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annotate src/progctrl.s @ 119:a6a53e5c04bd

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Make a call stack implementation that is more complete and maybe cleaner.
author William Astle <lost@l-w.ca>
date Fri, 29 Dec 2023 01:40:39 -0700
parents e74d00ac6b79
children 9d57279c900e
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1 *pragmapush list
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2 *pragma list
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3 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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4 ; The END command.
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5 cmd_end bne SNERROR ; error out if there is an argument
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6 ;jsr closeall ; close all files for END
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7 clra ; flag END (clear carry)
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8 bra cmd_stop0 ; go do the stop/end
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9 cmd_stop bne SNERROR ; raise error if there was an argument
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10 coma ; flag STOP - set carry
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11 cmd_stop0 ror endflag ; set stop/end flag
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12 cmd_stop1 clr filenum ; reset I/O to console
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13 ldx curline ; in immediate mode?
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14 beq cmd_stop2 ; brif so - don't save the continue pointers
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15 stx contline ; save pointer to current line for CONT
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16 ldx curstmt ; get current statement address
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17 stx contstmt ; save it for CONT
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18 cmd_stop2 rol endflag ; get STOP/END to C (1=STOP)
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19 bcc cmd_stop3 ; brif END - don't do message
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20 ldx #breakmsg ; do "BREAK IN"
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21 jmp ERROR2 ; the bottom half of the error handler can deal with the details
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22 cmd_stop3 puls x,pc ; lose return address and return to caller of interpretation loop
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23 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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24 ; The NEW command.
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25 ;
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26 ; This also includes several useful entry points:
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27 ;
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28 ; cmd_newraw: does the whole NEW but without any syntax checks
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29 ; cmd_newinptr: skips clearing the program text
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30 ; cmd_newvars: clears variables and resets the stack and other misc state
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31 ; cmd_newstack: just reset the stack and other misc state
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32 cmd_new bne cmd_new0 ; brif there was an argument - don't wipe things out on syntax error
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33 cmd_newraw ldx progtext ; point to start of program
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34 clr -1,x ; make sure there's a NUL before the start of the program
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35 clr ,x+ ; put a NULL pointer at the start of the program
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36 clr ,x+
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37 stx vartab ; set start of variables after that
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38 cmd_newinptr ldx progtext ;* set input pointer to the NUL before the program; this will cause the
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39 leax -1,x ;* the interpreter to drop to immediate mode no matter what it was
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40 stx inputptr ;* executing before this call if called from the main loop
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41 cmd_newvars ldx memsize ; get top of memory
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42 stx stringtab ; clear out string space
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43 ldx vartab ; get start of variables
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44 stx objecttab ; set start of large objects (arrays) there too (clear vars)
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45 stx freestart ; set start of free memory (end of large objects) (clear arrays)
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46 cmd_newstack ldx #stringstackend ; reset string stack (string stack counts down)
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47 stx stringstackptr
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48 ldx ,s ; get return address
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49 lds freetop ; reset stack to top of memory
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50 clr ,-s ; put a flag to stop stack searches (NEXT, RETURN)
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51 sts cstackptr ; reset pointer for call stack
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52 clr contstmt ; clear "CONT" destination
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53 clr contstmt+1
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54 jmp ,x ; return to caller
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55 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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56 ; REM and ' commands; also ELSE comes here since it needs to skip the rest of the line in that case.
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57 cmd_else
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58 cmd_apos
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59 cmd_rem clra ; clear carry
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60 ldx curline ; get start of current line
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61 beq cmd_stop3 ; brif immediate mode - fall back to caller
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62 ldx ,x ; get address of next line
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63 leax -1,x ; move back one
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64 stx inputptr ; put input pointer there
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65 cmd_new0 rts
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66 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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67 ; DATA command
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68 ;
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69 ; need to skip to the end of the current statement, which is either the end of the line OR a colon not included inside
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70 ; a quoted string
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71 cmd_data ldx inputptr ; get input pointer
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72 cmd_data0 lda ,x+ ; get character at pointer
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73 beq cmd_data1 ; brif end of line
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74 cmpa #': ; end of statement?
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75 bne cmd_data2 ; brif not
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76 cmd_data1 leax -1,x ; move back to the NUL or colon
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77 stx inputptr ; reset input pointer for interpreter
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78 rts
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79 cmd_data2 cmpa #'" ; start of constant string?
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80 bne cmd_data0 ; brif not - process more characters
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81 cmd_data3 lda ,x+ ; get next string character
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82 beq cmd_data1 ; brif end of line
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83 cmpa #'" ; string delimiter?
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84 bne cmd_data3 ; brif not - keep going
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85 bra cmd_data0 ; process stuff outside string
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86 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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87 ; RUN command
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88 cmd_run ;jsr closeall ; close all files
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89 jsr curchar ; what do we have as an argument?
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90 bcs cmd_goto ; brif a digit - it's a line number (RUN ###); do GOTO
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91 lbne SNERROR ; brif anything else on the line - not legit command
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92 ldx progtext ; point to start of program
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93 bra cmd_goto0 ; go transfer control to the start of the program
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94 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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95 ; GOTO command
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96 cmd_goto jsr parse_lineno ; parse the line number
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97 cmd_gosub0 jsr prog_findlinecl ; go look up line number
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98 bcc cmd_goto0 ; brif line found
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99 ULERROR ldb #err_ul ; raise undefined line error
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100 jmp ERROR
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101 cmd_goto0 stx curline ; make sure we aren't flagging immediate mode
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102 leax -1,x ; move input pointer to NUL before destination line
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103 stx inputptr ; put input pointer there
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104 rts ; resume interpretation at the new location
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105 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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106 ; GOSUB command
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107 cmd_gosub jsr parse_lineno ; parse the destination line so return location is after the line number
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108 ldd #tok_gosub*256+4 ; stack frame details
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109 jsr cstack_alloc ; make a stack frame
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110 ldx curline ; save current line pointer
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111 stx ,u
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112 ldx inputptr ; save current input pointer
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113 stx 2,u
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114 bra cmd_gosub0 ; go finish up as a GOTO
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115 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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116 ; RETURN command
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117 ; POP command
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118 ;
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119 ; RETURN will search the call stack for the first GOSUB frame and remove all other placeholders it finds. A frame type
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120 ; of 0 will cause it to stop.
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121 cmd_pop skip1lda ; set nonzero for POP
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122 cmd_return clra ; set zero for RETURN
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123 pshs a ; save operation type
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124 jsr cstack_first ; get first entry on call stack
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125 bne cmd_return1 ; brif there's a frame - don't error
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126 RG_ERROR ldb #err_rg ; raise RETURN without GOSUB
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127 jmp ERROR
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128 cmd_return0 jsr cstack_next ; move to next entry
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129 beq RG_ERROR ; brif end of stack - raise error
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130 cmd_return1 cmpb #tok_gosub ; do we have a GOSUB frame?
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131 bne cmd_return0 ; brif not - try again
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132 lda ,s+ ; is it "POP"?
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133 bne cmd_return2 ; brif so - don't change flow control but clear stack frame
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134 ldx ,u ; get back saved line pointer
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William Astle <lost@l-w.ca>
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135 stx curline
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136 ldx 2,u ; get back saved input pointer
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137 stx inputptr
119
a6a53e5c04bd Make a call stack implementation that is more complete and maybe cleaner.
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138 cmd_return2 jsr cstack_popto ; clean up call stack
74
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139 bra cmd_data ; move to end of statement (move past any "ON GOSUB" entries
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140 *pragmapop list