;===========================================================================
; Copyright (c) 1990-1999 Info-ZIP.  All rights reserved.
;
; See the accompanying file LICENSE, version 1999-Oct-05 or later
; (the contents of which are also included in zip.h) for terms of use.
; If, for some reason, both of these files are missing, the Info-ZIP license
; also may be found at:  ftp://ftp.cdrom.com/pub/infozip/license.html
;===========================================================================
; This is a 680x0 assembly language translation of the Info-ZIP source file
; deflate.c, by Paul Kienitz. The function longest_match is based in part
; on match.a by Carsten Steger, which in turn is partly based on match.s
; for 386 by Jean-loup Gailly and Kai Uwe Rommel.  Mostly, however, this
; material is based on deflate.c, by Gailly, Rommel, and Igor Mandrichenko.
; This code is not commented very much; see deflate.c for comments that explain
; what the functions are doing.
;
; The symbols that can be used to select different versions are as follows:
;
;   CPU020     if defined, use 68020 instructions always.
;
;   CPUTEST    if defined, check at runtime for CPU type.  Another symbol
;               specifying the platform-specific test must be used with this.
;               If neither of these is defined, use 68000 instructions only.
;               Runtime test is nonportable; it is different for each OS.
;
;   AMIGA      use Amiga-specific test for 68020, if CPUTEST defined.  Also
;               tells it that registers d0/a0/d1/a1 are not preserved by
;               function calls.  At present, if AMIGA is not defined, it
;               causes functions to preserve all registers.  ALL OF THIS CODE
;               CURRENTLY ASSUMES THAT REGISTERS D2-D7/A2-A6 WILL BE PRESERVED
;               BY ANY FUNCTIONS THAT IT CALLS.
;
;   DYN_ALLOC  should be defined here if it is defined for C source; tells us
;               that big arrays are allocated instead of static.
;
;   WSIZE      must be defined as the same number used for WSIZE in the C
;               source, and must be a power of two <= 32768.  As elsewhere,
;               the default value is 32768.
;
;   INT16      define this if ints are 16 bits; otherwise 32 bit ints assumed.
;
;   SMALL_MEM  define this if it is defined in the C source; otherwise it uses
;               the MEDIUM_MEM model.  BIG_MEM and MMAP are *not* supported.
;               The FULL_SEARCH option in deflate.c is also not supported.
;
;   DEBUG      activates some tracing output, as in the C source.
;
;   QUADLONG   this selects a different version of the innermost longest_match
;               loop code for 68020 operations, comparing bytes four at a time
;               instead of two at a time.  It seems to be a tiny bit faster on
;               average, but it's slower often enough that one can't generalize.
;
; This code currently assumes that function results are returned in D0 for
; all platforms.  It assumes that args to functions are pushed onto the stack,
; last arg first.  It also currently assumes that all C symbols have an
; underscore prepended when referenced from assembly.

    IFND    CPU020
     IFND   CPUTEST
CPU000  equ     1
     ENDC
    ENDC

; Use these macros for accessing variables of type int:
    IFD     INT16
MOVINT  MACRO
        move.w  \1,\2
        ENDM
CLRINT  MACRO
        clr.w   \1
        ENDM
INTSIZE equ     2
    ELSE    ; !INT16
MOVINT  MACRO
        move.l  \1,\2
        ENDM
CLRINT  MACRO
        clr.l   \1
        ENDM
INTSIZE equ     4
    ENDC

    IFD     DYN_ALLOC
BASEPTR MACRO
        move.l  \1,\2
        ENDM
    ELSE
BASEPTR MACRO
        lea     \1,\2
        ENDM
    ENDC

; constants we use, many of them adjustable:

MAX_MATCH       equ     258
MIN_MATCH       equ     3
TOO_FAR         equ     4096
    IFND    WSIZE
WSIZE           equ     32768
    ENDC
WMASK           equ     WSIZE-1
MAX_DIST        equ     WSIZE-MAX_MATCH-MIN_MATCH-1
MIN_LOOKAHEAD   equ     MAX_MATCH+MIN_MATCH+1
;    IFD     BIG_MEM      ; NOT supported -- type Pos needs to be 32 bits
;HASH_BITS      equ     15
;    ELSE
    IFD    SMALL_MEM
HASH_BITS       equ     13
    ELSE
HASH_BITS       equ     14      ; default -- MEDIUM_MEM
    ENDC
;    ENDC    ; BIG_MEM
HASH_SIZE       equ     1<<HASH_BITS
HASH_MASK       equ     HASH_SIZE-1
H_SHIFT         equ     (HASH_BITS+MIN_MATCH-1)/MIN_MATCH
B_SLOW          equ     1
B_FAST          equ     2
ZE_MEM          equ     4
EOF             equ     -1

; struct config is defined by these offsets:
Good_length     equ     0
Max_lazy        equ     2
Nice_length     equ     4
Max_chain       equ     6
Sizeof_config   equ     8


; external functions we call:
        xref    _ct_tally       ; int ct_tally(int, int)
        xref    _flush_block    ; unsigned long F(char *, unsigned long, int)
        xref    _ziperr         ; void ziperr(int, char *)
        xref    _error          ; void error(char *)
        xref    _calloc         ; stdlib function: void *calloc(size_t, size_t)
        xref    _free           ; stdlib function: void free(void *)
    IFD     DEBUG
        xref    _fputc          ; stdio function: int fputc(int, FILE *)
        xref    _stderr         ; pointer to FILE, which we pass to fputc
    ENDC

; our entry points:
        xdef    _lm_init        ; void lm_init(int level, unsigned short *flags)
        xdef    _lm_free        ; void lm_free(void)
        xdef    _deflate        ; void deflate(void)  ...the big one
        xdef    _fill_window    ; this line is just for debugging


; ============================================================================
; Here is where we have our global variables.

        section deflatevars,data

; external global variables we reference:
        xref    _verbose        ; signed int
        xref    _level          ; signed int
        xref    _read_buf       ; int (*read_buf)(char *, unsigned int)

; global variables we make available:

        xdef    _window
        xdef    _prev
        xdef    _head
        xdef    _window_size
        xdef    _block_start
        xdef    _strstart

    IFD     DYN_ALLOC
_prev:          ds.l    1       ; pointer to calloc()'d unsigned short array
_head:          ds.l    1       ; pointer to calloc()'d unsigned short array
_window:        ds.l    1       ; pointer to calloc()'d unsigned char array
    ELSE    ; !DYN_ALLOC
_prev:          ds.w    WSIZE           ; array of unsigned short
_head:          ds.w    HASH_SIZE       ; array of unsigned short
_window:        ds.b    2*WSIZE         ; array of unsigned char
    ENDC    ; ?DYN_ALLOC
_window_size:   ds.l    1               ; unsigned long
_block_start:   ds.l    1               ; unsigned long
_strstart:      ds.w    INTSIZE/2       ; unsigned int

; Now here are our private variables:

    IFD     CPUTEST
is020:          ds.w    1       ; bool: CPU type is '020 or higher
    ENDC
ins_h:          ds.w    1       ; unsigned short
sliding:        ds.w    1       ; bool: the file is read a piece at a time
eofile:         ds.w    1       ; bool: we have read in the end of the file
max_lazy_match: ds.w    1       ; unsigned short
lookahead:      ds.w    1       ; unsigned short

; These are NOT DECLARED AS STATIC in deflate.c, but currently could be:
max_chain_len:  ds.w    1       ; unsigned short (unsigned int in deflate.c)
prev_length:    ds.w    1       ; unsigned short (unsigned int in deflate.c)
good_match:     ds.w    1       ; unsigned short (unsigned int in deflate.c)
nice_match:     ds.w    1       ; unsigned short (signed int in deflate.c)
match_start:    ds.w    1       ; unsigned short (unsigned int in deflate.c)

; This array of struct config is a constant and could be in the code section:
config_table:   dc.w    0,0,0,0         ; level 0: store uncompressed
                dc.w    4,4,8,4         ; level 1: fastest, loosest compression
                dc.w    4,5,16,8        ; level 2
                dc.w    4,6,32,32       ; level 3: highest to use deflate_fast
                dc.w    4,4,16,16       ; level 4: lowest to use lazy matches
                dc.w    8,16,32,32      ; level 5
                dc.w    8,16,128,128    ; level 6: the default level
                dc.w    8,32,128,256    ; level 7
                dc.w    32,128,258,1024 ; level 8
                dc.w    32,258,258,4096 ; level 9: maximum compression, slow


;;CAL_SH  MACRO                   ; macro for calling zcalloc()
;;     IFD    INT16
;;        move.w  #2,-(sp)
;;        move.w  #\1,-(sp)
;;        jsr     _zcalloc
;;        addq    #4,sp
;;     ELSE
;;        pea     2
;;        pea     \1
;;        jsr     _zcalloc
;;        addq    #8,sp
;;     ENDC
;;        ENDM

CAL_SH  MACRO                   ; Okay, we're back to using regular calloc()...
        pea     2
        pea     \1
        jsr     _calloc
        addq    #8,sp
        ENDM

; ============================================================================
; And here we begin our functions.  match_init is for internal use only:

        section deflate,code

match_init:
    IFD     CPUTEST             ; now check for platform type
     IFD    AMIGA               ; Amiga specific test for '020 CPU:
        xref    _SysBase
        NOLIST
        INCLUDE       'exec/execbase.i'
        LIST

        clr.w   is020                   ; default value is 68000
        move.l  _SysBase,a0
        btst    #AFB_68020,AttnFlags+1(a0)
        beq.s   cheap
        move.w  #1,is020
cheap:
     ELSE   ; !AMIGA

        FAIL    Write an '020-detector for your system here!
; On the Macintosh, I believe GetEnvironment() provides the information.

     ENDC   ; AMIGA
    ENDC    ; CPUTEST
        rts     ; match_init consists only of rts if CPUTEST unset


; ============================================================================
; Here is longest_match(), the function that the rest of this was built up
; from, the hottest hot spot in the program and therefore the most heavily
; optimized.  It has two different versions, one for '020 and higher CPUs, and
; one for 68000/68010.  It can test at runtime which version to use if you
; create a test function in match_init for your platform.  Currently such a
; test is implemented for the Amiga.  It can also be assembled to use '000 or
; '020 code only.

Cur_Match       equr    d0              ; unsigned int, kept valid as long
Best_Len        equr    d1              ; unsigned int, kept valid as long
Scan_Start      equr    d3              ; pair of bytes
Scan_End        equr    d4              ; pair of bytes
Limit           equr    d5              ; unsigned int
Chain_Length    equr    d6              ; unsigned int
Scan_Test       equr    d7              ; counter, pair of bytes sometimes
Scan            equr    a0              ; pointer to unsigned char
Match           equr    a1              ; pointer to unsigned char
Prev_Address    equr    a2              ; pointer to unsigned short
Scan_Ini        equr    a3              ; pointer to unsigned char
Match_Ini       equr    a5              ; pointer to unsigned char
; Note: "pair of bytes" means the two low order bytes of the register in
; 68020 code, but means the lowest and third lowest bytes on the 68000.
    IFD     AMIGA
SAVEREGS        reg     d3-d7/a2/a3/a5      ; don't protect d0/d1/a0/a1
    ELSE    ; !AMIGA
SAVEREGS        reg     d1/d3-d7/a0-a3/a5   ; protect all except d0 return val
    ENDC    ; ?AMIGA
; d2, a4, a6 not used... on Amiga, a4 is used by small-data memory model


longest_match:
        movem.l SAVEREGS,-(sp)

; setup steps common to byte and word versions:
    IFD     INT16
        and.l   #$0000FFFF,Cur_Match    ; upper half must be zero!
; we use an and.l down here for the sake of ATSIGN/REGARGS.
        moveq   #0,Limit                ; so adding to Scan_Ini works
    ENDC
        move.w  max_chain_len,Chain_Length
        move.w  prev_length,Best_Len
        MOVINT  _strstart,Limit
        BASEPTR _prev,Prev_Address
        BASEPTR _window,Match_Ini
        move.l  Match_Ini,Scan_Ini
        addq    #MIN_MATCH,Match_Ini    ; optimizes inner loop
        add.l   Limit,Scan_Ini
        sub.w   #MAX_DIST,Limit
        bhi.s   limit_ok
        moveq   #0,Limit
limit_ok:
        cmp.w   good_match,Best_Len
        blo.s   length_ok
        lsr.w   #2,Chain_Length
length_ok:
        subq.w  #1,Chain_Length

    IFD     CPUTEST
        tst.w   is020                   ; can we use '020 stuff today?
        bne     WORD_match
    ENDC

    IFND    CPU020

; for 68000 or 68010, use byte operations:
        moveq   #0,Scan_Start           ; clear 2nd & 4th bytes, use 1st & 3rd
        moveq   #0,Scan_End             ; likewise
        moveq   #0,Scan_Test            ; likewise
        move.b  (Scan_Ini),Scan_Start
        swap    Scan_Start              ; swap is faster than 8 bit shift
        move.b  1(Scan_Ini),Scan_Start
        move.b  -1(Scan_Ini,Best_Len.w),Scan_End
        swap    Scan_End
        move.b  0(Scan_Ini,Best_Len.w),Scan_End
        bra.s   bdo_scan

blong_loop:
        move.b  -1(Scan_Ini,Best_Len.w),Scan_End
        swap    Scan_End
        move.b  0(Scan_Ini,Best_Len.w),Scan_End

bshort_loop:
        add.w   Cur_Match,Cur_Match     ; assert value before doubling < 32K
     IFNE   32768-WSIZE
        and.w   #(WMASK*2),Cur_Match
     ENDC
        move.w  (Prev_Address,Cur_Match.l),Cur_Match
        cmp.w   Limit,Cur_Match
        dbls    Chain_Length,bdo_scan
        bra     return

bdo_scan:
        move.l  Match_Ini,Match
        add.l   Cur_Match,Match
        move.b  -MIN_MATCH-1(Match,Best_Len.w),Scan_Test
        swap    Scan_Test
        move.b  -MIN_MATCH(Match,Best_Len.w),Scan_Test
        cmp.l   Scan_Test,Scan_End
        bne.s   bshort_loop
        move.b  -MIN_MATCH(Match),Scan_Test
        swap    Scan_Test
        move.b  -MIN_MATCH+1(Match),Scan_Test
        cmp.l   Scan_Test,Scan_Start
        bne.s   bshort_loop
        move.w  #(MAX_MATCH-3),Scan_Test
        lea     MIN_MATCH(Scan_Ini),Scan        ; offset optimizes inner loop

bscan_loop:
        cmp.b   (Match)+,(Scan)+
        dbne    Scan_Test,bscan_loop
        subq    #1,Scan

        sub.l   Scan_Ini,Scan           ; assert difference is 16 bits
        cmp.w   Best_Len,Scan
        bls.s   bshort_loop
        MOVINT  Scan,Best_Len
        move.w  Cur_Match,match_start
        cmp.w   nice_match,Best_Len
        blo.s   blong_loop
     IFD    CPUTEST
        bra     return
     ENDC

    ENDC    ; !CPU020

    IFND    CPU000
        MACHINE MC68020

; for 68020 or higher, use word operations even on odd addresses:
WORD_match:
        move.w  (Scan_Ini),Scan_Start
        move.w  -1(Scan_Ini,Best_Len.w),Scan_End
        bra.s   wdo_scan

wlong_loop:
        move.w  -1(Scan_Ini,Best_Len.w),Scan_End

wshort_loop:
        and.w   #WMASK,Cur_Match
        move.w  (Prev_Address,Cur_Match.w*2),Cur_Match  ; '020 addressing mode
        cmp.w   Limit,Cur_Match
        dbls    Chain_Length,wdo_scan
        bra.s   return

wdo_scan:
        move.l  Match_Ini,Match
        add.l   Cur_Match,Match
        cmp.w   -MIN_MATCH-1(Match,Best_Len.w),Scan_End
        bne.s   wshort_loop
        cmp.w   -MIN_MATCH(Match),Scan_Start
        bne.s   wshort_loop
     IFD    QUADLONG
; By some measurements, this version of the code is a little tiny bit faster.
; But on some files it's slower.  It probably pays off only when there are
; long match strings, and costs in the most common case of three-byte matches.
        moveq   #((MAX_MATCH-MIN_MATCH)/16),Scan_Test     ; value = 15
        lea     MIN_MATCH(Scan_Ini),Scan        ; offset optimizes inner loop

wscan_loop:
        cmp.l   (Match)+,(Scan)+                ; test four bytes at a time
        bne.s   odd
        cmp.l   (Match)+,(Scan)+
        bne.s   odd
        cmp.l   (Match)+,(Scan)+
        bne.s   odd
        cmp.l   (Match)+,(Scan)+
        dbne    Scan_Test,wscan_loop            ; '020 can cache a bigger loop
odd:
        subq    #4,Scan
        subq    #4,Match
        cmp.b   (Match)+,(Scan)+        ; find good bytes in bad longword
        bne.s   even
        cmp.b   (Match)+,(Scan)+
        bne.s   even
        cmp.b   (Match)+,(Scan)+
        beq.s   steven
even:   subq    #1,Scan
     ELSE   ; !QUADLONG
        moveq   #((MAX_MATCH-MIN_MATCH)/2),Scan_Test    ; value = 127
        lea     MIN_MATCH(Scan_Ini),Scan        ; offset optimizes inner loop

wscan_loop:
        cmp.w   (Match)+,(Scan)+
        dbne    Scan_Test,wscan_loop
        subq    #2,Scan
        move.b  -2(Match),Scan_Test
        cmp.b   (Scan),Scan_Test
        bne.s   steven
        addq    #1,Scan
     ENDC   ; ?QUADLONG
steven:
        sub.l   Scan_Ini,Scan           ; assert: difference is 16 bits
        cmp.w   Best_Len,Scan
        bls.s   wshort_loop
        MOVINT  Scan,Best_Len
        move.w  Cur_Match,match_start
        cmp.w   nice_match,Best_Len
        blo.s   wlong_loop

        MACHINE MC68000
    ENDC    ; !CPU000

return:
        MOVINT  Best_Len,d0         ; return value (upper half should be clear)
        movem.l (sp)+,SAVEREGS
        rts


; =============================================================================
; This is the deflate() function itself, our main entry point.  It calls
; longest_match, above, and some outside functions.  It is a hot spot, but not
; as hot as longest_match.  It uses no special '020 code.

; ================== Several macros used in deflate() and later functions:

; Arg 1 is D-reg that new ins_h value is to be left in,
; arg 2 is the byte value to be hashed into it, which must not be the same reg
UP_HASH MACRO
        move.w  ins_h,\1
        asl.w   #H_SHIFT,\1
        eor.b   \2,\1
        and.w   #HASH_MASK,\1           ; ((ins_h << H_SHIFT) ^ c) & HASH_MASK
        move.w  \1,ins_h                ; ins_h = that
        ENDM

; Arg 1 is scratch A, arg 2 is scratch D
IN_STR  MACRO
        move.l  Strst,\2
        addq.w  #MIN_MATCH-1,\2
        move.b  (Window,\2.l),\2        ; window[strstart + MIN_MATCH - 1]
        UP_HASH Head,\2
        add.l   Head,Head               ; assert upper word is zero before add
        BASEPTR _head,\1
        add.l   Head,\1
        move.w  (\1),Head               ; hash_head = head[ins_h]
        move.w  Strst,(\1)              ; head[ins_h] = strstart
        move.l  Strst,\2
    IFNE    WSIZE-32768
        and.w   #WMASK,\2
    ENDC
        add.w   \2,\2                   ; masks implicitly when WSIZE == 32768
        move.w  Head,(Prev,\2.l)        ; prev[str_start & WMASK] = hash_head
        ENDM

; Arg 1 is bool (int) EOF flag, flush_block result is in d0, trashes d1/a0/a1
FLUSH_B MACRO
    IFC     '\1','#0'
        CLRINT  -(sp)
    ELSE
        MOVINT  \1,-(sp)
    ENDC
        move.l  _block_start,d0
        blt.s   nenu\@
        move.l  Window,a0
        add.l   d0,a0
        bra.s   nun\@
nenu\@: sub.l   a0,a0           ; if block_start < 0, push NULL
nun\@:  sub.l   Strst,d0
        neg.l   d0
        move.l  d0,-(sp)
        move.l  a0,-(sp)
        jsr     _flush_block
        lea     8+INTSIZE(sp),sp
        ENDM

; This expands to nothing unless DEBUG is defined.
; Arg 1 is a byte to be trace-outputted -- if it is d0 it must be a valid int
TRACE_C MACRO
    IFD    DEBUG
        cmp.w  #1,_verbose+INTSIZE-2    ; test lower word only
        ble.s   qui\@
     IFNC    '\1','d0'
        moveq   #0,d0
        move.b  \1,d0
     ENDC
        move.l  _stderr,-(sp)
        MOVINT  d0,-(sp)
        jsr     _fputc
        addq    #4+INTSIZE,sp
qui\@:
    ENDC    ; DEBUG
        ENDM

; ================== Here are the register vars we use, and deflate() itself:

Window  equr    a2              ; cached address of window[]
Prev    equr    a3              ; cached address of prev[]
Strst   equr    d7              ; strstart cached as a longword
Look    equr    d6              ; lookahead cached as short
Head    equr    d5              ; local variable hash_head, short
PrevL   equr    d4              ; prev_length cached as short
MatchL  equr    d3              ; local variable match_length, unsigned short
Avail   equr    d2              ; local variable available_match, bool
PrevM   equr    a5              ; local variable prev_match, int in an A-reg

    IFD     AMIGA
DEFREGS reg     d2-d7/a2/a3/a5
    ELSE
DEFREGS reg     d0-d7/a0/a2/a3/a5       ; play it safe, preserve all regs
    ENDC


_deflate:           ; first, setup steps common to deflate and deflate_fast:
        movem.l DEFREGS,-(sp)
    IFD     INT16
        moveq   #0,Strst                ; make sure strstart is valid as a long
    ENDC
        moveq   #0,Head                 ; ditto for hash_head
        MOVINT  _strstart,Strst
        move.w  lookahead,Look
        move.w  prev_length,PrevL
        BASEPTR _window,Window
        BASEPTR _prev,Prev
        MOVINT  _level,d0
        cmp.w   #3,d0
        ble     deflate_fast
        moveq   #MIN_MATCH-1,MatchL
        moveq   #0,Avail

look_loop:
        tst.w   Look
        beq     last_tally
        IN_STR  a0,d0
        move.w  MatchL,PrevL
        move.w  match_start,PrevM
        move.w  #MIN_MATCH-1,MatchL

        tst.w   Head
        beq.s   no_new_match
        cmp.w   max_lazy_match,PrevL
        bhs.s   no_new_match
        move.w  Strst,d0
        sub.w   Head,d0
        cmp.w   #MAX_DIST,d0
        bhi.s   no_new_match
        move.w  PrevL,prev_length       ; longest_match reads these variables
        MOVINT  Strst,_strstart
        MOVINT  Head,d0                 ; parm for longest_match
        bsr     longest_match           ; sets match_start
        cmp.w   Look,d0                 ; does length exceed valid data?
        bls.s   stml
        move.w  Look,d0
stml:   move.w  d0,MatchL               ; valid length of match
        cmp.w   #MIN_MATCH,MatchL       ; is the match only three bytes?
        bne.s   no_new_match
        move.w  match_start,d0
        sub.w   Strst,d0
        cmp.w   #-TOO_FAR,d0
        bge.s   no_new_match
        moveq   #MIN_MATCH-1,MatchL     ; mark the current match as no good

no_new_match:
        cmp.w   #MIN_MATCH,PrevL
        blo     literal
        cmp.w   MatchL,PrevL
        blo     literal
        ; CHECK_MATCH   Strst-1,PrevM,PrevL
        MOVINT  Strst,_strstart         ; ct_tally reads this variable
        move.l  PrevL,d0
        subq.w  #MIN_MATCH,d0
        MOVINT  d0,-(sp)
        move.l  Strst,d0
        sub.w   PrevM,d0
        subq.w  #1,d0
        MOVINT  d0,-(sp)
        jsr     _ct_tally               ; sets d0 true if we have to flush
        addq    #2*INTSIZE,sp
        subq.w  #3,PrevL                ; convert for dbra (prev_length - 2)
        sub.w   PrevL,Look
        subq.w  #2,Look
insertmatch:
        addq.w  #1,Strst
        IN_STR  a0,d1                   ; don't clobber d0
        dbra    PrevL,insertmatch
        moveq   #0,Avail
        moveq   #0,PrevL                ; not needed?
        moveq   #MIN_MATCH-1,MatchL
        addq.w  #1,Strst
        tst.w   d0
        beq     refill
        FLUSH_B #0
        move.l  Strst,_block_start
        bra.s   refill

literal:
        tst.w   Avail
        bne.s   yeslit
        moveq   #1,Avail
        bra.s   skipliteral
yeslit: TRACE_C <-1(Window,Strst.l)>
        MOVINT  Strst,_strstart         ; ct_tally reads this variable
        moveq   #0,d0
        move.b  -1(Window,Strst.l),d0
        MOVINT  d0,-(sp)
        CLRINT  -(sp)
        jsr     _ct_tally
        addq    #2*INTSIZE,sp
        tst.w   d0
        beq.s   skipliteral
        FLUSH_B #0
        move.l  Strst,_block_start
skipliteral:
        addq.w  #1,Strst
        subq.w  #1,Look

refill:
        cmp.w   #MIN_LOOKAHEAD,Look
        bhs     look_loop
        bsr     fill_window
        bra     look_loop

last_tally:
        tst.w   Avail
        beq     last_flush
        MOVINT  Strst,_strstart         ; ct_tally reads this variable
        moveq   #0,d0
        move.b  -1(Window,Strst.l),d0
        MOVINT  d0,-(sp)
        CLRINT  -(sp)
        jsr     _ct_tally
        addq    #2*INTSIZE,sp
last_flush:
        FLUSH_B #1
        bra     deflate_exit

; ================== This is another version used for low compression levels:

deflate_fast:
        moveq   #0,MatchL
        moveq   #MIN_MATCH-1,PrevL
flook_loop:
        tst.w   Look
        beq     flast_flush

        IN_STR  a0,d0
        tst.w   Head
        beq.s   fno_new_match
        move.w  Strst,d0
        sub.w   Head,d0
        cmp.w   #MAX_DIST,d0
        bhi.s   fno_new_match
        move.w  PrevL,prev_length       ; longest_match reads these variables
        MOVINT  Strst,_strstart
        MOVINT  Head,d0                 ; parm for longest_match
        bsr     longest_match           ; sets match_start
        cmp.w   Look,d0                 ; does length exceed valid data?
        bls.s   fstml
        move.w  Look,d0
fstml:  move.w  d0,MatchL               ; valid length of match

fno_new_match:
        cmp.w   #MIN_MATCH,MatchL
        blo     fliteral
        ; CHECK_MATCH   Strst,match_start,MatchL
        MOVINT  Strst,_strstart         ; ct_tally reads this variable
        move.l  MatchL,d0
        subq.w  #MIN_MATCH,d0
        MOVINT  d0,-(sp)
        move.l  Strst,d0
        sub.w   match_start,d0
        MOVINT  d0,-(sp)
        jsr     _ct_tally               ; sets d0 true if we have to flush
        addq    #2*INTSIZE,sp
        sub.w   MatchL,Look
        cmp.w   max_lazy_match,MatchL
        bhi     ftoolong
        subq.w  #2,MatchL
finsertmatch:
        addq.w  #1,Strst
        IN_STR  a0,d1                   ; preserve d0
        dbra    MatchL,finsertmatch
        moveq   #0,MatchL               ; not needed?
        addq.w  #1,Strst
        bra.s   flushfill

ftoolong:
        add.w   MatchL,Strst
        moveq   #0,MatchL
        moveq   #0,d1                   ; preserve d0
        move.b  (Window,Strst.l),d1
        move.w  d1,ins_h
; My assembler objects to passing <1(Window,Strst.l)> directly to UP_HASH...
        move.b  1(Window,Strst.l),Avail ; Avail is not used in deflate_fast
        UP_HASH d1,Avail                ; preserve d0
    IFNE    MIN_MATCH-3
        FAIL  needs to UP_HASH another MIN_MATCH-3 times, but with what arg?
    ENDC
        bra.s   flushfill

fliteral:
        TRACE_C <(Window,Strst.l)>
        MOVINT  Strst,_strstart         ; ct_tally reads this variable
        moveq   #0,d0
        move.b  (Window,Strst.l),d0
        MOVINT  d0,-(sp)
        CLRINT  -(sp)
        jsr     _ct_tally               ; d0 set if we need to flush
        addq    #2*INTSIZE,sp
        addq.w  #1,Strst
        subq.w  #1,Look

flushfill:
        tst.w   d0
        beq.s   frefill
        FLUSH_B #0
        move.l  Strst,_block_start
frefill:
        cmp.w   #MIN_LOOKAHEAD,Look
        bhs     flook_loop
        bsr     fill_window
        bra     flook_loop

flast_flush:
        FLUSH_B #1                      ; sets our return value

deflate_exit:
        MOVINT  Strst,_strstart         ; save back cached values
        move.w  PrevL,prev_length
        move.w  Look,lookahead
        movem.l (sp)+,DEFREGS
        rts


; =========================================================================
; void fill_window(void) calls the input function to refill the sliding
; window that we use to find substring matches in.

More    equr    Head                    ; local variable in fill_window
WindTop equr    Prev                    ; local variable used for sliding
SlidIx  equr    PrevL                   ; local variable used for sliding

    IFD     AMIGA
FWREGS  reg     d2-d5/a2-a6             ; does NOT include Look and Strst
    ELSE
FWREGS  reg     d1-d5/a0-a6             ; likewise
    ENDC
; all registers available to be clobbered by the sliding operation:
; we exclude More, WindTop, SlidIx, Look, Strst, Window, a4 and a7.
SPAREGS reg     d0-d3/a0-a1/a5-a6
SPCOUNT equ     8                       ; number of registers in SPAREGS


_fill_window:                           ; C-callable entry point
        movem.l Strst/Look,-(sp)
    IFD     INT16
        moveq   #0,Strst                ; Strst must be valid as a long
    ENDC
        MOVINT  _strstart,Strst
        move.w  lookahead,Look
        BASEPTR _window,Window
        bsr.s   fill_window
        MOVINT  Strst,_strstart
        move.w  Look,lookahead
        movem.l (sp)+,Strst/Look
        rts

; strstart, lookahead, and window must be cached in Strst, Look, and Window:
fill_window:                            ; asm-callable entry point
        movem.l FWREGS,-(sp)
        tst.w   eofile                  ; we put this up here for speed
        bne     fwdone
        and.l   #$FFFF,Look             ; make sure Look is valid as long
fw_refill:
        move.l  _window_size,More       ; <= 64K
        sub.l   Look,More
        sub.l   Strst,More              ; Strst is already valid as long
        cmp.w   #EOF,More
        bne.s   notboundary
        subq.w  #1,More
        bra     checkend

notboundary:
        tst.w   sliding
        beq     checkend
        cmp.w   #WSIZE+MAX_DIST,Strst
        blo     checkend
    IFGT    32768-WSIZE
        lea     WSIZE(Window),WindTop   ; WindTop is aligned when Window is
    ELSE
        move.l  Window,WindTop
        add.l   #WSIZE,WindTop
    ENDC
        move.l  Window,d0
        and.w   #3,d0
        beq.s   isaligned
        subq.w  #1,d0
align:  move.b  (WindTop)+,(Window)+    ; copy up to a longword boundary
        dbra    d0,align
isaligned:
; This is faster than a simple move.l (WindTop)+,(Window)+ / dbra loop:
        move.w  #(WSIZE-1)/(4*SPCOUNT),SlidIx
slide:  movem.l (WindTop)+,SPAREGS      ; copy, 32 bytes at a time!
        movem.l SPAREGS,(Window)        ; a slight overshoot doesn't matter.
        lea     4*SPCOUNT(Window),Window        ; can't use (aN)+ as movem.l dest
        dbra    SlidIx,slide
        BASEPTR _window,Window                  ; restore cached value
        sub.w   #WSIZE,match_start
        sub.w   #WSIZE,Strst
        sub.l   #WSIZE,_block_start
        add.w   #WSIZE,More
        BASEPTR _head,a0
        move.w  #HASH_SIZE-1,d0
fixhead:
        move.w  (a0),d1
        sub.w   #WSIZE,d1
        bpl.s   headok
        moveq   #0,d1
headok: move.w  d1,(a0)+
        dbra    d0,fixhead
        BASEPTR _prev,a0
        move.w  #WSIZE-1,d0
fixprev:
        move.w  (a0),d1
        sub.w   #WSIZE,d1
        bpl.s   prevok
        moveq   #0,d1
prevok: move.w  d1,(a0)+
        dbra    d0,fixprev
        TRACE_C #'.'

checkend:                               ; assert eofile is false
        MOVINT  More,-(sp)              ; assert More's upper word is zero
        move.l  Strst,d0
        add.w   Look,d0
        add.l   Window,d0
        move.l  d0,-(sp)
        move.l  _read_buf,a0
        jsr     (a0)                    ; refill the upper part of the window
        addq    #4+INTSIZE,sp
        tst.w   d0
        beq.s   iseof
        cmp.w   #EOF,d0
        beq.s   iseof
        add.w   d0,Look
        cmp.w   #MIN_LOOKAHEAD,Look
        blo     fw_refill               ; eofile is still false

        bra.s   fwdone
iseof:  move.w  #1,eofile
fwdone: movem.l (sp)+,FWREGS
        rts


; =========================================================================
; void lm_free(void) frees dynamic arrays in the DYN_ALLOC version.

        xdef    _lm_free                ; the entry point

_lm_free:
    IFD     DYN_ALLOC
        move.l  _window,d0
        beq.s   lf_no_window
        move.l  d0,-(sp)
        jsr     _free
        addq    #4,sp
        clr.l   _window
lf_no_window:
        move.l  _prev,d0
        beq.s   lf_no_prev
        move.l  d0,-(sp)
        jsr     _free
        move.l  _head,(sp)              ; reuse the same stack arg slot
        jsr     _free
        addq    #4,sp
        clr.l   _prev
        clr.l   _head
lf_no_prev:
    ENDC
        rts

; ============================================================================
; void lm_init(int pack_level, unsigned short *flags) allocates dynamic arrays
; if any, and initializes all variables so that deflate() is ready to go.

        xdef    _lm_init                ; the entry point

Level   equr    d2
;Window equr    a2      ; as in deflate()
    IFD     AMIGA
INIREGS reg     d2/a2
    ELSE
INIREGS reg     d0-d2/a0-a1
    ENDC

_lm_init:
        MOVINT  4(sp),d0
        move.l  4+INTSIZE(sp),a0
        movem.l INIREGS,-(sp)
        move.w  d0,Level
        cmp.w   #1,Level
        blt.s   levelerr
        bgt.s   try9
        bset.b  #B_FAST,1(a0)
try9:   cmp.w   #9,Level
        bgt.s   levelerr
        blt.s   levelok
        bset.b  #B_SLOW,1(a0)
        bra.s   levelok
levelerr:
        pea     level_message
        jsr     _error                  ; never returns
levelok:
        clr.w   sliding
        tst.l   _window_size
        bne.s   gotawindowsize
        move.w  #1,sliding
        move.l  #2*WSIZE,_window_size
gotawindowsize:

        BASEPTR _window,Window
    IFD     DYN_ALLOC
        move.l  Window,d0               ; fake tst.l
        bne.s   gotsomewind
        CAL_SH  WSIZE
        move.l  d0,Window
        move.l  d0,_window
        bne.s   gotsomewind
        pea     window_message
        MOVINT  #ZE_MEM,-(sp)
        jsr     _ziperr                 ; never returns
gotsomewind:
        tst.l   _prev
        bne.s   gotsomehead
        CAL_SH  WSIZE
        move.l  d0,_prev
        beq.s   nohead
        CAL_SH  HASH_SIZE
        move.l  d0,_head
        bne.s   gotfreshhead            ; newly calloc'd memory is zeroed
nohead: pea     hash_message
        MOVINT  #ZE_MEM,-(sp)
        jsr     _ziperr                 ; never returns
gotsomehead:
    ENDC    ; DYN_ALLOC

        move.w  #(HASH_SIZE/2)-1,d0     ; two shortwords per loop
        BASEPTR _head,a0
wipeh:  clr.l   (a0)+
        dbra    d0,wipeh
gotfreshhead:
        move.l  Level,d0
    IFEQ    Sizeof_config-8
        asl.l   #3,d0
    ELSE
        mulu    #Sizeof_config,d0
    ENDC
        lea     config_table,a0
        add.l   d0,a0
        move.w  Max_lazy(a0),max_lazy_match
        move.w  Good_length(a0),good_match
        move.w  Nice_length(a0),nice_match
        move.w  Max_chain(a0),max_chain_len
        CLRINT  _strstart
        clr.l   _block_start
        bsr     match_init

        clr.w   eofile
        MOVINT  #WSIZE,-(sp)    ; We read only 32K because lookahead is short
        move.l  Window,-(sp)    ; even when int size is long, as if deflate.c
        move.l  _read_buf,a0    ; were compiled with MAXSEG_64K defined.
        jsr     (a0)
        addq    #4+INTSIZE,sp
        move.w  d0,lookahead
        beq.s   noread
        cmp.w   #EOF,d0
        bne.s   irefill
noread: move.w  #1,eofile
        clr.w   lookahead
        bra.s   init_done

irefill:
        move.w  lookahead,d0
        cmp.w   #MIN_LOOKAHEAD,d0
        bhs.s   hashify
        bsr     _fill_window            ; use the C-callable version
hashify:
        clr.w   ins_h
        moveq   #MIN_MATCH-2,d0
hash1:  move.b  (Window)+,d1
        UP_HASH Level,d1
        dbra    d0,hash1

init_done:
        movem.l (sp)+,INIREGS
        rts

; strings for error messages:
hash_message    dc.b    'hash table allocation',0
window_message  dc.b    'window allocation',0
level_message   dc.b    'bad pack level',0

        end