NOTE: I recommend using the latest version. The previous versions are mainly there for archival purposes. I started this a while ago due to a conversation on discord, regarding improving Enigma and taking notes for a potential "Enigma+". It's gone through some needed revisions over time (my original attempt was embarrassing in hindsight), but I'm confident enough in its current state to release it. It comes with four flags, two for balancing between size and speed, one for enabling error free odd-addressing, and one for compatibility with segas original implementation: they didn't trash d0/a0-a1, and I planned to trash them because they usually aren't that useful when decompression is over. However, an incompatibility is an incompatibility, so I made a flag to switch between either. By default, it favours size and compatibility. This was made for AS. I'm not gonna bother porting it asm68k, but it should be simple enough to port over. You can either read the code here or get an .asm file from the .zip file Spoiler Code: ; --------------------------------------------------------------------------- ; Enigma Decompression Algorithm ; For format explanation see http://info.sonicretro.org/Enigma_compression ; this one is optimised from the original, with the more rom-intensive ; speedups enabled by some flags down below ; --------------------------------------------------------------------------- ; INPUTS: ; d0 = starting art tile (added to each 8x8 before writing to destination) ; a0 = source address ; a1 = destination address ; TRASHES: ; d0,a0,a1 ; STACK: ; - saved registers d1-d7/a2-a6 (13x4 bytes) ; - 4 bytes for one bsr (GetInlineCopyVal and ChkGetNextByte) ; - 2 bytes for word conversion ; --------------------------------------------------------------------------- _Eni_CompatibilityMode = 1 ; if 1, stay compatible with the original Enigma ; (they saved d0 and a1, and made a0 point to the end of the file) _Eni_EvenAligned = 0 ; if 1, allows Enigma compressed files to be at an odd numbered address _Eni_RemoveJmpTable = 0 ; if 1, saves 22 cycles per loop (12 for SubE) at the cost of some rom space _Eni_InlineBitStream = 0 ; if 1, inlines ChkGetNextByte in EniDec_Loop, for a speedup of 34 cycles per loop ; funny how this simple speedup greatly overshadows _Eni_RemoveJmpTable ; that one required infinitely more effort then this. oh well. ; for removejmpto, routines needs to be 16 ($10) bytes from the next routine ; the only exception is SubE; the last one ; this macro should be easy enough to port to more primative macro formats enidecpad16 macro routine if *-routine>16 ; if it exceeds 16, throw an error fatal "ADDR ERROR - EXCEED: routine exceeds 16 bytes! ($\{*-routine} bytes)" elseif *-routine<16 ; if it's below 16, pad it to 16 ; message "routine got padded by $\{16-(*-routine)} bytes" ; debug dc.b [16-(*-routine)]$69 endif endm ; this was just repetitive enidec_checktileflags macro bit,setmode add.b d1,d1 bcc.s .skip ; if that bit wasn't set, branch subq.w #1,d6 ; get next bit number btst d6,d5 ; is this tile flag bit set? beq.s .skip ; if not, branch if setmode=0 ori.w #1<<bit,d3 else addi.w #1<<bit,d3 endif .skip endm ; =========================================================================== EniDec: if _Eni_CompatibilityMode=0 movem.l d1-d7/a2-a6,-(sp) else movem.l d0-d7/a1-a6,-(sp) endif ; for compatibility with old assemblers I can't use a proper equation, so lemme explain ; the exact value will depend on codebases amount of stack use after the saved registers ; basically just count how many bsrs, jsrs or peas can lead into another one... ; ...make it a negative number and multiply that by 4 ; for this version of the code, that's 1 ; then add -2, because we need a word-sized buffer ; -(1*4)-2 = -6 lea -6(sp),a6 ; load byte-to-word ram buffer in a6 ; set subroutine loop address ; compared to a bra, jmp (aN) saves 2 cycles per loop lea EniDec_Loop(pc),a5 movea.w d0,a3 ; store starting art tile move.b (a0)+,d0 ext.w d0 movea.w d0,a2 ; set initial bit amount for inline copy move.b (a0)+,d0 ; 000PCCHV ; set vram flag permits lsl.b #3,d0 ; PCCHV000 ; shift by 3 move.w d0,d2 ; store in the high word of d2 swap d2 ; set increment word if _Eni_EvenAligned=0 move.w (a0)+,d4 else move.b (a0)+,(a6)+ move.b (a0)+,(a6)+ move.w -(a6),d4 endif add.w a3,d4 ; add starting art tile ; set static word if _Eni_EvenAligned=0 move.w (a0)+,d0 else move.b (a0)+,(a6)+ move.b (a0)+,(a6)+ move.w -(a6),d0 endif add.w a3,d0 ; add starting art tile movea.w d0,a4 ; store in a4 (moves and adds are faster on dN.w, saves 4 cycles) ; set initial subroutine flag if _Eni_EvenAligned=0 move.w (a0)+,d5 else move.b (a0)+,(a6)+ move.b (a0)+,(a6)+ move.w -(a6),d5 endif ; set bit counter moveq #16,d6 ; 16 bits = 2 bytes EniDec_Loop: moveq #7,d0 ; process 7 bits at a time move.w d6,d7 ; move d6 to d7 sub.w d0,d7 ; subtract by 7 (convenient) move.w d5,d1 ; copy d5 into d1 lsr.w d7,d1 ; right shift by value in d7 move.w d1,d2 ; move d1 to d2 andi.w #%01110000,d1 ; keep only 3 bits. Lower 4 are for d2, sign bit unused cmpi.w #1<<6,d1 ; is bit 6 set? bhs.s .7bitcommand ; if it is, branch moveq #6,d0 ; if not, process 6 bits instead of 7 lsr.w #1,d2 ; bitfield now becomes TTSSSS instead of TTTSSSS .7bitcommand: if _Eni_InlineBitStream=0 bsr.w EniDec_ChkGetNextByte ; uses d0, doesn't touch d1 or d2 else ;EniDec_ChkGetNextByte: sub.w d0,d6 ; subtract d0 from d6 cmpi.w #8,d6 ; has it hit 8 or lower? bhi.s .nonewbyte ; if not, branch addq.w #8,d6 ; 8 bits = 1 byte asl.w #8,d5 ; shift up by a byte move.b (a0)+,d5 ; store next byte in lower register byte .nonewbyte: endif moveq #$F,d3 ; d3 is also used for SubE and.w d3,d2 ; keep only lower nybble if _Eni_RemoveJmpTable=0 ; JmpTable addresses are word-sized. ; Due to its placement in rom, SubE just falls into itself lsr.w #4-1,d1 ; store upper nybble multiplied by 2 (max value = 7) jmp EniDec_JmpTable(pc,d1.w) else ; all subroutines are offset by 16 bytes. Some of them barely fit, I'm quite proud of that ; SubE exceeds this, but it's the last one so it doesn't matter jmp EniDec_Sub0(pc,d1.w) endif ; --------------------------------------------------------------------------- EniDec_Sub0: .loop: move.w d4,(a1)+ ; write to destination addq.w #1,d4 ; increment dbra d2,.loop ; repeat jmp (a5) ; EniDec_Loop if _Eni_RemoveJmpTable<>0 enidecpad16 EniDec_Sub0 EniDec_Sub2: .loop: move.w d4,(a1)+ ; write to destination addq.w #1,d4 ; increment dbra d2,.loop ; repeat jmp (a5) ; EniDec_Loop enidecpad16 EniDec_Sub2 endif ; --------------------------------------------------------------------------- EniDec_Sub4: .loop: move.w a4,(a1)+ ; write to destination dbra d2,.loop ; repeat jmp (a5) ; EniDec_Loop if _Eni_RemoveJmpTable<>0 enidecpad16 EniDec_Sub4 EniDec_Sub6: .loop: move.w a4,(a1)+ ; write to destination dbra d2,.loop ; repeat jmp (a5) ; EniDec_Loop enidecpad16 EniDec_Sub6 endif ; --------------------------------------------------------------------------- EniDec_Sub8: bsr.s EniDec_GetInlineCopyVal .loop: move.w d1,(a1)+ dbra d2,.loop jmp (a5) ; EniDec_Loop if _Eni_RemoveJmpTable<>0 enidecpad16 EniDec_Sub8 endif ; --------------------------------------------------------------------------- EniDec_SubA: bsr.s EniDec_GetInlineCopyVal .loop: move.w d1,(a1)+ addq.w #1,d1 dbra d2,.loop jmp (a5) ; EniDec_Loop if _Eni_RemoveJmpTable<>0 enidecpad16 EniDec_SubA endif ; --------------------------------------------------------------------------- EniDec_SubC: bsr.s EniDec_GetInlineCopyVal .loop: move.w d1,(a1)+ subq.w #1,d1 dbra d2,.loop jmp (a5) ; EniDec_Loop if _Eni_RemoveJmpTable<>0 enidecpad16 EniDec_SubC else ; --------------------------------------------------------------------------- EniDec_JmpTable: bra.s EniDec_Sub0 bra.s EniDec_Sub0 ; Sub2 bra.s EniDec_Sub4 bra.s EniDec_Sub4 ; Sub6 bra.s EniDec_Sub8 bra.s EniDec_SubA bra.s EniDec_SubC ;bra.s EniDec_SubE ; fall into SubE endif ; --------------------------------------------------------------------------- ; EniDec_SubE is truly a special case EniDec_SubE: cmp.w d3,d2 ; d3 = $F ; is the loop set to 16? beq.s EniDec_End ; if so, branch (signifies to end .loop: bsr.s EniDec_GetInlineCopyVal move.w d1,(a1)+ dbra d2,.loop jmp (a5) ; EniDec_Loop EniDec_End: if _Eni_CompatibilityMode=0 movem.l (sp)+,d1-d7/a2-a6 else ; this code figures out where a0 should end subq.w #1,a0 cmpi.w #16,d6 ; were we going to start on a completely new byte? bne.s .got_byte ; if not, branch subq.w #1,a0 .got_byte: move.w a0,d0 lsr.w #1,d0 ; are we on an odd byte? bhs.s .even_loc ; if not, branch addq.w #1,a0 ; ensure we're on an even byte .even_loc: movem.l (sp)+,d0-d7/a1-a6 endif rts ; =========================================================================== EniDec_GetInlineCopyVal: move.w a3,d3 ; starting art tile ; original didn't need to use a high word ; this is a 4 cycle loss, though it's usually made up for everywhere else move.l d2,d1 ; get vram tile flags swap d1 ; (it's in the high word of d2) enidec_checktileflags 15,0 enidec_checktileflags 14,1 enidec_checktileflags 13,1 enidec_checktileflags 12,0 enidec_checktileflags 11,0 move.w d5,d1 move.w d6,d7 ; get remaining bits sub.w a2,d7 ; subtract minimum bit number bhs.s .got_enough ; if we're beyond that, branch move.w d7,d6 addi.w #16,d6 ; 16 bits = 2 bytes neg.w d7 ; calculate bit deficit lsl.w d7,d1 ; make space for this many bits move.b (a0),d5 ; get next byte rol.b d7,d5 ; make the upper X bits the lower X bits add.w d7,d7 and.w .andvalues-2(pc,d7.w),d5; only keep X lower bits add.w d5,d1 ; compensate for the bit deficit .got_field: move.w a2,d0 add.w d0,d0 and.w .andvalues-2(pc,d0.w),d1; only keep as many bits as required add.w d3,d1 ; add starting art tile ; move.b (a0)+,d5 ; 08 ; get current byte, move onto next byte ; lsl.w #8,d5 ; 22 ; shift up by a byte ; move.b (a0)+,d5 ; 08 ; store next byte in lower register byte ; 38 ; saves 4 cycles per branch, at the cost of saving and restoring a6, and setting up the register ; those caveats add around 24 cycles, but from my tests, it usually results in a speedup move.b (a0)+,(a6)+ ; 12 ; temporarily write into the destination move.b (a0)+,(a6)+ ; 12 move.w -(a6),d5 ; 10 ; move result to d5, set destination back to correct spot ; 34 rts ; --------------------------------------------------------------------------- .andvalues: dc.w 1, 3, 7, $F dc.w $1F, $3F, $7F, $FF dc.w $1FF, $3FF, $7FF, $FFF dc.w $1FFF,$3FFF,$7FFF,$FFFF ; --------------------------------------------------------------------------- .got_exact: moveq #16,d6 ; 16 bits = 2 bytes bra.s .got_field ; --------------------------------------------------------------------------- .got_enough: beq.s .got_exact ; if the exact number of bits are leftover, branch lsr.w d7,d1 ; remove unneeded bits move.w a2,d0 add.w d0,d0 and.w .andvalues-2(pc,d0.w),d1 ; only keep as many bits as required add.w d3,d1 ; add starting art tile move.w a2,d0 ; store number of bits used up by inline copy ; bra.s EniDec_ChkGetNextByte ; move onto next byte EniDec_ChkGetNextByte: sub.w d0,d6 ; subtract d0 from d6 cmpi.w #8,d6 ; has it hit 8 or lower? bhi.s .nonewbyte ; if not, branch addq.w #8,d6 ; 8 bits = 1 byte ; shift lowest byte to highest byte, and load a new value into low byte asl.w #8,d5 ; 22 ; shift up by a byte move.b (a0)+,d5 ; 08 ; store next byte in lower register byte ; 30 ; move.b d5,(a6)+ ; 08 ; move.b (a0)+,(a6)+ ; 12 ; move.w -(a6),d5 ; 10 ; 30, sad. .nonewbyte: rts ; ---------------------------------------------------------------------------
I'm doing another release, for two reasons: Firstly, Orion ported it to ASM68K. I knew it was possible, but didn't bother; mainly due to my lack of knowledge on ASM68K macros. Now there's native support... with another flag. _Eni_Assembler changes what assembler it targets: 0 for ASM68K, 1 for AS. Big thanks Orion, I'll definitely be taking notes from this for the future. Secondly, my original implementation had a race condition with some stack data, potentially causing issues with decompression when interrupts are enabled. Register a6 is used to retrieve potentially odd-addressed word-sized data (doing so without a process like this would cause an address error), and to do that quickly without requiring extra ram, is positioned at the end of where stack would reach in the decompressors code. However, that end is unprotected from say, vertical interrupts, meaning there is a short window where the data can be corrupted. This can wildly vary in severity, but most recorded cases are dire. For example, Sonic 1 uses Enigma compression for its block data, and those can sometimes break, resulting in this: Now it properly allocates a safe area of stack, instead of being just outside of it. Thanks to DSK for finding this before I did, that really helped to narrow it down. I'll be keeping the original file up, but highly recommend using v1.1, or whatever the highest revision is at the time. The zip file updates will be uploaded onto the first post, so you don't have to dig for it. v1.1 code Code: ; --------------------------------------------------------------------------- ; Enigma Decompression Algorithm ; For format explanation see http://info.sonicretro.org/Enigma_compression ; this one is optimised from the original, but with the more rom-intensive ; speedups locked behind some flags down below ; --------------------------------------------------------------------------- ; proper ASM68K support added by OrionNavattan _Eni_Assembler: equ 1 ; ASM68K = 0, AS = 1 ; --------------------------------------------------------------------------- ; INPUTS: ; d0 = starting art tile (added to each 8x8 before writing to destination) ; a0 = source address ; a1 = destination address ; TRASHES: ; d0,a0,a1 ; STACK: ; - saved registers d1-d7/a2-a6 (13x4 bytes) ; - 4 bytes for one bsr (EniDec_GetInlineCopyVal and EniDec_ChkGetNextByte) ; - 2 bytes for word conversion ; --------------------------------------------------------------------------- ; equ instead of = for ASM68K compatibility _Eni_CompatibilityMode: equ 1 ; if 1, stay compatible with the original Enigma ; (they saved d0 and a1, and made a0 point to the end of the file) _Eni_EvenAligned: equ 0 ; if 1, allows Enigma compressed files to be at an odd numbered address _Eni_RemoveJmpTable: equ 0 ; if 1, saves 22 cycles per loop (12 for SubE) at the cost of some rom space _Eni_InlineBitStream: equ 0 ; if 1, inlines ChkGetNextByte in EniDec_Loop, for a speedup of 34 cycles per loop ; funny how this simple speedup greatly overshadows _Eni_RemoveJmpTable ; that one required infinitely more effort then this. oh well. ; macro explanations ; enidecpad16: ; - for RemoveJmpTable, routines needs to be aligned in 16($10) byte chunks ; none of the routines can exceed that boundary, or the code won't work ; the only exception to this is SubE; the last one ; enidec_checktileflags: ; - this was just repetitive if _Eni_Assembler=0 pusho ; save current options opt l. ; use "." as local label symbol enidecpad16: macro routine if (*-routine)>16 ; if it exceeds 16, throw an error inform 3,"ADDR ERROR - EXCEED: routine exceeds 16 bytes! ($%h bytes)",*-routine elseif (*-routine)<16 ; if it's below 16, pad it to 16 ; inform 0,"routine got padded by $%h bytes",*-routine ; debug dcb.b 16-(*-routine),0 endif endm enidec_checktileflags: macro bit,setmode add.b d1,d1 bcc.s .skip\@ ; if that bit wasn't set, branch subq.w #1,d6 ; get next bit number btst d6,d5 ; is this tile flag bit set? beq.s .skip\@ ; if not, branch if setmode=0 ori.w #1<<bit,d3 else addi.w #1<<bit,d3 endif .skip\@: endm else enidecpad16 macro routine if *-routine>16 ; if it exceeds 16, throw an error fatal "ADDR ERROR - EXCEED: routine exceeds 16 bytes! ($\{*-routine} bytes)" elseif *-routine<16 ; if it's below 16, pad it to 16 ; message "routine got padded by $\{16-(*-routine)} bytes" ; debug dc.b [16-(*-routine)]$69 endif endm enidec_checktileflags macro bit,setmode add.b d1,d1 bcc.s .skip ; if that bit wasn't set, branch subq.w #1,d6 ; get next bit number btst d6,d5 ; is this tile flag bit set? beq.s .skip ; if not, branch if setmode=0 ori.w #1<<bit,d3 else addi.w #1<<bit,d3 endif .skip endm endif ; =========================================================================== EniDec: if _Eni_CompatibilityMode=0 movem.l d1-d7/a2-a6,-(sp) else movem.l d0-d7/a1-a6,-(sp) endif ; compared to my original implementation, this prevents a race condition ; big thanks to DSK for finding this first subq.l #2,sp ; allocate 2 bytes from stack lea (sp),a6 ; use those bytes (via a6) for conversions ; set subroutine loop address ; compared to a bra, jmp (aN) saves 2 cycles per-loop lea EniDec_Loop(pc),a5 movea.w d0,a3 ; store starting art tile move.b (a0)+,d0 ext.w d0 movea.w d0,a2 ; set initial bit amount for inline copy move.b (a0)+,d0 ; 000PCCHV ; set vram flag permits lsl.b #3,d0 ; PCCHV000 ; shift by 3 move.w d0,d2 ; store in the high word of d2 swap d2 ; set increment word if _Eni_EvenAligned=0 move.w (a0)+,d4 else move.b (a0)+,(a6)+ move.b (a0)+,(a6)+ move.w -(a6),d4 endif add.w a3,d4 ; add starting art tile ; set static word if _Eni_EvenAligned=0 move.w (a0)+,d0 else move.b (a0)+,(a6)+ move.b (a0)+,(a6)+ move.w -(a6),d0 endif add.w a3,d0 ; add starting art tile movea.w d0,a4 ; store in a4 (moves and adds are faster on dN.w, saves 4 cycles) ; set initial subroutine flag if _Eni_EvenAligned=0 move.w (a0)+,d5 else move.b (a0)+,(a6)+ move.b (a0)+,(a6)+ move.w -(a6),d5 endif ; set bit counter moveq #16,d6 ; 16 bits = 2 bytes EniDec_Loop: moveq #7,d0 ; process 7 bits at a time move.w d6,d7 ; move d6 to d7 sub.w d0,d7 ; subtract by 7 (convenient) move.w d5,d1 ; copy d5 into d1 lsr.w d7,d1 ; right shift by value in d7 move.w d1,d2 ; move d1 to d2 andi.w #%01110000,d1 ; keep only 3 bits. Lower 4 are for d2, sign bit unused cmpi.w #1<<6,d1 ; is bit 6 set? bhs.s .prcocess7bits ; if it is, branch moveq #6,d0 ; if not, process 6 bits instead of 7 lsr.w #1,d2 ; bitfield now becomes TTSSSS instead of TTTSSSS .prcocess7bits: if _Eni_InlineBitStream=0 bsr.w EniDec_ChkGetNextByte ; uses d0, doesn't touch d1 or d2 else ;EniDec_ChkGetNextByte: sub.w d0,d6 ; subtract d0 from d6 cmpi.w #8,d6 ; has it hit 8 or lower? bhi.s .nonewbyte ; if not, branch addq.w #8,d6 ; 8 bits = 1 byte asl.w #8,d5 ; shift up by a byte move.b (a0)+,d5 ; store next byte in lower register byte .nonewbyte: endif moveq #$F,d3 ; d3 is also used for SubE and.w d3,d2 ; keep only lower nybble if _Eni_RemoveJmpTable=0 ; JmpTable addresses are word-sized. ; Due to its placement in rom, SubE just falls into itself lsr.w #4-1,d1 ; store upper nybble multiplied by 2 (max value = 7) jmp EniDec_JmpTable(pc,d1.w) else ; all subroutines are offset by 16 bytes. Some of them barely fit, I'm quite proud of that ; SubE exceeds this, but it's the last one so it doesn't matter jmp EniDec_Sub0(pc,d1.w) endif ; --------------------------------------------------------------------------- EniDec_Sub0: .loop: move.w d4,(a1)+ ; write to destination addq.w #1,d4 ; increment dbra d2,.loop ; repeat jmp (a5) ; EniDec_Loop if _Eni_RemoveJmpTable<>0 enidecpad16 EniDec_Sub0 EniDec_Sub2: .loop: move.w d4,(a1)+ ; write to destination addq.w #1,d4 ; increment dbra d2,.loop ; repeat jmp (a5) ; EniDec_Loop enidecpad16 EniDec_Sub2 endif ; --------------------------------------------------------------------------- EniDec_Sub4: .loop: move.w a4,(a1)+ ; write to destination dbra d2,.loop ; repeat jmp (a5) ; EniDec_Loop if _Eni_RemoveJmpTable<>0 enidecpad16 EniDec_Sub4 EniDec_Sub6: .loop: move.w a4,(a1)+ ; write to destination dbra d2,.loop ; repeat jmp (a5) ; EniDec_Loop enidecpad16 EniDec_Sub6 endif ; --------------------------------------------------------------------------- EniDec_Sub8: bsr.s EniDec_GetInlineCopyVal .loop: move.w d1,(a1)+ dbra d2,.loop jmp (a5) ; EniDec_Loop if _Eni_RemoveJmpTable<>0 enidecpad16 EniDec_Sub8 endif ; --------------------------------------------------------------------------- EniDec_SubA: bsr.s EniDec_GetInlineCopyVal .loop: move.w d1,(a1)+ addq.w #1,d1 dbra d2,.loop jmp (a5) ; EniDec_Loop if _Eni_RemoveJmpTable<>0 enidecpad16 EniDec_SubA endif ; --------------------------------------------------------------------------- EniDec_SubC: bsr.s EniDec_GetInlineCopyVal .loop: move.w d1,(a1)+ subq.w #1,d1 dbra d2,.loop jmp (a5) ; EniDec_Loop if _Eni_RemoveJmpTable<>0 enidecpad16 EniDec_SubC else ; --------------------------------------------------------------------------- EniDec_JmpTable: bra.s EniDec_Sub0 bra.s EniDec_Sub0 ; Sub2 bra.s EniDec_Sub4 bra.s EniDec_Sub4 ; Sub6 bra.s EniDec_Sub8 bra.s EniDec_SubA bra.s EniDec_SubC ;bra.s EniDec_SubE ; fall into SubE endif ; --------------------------------------------------------------------------- ; EniDec_SubE is truly a special case EniDec_SubE: cmp.w d3,d2 ; d3 = $F ; is the loop set to 16? beq.s EniDec_End ; if so, branch (signifies to end .loop: bsr.s EniDec_GetInlineCopyVal move.w d1,(a1)+ dbra d2,.loop jmp (a5) ; EniDec_Loop EniDec_End: addq.l #2,sp ; deallocate those 2 bytes if _Eni_CompatibilityMode=0 movem.l (sp)+,d1-d7/a2-a6 else ; this code figures out where a0 should end subq.w #1,a0 cmpi.w #16,d6 ; were we going to start on a completely new byte? bne.s .got_byte ; if not, branch subq.w #1,a0 .got_byte: if _Eni_EvenAligned=0 ; TODO: thorough testing ; Orion: small optimization, saves 8-10 cycles move.w a0,d0 andi.w #1,d0 adda.w d0,a0 ; ensure we're on an even byte endif movem.l (sp)+,d0-d7/a1-a6 endif rts ; =========================================================================== EniDec_GetInlineCopyVal: move.w a3,d3 ; starting art tile ; original didn't need to use a high word ; this is a 4 cycle loss, though it's usually made up for everywhere else move.l d2,d1 ; get vram tile flags swap d1 ; (it's in the high word of d2) enidec_checktileflags 15,0 enidec_checktileflags 14,1 enidec_checktileflags 13,1 enidec_checktileflags 12,0 enidec_checktileflags 11,0 move.w d5,d1 move.w d6,d7 ; get remaining bits sub.w a2,d7 ; subtract minimum bit number bhs.s .got_enough ; if we're beyond that, branch move.w d7,d6 addi.w #16,d6 ; 16 bits = 2 bytes neg.w d7 ; calculate bit deficit lsl.w d7,d1 ; make space for this many bits move.b (a0),d5 ; get next byte rol.b d7,d5 ; make the upper X bits the lower X bits add.w d7,d7 and.w .andvalues-2(pc,d7.w),d5; only keep X lower bits add.w d5,d1 ; compensate for the bit deficit .got_field: move.w a2,d0 add.w d0,d0 and.w .andvalues-2(pc,d0.w),d1; only keep as many bits as required add.w d3,d1 ; add starting art tile ; move.b (a0)+,d5 ; 08 ; get current byte, move onto next byte ; lsl.w #8,d5 ; 22 ; shift up by a byte ; move.b (a0)+,d5 ; 08 ; store next byte in lower register byte ; 38 ; saves 4 cycles per branch, at the cost of saving and restoring a6, and setting up the register ; those caveats add around 24 cycles, but from my tests, it usually results in a speedup move.b (a0)+,(a6)+ ; 12 ; temporarily write into the destination move.b (a0)+,(a6)+ ; 12 move.w -(a6),d5 ; 10 ; move result to d5, set destination back to correct spot ; 34 rts ; --------------------------------------------------------------------------- .andvalues: dc.w 1, 3, 7, $F dc.w $1F, $3F, $7F, $FF dc.w $1FF, $3FF, $7FF, $FFF dc.w $1FFF,$3FFF,$7FFF,$FFFF ; --------------------------------------------------------------------------- .got_exact: moveq #16,d6 ; 16 bits = 2 bytes bra.s .got_field ; --------------------------------------------------------------------------- .got_enough: beq.s .got_exact ; if the exact number of bits are leftover, branch lsr.w d7,d1 ; remove unneeded bits move.w a2,d0 add.w d0,d0 and.w .andvalues-2(pc,d0.w),d1 ; only keep as many bits as required add.w d3,d1 ; add starting art tile move.w a2,d0 ; store number of bits used up by inline copy ; bra.s EniDec_ChkGetNextByte ; move onto next byte EniDec_ChkGetNextByte: sub.w d0,d6 ; subtract d0 from d6 cmpi.w #8,d6 ; has it hit 8 or lower? bhi.s .nonewbyte ; if not, branch addq.w #8,d6 ; 8 bits = 1 byte ; shift lowest byte to highest byte, and load a new value into low byte asl.w #8,d5 ; 22 ; shift up by a byte move.b (a0)+,d5 ; 08 ; store next byte in lower register byte ; 30 ; move.b d5,(a6)+ ; 08 ; move.b (a0)+,(a6)+ ; 12 ; move.w -(a6),d5 ; 10 ; 30, sad. .nonewbyte: rts ; --------------------------------------------------------------------------- if _Eni_Assembler=0 popo ; restore previous options endif
