#!/bin/sh

# split data from stdin to multiple invocations of a command
# without creating temporary files

# License: LGPLv2
# Author:
#    http://www.pixelbeat.org/
# Notes:
#    This script may be useful for chunking a stream before
#    sending to an FTP server supporting limited file sizes for e.g.
#      Using `ifne` from moreutils is not possible as it consumes BUFSIZ,
#    and doesn't indicate when no more data is available.  I.E. it's good
#    for conditional _single_ invocations of a command only.
# Changes:
#    V0.1, 29 Nov 2010, Initial release
#      http://github.com/pixelb/scripts/commits/master/scripts/split_to


if test "$Argc" -lt 1 {
  setglobal me = $[basename $0]
  echo "Usage: $me size [-n] [command]" > !2
  echo "split data from stdin to multiple invocations of a command" > !2
  echo > !2
  echo "   -n    pass the chunk number as the first parameter to command" > !2
  echo "Examples:" > !2
  echo "   $0 10000 'wc -c' < /bin/ls" > !2
  echo "   $0 10000 < /bin/ls" > !2
  echo "   $0 10000 -n < /bin/ls" > !2
  exit 1
}

setglobal chunk_size = $1; shift
test $1 = -n && do { setglobal pass_part = '1'; shift; }
test $1 && setglobal cmd = "$ifsjoin(Argv)" || setglobal cmd = 'example_cmd'

proc example_cmd { echo "processing part $1 ($[wc -c] bytes)"; }

setglobal part = '1'
while true {
  setglobal c = $[od -to1 -An -N1] # getc
  test $c || break
  setglobal c = $[echo $c] # trim
  test $pass_part && setglobal ppart = $part
  do {
    printf "\\$c" # ungetc
    head -c$shExpr('$chunk_size-1')
  } | $cmd $ppart || break
  setglobal part = $shExpr('$part+1')
}