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1706
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1 *
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2 * Save compression routines.
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3 * VEFSquash: Squashes data for VEF format.
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4 * CM3Compress: Compresses altbuff using CM3 compression
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5 * MGEsame: copy linebuff to altbuff
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6 *
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7
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8 ifp1
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1912
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9 use os9defs.d
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1706
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10 endc
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11
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12 check macro
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13 pshs b,cc
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14 ldb #\1
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15 os9 F$PErr
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16 puls b,cc
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17 endm
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18
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19 psect view_savecomp_a,0,0,0,0,0
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20
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21 *
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22 * Compress one line with CM3 compression.
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23 * Expects: line data in altbuff
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24 * Returns: compressed line in altbuff, preceded by 2-byte size
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25 * Uses: alt2buff to store last line of data
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26 Stash equ 160 Stash new line at end of old line
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27 CM3compress:
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28 pshs a,b
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29 bsr CM3stash Stash line at alt2buff+Stash
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30 lbsr CM3docomp Try to compress it
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31 ldd altbuff,y Get the result size
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32 cmpd #160
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33 bls CM3comp0 If its small, use compressed line
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34 bsr CM3nocomp Else don't compress it
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35 CM3comp0
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36 bsr CM3save Save old line
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37 puls a,b,pc
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38
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39 * Copy from altbuff to stash area
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40 CM3stash
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41 pshs a,b,x,u
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42 leax altbuff,y
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43 leau alt2buff+Stash,y
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44 ldb #160
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45 CM3st1
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46 lda ,x+
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47 sta ,u+
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48 decb
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49 bne CM3st1
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50 puls a,b,x,u,pc
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51
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52 * Copy from stash area to save area
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53 CM3save
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54 pshs a,b,x,u
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55 leax alt2buff+Stash,y
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56 leau alt2buff,y
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57 ldb #160
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58 CM3save1
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59 lda ,x+
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60 sta ,u+
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61 decb
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62 bne CM3save1
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63 puls a,b,x,u,pc
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64
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65 * No compression: from stash area to altbuff
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66 CM3nocomp
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67 pshs a,b,x,y,u
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68 leax altbuff,y First try, no compression at all.
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69 ldd #161
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70 std ,x++
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71 ldb #160
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72 stb ,x+
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73 leau alt2buff+Stash,y Get data from stash area.
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74 CM3noc1
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75 lda ,u+
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76 sta ,x+
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77 decb
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78 bne CM3noc1
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79 puls a,b,x,y,u,pc
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80
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81 vsect dp
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82 ImagePtr rmb 2
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83 ImageBit rmb 1
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84 ActionPtr rmb 2
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85 ActionBit rmb 1
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86 endsect
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87
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88 SetAction
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89 pshs a,x
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90 lda ActionBit
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91 ldx ActionPtr
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92 ora ,x
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93 sta ,x
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94 puls a,x
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95 ClrAction
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96 pshs a,x
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97 lda ActionBit
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98 lsra
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99 bcc ClrAct1
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100 ldx ActionPtr
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101 leax 1,x
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102 stx ActionPtr
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103 inc altbuff+2,y Increment count of Action bytes.
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104 rora
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105 ClrAct1
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106 sta ActionBit
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107 puls a,x,pc
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108
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109 SetImage
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110 pshs a,x
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111 lda ImageBit
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112 ldx ImagePtr
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113 ora ,x
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114 sta ,x
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115 puls a,x
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116 ClrImage
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117 pshs a,x
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118 lda ImageBit
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119 lsra
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120 bcc ClrIm1
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121 ldx ImagePtr
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122 leax 1,x
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123 stx ImagePtr
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124 rora
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125 ClrIm1
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126 sta ImageBit
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127 puls a,x,pc
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128
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129 * Try doing CM3 compression
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130 CM3docomp
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131 pshs a,b,x,y,u
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132
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133 leax altbuff,y Clear out receiving area.
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134 clrb
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135 CM3do1
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136 clr ,x+
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137 decb
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138 bne CM3do1
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139
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140 leax altbuff+2+1,y Set up Image and Action stuff
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141 stx ImagePtr
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142 leax altbuff+2+1+20,y
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143 stx ActionPtr
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144 lda #$80
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145 sta ImageBit Start with MSBit
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146 sta ActionBit
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147 lda #1
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148 sta altbuff+2,y Set # Action bytes to 1
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149
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150 leax alt2buff+Stash,y Point to line data
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151 leau altbuff+2+1+20+20,y Point to space for extra bytes.
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152 ldb #160 Number of bytes.
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153 CM3do3
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154 lda ,x+ Get next byte
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155 cmpa -2,x Same as previous?
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156 bne CM3do4
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157 bsr ClrImage Yes, mark it.
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158 bra CM3do6
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159 CM3do4
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160 bsr SetImage
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161 cmpa -(Stash+1),x Same as above?
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162 bne CM3do5
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163 bsr ClrAction Mark as such
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164 bra CM3do6
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165 CM3do5
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166 lbsr SetAction
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167 sta ,u+ Store byte value
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168 CM3do6
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169 decb
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170 bne CM3do3
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171
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172 ldb altbuff+2,y Minimize this value.
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173 lda ActionBit
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174 cmpa #$80 If this is true, then last action byte hasn't been used.
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175 bne CM3do7
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176 decb so we can decrement it.
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177 beq CM3do7 ... but not to zero.
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178 stb altbuff+2,y
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179 CM3do7
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180
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181 leax altbuff+2+1+20+20,y Point to start of extra bytes
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182 ldb altbuff+2,y Get # of action bytes
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183 subb #20 Number of unused action bytes
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184 bne CM3do8 If none are unused, just leave extra bytes in place.
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185 tfr u,x Set X to end.
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186 bra CM3do11
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187 CM3do8
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188
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189 pshs u Save end of extra bytes
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190 CM3do9
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191 cmpx ,s
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192 beq CM3do10
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193 lda ,x
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194 sta b,x
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195 leax 1,x Move extra bytes down
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196 bra CM3do9
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197 CM3do10
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198
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199 puls u
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200 leax b,x Point to new end of extra bytes.
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201 CM3do11
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202
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203 tfr x,d
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204 leax altbuff+2,y
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205 pshs x
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206 subd ,s D holds size of compressed data
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207 puls x
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208 std altbuff,y store size.
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209 puls a,b,x,y,u,pc
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210
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211 *
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212 * Squash one packet worth of data
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213 * Expects: Number of bytes to squash in D.
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214 * Bytes to squash pointed to by X.
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215 * Returns: Squashed packet in altbuff
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216 VEFSquash:
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217 pshs a,b,x,y,u
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218 leau altbuff+1,y Data goes here
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219 tfr d,y Size of data to compress
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220 clrb This will count up size of compressed packet
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221 Sq1
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222 lda ,x
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223 cmpa 1,x
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224 bne Sq2
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225 cmpa 2,x If three bytes are the same, then do compression.
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226 bne Sq2
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227 bsr sqcomprs Get a compressed subpacket.
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228 bra Sq3
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229 Sq2
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230 bsr sqstraight
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231 Sq3
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232 sty -2,s Same as tsty
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233 bne Sq1
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234 ldy 4,s Restore Y
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235 stb altbuff,y Store packet size.
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236 puls a,b,x,y,u,pc
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237
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238 * Encode a sequence of straight data
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239 *
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240 sqstraight
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241 pshs u Save address of subpacket size.
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242 clr ,u+ Set zero count.
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243 lda ,x+
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244 sqstr1
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245 sta ,u+
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246 incb Increment total bytes
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247 inc [,s] Increment subpacket size
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248 leay -1,y Count down bytes to compress
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249 beq sqstr2
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250 lda ,x+
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251 cmpa ,x Three like bytes mean we stop here.
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252 bne sqstr1
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253 cmpa 1,x
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254 bne sqstr1
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255 leax -1,x
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256 sqstr2
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257 incb Include subpacket size in total count.
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258 leas 2,s Clean up stack.
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259 rts
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260
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261 * Encode a sequence of compressed data
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262 * B is increased by 2, X points to byte after repeated data,
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263 * U is increased by 2, Y is decreased by number of bytes compressed.
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264 sqcomprs
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265 lda ,x+ Store the byte as the second byte.
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266 sta 1,u
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267 clr ,u Clear our count
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268 sqcomprs1
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269 inc ,u
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270 leay -1,y
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271 beq sqcomprs2 Abort the loop if Y goes to zero.
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272 cmpa ,x+
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273 beq sqcomprs1
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274 leax -1,x Backup to point to different byte
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275 sqcomprs2
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276 lda ,u
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277 ora #$80 Set high bit for compressed subpacket
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278 sta ,u
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279 leau 2,u Move past this subpacket
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280 addb #2 and bump total packet size.
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281 rts
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282
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283 *
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284 * MGEsame -- copy linebuff to altbuff
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285 *
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286 MGEsame:
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287 pshs a,b,x,u
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288 leax linebuff,y
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289 leau altbuff,y
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290 ldb #160
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291 MGEsameloop
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292 lda ,x+
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293 sta ,u+
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294 decb
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295 bne MGEsameloop
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296 puls a,b,x,u,pc
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297
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298 endsect
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