_benchmark(const char *pszInFilename, const char *pszOutFilenam
    nFlags = 0;
    if (nOptions & OPT_RAW)
       nFlags |= LZSA_FLAG_RAW_BLOCK;
+   if (nOptions & OPT_RAW_BACKWARD)
+      nFlags |= LZSA_FLAG_RAW_BACKWARD;
 
    if (pszDictionaryFilename) {
       fprintf(stderr, "in-memory benchmarking does not support dictionaries\n");
@@ -987,6 +1000,13 @@ int main(int argc, char **argv) {
          else
             bArgsError = true;
       }
+      else if (!strcmp(argv[i], "-b")) {
+         if ((nOptions & OPT_RAW_BACKWARD) == 0) {
+            nOptions |= OPT_RAW_BACKWARD;
+         }
+         else
+            bArgsError = true;
+      }
       else {
          if (!pszInFilename)
             pszInFilename = argv[i];
@@ -999,6 +1019,11 @@ int main(int argc, char **argv) {
       }
    }
 
+   if (!bArgsError && (nOptions & OPT_RAW_BACKWARD) && !(nOptions & OPT_RAW)) {
+      fprintf(stderr, "error: -b (compress backwards) requires -r (raw block format)\n");
+      return 100;
+   }
+
    if (!bArgsError && cCommand == 't') {
       return do_self_test(nOptions, nMinMatchSize, nFormatVersion);
    }
@@ -1014,6 +1039,7 @@ int main(int argc, char **argv) {
       fprintf(stderr, "       -v: be verbose\n");
       fprintf(stderr, "       -f <value>: LZSA compression format (1-2)\n");
       fprintf(stderr, "       -r: raw block format (max. 64 Kb files)\n");
+      fprintf(stderr, "       -b: compress backward (requires -r and a backward decompressor)\n");
       fprintf(stderr, "       -D <filename>: use dictionary file\n");
       fprintf(stderr, "       -m <value>: minimum match size (3-5) (default: 3)\n");
       fprintf(stderr, "       --prefer-ratio: favor compression ratio (default)\n");

src/shrink_block_v2.c

@@ -188,7 +188,6 @@ static void lzsa_optimize_matches_v2(lzsa_compressor *pCompressor, const int nSt
    int *cost = (int*)pCompressor->pos_data;  /* Reuse */
    int *prev_match = (int*)pCompressor->intervals; /* Reuse */
    lzsa_repmatch_opt *repmatch_opt = pCompressor->repmatch_opt;
-   lzsa_match *pBestMatch = pCompressor->best_match;
    int nLastLiteralsOffset;
    int nMinMatchSize = pCompressor->min_match_size;
    const int nFavorRatio = (pCompressor->flags & LZSA_FLAG_FAVOR_RATIO) ? 1 : 0;
@@ -805,7 +804,6 @@ static int lzsa_get_compressed_size_v2(lzsa_compressor *pCompressor, lzsa_match
    }
 
    {
-      int nTokenLiteralsLen = (nNumLiterals >= LITERALS_RUN_LEN_V2) ? LITERALS_RUN_LEN_V2 : nNumLiterals;
       int nCommandSize = 8 /* token */ + lzsa_get_literals_varlen_size_v2(nNumLiterals) + (nNumLiterals << 3);
 
       nCompressedSize += nCommandSize;

src/shrink_context.c

@@ -37,6 +37,7 @@
 #include "shrink_block_v2.h"
 #include "format.h"
 #include "matchfinder.h"
+#include "lib.h"
 
 /**
  * Initialize compression context
@@ -188,23 +189,43 @@ void lzsa_compressor_destroy(lzsa_compressor *pCompressor) {
  *
  * @return size of compressed data in output buffer, or -1 if the data is uncompressible
  */
-int lzsa_compressor_shrink_block(lzsa_compressor *pCompressor, const unsigned char *pInWindow, const int nPreviousBlockSize, const int nInDataSize, unsigned char *pOutData, const int nMaxOutDataSize) {
+int lzsa_compressor_shrink_block(lzsa_compressor *pCompressor, unsigned char *pInWindow, const int nPreviousBlockSize, const int nInDataSize, unsigned char *pOutData, const int nMaxOutDataSize) {
-   if (lzsa_build_suffix_array(pCompressor, pInWindow, nPreviousBlockSize + nInDataSize))
+   int nCompressedSize;
-      return -1;
-   if (nPreviousBlockSize) {
-      lzsa_skip_matches(pCompressor, 0, nPreviousBlockSize);
-   }
-   lzsa_find_all_matches(pCompressor, nPreviousBlockSize, nPreviousBlockSize + nInDataSize);
 
-   if (pCompressor->format_version == 1) {
+   if (pCompressor->flags & LZSA_FLAG_RAW_BACKWARD) {
-      return lzsa_optimize_and_write_block_v1(pCompressor, pInWindow, nPreviousBlockSize, nInDataSize, pOutData, nMaxOutDataSize);
+      lzsa_reverse_buffer(pInWindow + nPreviousBlockSize, nInDataSize);
-   }
-   else if (pCompressor->format_version == 2) {
-      return lzsa_optimize_and_write_block_v2(pCompressor, pInWindow, nPreviousBlockSize, nInDataSize, pOutData, nMaxOutDataSize);
    }
+
+   if (lzsa_build_suffix_array(pCompressor, pInWindow, nPreviousBlockSize + nInDataSize))
+      nCompressedSize = -1;
    else {
-      return -1;
+      if (nPreviousBlockSize) {
+         lzsa_skip_matches(pCompressor, 0, nPreviousBlockSize);
+      }
+      lzsa_find_all_matches(pCompressor, nPreviousBlockSize, nPreviousBlockSize + nInDataSize);
+
+      if (pCompressor->format_version == 1) {
+         nCompressedSize = lzsa_optimize_and_write_block_v1(pCompressor, pInWindow, nPreviousBlockSize, nInDataSize, pOutData, nMaxOutDataSize);
+         if (nCompressedSize != -1 && (pCompressor->flags & LZSA_FLAG_RAW_BACKWARD)) {
+            lzsa_reverse_buffer(pOutData, nCompressedSize);
+         }
+      }
+      else if (pCompressor->format_version == 2) {
+         nCompressedSize = lzsa_optimize_and_write_block_v2(pCompressor, pInWindow, nPreviousBlockSize, nInDataSize, pOutData, nMaxOutDataSize);
+         if (nCompressedSize != -1 && (pCompressor->flags & LZSA_FLAG_RAW_BACKWARD)) {
+            lzsa_reverse_buffer(pOutData, nCompressedSize);
+         }
+      }
+      else {
+         nCompressedSize = -1;
+      }
    }
+
+   if (pCompressor->flags & LZSA_FLAG_RAW_BACKWARD) {
+      lzsa_reverse_buffer(pInWindow + nPreviousBlockSize, nInDataSize);
+   }
+
+   return nCompressedSize;
 }
 
 /**

src/shrink_context.h

@@ -123,7 +123,7 @@ void lzsa_compressor_destroy(lzsa_compressor *pCompressor);
  *
  * @return size of compressed data in output buffer, or -1 if the data is uncompressible
  */
-int lzsa_compressor_shrink_block(lzsa_compressor *pCompressor, const unsigned char *pInWindow, const int nPreviousBlockSize, const int nInDataSize, unsigned char *pOutData, const int nMaxOutDataSize);
+int lzsa_compressor_shrink_block(lzsa_compressor *pCompressor, unsigned char *pInWindow, const int nPreviousBlockSize, const int nInDataSize, unsigned char *pOutData, const int nMaxOutDataSize);
 
 /**
  * Get the number of compression commands issued in compressed data blocks

src/shrink_inmem.c

@@ -62,7 +62,7 @@ size_t lzsa_get_max_compressed_size_inmem(size_t nInputSize) {
  *
  * @return actual compressed size, or -1 for error
  */
-size_t lzsa_compress_inmem(const unsigned char *pInputData, unsigned char *pOutBuffer, size_t nInputSize, size_t nMaxOutBufferSize,
+size_t lzsa_compress_inmem(unsigned char *pInputData, unsigned char *pOutBuffer, size_t nInputSize, size_t nMaxOutBufferSize,
                              const unsigned int nFlags, const int nMinMatchSize, const int nFormatVersion) {
    lzsa_compressor compressor;
    size_t nOriginalSize = 0;

src/shrink_inmem.h

@@ -61,7 +61,7 @@ size_t lzsa_get_max_compressed_size_inmem(size_t nInputSize);
  *
  * @return actual compressed size, or -1 for error
  */
-size_t lzsa_compress_inmem(const unsigned char *pInputData, unsigned char *pOutBuffer, size_t nInputSize, size_t nMaxOutBufferSize,
+size_t lzsa_compress_inmem(unsigned char *pInputData, unsigned char *pOutBuffer, size_t nInputSize, size_t nMaxOutBufferSize,
    const unsigned int nFlags, const int nMinMatchSize, const int nFormatVersion);
 
 #ifdef __cplusplus

src/shrink_streaming.c

@@ -70,6 +70,7 @@ static void lzsa_delete_file(const char *pszInFilename) {
  * @param pOriginalSize pointer to returned input(source) size, updated when this function is successful
  * @param pCompressedSize pointer to returned output(compressed) size, updated when this function is successful
  * @param pCommandCount pointer to returned token(compression commands) count, updated when this function is successful
+ * @param pSafeDist pointer to return safe distance for raw blocks, updated when this function is successful
  *
  * @return LZSA_OK for success, or an error value from lzsa_status_t
  */
@@ -127,6 +128,7 @@ lzsa_status_t lzsa_compress_file(const char *pszInFilename, const char *pszOutFi
  * @param pOriginalSize pointer to returned input(source) size, updated when this function is successful
  * @param pCompressedSize pointer to returned output(compressed) size, updated when this function is successful
  * @param pCommandCount pointer to returned token(compression commands) count, updated when this function is successful
+ * @param pSafeDist pointer to return safe distance for raw blocks, updated when this function is successful
  *
  * @return LZSA_OK for success, or an error value from lzsa_status_t
  */

src/shrink_streaming.h

@@ -57,6 +57,7 @@ typedef enum _lzsa_status_t lzsa_status_t;
  * @param pOriginalSize pointer to returned input(source) size, updated when this function is successful
  * @param pCompressedSize pointer to returned output(compressed) size, updated when this function is successful
  * @param pCommandCount pointer to returned token(compression commands) count, updated when this function is successful
+ * @param pSafeDist pointer to return safe distance for raw blocks, updated when this function is successful
  *
  * @return LZSA_OK for success, or an error value from lzsa_status_t
  */
@@ -80,6 +81,7 @@ lzsa_status_t lzsa_compress_file(const char *pszInFilename, const char *pszOutFi
  * @param pOriginalSize pointer to returned input(source) size, updated when this function is successful
  * @param pCompressedSize pointer to returned output(compressed) size, updated when this function is successful
  * @param pCommandCount pointer to returned token(compression commands) count, updated when this function is successful
+ * @param pSafeDist pointer to return safe distance for raw blocks, updated when this function is successful
  *
  * @return LZSA_OK for success, or an error value from lzsa_status_t
  */