; Public Domain

%include "lmacros3.mac"

numdef DOSEXIT, 0
numdef DOSENTRY, 0
numdef LARGEFILL, 0
numdef RELOC, 1
numdef BASESEGMENT, 0
numdef RELOCEXE, 0


        cpu 8086
%if _RELOCEXE
%assign ORIGIN 0
        org ORIGIN
        addsection HEADER, start=0
header_start:
        db "MZ"         ; exeSignature
FILESIZE equ fromparas(header_size_p + BEHINDSEGMENT)
        dw FILESIZE % 512       ; exeExtraBytes
        dw (FILESIZE + 511) / 512       ; exePages
        dw relocationtable.amount       ; exeRelocItems
        dw header_size_p        ; exeHeaderSize
        dw paras(512)           ; exeMinAlloc
        dw paras(512)           ; exeMaxAlloc
        dw +BEHINDSEGMENT       ; exeInitSS
        dw 512                  ; exeInitSP
        dw 0            ; exeChecksum
        dw 0, +0        ; exeInitCSIP
        dw relocationtable      ; exeRelocTable

        addsection FIRST, vstart=0 align=16 follows=HEADER
%elif _DOSENTRY
%assign ORIGIN 256
        org ORIGIN
        addsection FIRST, start=ORIGIN
%else
%assign ORIGIN 0
        org ORIGIN
        addsection FIRST, start=ORIGIN
%endif
first_start:
        addsection SECOND, vstart=0 align=16 follows=FIRST
second_start:
        addsection THIRD, vstart=0 align=16 follows=SECOND
third_start:

first_size equ first_end - first_start
endarea first, 1
second_size equ second_end - second_start
endarea second, 1
third_size equ third_end - third_start
endarea third, 1
%if _RELOCEXE
header_size equ header_end - header_start
endarea header, 1
%endif

FIRSTSEGMENT equ _BASESEGMENT + 0
SECONDSEGMENT equ _BASESEGMENT + paras(ORIGIN) + first_size_p
THIRDSEGMENT equ _BASESEGMENT + paras(ORIGIN) + first_size_p + second_size_p
BEHINDSEGMENT equ _BASESEGMENT + paras(ORIGIN) + first_size_p + second_size_p + third_size_p

%define RELOCATIONFROMFIRST ""
%define RELOCATIONFROMSECOND ""
%define RELOCATIONFROMTHIRD ""
        %imacro relocation 0-1.nolist -2
%%reloc equ $ + %1
%ifidn _CURRENT_SECTION, FIRST
 %xdefine RELOCATIONFROMFIRST RELOCATIONFROMFIRST, %%reloc, FIRSTSEGMENT
%elifidn _CURRENT_SECTION, SECOND
 %xdefine RELOCATIONFROMSECOND RELOCATIONFROMSECOND, %%reloc, SECONDSEGMENT
%elifidn _CURRENT_SECTION, THIRD
 %xdefine RELOCATIONFROMTHIRD RELOCATIONFROMTHIRD, %%reloc, THIRDSEGMENT
%else
 %error Unknown section for relocation
%endif
        %endmacro

        usesection FIRST
start:
        mov dx, cs
        mov ds, dx
%if !_RELOCEXE && _RELOC
        mov si, relocationtable
        mov cx, relocationtable.amount
        jcxz .noreloc
@@:
        lodsw
        xchg bx, ax
        lodsw
        add ax, dx
        mov es, ax
        add word [es:bx], dx
        loop @B
.noreloc:
%endif

displayfirst:
        mov si, firstmsg
        mov bx, 7
        mov ah, 0Eh
        db __TEST_IMM16         ; (skip int 10h)
@@:
        int 10h
        lodsb
        test al, al
        jnz @B

        call SECONDSEGMENT:secondentry
relocation

exit:
%if _DOSEXIT
        mov ax, 4C00h
        int 21h
%else
        xor ax, ax
        int 16h
        int 19h
%endif  


bouncetothird:
        jmp THIRDSEGMENT:bounced
relocation


firstmsg:       asciz "Hello from first!",13,10


        usesection SECOND

secondmsg:      asciz "Hello from second!",13,10

secondentry:
displaysecond:
        mov si, secondmsg
        mov bx, 7
        mov ah, 0Eh
        db __TEST_IMM16         ; (skip int 10h)
@@:
        int 10h
        cs lodsb
        test al, al
        jnz @B

        jmp THIRDSEGMENT:thirdentry
relocation


        usesection THIRD

        align 2, db 0
indirect_to_bounce:
                dw bouncetothird
relocation 0
                dw FIRSTSEGMENT

thirdmsg:       asciz "Hello from third!",13,10

thirdentry:
        jmp far [cs:indirect_to_bounce]

bounced:
displaythird:
        mov si, thirdmsg
        mov bx, 7
        mov ah, 0Eh
        db __TEST_IMM16         ; (skip int 10h)
@@:
        int 10h
        cs lodsb
        test al, al
        jnz @B

        retf


%ifn _RELOCEXE
        usesection FIRST
%else
        usesection HEADER
%endif
%if _RELOCEXE || _RELOC
        align 4, db 0
relocationtable:
.:
        dw RELOCATIONFROMFIRST
        dw RELOCATIONFROMSECOND
        dw RELOCATIONFROMTHIRD
.end:
.amount: equ (.end - .) / 4
%endif
%if _RELOCEXE
        align 16
header_end:
%endif

%if _LARGEFILL
        usesection SECOND
        _fill fromkib(64), 0CCh, second_start
%endif

        usesection FIRST
        align 16
first_end:
        usesection SECOND
        align 16
second_end:
        usesection THIRD
        align 16
third_end: