For extracting GOG Konami Collector's Series

gog_extract_konami_collectors_series.sh

#!/bin/bash

# Extractor for game ROMs from Konami Collector's Series.
#
# Usage: gog_extract_konami_collectors_series.sh <path_to>/cc.exe
#
# Make sure you have xxd hexdump tool and dd installed.
#

# Games locations:
#
# Castlevania    : 01E570 - 03E56F (0x20000 bytes)
# Castlevania II : 03E570 - 07E56F (0x40000 bytes)
# Castlevania III: 07E570 - 0DE56F (0x60000 bytes)
# Contra         : 0DE570 - 0FE56F (0x20000 bytes)
# Jackal         : 0FE580 - 11E57F (0x20000 bytes)
# Super C        : 11E580 - 15E57F (0x40000 bytes)

header_hex1='4E45531A080021000000000000000000'
header_hex2='4E45531A081010000000000000000000'
header_hex3='4E45531A101050000000000000000000'
header_hex4='4E45531A081041000000000000000000'

source="$1"
if ! [ -e "$source" ]; then
   echo "Error: can't find ${source}!"
   exit 1
fi

declare -A roms

roms["castlevania"]="0x1E570:0x20000"
roms["castlevania_ii"]="0x3E570:0x40000"
roms["castlevania_iii"]="0x7E570:0x60000"
roms["contra"]="0xDE570:0x20000"
roms["jackal"]="0xFE580:0x20000"
roms["super_c"]="0x11E580:0x40000"

declare -A headers

headers["castlevania"]=$header_hex1
headers["castlevania_ii"]=$header_hex2
headers["castlevania_iii"]=$header_hex3
headers["contra"]=$header_hex1
headers["jackal"]=$header_hex1
headers["super_c"]=$header_hex4

for rom in "${!roms[@]}"; do
  offset=${roms[$rom]%%:*}
  length=${roms[$rom]##*:}

  target="${rom}.nes"
  echo "Composing ${target}"

  dd if="$source" of="${rom}.tmp" skip=$(($offset))B count=$(($length))B bs=10M
  cat <(echo ${headers[$rom]} | xxd --revert --plain) "${rom}.tmp" > "$target"
  rm -v "${rom}.tmp"
done

Speeding up dd usage with large block size and byte offest / count (that seems to be a poorly documented dd feature).