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dos_compilers/Microsoft QuickBASIC v3/INT86.ASM

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quick basic v3
2024-07-01 22:00:14 +02:00
TITLE INT86 - BASCOM software interrupt calling routine
;-----------------------------------------------------------------------
; R E V I S I O N H I S T O R Y
; 11-Mar-87 [1] RDK Since VARPTR returns negative values for DGROUP
; offsets 32K to 64K, add 64K to these values.
;-----------------------------------------------------------------------
;
; Microsoft Math Version
;
;
; Frame structure definition
; The following is used in INT86, INT86X, and PTR86.
ARG1 = 0AH ;pointer to first of three arguments
ARG2 = 08H ;pointer to second of three arguments
ARG3 = 06H ;pointer to third of three arguments
UCODE_SEG = 04H ;user code return pointer - segment
UCODE_OFF = 02H ;user code return pointer - offset
UCODE_BP = 00H ;user code BP register value (FRAME base)
; The following frame temp variables are used in INT86 and INT86X.
UCODE_FLGS = -02H ;user code flag register value
OUTARY_SEG = -04H ;output array pointer - segment
OUTARY_OFF = -06H ;output array pointer - offset
REG_NUM = -08H ;number of regs used (INT86=8, INT86X=10)
INT_ES = -0AH ;INT ES register value
INT_DS = -0CH ;INT DS register value
INT_FLGS = -0EH ;INT flags register value
INT_DI = -10H ;INT DI register value
INT_SI = -12H ;INT SI register value
INT_BP = -14H ;INT BP register value
INT_DX = -16H ;INT DX register value
INT_CX = -18H ;INT CX register value
INT_BX = -1AH ;INT BX register value
INT_AX = -1CH ;INT AX register value
FRM_SIZ = -1CH ;negative size of frame temporaries
; Locations past frame allocation used to recover post-INT BP value.
FRM_BP = -1EH ;frame BP saved for post-INT recovery
INT_BP_TMP = -20H ;temp location for INT BP register value
;***
; INT86, INT86X - BASCOM software interrupt calling interface
; Purpose:
; To allow a BASIC Compiler program to perform any software
; interrupt. The interrupt is executed with the registers
; set to values specified in an integer array. The post-
; interrupt values of the registers are then stored in
; another integer array.
;
; CALL INT86[X] (int_no%,VARPTR(in_ary%(x)),VARPTR(out_ary%(y)))
;
; Inputs:
; int_no% = interrupt number (range 0 to 255) to execute
; in_ary%(x) to in_ary%(x+7) = input array. (INT86)
; in_ary%(x) to in_ary%(x+9) = input array. (INT86X)
; This array specifies the register values at the INT as
; follows (INT86 uses DGROUP to set DS and ES, not array
; elements 8 and 9.):
; in_ary%(x) = AX
; in_ary%(x+1) = BX
; in_ary%(x+2) = CX
; in_ary%(x+3) = DX
; in_ary%(x+4) = BP
; in_ary%(x+5) = SI
; in_ary%(x+6) = DI
; in_ary%(x+7) = flags
; in_ary%(x+8) = DS (if -1, then use DGROUP value) (INT86X only)
; in_ary%(x+9) = ES (if -1, then use DGROUP value) (INT86X only)
; Outputs:
; If no error:
; int_no% = unchanged (range 0 to 255)
; out_ary%(y) to out_ary%(y+9) = output array.
; This array will be set to the post-interrupt
; register values. It has the same structure
; as in_ary%.
; If error:
; int_no% = -1
; out_ary% unchanged. INT call is not performed.
; error occurs:
; first argument not 0 to 255 (2^8-1)
;[1] second or third arguments not in VARPTR range
;[1] -32767 (-2^15+1) to 1048575 (2^20-1)
; Modifies:
; All, except BP, DS, and flags.
; Also, possible side effects of INT call.
; Exceptions:
; INT 24H call may result from some INT 21H MS-DOS calls.
;***
DATA SEGMENT WORD PUBLIC 'DATA'
DATA ENDS
DGROUP GROUP DATA
CODE SEGMENT BYTE PUBLIC 'CODE'
ASSUME CS:CODE,DS:DGROUP,ES:DGROUP,SS:DGROUP
PUBLIC INT86
INT86 PROC FAR
PUSH BP ;save BASCOM frame pointer on stack
MOV BP,SP ;establish program frame reference
ADD SP,FRM_SIZ ;allocate working space for frame
MOV WORD PTR [BP].REG_NUM,08H ;eight regs used (not DS or ES)
JMP SHORT INT86_COMMON ;jump to common code
PUBLIC INT86X
INT86X PROC FAR
PUSH BP ;save BASCOM frame pointer on stack
MOV BP,SP ;establish program frame reference
ADD SP,FRM_SIZ ;allocate working space for frame
MOV WORD PTR [BP].REG_NUM,0AH ;ten regs used (including DS and ES)
; Save a copy of the processor flags in the stack frame.
INT86_COMMON:
PUSHF ;push the flags on the stack
POP [BP].UCODE_FLGS ;put value in the stack frame
; From the third CALL argument on the stack, get the pointer to the
; VARPTR value of the output array and compute a far pointer to
; it. Then save the far pointer segment and offset in the frame.
MOV SI,[BP].ARG3 ;get pointer to s.p. VARPTR value
CALL SP_TO_PTR ;convert to far pointer in DX:AX
JC INT_ERROR_JUMP ;if error, then jump
MOV [BP].OUTARY_SEG,DX ;save far pointer segment in frame
MOV [BP].OUTARY_OFF,AX ;save far pointer offset in frame
; From the second CALL argument on the stack, obtain the far
; pointer to the input array in the same manner as above.
MOV SI,[BP].ARG2 ;get pointer to s.p. VARPTR value
CALL SP_TO_PTR ;convert to far pointer in DX:AX
JNC NO_INT_ERROR ;if no error, then jump
INT_ERROR_JUMP:
JMP INT_ERROR ;long jump to error routine
NO_INT_ERROR:
; Move eight or ten words (depending if executing INT86 or INT86X)
; of the integer input array from the far pointer computed to the frame.
MOV DS,DX ;move array pointer segment
MOV SI,AX ;and array offset - far pointer in DS:SI
LEA DI,[BP].FRM_SIZ ;get frame offset - ES = SS = DGROUP
MOV CX,[BP].REG_NUM ;eight or ten words to move
CLD ;movement is to higher memory
REP MOVSW ;move the array into the stack frame
PUSH ES ;get compiler data segment value on stack
POP DS ;restore so DS = ES = SS = compiler data seg
; Save stack frame pointer to recover its value after the INT call.
PUSH BP ;saved to first word past the stack frame
; Create a two-instruction program on the stack to execute the
; INT call requested and return with stack cleanup.
;
; INT XX (hex: CD XX) <--- fourth word past stack frame
; RETF 06 (hex: CA 06 00) <--- third and second word
XOR AX,AX ;value of second word past frame
PUSH AX ;put on stack - 00 byte of RETF and filler
MOV AX,06CAH ;value of third word past frame
PUSH AX ;put on stack - CA 06 bytes of RETF
MOV SI,[BP].ARG1 ;ptr to first CALL arg - interrupt number
MOV AX,[SI] ;from pointer, get integer value of INT type
OR AH,AH ;test if in range, 00 to FFH is legal
JNZ INT_ERROR_JUMP ;if not, then error - jump
MOV AH,AL ;move interrupt number to upper byte of AX
MOV AL,0CDH ;value of fourth word past frame
PUSH AX ;put on stack - CD XX bytes of INT XX
; Push far pointer of return address after the stack program
; executes, which is INT_RET in this code segment.
PUSH CS ;push current code segment for return segment
MOV AX,OFFSET CODE:INT_RET ;offset just after stack program call
PUSH AX ;push value for return offset
; Push far pointer pointer to the start of the stack program.
; The stack program will be entered by executing a RETF after the
; registers are set up.
PUSH SS ;push current stack segment for starting ptr
MOV AX,SP ;get current stack offset
ADD AX,6 ;move past the last three stack entries
PUSH AX ;push offset for starting ptr of stack program
; Move the input array values from the stack to their actual registers.
MOV AX,[BP].INT_FLGS ;get input flag register value
AND AX,0000111111010101B ;mask out undefined 8086 flags
PUSH AX ;push masked flag register value
MOV AX,[BP].INT_AX ;set up input AX value
MOV BX,[BP].INT_BX ;set up input BX value
MOV CX,[BP].INT_CX ;set up input CX value
MOV DX,[BP].INT_DX ;set up input DX value
MOV SI,[BP].INT_SI ;set up input SI value
MOV DI,[BP].INT_DI ;set up input DI value
; For DS and ES, leave in the compiler data segment values if:
; executing INT86; or executing INT86X with array values of -1.
CMP WORD PTR [BP].REG_NUM,08H ;test if executing INT86
JE INT_ES_DEF ;if so, then use both default values
CMP [BP].INT_DS,0FFFFH ;test if default DS to be used
JE INT_DS_DEF ;if so, then leave it unchanged
MOV DS,[BP].INT_DS ;set up input DS value
INT_DS_DEF:
CMP [BP].INT_ES,0FFFFH ;test if default ES to be used
JE INT_ES_DEF ;if so, then leave it unchanged
MOV ES,[BP].INT_ES ;set up input ES value
INT_ES_DEF:
MOV BP,[BP].INT_BP ;set up input BP value
;must be last move using BP
POPF ;set up input flag register value
; With all registers set according to the input array, execute the
; stack program.
;
; The following RETF pops the last two stack entries, which are
; interpreted as a far pointer to the stack program.
;
; The stack program executes the INT XX call which changes the
; registers (flags included) to the values to be put into the
; output array.
;
; The stack program then executes the RETF 06 instruction which
; does two operations. First, the next two entries on stack are
; popped and interpreted as a far ptr return address, which points
; the code at INT_RET in this code segment. Second, the stack
; pointer is then adjusted by six bytes to remove the six-byte
; program from the stack.
RET ;far return to execute stack program, etc.
INT_RET:
; The stack should now contain only the first entry past the
; frame, the value of the stack frame pointer itself. First
; save the BP value from the INT call, then get the old value
; to reference the frame.
PUSH BP ;save post-INT value of BP
MOV BP,SP ;temporary frame is second word past frame
MOV BP,[BP+02H] ;get real frame reference value
; Put post-INT value of all registers into the frame variables
; to be subsequently written into the output array.
PUSHF ;put flags on the stack
POP [BP].INT_FLGS ;put in post-INT flag register value
PUSH [BP].UCODE_FLGS ;get old copy of flags from frame
POPF ;and restore the old flag values
MOV [BP].INT_AX,AX ;put in post-INT AX value
MOV [BP].INT_BX,BX ;put in post-INT BX value
MOV [BP].INT_CX,CX ;put in post-INT CX value
MOV [BP].INT_DX,DX ;put in post-INT DX value
MOV AX,[BP].INT_BP_TMP ;get post-INT BP value (one entry past frame)
MOV [BP].INT_BP,AX ;put in post-INT BP value
MOV [BP].INT_SI,SI ;put in post-INT SI value
MOV [BP].INT_DI,DI ;put in post-INT DI value
MOV [BP].INT_DS,DS ;put in post-INT DS value
MOV [BP].INT_ES,ES ;put in post-INT ES value
; Restore DS to SS. Move frame register values to the output
; array whose far pointer is in the frame.
PUSH SS ;put compiler data segment on stack
POP DS ;and restore DS register to it
LEA SI,[BP].FRM_SIZ ;get start of register area in frame
MOV ES,[BP].OUTARY_SEG ;get output array segment
MOV DI,[BP].OUTARY_OFF ;get output array offset
MOV CX,[BP].REG_NUM ;eight or ten words to move
CLD ;movement is toward upper memory
REP MOVSW ;perform the transfer
; Clean up stack to remove frame. Remove CALL arguments with RETF.
MOV SP,BP ;deallocate temporary frame variables
POP BP ;return compiler frame pointer
RET 06 ;remove three CALL arguments and far return
; If error, then restore DS, set int_no% to -1 to report error,
; clean up, and exit.
INT_ERROR:
PUSH SS ;put compiler data segment value on stack
POP DS ;and restore DS to its original value
MOV SI,[BP].ARG1 ;ptr to first CALL arg - interrupt number
MOV [SI],0FFFFH ;set interrupt number to -1 for error
MOV SP,BP ;deallocate temporary frame variables
POP BP ;return compiler frame pointer
RET 06 ;remove three CALL arguments and far return
INT86X ENDP
INT86 ENDP
;***
; PTR86 - Compute segment/offset from variable VARPTR value.
; Purpose:
; From a s.p. VARPTR of a compiler data variable, compute an
; equivalent segment and offset integer values. These variables
; are used to set INT86X register input array values.
;
; CALL PTR86 (varseg%,varoff%,VARPTR(var))
;
; Inputs:
; var = data variable (any type)
; Outputs:
; if no error, varseg% = segment part of far pointer to var
; varoff% = offset part of far pointer to var
; if error, varseg% = -1
; Modifies:
; AX, DX, and SI.
; Exceptions:
; None.
;***
PUBLIC PTR86
PTR86 PROC FAR
PUSH BP ;save BASCOM frame pointer on stack
MOV BP,SP ;establish program frame reference
MOV SI,[BP].ARG3 ;ptr to third CALL arg - VARPTR of variable
CALL SP_TO_PTR ;compute segment:offset in DX:AX
MOV SI,[BP].ARG1 ;ptr to first CALL arg - segment result
JC PTR86_ERROR ;if error, then jump
MOV [SI],DX ;put segment value into argument
MOV SI,[BP].ARG2 ;ptr to second CALL arg - offset result
MOV [SI],AX ;put offset value into argument
POP BP ;restore old frame pointer
RET 06H ;far return to caller - remove three stack args
PTR86_ERROR:
MOV [SI],0FFFFH ;put -1 in first arg for error report
POP BP ;restore old frame pointer
RET 06H ;far return to caller - remove three stack args
PTR86 ENDP
;***
; SP_TO_PTR - converts s.p. VARPTR value to segment/offset values
; Purpose:
; From the s.p. value pointed by DS:SI, convert to an integer
;[1] value. Report an error if not in the range -2^15 to 2^20-1.
;[1] Negative values are adjusted by 2^16 (65535) since VARPTR
;[1] maps the values 32768...65535 to -32768...-1 for interpreter
;[1] compatibility. Convert 20-bit address to segment and offset
; integer values using the standard 8086/8088 address computation:
;
; (16-bit segment)*16 + (16-bit offset) = 20-bit address
;
; Inputs:
; SI = pointer to s.p. address value
;
; The value is represented in Microsoft binary format, consisting
; of four bytes starting at the pointer given. The first three
; bytes are the low, middle, and high bytes of the number's
; mantissa while the fourth is the exponent. Sign-magnitude
; representation is used with the sign being the MSB of the high
; mantissa byte. All values are stored normalized with the
; mantissa MSB hidden with the sign bit. The binary point of the
; mantissa is before its MSB. The exponent is biased by 80H.
; A zero exponent implies a zero value independent of the mantissa's
; contents.
; Outputs:
; If no error:
; CF = 0 (carry cleared)
; DX = pointer segment integer result
; AX = pointer offset integer result
; If error:
; CF = 1 (carry set)
; DX,AX = undefined
; Modifies:
; None.
; Exceptions:
; None.
;***
SP_TO_PTR PROC NEAR
; Load s.p. number into DX:AX.
MOV AX,[SI] ;AH=middle mantissa - AL=low mantissa
MOV DX,[SI+2] ;DH=exponent - DL=sign/high mantissa
; If exponent is zero, then number value is zero.
OR DH,DH ;test if exponent is zero
JZ SP_ZERO ;if so, then jump
; Put in hidden MSB of mantissa.
OR DL,80H ;set hidden high-order mantissa bit
; Move data so DX:AX has 24-bit mantissa right-justified in 32 bits;
; and CX has 8-bit exponent right-justified in 16 bits.
PUSH CX ;save register...
XOR CX,CX ;clear both CH and CL
XCHG CL,DH ;DX:AX=24-bit mantissa - CX=exponent
; Remove 80H bias from exponent. Also subtract 12 (0CH) to move
; the binary from left of the 24th bit to left of the 12th bit of
; DX:AX. The resulting value is the number of left shifts of DX:AX
; resulting in a binary value with 20 bits left of the binary point
; and 12 bits right of it.
SUB CX,8CH ;remove 80H bias and 0CH to move b.pt. 12 bits
JE SP_NO_SHIFT ;if no shifting needed, then jump
JB SP_RIGHT_SHIFT ;if negative, then right shifting needed
SP_LEFT_SHIFT_LOOP:
SHL AX,1 ;shift low-order word left once
RCL DX,1 ;shift carry into high-order word
LOOP SP_LEFT_SHIFT_LOOP ;shift until done
JMP SHORT SP_NO_SHIFT ;shifting left done - jump
; A negative shift count is the inverse of the number of right
; shifts needed.
SP_RIGHT_SHIFT:
NEG CX ;compute shift count of DX:AX to the right
SP_RIGHT_SHIFT_LOOP:
SHR DX,1 ;shift high-order word right once
RCR AX,1 ;shift carry into low-order word
LOOP SP_RIGHT_SHIFT_LOOP ;loop until done...
;[1] If input value was negative, test magnitude for legal range
;[1] of 1 to 32768 (1 to 8000H). First decrement the value, so the
;[1] range is now 0 to 7FFFH. Test for the range and, if legal,
;[1] invert the significant bits.
SP_NO_SHIFT:
TEST BYTE PTR [SI+2],80H ;[1]test if value was negative
JZ SP_NOT_NEG ;[1]if not, then jump
SUB AH,10H ;[1]decrement value in high nybble of AH
SBB DX,0 ;[1]propagate if borrow was needed
TEST DX,NOT 7FFH ;[1]test if in legal range
JNZ SP_ERROR ;[1]jump to return error
XOR AH,0F0H ;[1]invert high nybble of AH
XOR DX,0FFFH ;[1]invert rest of value in DX
; The lower 4 bits of the 20-bit integer value are in the upper
; nybble of AX. Rotate and mask to move to lower nybble which
; will be the offset returned.
SP_NOT_NEG: ;[1]
ROL AX,1 ;rotate leftmost nybble in AX to rightmost...
ROL AX,1 ;second bit...
ROL AX,1 ;third bit...
ROL AX,1 ;fourth bit - done
AND AX,000FH ;leave only rightmost nybble left
; The upper 16 bits of the 20-bit integer value are in DX.
; This value is the integer divided by 16 and is therefore the
; paragraph value of the pointer. Since VARPTR values are
; relative to the compiler data segment, add the data segment
; value to compute the pointer segment.
MOV CX,DS ;get compiler data segment value
ADD DX,CX ;add to get pointer (permit wraparound)
POP CX ;restore register
CLC ;clear carry for success
RET ;near return to caller
; If zero, report 0 as the offset and the compiler data segment.
SP_ZERO:
XOR AX,AX ;clear offset result
MOV DX,DS ;set segment result to compiler DS
CLC ;clear carry for success
RET ;near return to caller
; If error, then set carry to report it.
SP_ERROR: ;[1]
POP CX ;[1]
STC ;set carry for failure
RET ;near return to caller
SP_TO_PTR ENDP
CODE ENDS
END
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