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Split some code into separate files for easier management (4) Because the source for lwbasic is so large, split it into several different files to make it easier to navigate and modify. This is part four of the split.
author William Astle <lost@l-w.ca>
date Sun, 06 Aug 2023 00:51:22 -0600
parents 5f8f0b0781e8
children ac183a519439
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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e74d00ac6b79 Split some code into separate files for easier management (2)
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1 *pragmapush list
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2 *pragma list
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3 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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4 ; Fetch next input character, skip spaces. This is structured the way it is to avoid burning any register except A
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5 ; which is used for the returned value. Z will be set if the input character is NUL or a colon. C will be set if the
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6 ; input character is an ASCII digit. This allows testing Z to identify the end of a command due to either a colon or
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7 ; the end of a line.
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8 ;
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9 ; Compared to Color Basic, the instruction sequence only varies in the handling of the LDA. In Color Basic, the sequence
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10 ; is an LDA extended followed by a JMP extended. This totals to 9 cycles (5 for LDA, 4 for JMP). In LWBasic, an LDA
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11 ; with extended indirect addressing is used. This also totals 9 cycles. The only other difference is when a space is
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12 ; detected where the branch can be direct to the nextchar code instead of having to branch around a direct page JUMP
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13 ; which saves 3 cycles for the case where a space is detected. In other words, this is only slower by virtue of the
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14 ; fact that it is called with an extended JSR instead of a direct JSR which causes one extra cycle to be used there
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15 ; and one extra byte for each call to nextchar or curchar.
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16 ;
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17 ; On 6309, native move saves an extra cycle in the LDA sequence using the LDA extended followed by JMP extended
e74d00ac6b79 Split some code into separate files for easier management (2)
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18 ; sequence.
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19 ;
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20 ; This whole thing could be sped up by keeping the input pointer in a register. However, retaining the ability to
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21 ; use Y without having to save it first is likely more beneficial.
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22 nextchar inc inputptr+1 ; bump LSB of input pointer
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23 bne curchar ; brif no carry
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24 inc inputptr ; bump MSB
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25 curchar lda [inputptr] ; read the byte
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26 cmpa #'9+1 ; clear C if above ASCII digits, Z if colon
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27 bhs curchar0 ; brif above the ASCII digits
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28 cmpa #0x20 ; is it a space?
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29 beq nextchar ; brif so - skip over it
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30 suba #'0 ; clever way to set C if >= ASCII 0, Z if zero
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31 suba #-'0
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32 curchar0 rts
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33 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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34 ; This is exactly the same as nextchar except it doesn't skip spaces. Unfortunately, for efficiency purposes, we need
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35 ; to actually duplicate code here.
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36 nextcharraw inc inputptr+1 ; bump LSB of input pointer
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37 bne curchar ; brif no carry
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38 inc inputptr ; bump MSB
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39 curcharraw lda [inputptr] ; fetch the byte
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40 cmpa #'9+1 ; clear C if above digits, set Z if colon
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41 bhs curcharraw0 ; brif above digits
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42 suba #'0 ; clever way to set C if >= ASCII 0, Z if zero
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43 suba #-'0
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44 curcharraw0 rts
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45 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
76
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46 ; Set carry if upper/lower case alpha
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47 setcifalpha cmpa #'z+1 ; is it above lower case Z?
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48 bhs setcifalpha0 ; brif so, C clear
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49 suba #'a ; set C if >= lower case A
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50 suba #-'a
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51 bcs setcifalpha0 ; brif lower case alpha
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52 setcifualpha cmpa #'Z+1 ; is it above upper case Z?
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53 bhs setcifalpha0 ; brif so, C clear
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54 suba #'A ; set C if >= upper case A
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55 suba #-'A
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56 setcifalpha0 rts
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57 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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58 ; Set carry if digit
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59 setcifdigit cmpa #'9+1 ; is it above digit 9?
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60 bhs setcifdigit0 ; brif so, C clear
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61 suba #'0 ; set C if >= digit 0
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62 suba #-'0
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63 setcifdigit0 rts
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64 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
74
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65 ; Immediate mode handler
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66 immediate jsr writecondnl ; do newline if required
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67 ldx #prompt ; point to prompt string
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68 jsr console_outstrn
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69 immediate0 jsr readline ; read input line
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70 bcs immediate0 ; brif ended with BREAK
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71 ldx #linebuff ; point to start of line input buffer
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72 stx inputptr ; set input pointer
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73 jsr curchar ; skip spaces and set flags
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74 bcs immediate1 ; brif there's a line number
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75 tsta ; is there anything there at all (end of line)?
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76 beq immediate0 ; brif not - read another line
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77 ldx inputptr ; get the modified input pointer processing above
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78 jsr tokenize ; tokenize the line at inputptr, return with result at tokebuff and X
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79 jsr interpretline ; go interpret the tokenized line
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80 bra immediate ; go handle another line
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81 immediate1 bsr parse_lineno ; parse the line number
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82 bsr prog_findline ; go see if the line is in the program
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83 bne immediate3 ; brif not - no need to delete it
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84 ldu ,x ; get next line pointer which is where we start the copy from
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85 leay ,x ; use temp pointer for copying
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86 immediate2 lda ,u+ ; get source byte
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87 sta ,y+ ; stash it
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88 cmpu vartab ; did we reach the end of the program text?
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89 blo immediate2 ; brif not
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90 sty vartab ; save new end of program
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91 immediate3 jsr curchar ; skip any spaces after line number
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92 tsta ; is it the end of input (don't test for colon)
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93 beq immediate6 ; brif so - we don't need to insert a line
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94 pshs x ; save program insert location and line number
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95 ldx inputptr ; point to line text
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96 jsr tokenize ; tokenize line, get length to D
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97 leay ,x ; save tokenized line pointer
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98 addd #4 ; account for next line pointer and line number
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99 ldx vartab ; get start of copy location
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100 leau d,x ; set destination copy location D bytes further up
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101 stu vartab ; save new end of program
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102 immediate4 lda ,-x ; get byte from program
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103 sta ,-u ; stash it above the empty space
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104 cmpx ,s ; did we reach the insertion point?
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105 bne immediate4 ; brif not - keep going
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106 leas 2,s ; clear insertion location
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107 stu ,x++ ; set next line pointer to not null
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108 ldd binval ; set the line number for the program
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109 std ,x++
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110 immediate5 lda ,y+ ; get byte from tokenized line
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111 sta ,x+ ; stash it in the program
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112 bne immediate5 ; brif not at end of tokenized line (see note for fixlineptrs)
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113 immediate6 bsr prog_fixlineptrs ; fix up line pointers (all of them)
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114 ldx vartab ; clear out variables
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115 stx objecttab
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116 stx freestart
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117 bra immediate0 ; go handle more input
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118 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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119 ; Fix up next line pointers. Enter at prog_fixlineptrs to do the entire program. Enter at prog_fixlineptrsx to start
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120 ; at the line pointered to by X, which MUST NOT point to the end of the program.
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121 ;
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122 ; Works by simply scanning for a NUL in the program text after a line header (pointer to next line and line number)
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123 ; and uses that as the new next line pointer. A NULL next line pointer flags the end of the program.
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124 ;
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125 ; Observation: if the program text format is changed such that it can include NULs embedded within a line, this routine
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126 ; will need to be updated to grok that.
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127 prog_fixlineptrs
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128 ldx progtext ; point to start of program
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129 prog_fixlineptrsx
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130 ldu ,x ; are we at the end of the program?
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131 beq prog_findline2 ; brif not (borrow RTS from findline)
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132 leau 4,x ; point to line text (past pointer and line number)
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133 prog_fixlineptrs1
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134 lda ,u+ ; are we at the end of this line?
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135 bne prog_fixlineptrs1 ; brif not
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136 stu ,x ; set the next pointer for the previous line
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137 leax ,u ; move to the next line
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138 bra prog_fixlineptrsx ; go handle the next line
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139 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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140 ; Find a line in the program. Returns with C set and Z clear if no match and C clear and Z set if a match is found. X
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141 ; will point to either the exact matched line *or* the line that would be immediately after the desired line number if
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142 ; the line had been present, which could be the end of the program. D and U are clobbered. Enter at prog_findlinex to
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143 ; start searching at the line pointed to by X. Enter at prog_findline to start at the beginning of the program. Enter
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144 ; with the desired line number in binval.
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145 prog_findlinecl ldx curline ; get current line pointer
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146 beq prog_findline ; brif immediate mode
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147 ldd binval ; get desired line number
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148 cmpd 2,x ; is the desired line number >= current line?
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149 beq prog_findline2 ; brif this is the right line (optimizes goto self)
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150 bhi prog_findlinex ; brif desired line higher: start here instead of program start
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151 prog_findline ldx progtext ; point to start of program
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152 prog_findlinex ldu binval ; get line number to search for
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153 prog_findline0 ldd ,x ; end of program?
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154 beq prog_findline1 ; brif not
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155 cmpu 2,x ; does line number match? Z set if so, clear if not; C set not found
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156 bls prog_findline2
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157 ldx ,x ; move to next line
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158 bra prog_findline0 ; see if we found the line yet
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159 prog_findline1 coma ; set carry for not found; also clears Z because D is zero from above
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160 prog_findline2 rts
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161 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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162 ; Parse a line number and return it in binval; raise syntax error if the line number overflows 16 bits unsigned.
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163 ; Preserves; registers except D. This will accept the entire 16 bit unsigned number range which is why there is
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164 ; a BCS after every shift or add. Enter with the input pointer pointing to the number to parse.
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165 parse_lineno ldd zero ; clear out accumlator but preserve carry flag
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166 std binval
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167 jsr curchar ; set flags on current character; skip spaces
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168 bcc parse_lineno1 ; brif first character wasn't a digit - default to zero
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169 parse_lineno0 suba #0x30 ; adjust to binary digit
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170 pshs a ; save digit so we can add it later
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171 ldd binval ; get accumulated number
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172 lslb ; multiply accumulator by 10
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173 rola ; times 2
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174 bcs SNERROR ; brif overflow
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175 lslb
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176 rola ; times 4
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177 bcs SNERROR ; brif overflow
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178 addd binval ; times 5 (add orignal value to times 4)
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179 bcs SNERROR ; brif overflow
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180 lslb
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181 rola ; times 10
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182 bcs SNERROR ; brif overflow
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183 addb ,s+ ; add in accumulated digit
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184 adca #0
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185 bcs SNERROR ; brif overflow
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186 std binval ; save accumulated number
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187 jsr nextcharraw ; get next input character; DO NOT skip spaces
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188 bcs parse_lineno0 ; brif it's also a digit
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189 parse_lineno1 rts
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190 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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191 ; Main interpretation loop
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192 ;
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193 ; Enter at interpret with inputptr pointing to the code stream to interpret.
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194 ; Enter at interpretline with X pointing to the command stream to interpret which will return to the caller one the
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195 ; command stream has completed. STOP or BREAK will return with carry set while END or falling off the end of the
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196 ; code will return with carry clear. In the event of an error, the usual error processing will be done and control
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197 ; will return to immediate mode with the stack reset.
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198 interpret jsr breakcheck ; check for BREAK
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199 bcs cmd_stop0 ; brif BREAK detected - go stop the program
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200 ldx inputptr ; get interpration address
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201 stx curstmt ; save address of the current statement (needed for some stuff)
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202 lda ,x+ ; are we at the end of the line?
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203 beq interpret0 ; brif so
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204 cmpa #': ; end of statement?
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205 beq interpret3 ; brif so - do a statement
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206 SNERROR ldb #err_sn ; raise a syntax error
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207 jmp ERROR
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208 interpret0 sta endflag ; flag the program exit state as "END" (will be zero)
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209 ldd curline ; were we in immediate mode?
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210 bne interpret1 ; brif not
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211 clra ; clear carry to indicate normal exit
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212 rts ; return to caller
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213 interpret1 ldd ,x ; are we at the end of the program?
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214 beq interpret4 ; brif so - bail out
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215 stx curline ; save pointer to current line
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216 leax 3,x ; set input pointer one before the start of the line text
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217 interpret2 stx inputptr
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218 interpret3 jsr nextchar ; fetch first character of next statement
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219 beq interpret ; brif end of statement - do the next statement dance
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220 tsta ; set flags properly for token
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221 lbpl cmd_let ; brif no command - do assignment (LET command is optional)
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parents:
diff changeset
222 ldx #primaryjump ; point to jump table
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parents:
diff changeset
223 anda #0x7f ; lose bit 7
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parents:
diff changeset
224 leax a,x ; get half way to the correct offset
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parents:
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225 ldx a,x ; get the address the other half of the way from here
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parents:
diff changeset
226 jsr nextchar ; skip past token and set flags
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parents:
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227 jsr ,x ; call the routine
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228 bra interpret ; go handle the next statement dance
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229 interpret4 bsr cmd_stop1 ; make sure stack is aligned correctly (will not return)
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parents:
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230 interpretline clr curline ; blank out current line pointer (for immediate mode)
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parents:
diff changeset
231 clr curline+1
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parents:
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232 leax -1,x ; move back before start of code stream
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233 bra interpret2 ; go interpret this statement and then continue with stuff
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parents:
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234 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
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235 ; Check for character in B and raise a syntax error if not found at current input pointer. If it is found, fetch the
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parents:
diff changeset
236 ; next input character.
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237 syncheckb cmpb [inputptr] ; do we have a syntax match?
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parents:
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238 bne SNERROR ; brif not
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parents:
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239 jmp nextchar ; return next input character
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parents:
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240 *pragmapop list