From 626dbc1eac85cff73407d6410a0b84ea566ae4e1 Mon Sep 17 00:00:00 2001
From: FeralChild64 <you@example.com>
Date: Thu, 16 Jul 2020 15:45:57 +0200
Subject: [PATCH] string variables can be assigned both in direct and program
 mode

---
 src/basic/basic_commands/cmd_let.s            | 63 +++++++++++++------
 .../helper_let_strvarcpy_46K_50K.s            | 46 ++++++++++++++
 src/basic/engine/ad9e.frmevl.s                | 43 ++++++++++++-
 src/basic/engine/helper_frmevl_46K_50K.s      | 40 ++++++++++++
 src/basic/engine/varstr_alloc.s               | 37 ++++++-----
 src/basic/engine/varstr_free.s                |  4 +-
 6 files changed, 192 insertions(+), 41 deletions(-)
 create mode 100644 src/basic/basic_commands/helper_let_strvarcpy_46K_50K.s
 create mode 100644 src/basic/engine/helper_frmevl_46K_50K.s

diff --git a/src/basic/basic_commands/cmd_let.s b/src/basic/basic_commands/cmd_let.s
index d212a6bd..9a81e8a0 100644
--- a/src/basic/basic_commands/cmd_let.s
+++ b/src/basic/basic_commands/cmd_let.s
@@ -175,7 +175,7 @@ cmd_let_assign_string:
 
 #if CONFIG_MEMORY_MODEL_60K
 	ldx #<VARPNT
-	jsr poke_under_rom
+	jsr poke_under_roms
 #else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
 	sta (VARPNT), y
 #endif
@@ -226,13 +226,13 @@ cmd_let_assign_string_not_same:
 
 	ldy #$00
 	lda __FAC1+0
-	jsr poke_under_rom
+	jsr poke_under_roms
 	iny
 	lda __FAC1+1
-	jsr poke_under_rom
+	jsr poke_under_roms
 	iny
 	lda __FAC1+2
-	jsr poke_under_rom
+	jsr poke_under_roms
 
 #else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
 
@@ -260,17 +260,27 @@ cmd_let_assign_string_not_text_area:
 
 	// XXX
 
-	// Free the memory of the old string, it is not possible to reuse it
-
-	// XXX
-
 	// Check if the new string is a temporary one - if so, reuse already done alocation
 
 	// XXX
 
-	// No special case optimization is possible - alocate new memory area and copy the string
+	// No special case optimization is possible - alocate new memory area
 
-	// XXX
+	ldy #$00
+
+#if CONFIG_MEMORY_MODEL_60K
+	ldx #<VARPNT
+	jsr poke_under_roms
+#else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	sta (VARPNT), y
+#endif
+
+	lda __FAC1+0
+	sta (VARPNT), y
+
+	jsr varstr_alloc
+
+	// Copy the string
 
 #if CONFIG_MEMORY_MODEL_60K
 	
@@ -279,18 +289,33 @@ cmd_let_assign_string_not_text_area:
 	// XXX
 
 #elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	// XXX consider optimized version without multiple JSRs
-
-	// XXX
-	// XXX: implement this
-	// XXX
+	
+	jsr helper_let_strvarcpy
 
 #else // CONFIG_MEMORY_MODEL_38K
 
-	// XXX
-	// XXX: implement this
-	// XXX
+	// Retrieve pointer to destination
+
+	ldy #$02
+	lda (VARPNT), y
+	sta DSCPNT+2
+	dey
+	lda (VARPNT), y
+	sta DSCPNT+1
+	dey
+
+	// .Y is now 0 - copy the content
+!:
+	lda (__FAC1+1),y
+	sta (DSCPNT+1),y
+	iny
+	cpy __FAC1+0
+	bne !-
 
 #endif
 
-	jmp do_NOT_IMPLEMENTED_error
+	// Free the memory of the old string
+
+	// XXX
+
+	rts
diff --git a/src/basic/basic_commands/helper_let_strvarcpy_46K_50K.s b/src/basic/basic_commands/helper_let_strvarcpy_46K_50K.s
new file mode 100644
index 00000000..538db97b
--- /dev/null
+++ b/src/basic/basic_commands/helper_let_strvarcpy_46K_50K.s
@@ -0,0 +1,46 @@
+// #LAYOUT# STD *       #TAKE-HIGH
+// #LAYOUT# *   BASIC_0 #TAKE-HIGH
+// #LAYOUT# *   *       #IGNORE
+
+// This has to go $E000 or above - routines below banks out the main BASIC ROM!
+
+//
+// Helper routine to copy string variable content, for LET command
+//
+
+
+#if CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+
+helper_let_strvarcpy:
+
+	// Unmap BASIC lower ROM
+
+	lda #$26
+	sta CPU_R6510
+
+	// Retrieve pointer to destination
+
+	ldy #$02
+	lda (VARPNT), y
+	sta DSCPNT+2
+	dey
+	lda (VARPNT), y
+	sta DSCPNT+1
+	dey
+
+	// .Y is now 0 - copy the content
+!:
+	lda (__FAC1+1),y
+	sta (DSCPNT+1),y
+	iny
+	cpy __FAC1+0
+	bne !-
+
+	// Restore default memory mapping
+
+	lda #$27
+	sta CPU_R6510
+
+	rts
+
+#endif
diff --git a/src/basic/engine/ad9e.frmevl.s b/src/basic/engine/ad9e.frmevl.s
index 447f746d..7959d4ea 100644
--- a/src/basic/engine/ad9e.frmevl.s
+++ b/src/basic/engine/ad9e.frmevl.s
@@ -78,8 +78,49 @@ FRMEVL_loop:
 	dew TXTPTR
 #endif
 	jsr fetch_variable
-	bcc FRMEVL_got_value
+	bcs !+
 
+	// Found the variable - copy descriptor to FAC1
+
+#if CONFIG_MEMORY_MODEL_60K
+	
+	ldx #<VARPNT
+
+	ldy #$00
+	jsr peek_under_roms
+	sta __FAC1+0
+	iny
+	jsr peek_under_roms
+	sta __FAC1+1
+	iny
+	jsr peek_under_roms
+	sta __FAC1+2
+
+#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	
+	jsr helper_frmevl_strdesccpy
+
+#else // CONFIG_MEMORY_MODEL_38K
+
+	ldy #$00
+	lda (VARPNT),y
+	sta __FAC1+0
+	iny
+	lda (VARPNT),y
+	sta __FAC1+1
+	iny
+	lda (VARPNT),y
+	sta __FAC1+2
+
+#endif
+
+#if HAS_OPCODES_65C02
+	bra FRMEVL_got_value
+#else
+	jmp FRMEVL_got_value
+#endif
+
+!:
 	// There is one possibility left - a floating point value
 
 
diff --git a/src/basic/engine/helper_frmevl_46K_50K.s b/src/basic/engine/helper_frmevl_46K_50K.s
new file mode 100644
index 00000000..bf6249a6
--- /dev/null
+++ b/src/basic/engine/helper_frmevl_46K_50K.s
@@ -0,0 +1,40 @@
+// #LAYOUT# STD *       #TAKE-HIGH
+// #LAYOUT# *   BASIC_0 #TAKE-HIGH
+// #LAYOUT# *   *       #IGNORE
+
+// This has to go $E000 or above - routines below banks out the main BASIC ROM!
+
+//
+// Helper routine to copy string descriptor, for expression evaluator
+//
+
+
+#if CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+
+helper_frmevl_strdesccpy:
+
+	// Unmap BASIC lower ROM
+
+	lda #$26
+	sta CPU_R6510
+
+	// Copy string descriptor
+
+	ldy #$00
+	lda (VARPNT),y
+	sta __FAC1+0
+	iny
+	lda (VARPNT),y
+	sta __FAC1+1
+	iny
+	lda (VARPNT),y
+	sta __FAC1+2
+
+	// Restore default memory mapping
+
+	lda #$27
+	sta CPU_R6510
+
+	rts
+
+#endif
diff --git a/src/basic/engine/varstr_alloc.s b/src/basic/engine/varstr_alloc.s
index 017063b2..d5bc5e04 100644
--- a/src/basic/engine/varstr_alloc.s
+++ b/src/basic/engine/varstr_alloc.s
@@ -15,7 +15,9 @@
 // - https://sites.google.com/site/h2obsession/CBM/basic/variable-format
 //
 // Input:
-// - DSCPNT+1, DSCPNT+2 - pointer to string descriptor, first pointed byte should contain desired length
+// - VARPNT - pointer to string descriptor, first pointed byte should contain desired length
+// Output:
+// - fills-in pointer in the string descriptor
 //
 
 // XXX test this routine
@@ -39,7 +41,7 @@ varstr_alloc_retry:
 	lda FRETOP+1
 	sta INDEX+1
 
-	// Lower FRETOP to make space for string descriptor
+	// Lower FRETOP to make space for the back-pointer
 
 #if !HAS_OPCODES_65CE02
 
@@ -60,7 +62,7 @@ varstr_alloc_retry:
 	// Create the back-pointer to the string descriptor
 
 	ldy #$00
-	lda DSCPNT+1
+	lda VARPNT+0
 
 #if CONFIG_MEMORY_MODEL_60K
 	ldx #<FRETOP
@@ -70,7 +72,7 @@ varstr_alloc_retry:
 #endif
 
 	iny
-	lda DSCPNT+2
+	lda VARPNT+1
 
 #if CONFIG_MEMORY_MODEL_60K
 	jsr poke_under_roms
@@ -80,15 +82,15 @@ varstr_alloc_retry:
 
 	// Now lower FRETOP again to make space for the string content
 
-	dey                                          // $01 -> $00
+	ldy #$00
 
 #if CONFIG_MEMORY_MODEL_60K
-	ldx #<DSCPNT+1
+	ldx #<VARPNT
 	jsr peek_under_roms
 #elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	jsr peek_under_roms_via_DSCPNT_PLUS_1
+	jsr peek_under_roms_via_VARPNT
 #else // CONFIG_MEMORY_MODEL_38K
-	lda (DSCPNT+1),y
+	lda (VARPNT),y
 #endif
 
 	jsr varstr_FRETOP_down_A
@@ -96,24 +98,21 @@ varstr_alloc_retry:
 
 	// Success - fill in the string descriptor
 
-	iny                                          // $00 -> $01
-	lda FRETOP+0
+	ldy #$01
 
 #if CONFIG_MEMORY_MODEL_60K
-	ldx #<FRETOP
+	ldx #<VARPNT
+	lda FRETOP+0
 	jsr poke_under_roms
-#else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	sta (FRETOP), y
-#endif
-
 	iny
 	lda FRETOP+1
-
-#if CONFIG_MEMORY_MODEL_60K
-	ldx #<DSCPNT+1
 	jsr poke_under_roms
 #else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
-	sta (DSCPNT+1), y
+	lda FRETOP+0
+	sta (VARPNT), y
+	iny
+	lda FRETOP+1
+	sta (VARPNT), y
 #endif
 
 	// The end
diff --git a/src/basic/engine/varstr_free.s b/src/basic/engine/varstr_free.s
index 403601c6..95fb88b1 100644
--- a/src/basic/engine/varstr_free.s
+++ b/src/basic/engine/varstr_free.s
@@ -12,7 +12,7 @@
 // XXX test this routine
 // XXX check if this entry point is needed
 
-varstr_free:
+varstr_free: // XXX is it needed? if not, we do not need peek_under_roms_via_DSCPNT_PLUS_1
 
 	// First copy the string descriptor data to DSCPNT
 	// XXX write optimized version for CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
@@ -58,7 +58,7 @@ varstr_free:
 
 varstr_free_DSCPNT_set:
 
-	// consider moving size check (DSCPNT+0) here
+	// XXX consider moving size check (DSCPNT+0) here
 
 	// XXX
 	// XXX check if string is located above FRETOP, handle case if it is not