104 lines
2.0 KiB
ArmAsm
104 lines
2.0 KiB
ArmAsm
// #LAYOUT# STD * #TAKE
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// #LAYOUT# * BASIC_0 #TAKE
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// #LAYOUT# * * #IGNORE
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//
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// Releases back memory used by string
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//
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// Input:
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// - DSCPNT+0 - string size
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// - DSCPNT+1, DSCPNT+2 - pointer to string
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//
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varstr_free:
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// Check the string size - do not do anything if 0
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lda DSCPNT+0
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bne !+
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rts
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!:
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// Check if string is above FRETOP (in string area)
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jsr helper_cmp_fretop
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bcs varstr_free_no_checks
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// No, it does not belong to string area - quit
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rts
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varstr_free_no_checks: // entry point to be used when it is clear that string is not empty and above FRETOP
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// Check if this is the lowest string
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bne varstr_free_inside
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// This is the lowest string - so just increase FRETOP, this way
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// the garbage collector will not be needed that quickly
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jsr helper_FRETOP_up // free the string data
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#if !HAS_OPCODES_65CE02
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lda #$02 // free the back-pointer
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sta DSCPNT+0
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jmp helper_FRETOP_up
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#else // HAS_OPCODES_65CE02
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inw FRETOP // free the back-pointer
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inw FRETOP
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rts
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#endif
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varstr_free_inside:
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// This is not the lowest string; mark it as free
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// First preserve the string size, it will make it easier for the garbage collector
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// Increase DSCPNT+1/+2 to point to the back-pointer minus 1
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dec DSCPNT+0
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clc
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lda DSCPNT+1
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adc DSCPNT+0
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sta DSCPNT+1
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bcc !+
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inc DSCPNT+2
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!:
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// Put the size-1, garbage collector will make use of this value
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lda DSCPNT+0
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ldy #$00
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#if CONFIG_MEMORY_MODEL_60K
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ldx #<DSCPNT+1
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jsr poke_under_roms
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#else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
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sta (DSCPNT+1), y
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#endif
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// Now fill-in the back-pointer with 0's
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tya
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iny
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#if CONFIG_MEMORY_MODEL_60K
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jsr poke_under_roms
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#else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
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sta (DSCPNT+1), y
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#endif
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iny
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#if CONFIG_MEMORY_MODEL_60K
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jmp poke_under_roms
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#else // CONFIG_MEMORY_MODEL_38K || CONFIG_MEMORY_MODEL_46K || CONFIG_MEMORY_MODEL_50K
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sta (DSCPNT+1), y
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rts
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#endif
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