# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1435527002 -7200
# Node ID c3c68373ee6d07f24ca24687c058dd9934fa32af
# Parent  a0b9ea4264242ab2e8acbf2deebbc7bd3334fd15
Added comments and tidied label usage.

diff -r a0b9ea426424 -r c3c68373ee6d macros.oph
--- a/macros.oph	Sun Jun 28 23:20:20 2015 +0200
+++ b/macros.oph	Sun Jun 28 23:30:02 2015 +0200
@@ -174,15 +174,15 @@
 
 .macro pushA
     sei
-    php
-    pha
+    php ; F -> stack
+    pha ; A -> stack
     sty TEMP
     ldy #0
     sta (USER), y
     .invoke sub16 2, USER
     ldy TEMP
-    pla
-    plp
+    pla ; stack -> A
+    plp ; stack -> F
     cli
 .macend
 
@@ -192,13 +192,13 @@
 
 .macro pullA
     sei
-    php
+    php ; F -> stack
     sty TEMP
     .invoke add16 2, USER
     ldy #0
     lda (USER), y
     ldy TEMP
-    plp
+    plp ; stack -> F
     cli
 .macend
 
@@ -211,8 +211,8 @@
 
 .macro call
     sei
-    php
-    pha
+    php ; F -> stack
+    pha ; A -> stack
     sty TEMP
     ldy #0
     lda #<_2
@@ -222,8 +222,8 @@
     sta (USER), y
     .invoke sub16 2, USER
     ldy TEMP
-    pla
-    plp
+    pla ; stack -> A
+    plp ; stack -> F
     cli
     jmp _1
 .macend
@@ -234,12 +234,12 @@
 
 .macro return
     sei
-    php
-    pha
+    php ; F -> stack
+    pha ; A -> stack
     .invoke add16 2, USER
     .invoke mov16_from_ref USER, ABSTEMP
-    pla
-    plp
+    pla ; stack -> A
+    plp ; stack -> F
     cli
     jmp (ABSTEMP)
 .macend
diff -r a0b9ea426424 -r c3c68373ee6d switcher.oph
--- a/switcher.oph	Sun Jun 28 23:20:20 2015 +0200
+++ b/switcher.oph	Sun Jun 28 23:30:02 2015 +0200
@@ -70,33 +70,32 @@
 *   .invoke store16 second_task, ARG0
     .invoke call new_task, +
 *   .invoke store16 third_task, ARG0
-    .invoke call new_task, wait
+    .invoke call new_task, main_wait
 
     ; loop while other tasks exist
 
-wait:
+main_wait:
     ldx #7
     sei
     lda tasks, x ; check for the third task
     cli
     cmp #0
-    bne wait
+    bne main_wait
 
     ; where no other tasks exist, remove this task by updating its PC to the
     ; end label and removing its entry
 
-    .invoke store16 end, main_task+6
+    .invoke store16 main_end, main_task+6
     lda #0
-    .invoke call remove_task, shutdown
+    .invoke call remove_task, +
 
     ; wait for shutdown
 
-shutdown:
-    jmp shutdown
+*   jmp -
 
     ; return here with the initial main program stack
 
-end:
+main_end:
     rts
 
 
@@ -146,8 +145,6 @@
     .invoke push16 NEXT
     .invoke push16 CURRENT
 
-init_sp:
-
     ; initialise the stack frame pointer
 
     dex ; make the frame compatible with the task structure
@@ -156,8 +153,6 @@
     lda #$01 ; $01xx
     sta SPH
 
-test_pc:
-
     ; test PC for execution of ROM routines
     ; these are probably not re-entrant
 
@@ -171,9 +166,7 @@
     cmp #$80
 
     ; exit if PC MSB & $80 != 0
-    beq exit_handler
-
-evict_task:
+    beq handler_exit
 
     ; obtain the current task using the task offset
 
@@ -197,7 +190,7 @@
     cpy #2
     bpl -
 
-load_task:
+handler_load_task:
 
     ; examine the next task
 
@@ -207,21 +200,19 @@
     ; reset the task index if necessary
 
     cpx #TASK_TABLE_LENGTH
-    bne test_task
+    bne +
     ldx #0
 
-test_task:
-
     ; obtain task location MSB
 
-    inx
+*   inx
     lda tasks, x
     sta NEXTH
 
     ; install if not a null task (tasks do not reside in zero page)
 
     cmp #0
-    bne restore_task
+    bne handler_restore_task
 
     ; test against the start index
     ; where a complete circuit of the task table has not been performed,
@@ -230,7 +221,7 @@
     dex
     txa
     cmp task_offset
-    bne load_task
+    bne handler_load_task
 
     ; where a complete circuit has been performed without finding any tasks
     ; uninstall the handler and install the details of the end handler
@@ -246,7 +237,7 @@
     lda tasks, x
     sta NEXTH
 
-restore_task:
+handler_restore_task:
 
     dex
     lda tasks, x
@@ -265,7 +256,7 @@
 
     .invoke mov16_from_ref NEXT, USER
 
-exit_handler:
+handler_exit:
 
     ; restore zero-page locations used in the handler
 
@@ -315,20 +306,20 @@
 
     ldy #1
 
-check_new_task:
+new_task_check:
     lda tasks, y
     cmp #0
-    beq add_new_task
+    beq new_task_add
     iny
     iny
 
     ; if no space is found by the end of the table, exit
 
     cpy #TASK_TABLE_LENGTH
-    bpl no_new_task
-    jmp check_new_task
+    bpl new_task_failed
+    jmp new_task_check
 
-add_new_task:
+new_task_add:
 
     ; copy the task structure location to the table
 
@@ -343,7 +334,7 @@
     lda #0
     .invoke return
 
-no_new_task:
+new_task_failed:
     lda #1
     .invoke return
 
@@ -412,21 +403,21 @@
     .word third_task_start ; saved PC
 third_task_start:
     ldx #2
-_begin:
+third_task_begin:
     ldy #0 ; reset counter LSB
     lda #0 ; reset counter MSB
     sta $7021
-_loop:
+third_task_loop:
     stx $7028
     sty $7020
     cpy #$ff
-    bne _continue
+    bne third_task_continue
     clc
     lda $7021 ; next MSB
     adc #1
     sta $7021
     cmp #$ff
-    bne _continue
+    bne third_task_continue
     txa
     .invoke pushA
     .invoke call remove_task, +
@@ -435,14 +426,13 @@
     inx ; move to next offset
     inx ; which is 2 locations away
     cpx #TASK_TABLE_LENGTH
-    beq _next
-    jmp _begin
-_next:
-    ldx #0
-    jmp _begin
-_continue:
+    beq +
+    jmp third_task_begin
+*   ldx #0
+    jmp third_task_begin
+third_task_continue:
     iny
-    jmp _loop
+    jmp third_task_loop
 third_task_stack:
     .word 0
     .word 0