Brandonw: msdDetect entry point

2006-11-19T15:16:23Z

msdDetect entry point

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== Synopsis ==
'''Name:''' msdDetect

'''Minimum usb8x version:''' 0.12

Detects and loads 83P/8XP levels from specified directory based on detection string. This is the mass storage version of ionDetect.

=== Inputs ===
* HL is starting cluster of directory to search (obtained with [[../FAT_getStartingCluster|FAT_getStartingCluster]])
* BC is entry number of level (pass -1 on first call to this entry point)
* DE points to zero-terminated detection string

=== Outputs ===
* Level/variable data is loaded into temporary RAM
* BC is entry number of this variable (to be passed in subsequent calls to this function)
* HL points to variable data (just beyond detection string)
* C set if problems
* A contains error code
{| border="1" cellpadding="2" cellspacing="0"
|-
|0 || No more 83P/8XP files in specified directory
|-
|1 || Not enough free memory to load level (for found level; subsequent calls may succeed)
|}

=== Destroys ===
* AF, BC, DE, HL, IX

== Notes ==
This is the mass storage version of ionDetect. It works exactly the same in that it loads the current level to (tempMem) if possible.

Pass -1 in BC on first call to this entry point, and then its BC output on future calls. When the carry flag is set and A = 0, you have gone through all the variables in that directory.

Example code to search for first BYTES level in the "\FILES\" subdirectory:
<code>
ld hl,sDir
rst 20h
ld hl,OP1
U_CALL FAT_getStartingCluster ;get starting cluster of this directory
push hl
ld hl,sDetectString
rst 20h
pop hl
ld bc,-1
ld de,OP1
U_CALL msdDetect
ret c ;no variables found
;HL now points to level data
...
sDir:
DB "\FILES",0
sDetectString:
DB "BY1JW",0 ;detection string for BYTES levels
</code>

Strings are copied to RAM first so they can be seen from usb8x.

== See Also ==
* [[../MSD_Initialize|MSD_Initialize]] - Initialize mass storage driver

83Plus:Software:usb8x/Asm Interface/MSD/msdDetect - Revision history

Brandonw: msdDetect entry point