# Collect a set of files from the rootfs and "pack" it to UserDef. Each file
# consists of
#
#   4 bytes:    file size S (little endian)
#   S bytes:    file data
#   1 byte:     length L of the file name
#   1 byte:     '=' (ignored)
#   L bytes:    file name
#   0..3 bytes: padding (with 0) to get a 32-bit alignment for the next size
#
# The sequence ends if a file size of 0 is found.

# List of files to load; it is OK if a file does not exist
setenv path "/root"
setenv files "file1 file2 file3"

# Mount the rootfs
ubi part TargetFS
ubifsmount ubi0:rootfs

# Save loadaddr
setenv start $loadaddr
setenv current $loadaddr

# If a file exists, store its information at $current, then increment position
# and pad with zeroes. For storing the file name, env export is used. This
# stores a name=value pair. The name is 'x' and is overwritten by the file
# name length afterwards, but this explains why the '=' remains visible.
for i in $files; do
  setexpr data $current + 4
  if ubifsload $data $path/$i; then
    # Successful loading sets $filesize, store as size S
    mw.l $current $filesize
    setexpr current $data + $filesize

    # Set file name; the local variable i can not be exported, so copy to
    # regular environment variable x first
    setenv x "$i"
    env export -b $current x

    # Find terminating zero and compute file name length
    setenv fname $current
    while itest.b *$current != 0; do
      setexpr current $current + 1
    done

    # Write file name length L (counted without the leading "x=")
    setexpr length $current - $fname
    setexpr length $length - 2
    mw.b $fname $length

    # Align $current to next 32 bit boundary, pad with zeroes
    while
      setexpr t $current \& 3
      itest $t != 0
    do
      mw.b $current 0
      setexpr current $current + 1
    done
  fi
done

# Add final size 0 to indicate end of list
mw.l $current 0
setexpr current $current + 4

# Restore loadaddr
setenv loadaddr $start

# Save file collection to UserDef
setexpr size $current - $start
nand erase.part UserDef
nand write . UserDef $size