From 1682cc8934f6248ca4db0f061dca706e8794fc81 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Sun, 2 Aug 2020 12:05:34 +0200
Subject: [PATCH] started work on backpointer refresh

---
 src/basic/engine_variables/fetch_variable.s   |  34 ++---
 .../helper_array_refresh_bptrs.s              | 122 ++++++++++++++++++
 2 files changed, 132 insertions(+), 24 deletions(-)
 create mode 100644 src/basic/engine_variables/helper_array_refresh_bptrs.s

diff --git a/src/basic/engine_variables/fetch_variable.s b/src/basic/engine_variables/fetch_variable.s
index edb8d0dc..7678a458 100644
--- a/src/basic/engine_variables/fetch_variable.s
+++ b/src/basic/engine_variables/fetch_variable.s
@@ -152,29 +152,6 @@ fetch_variable_alocate_space_OK:
 
 	jsr shift_mem_up
 
-	// Now, we need to recreate the back-pointers
-
-#if CONFIG_MEMORY_MODEL_60K
-	
-	// XXX!
-	// XXX: implement this for arrays
-	// XXX
-
-#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	// XXX consider optimized version without multiple JSRs
-
-	// XXX!
-	// XXX: implement this for arrays
-	// XXX
-
-#else // CONFIG_MEMORY_MODEL_38K
-
-	// XXX!
-	// XXX: implement this for arrays
-	// XXX
-
-#endif
-
 	// FALLTROUGH
 
 fetch_variable_alocate_adjust_vars:
@@ -198,7 +175,16 @@ fetch_variable_alocate_adjust_vars:
 !:
 	// VARPNT already points to the start of the variable descriptor
 
-	// Fill-in the new variable name, descriptor (it is enough to zero first 2 bytes of content)
+	// We need to recreate the back-pointers to string arrays
+
+	lda ARYTAB+0
+	sta INDEX+0
+	lda ARYTAB+1
+	sta INDEX+1
+
+	jsr helper_array_refresh_bptrs
+
+	// Fill-in the new variable name and descriptor (it is enough to zero first 2 bytes of content)
 
 	ldy #$00
 
diff --git a/src/basic/engine_variables/helper_array_refresh_bptrs.s b/src/basic/engine_variables/helper_array_refresh_bptrs.s
new file mode 100644
index 00000000..3473d866
--- /dev/null
+++ b/src/basic/engine_variables/helper_array_refresh_bptrs.s
@@ -0,0 +1,122 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+//
+// Refresh back-pointer to arrays
+//
+
+
+#if CONFIG_MEMORY_MODEL_38K // XXX! create versions for other memory models
+
+helper_array_refresh_bptrs:
+
+	// Refresh back-pointers to arrays
+
+	lda ARYTAB+0
+	sta INDEX+0
+	lda ARYTAB+1
+	sta INDEX+1
+
+	// FALLTROUGH
+
+helper_array_refresh_bptrs_loop_1:
+
+	// Check if we reached end of arays
+
+	lda INDEX+1
+	cmp STREND+1
+	bne !+
+	lda INDEX+0
+	cmp STREND+0
+	beq helper_array_refresh_bptrs_end
+!:
+	// Calculate start address of the next array, store it in INDEX+2/+3
+
+	ldy #$02
+
+	lda (INDEX+0), y // XXX
+	clc
+	adc INDEX+0
+	sta INDEX+2 
+	iny
+	lda (INDEX+0), y // XXX
+	adc INDEX+1
+	sta INDEX+3
+
+	// Check if the current array is a string - if not, go to next array
+
+	ldy #$00
+	lda (INDEX+0), y // XXX
+	bmi helper_array_refresh_bptrs_loop_next
+	iny
+	lda (INDEX+0), y // XXX
+	bpl helper_array_refresh_bptrs_loop_next
+
+	// It's a string array - scroll INDEX+0/+1 to the first descriptor
+
+	ldy #$04
+	lda (INDEX+0), y // XXX
+	asl
+	clc
+	adc #$05
+	jsr helper_INDEX_up_A
+
+	// FALLTROUGH
+
+helper_array_refresh_bptrs_loop_2:
+
+	// Recreate the back-pointer
+
+	ldy #$00
+	lda (INDEX+0), y // XXX
+	beq helper_array_refresh_bptrs_skip      // skip empty strings
+
+	iny
+	clc
+	adc (INDEX+0), y // XXX
+	sta INDEX+4
+	iny
+	lda #$00
+	adc (INDEX+0), y // XXX
+	sta INDEX+5
+
+	ldy #$00
+	lda INDEX+0
+	sta (INDEX+4), y // XXX
+	iny
+	lda INDEX+1
+	sta (INDEX+4), y // XXX
+
+	// FALLTROUGH
+
+helper_array_refresh_bptrs_skip:
+
+	// Shift INDEX+0/+1 to the next string
+
+	lda #$03
+	jsr helper_INDEX_up_A
+
+	// Check if this is the last string of the array
+
+	lda INDEX+0
+	cmp INDEX+2
+	bne helper_array_refresh_bptrs_loop_2
+	lda INDEX+1
+	cmp INDEX+3
+	bne helper_array_refresh_bptrs_loop_2
+
+helper_array_refresh_bptrs_loop_next:
+
+	lda INDEX+3
+	sta INDEX+1
+	lda INDEX+2
+	sta INDEX+0
+
+	jmp_8 helper_array_refresh_bptrs_loop_1
+
+helper_array_refresh_bptrs_end:
+
+	rts
+
+#endif