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0808: THE 'LOAD' CONTROL ROUTINE
Used by the routine at SAVE_ETC.
This routine controls the LOADing of a BASIC program, and its variables, or an array.
Input
HL Destination address (PROG, or the address of the array, or +0000 for a new array)
IX Address of the header loaded from tape
Output
LD_CONTRL 0808 LD E,(IX+$0B) Fetch the 'number of bytes' as given in the 'new header'.
080B LD D,(IX+$0C)
080E PUSH HL Save the 'destination pointer'.
080F LD A,H Jump forward unless trying to LOAD a previously undeclared array.
0810 OR L
0811 JR NZ,LD_CONT_1
0813 INC DE Add three bytes to the length - for the name, the low length and the high length of a new variable.
0814 INC DE
0815 INC DE
0816 EX DE,HL
0817 JR LD_CONT_2 Jump forward.
Consider now if there is enough room in memory for the new data block.
LD_CONT_1 0819 LD L,(IX-$06) Fetch the size of the existing 'program+variables or array'.
081C LD H,(IX-$05)
081F EX DE,HL
0820 SCF Jump forward if no extra room will be required (taking into account the reclaiming of the presently used memory).
0821 SBC HL,DE
0823 JR C,LD_DATA
Make the actual test for room.
LD_CONT_2 0825 LD DE,$0005 Allow an overhead of five bytes.
0828 ADD HL,DE
0829 LD B,H Move the result to the BC register pair and make the test.
082A LD C,L
082B CALL TEST_ROOM
Now deal with the LOADing of arrays.
LD_DATA 082E POP HL Fetch the 'pointer' anew.
082F LD A,(IX+$00) Jump forward if LOADing a BASIC program.
0832 AND A
0833 JR Z,LD_PROG
0835 LD A,H Jump forward if LOADing a new array.
0836 OR L
0837 JR Z,LD_DATA_1
0839 DEC HL Fetch the 'length' of the existing array by collecting the length bytes from the variables area.
083A LD B,(HL)
083B DEC HL
083C LD C,(HL)
083D DEC HL Point to its old name.
083E INC BC Add three bytes to the length - one for the name and two for the 'length'.
083F INC BC
0840 INC BC
0841 LD ($5C5F),IX Save the IX register pair temporarily (in X-PTR) whilst the old array is reclaimed.
0845 CALL RECLAIM_2
0848 LD IX,($5C5F)
Space is now made available for the new array - at the end of the present variables area.
LD_DATA_1 084C LD HL,($5C59) Find the pointer to the end-marker of the variables area - the '+80-byte' (E-LINE).
084F DEC HL
0850 LD C,(IX+$0B) Fetch the 'length' of the new array.
0853 LD B,(IX+$0C)
0856 PUSH BC Save this 'length'.
0857 INC BC Add three bytes - one for the name and two for the 'length'.
0858 INC BC
0859 INC BC
085A LD A,(IX-$03) 'IX+0E' of the old header gives the name of the array.
085D PUSH AF The name is saved whilst the appropriate amount of room is made available. In effect BC spaces before the 'new +80-byte'.
085E CALL MAKE_ROOM
0861 INC HL
0862 POP AF
0863 LD (HL),A The name is entered.
0864 POP DE The 'length' is fetched and its two bytes are also entered.
0865 INC HL
0866 LD (HL),E
0867 INC HL
0868 LD (HL),D
0869 INC HL HL now points to the first location that is to be filled with data from the tape.
086A PUSH HL This address is moved to the IX register pair; the carry flag set; 'data block' is signalled; and the block LOADed.
086B POP IX
086D SCF
086E LD A,$FF
0870 JP LD_BLOCK
Now deal with the LOADing of a BASIC program and its variables.
LD_PROG 0873 EX DE,HL Save the 'destination pointer'.
0874 LD HL,($5C59) Find the address of the end marker of the current variables area - the '+80-byte' (E-LINE).
0877 DEC HL
0878 LD ($5C5F),IX Save IX temporarily (in X-PTR).
087C LD C,(IX+$0B) Fetch the 'length' of the new data block.
087F LD B,(IX+$0C)
0882 PUSH BC Keep a copy of the 'length' whilst the present program and variables areas are reclaimed.
0883 CALL RECLAIM_1
0886 POP BC
0887 PUSH HL Save the pointer to the program area and the length of the new data block.
0888 PUSH BC
0889 CALL MAKE_ROOM Make sufficient room available for the new program and its variables.
088C LD IX,($5C5F) Restore the IX register pair from X-PTR.
0890 INC HL The system variable VARS has also to be set for the new program.
0891 LD C,(IX+$0F)
0894 LD B,(IX+$10)
0897 ADD HL,BC
0898 LD ($5C4B),HL
089B LD H,(IX+$0E) If a line number was specified then it too has to be considered.
089E LD A,H
089F AND $C0
08A1 JR NZ,LD_PROG_1 Jump if 'no number'; otherwise set NEWPPC and NSPPC.
08A3 LD L,(IX+$0D)
08A6 LD ($5C42),HL
08A9 LD (IY+$0A),$00
The data block can now be LOADed.
LD_PROG_1 08AD POP DE Fetch the 'length'.
08AE POP IX Fetch the 'start'.
08B0 SCF Signal 'LOAD'.
08B1 LD A,$FF Signal 'data block' only.
08B3 JP LD_BLOCK Now LOAD it.
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