| Routines

07CB: THE 'VERIFY' CONTROL ROUTINE

Used by the routine at SAVE_ETC. The verification process involves the loading of a block of data, a byte at a time, but the bytes are not stored - only checked. This routine is also used to load blocks of data that have been described with 'SCREEN$' or 'CODE'.
Input
HL | Block start address
VR_CONTRL | 07CB | PUSH HL | Save the 'pointer'.
| 07CC | LD L,(IX-$06) | Fetch the 'number of bytes' as described in the 'old' header.
| 07CF | LD H,(IX-$05)
| 07D2 | LD E,(IX+$0B) | Fetch also the number from the 'new' header.
| 07D5 | LD D,(IX+$0C)
| 07D8 | LD A,H | Jump forward if the 'length' is unspecified, e.g. 'LOAD name CODE' only.
| 07D9 | OR L
| 07DA | JR Z,VR_CONT_1
| 07DC | SBC HL,DE | Give report R if attempting to load a larger block than has been requested.
| 07DE | JR C,REPORT_R
| 07E0 | JR Z,VR_CONT_1 | Accept equal 'lengths'.
| 07E2 | LD A,(IX+$00) | Also give report R if trying to verify blocks that are of unequal size. ('Old length' greater than 'new length'.)
| 07E5 | CP $03
| 07E7 | JR NZ,REPORT_R
The routine continues by considering the 'destination pointer'.
VR_CONT_1 | 07E9 | POP HL | Fetch the 'pointer', i.e. the 'start'.
| 07EA | LD A,H | This 'pointer' will be used unless it is zero, in which case the 'start' found in the 'new' header will be used instead.
| 07EB | OR L
| 07EC | JR NZ,VR_CONT_2
| 07EE | LD L,(IX+$0D)
| 07F1 | LD H,(IX+$0E)
The verify/load flag is now considered and the actual load made.
VR_CONT_2 | 07F4 | PUSH HL | Move the 'pointer' to the IX register pair.
| 07F5 | POP IX
| 07F7 | LD A,($5C74) | Jump forward unless using the VERIFY command (T-ADDR-lo=+02), with the carry flag signalling 'LOAD'.
| 07FA | CP $02
| 07FC | SCF
| 07FD | JR NZ,VR_CONT_3
| 07FF | AND A | Signal 'VERIFY'.
VR_CONT_3 | 0800 | LD A,$FF | Signal 'accept data block only' before loading the block.
This routine continues into LD_BLOCK.