variable support cleanup

src/basic/engine_runtime/execute_line_statements.s

@@ -0,0 +1,253 @@
+// #LAYOUT# STD *       #TAKE
+// #LAYOUT# *   BASIC_0 #TAKE
+// #LAYOUT# *   *       #IGNORE
+
+//
+// Tries to execute the statement, and all the subsequent ones
+//
+
+
+execute_statements:
+
+	// Check for RUN/STOP
+
+	lda STKEY
+	bpl_16 cmd_stop
+
+	// Skip over any white spaces and colons (':')
+!:
+	jsr fetch_character_skip_spaces
+	cmp #$3A                           // colon, can be skipped
+	beq !-
+	
+	// Check if end of the line
+
+	cmp #$00
+	beq execute_statements_end_of_line
+
+	// Not end of the line - it seems we actually have something to execute	
+
+	// Move token code to .X
+	tax
+
+	// Push the 'end_of_statement' address for RTS
+
+	lda #>(end_of_statement - 1)
+	pha
+	lda #<(end_of_statement - 1)
+	pha
+
+	// Check if token is valid for execution
+
+	cpx #$7F
+	bcc_16 execute_statements_var_assign         // not a token - try variable assign
+
+	cpx #$A6
+	bcs execute_statements_extended
+
+#if !HAS_OPCODES_65C02
+
+	// Get the jump table entry for it, push it on the stack, and then RTS to start it.
+
+	lda command_jumptable_hi - $80, x
+	pha
+	lda command_jumptable_lo - $80, x
+	pha
+	
+	rts
+
+#else // HAS_OPCODES_65C02
+
+	// Use jumptable to go to the command routine
+
+	txa
+	asl
+	tax
+	jmp (command_jumptable, x)
+
+#endif
+
+
+execute_statements_extended:
+
+	// Support for extended BASIC commands
+
+	cpx #$CC
+	beq execute_statements_CC
+	cpx #$CD
+	beq execute_statements_CD
+
+	// 'GO' command has a strange token, it is placed after function tokens
+
+	cpx #$CB                                     
+	beq_16 cmd_go
+
+	jmp do_SYNTAX_error
+
+
+execute_statements_CC:
+
+	// Get the sub-token, check that it is valid
+
+	jsr fetch_character
+	cmp #$00
+	beq_16 do_SYNTAX_error
+
+	cmp #(TK__MAXTOKEN_keywords_CC+1)
+	bcs_16 do_SYNTAX_error
+
+	// Execute command
+
+#if !HAS_OPCODES_65C02
+
+	// Get the jump table entry for it, push it on the stack, and then RTS to start it.
+
+	tax
+	lda command_CC_jumptable_hi - 1, x
+	pha
+	lda command_CC_jumptable_lo - 1, x
+	pha
+	
+	rts
+
+#else // HAS_OPCODES_65C02
+
+	// Use jumptable to go to the command routine
+
+	asl
+	tax
+	jmp (command_CC_jumptable - 2, x)
+
+#endif
+
+
+execute_statements_CD:
+
+	// Get the sub-token, check that it is valid
+
+	jsr fetch_character
+	cmp #$00
+	beq_16 do_SYNTAX_error
+
+	cmp #(TK__MAXTOKEN_keywords_CD+1)
+	bcs_16 do_SYNTAX_error
+
+	// Execute command
+
+#if !HAS_OPCODES_65C02
+
+	// Get the jump table entry for it, push it on the stack, and then RTS to start it.
+
+	tax
+	lda command_CD_jumptable_hi - 1, x
+	pha
+	lda command_CD_jumptable_lo - 1, x
+	pha
+	
+	rts
+
+#else // HAS_OPCODES_65C02
+
+	// Use jumptable to go to the command routine
+
+	asl
+	tax
+	jmp (command_CD_jumptable - 2, x)
+
+#endif
+
+
+execute_statements_end_of_line:
+
+	// First check, if we are in direct mode - if so,
+	// end the execution and go to main loop
+
+	ldx CURLIN+1
+	inx
+	beq_16 shell_main_loop
+
+	// Advance to the next line - first copy the line number
+	// to previous line number
+
+	lda CURLIN+0
+	sta OLDLIN+0
+	lda CURLIN+1
+	sta OLDLIN+1
+		
+	// Advance the basic line pointer to the next line; if end,
+	// go to the main loop
+
+	jsr follow_link_to_next_line
+
+	lda OLDTXT+0
+	ora OLDTXT+1
+	beq_16 shell_main_loop
+	
+	// FALLTROUGH
+
+execute_line:
+
+	// Check if pointer is null, if so, we are at the end of the program
+
+	ldy #0
+	jsr peek_line_pointer_null_check
+	bcc_16 shell_main_loop             // branch if end of program reached
+
+	// Skip pointer and line number to get address of first statement
+
+	lda OLDTXT+0
+	clc
+	adc #$04
+	sta TXTPTR+0
+	lda OLDTXT+1
+	adc #$00
+	sta TXTPTR+1
+
+	ldy #$02
+
+#if CONFIG_MEMORY_MODEL_60K
+	ldx #<OLDTXT
+	jsr peek_under_roms
+#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	jsr peek_under_roms_via_OLDTXT
+#else // CONFIG_MEMORY_MODEL_38K
+	lda (OLDTXT),y
+#endif
+
+	sta CURLIN+0
+	iny
+
+#if CONFIG_MEMORY_MODEL_60K
+	jsr peek_under_roms
+#elif CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
+	jsr peek_under_roms_via_OLDTXT
+#else // CONFIG_MEMORY_MODEL_38K
+	lda (OLDTXT),y
+#endif
+
+	sta CURLIN+1
+
+	jmp execute_statements
+
+
+execute_statements_var_assign:
+
+	// Prevent wedges from being executed within a program
+
+#if CONFIG_TAPE_WEDGE
+	cpx #$40
+	beq_16 do_DIRECT_MODE_ONLY_error
+#endif
+#if CONFIG_DOS_WEDGE
+	cpx #$5F
+	beq_16 do_DIRECT_MODE_ONLY_error
+#endif
+
+	// Try variable assignment - execute as LET command
+
+#if !HAS_OPCODES_65CE02
+	jsr unconsume_character
+#else
+	dew TXTPTR
+#endif
+	jmp assign_variable