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#!/usr/bin/env python3
# basic rle compression program
# by nicklausw

# this format works as follows.
# one byte is read, and that is
# how many of the next byte to copy over. repeat.
# when the first byte is $ff, the copy is done.

import sys
import argparse

parser = argparse.ArgumentParser()
parser.add_argument("in_file", help="the chr data to be rle'd")
parser.add_argument("out_file", help="the rle'd output")
args = parser.parse_args()

f_in = open(args.in_file, 'rb')
f_out = open(args.out_file, 'wb')

# python doesn't need variable initialization i think,
# but for clarity's sake.
byte_n = 0 # byte
byte_c = 1 # byte count 

for c in f_in.read():
  if c != byte_n or byte_c == 0xFE:
    f_out.write(bytes([byte_c]))
    f_out.write(bytes([byte_n]))
    byte_c = 1
    byte_n = c
  else:
    byte_c += 1

# now catch the last time around
f_out.write(bytes([byte_c]))
f_out.write(bytes([byte_n]))

# the end mark
f_out.write(bytes([0xFF]))

f_in.close()
f_out.close()

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.proc rle_copy_ppu
  setxy16
  seta8
  ldy #$00

 loop: 
  seta8
  lda (rle_cp_ram), y
  cpa #$ff
  beq done
  seta16
  and #$ff
  tax
  iny
  seta8
  lda (rle_cp_ram),y
  jsr rle_loop
  iny
  jmp loop
  
done:
  rts

rle_loop:
  seta16
  ;and #$ff
 loop2:
  sta PPUDATA
  dex
  bne loop2
  rts
.endproc

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; copy font
  setaxy16
  stz PPUADDR  ; we will start video memory at $0000
  lda #font
  sta rle_cp_ram
  jsr rle_copy_ppu

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#!/usr/bin/env python3
# basic rle compression program
# by nicklausw
# public domain.

# this format works as follows.
# one byte is read, and that is
# how many of the next byte to copy over. repeat.
# when the first byte is $ff, the copy is done.

import sys
import argparse

parser = argparse.ArgumentParser()
parser.add_argument("in_file", help="the chr data to be rle'd")
parser.add_argument("out_file", help="the rle'd output")
args = parser.parse_args()

f_in = open(args.in_file, 'rb')
f_out = open(args.out_file, 'wb')

# python doesn't need variable initialization i think,
# but for clarity's sake.
byte_n = int.from_bytes(f_in.read(1), byteorder='little') # byte
byte_c = 0 # byte count

f_in.seek(0) 

for c in f_in.read():
  if c != byte_n or byte_c == 0xFE:
    f_out.write(bytes([byte_c]))
    f_out.write(bytes([byte_n]))
    byte_c = 1
    byte_n = c
  else:
    byte_c += 1

# now catch the last time around
f_out.write(bytes([byte_c]))
f_out.write(bytes([byte_n]))

# the end mark
f_out.write(bytes([0xFF]))

f_in.close()
f_out.close()

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.proc rle_copy_ppu
  setxy16
  seta8
  ldy #$00
  lda #0	; clear Accum. hi-byte
  xba

 loop: 
  lda (rle_cp_ram), y
  cpa #$ff
  beq done
  tax
  iny
  lda (rle_cp_ram),y
  jsr rle_loop
  iny
  bra loop
  
done:
  rts

; IN: X = count
;      A = byte
rle_loop:
; INCOMPLETE / WILL NOT WORK (for above mentioned reasons in forum post)
; Please finish reading forum post and reply so we can work out your needs
  sta PPUDATA	; this is only writes the low byte.
  dex
  bne rle_loop
  rts
.endproc

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byte_n = int.from_bytes(f_in.read(1), byteorder='little') # byte
byte_c = 0 # byte count

f_in.seek(0)

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byte_n = int.from_bytes(f_in.read(1), byteorder='little') # byte
byte_c = 1 # byte count

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.segment "ZEROPAGE"
  rle_cp_ram: .res 2
  rle_cp_num: .res 2
  
.segment "BSS"
  rle_cp_dat: .res 2 ; a LOT more

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.proc rle_copy_ram
  setxy16
  seta8
  ldy #$00
  sty rle_cp_num
  lda #0   ; clear Accum. hi-byte
  xba

 loop:
  lda (rle_cp_ram), y
  cpa #$ff
  beq done
  tax
  iny
  lda (rle_cp_ram),y
  jsr rle_loop
  iny
  bra loop
 
done:
  rts

; IN: X = count
;      A = byte
rle_loop:
  phy
  ldy rle_cp_num
rle_inter:
  sta rle_cp_dat,y
  iny
  dex
  bne rle_inter
  sty rle_cp_num
  ply
  rts
.endproc