create LOAD_FILE_AT macro

src/constants.a

@@ -142,11 +142,14 @@ HAS_VIDHD      = %00010000
 SUPPORTS_SHR   = %00110000
 CHEATS_ENABLED = %00001000
 
-; shared symbols
+; shared symbols for prelaunch and effects to call ProRWTS2 functions
+iCurBlockLo    = $D401
+iCurBlockHi    = $D403
 iProDOS_enter  = $D678
 LoadFileDirect = $DB01
 launchpatch    = $D616
 iAddToPath     = $FEC3
 itraverse      = $D8E0
+ldrhi          = $56
 namlo          = $57
 namhi          = $58

src/macros.a

@@ -364,3 +364,21 @@
          lsr
          sta   $FFFC      ; LC reset vector fix
 }
+
+; load an external file by pathname
+; LC RAM 2 MUST BE BANKED IN
+; LOW BYTE OF .addr MUST BE $00
+!macro   LOAD_FILE_AT .filepath, .addr {
+         lda   #>.addr
+         sta   ldrhi
+         lda   iCurBlockLo
+         pha
+         lda   iCurBlockHi
+         pha
+         +LDADDR .filepath
+         jsr   LoadFileDirect
+         pla
+         sta   iCurBlockHi
+         pla
+         sta   iCurBlockLo
+}

src/prelaunch/berzap.a

@@ -27,20 +27,9 @@ callback2
          lda   #0
          sta   $b4d7
          lda   #2
-         sta   $56        ; ldrhi
          sta   $b4d8
          +READ_RAM2_WRITE_RAM2
-         lda   $D401
-         pha
-         lda   $D403
-         pha
-         lda   #<berzap_mb
-         ldy   #>berzap_mb
-         jsr   LoadFileDirect
-         pla
-         sta   $D403
-         pla
-         sta   $D401
+         +LOAD_FILE_AT berzap_mb, $200
          jsr   DisableAccelerator
          jmp   $200
 

src/prelaunch/rescue.raiders.a

@@ -9,19 +9,7 @@
 
          +READ_RAM2_WRITE_RAM2
          jsr   EnableAccelerator
-         lda   #3
-         sta   $56        ; ldrhi
-         lda   $D401
-         pha
-         lda   $D403
-         pha
-         lda   #<rraiders_mb
-         ldy   #>rraiders_mb
-         jsr   LoadFileDirect
-         pla
-         sta   $D403
-         pla
-         sta   $D401
+         +LOAD_FILE_AT rraiders_mb, $300
          +READ_ROM_NO_WRITE
          jmp   $300