#!/bin/bash

: <<=cut
=pod

=head1 NAME

iothrottle - Limit IO to a given speed


=head1 SYNOPSIS

B<iothrottle> [-i read-speed] [-o write-speed] I<command>


=head1 DESCRIPTION

B<iothrottle> limits B<read>(2) and B<write>(2) to a given speed.


=head1 OPTIONS

=over 4

=item B<-i> I<input-speed>

Throttle B<read>(2) to I<input-speed> bytes per second.

To I<input-speed> you can append k, K, m, M, g, G to multiply by 1000,
1024, 1000000, 1048576 respectively.


=item B<-o> I<output-speed>

Throttle B<write>(2) to I<output-speed> bytes per second.

To I<output-speed> you can append k, K, m, M, g, G to multiply by 1000,
1024, 1000000, 1048576 respectively.

=back


=head1 EXAMPLE

Copy mydir at 1MB/s:

  iothrottle -i 1M cp -a mydir/ /other/filesystem/


=head1 BUGS

Not all program use B<read>(2) and B<write>(2) for I/O.

These all use other methods: cp (to same filesystem), seq

File a bug report when you find other programs:
https://git.data.coop/tange/tangetools/issues


=head1 ENVIRONMENT VARIABLES

=over 9

=item $IOTHROTTLE_DEBUG=1

Turn on debugging.

=back


=head1 AUTHOR

Copyright (C) 2024 Ole Tange,
http://ole.tange.dk and Free Software Foundation, Inc.


=head1 LICENSE

Copyright (C) 2012 Free Software Foundation, Inc.

This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or
at your option any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program.  If not, see <http://www.gnu.org/licenses/>.


=head1 DEPENDENCIES

B<iothrottle> uses B<bash>.


=head1 SEE ALSO

B<ionice>, B<bwlimit>


=cut


_hex() {
    local hex=dummy
    echo $hex
}

_iothrottle.so() {
    local iothrottleso=$(mktemp)
    _hex |
	LC_ALL=C awk '{for (i=1; i<=length($0); i+=2) printf "%c", strtonum("0x" substr($0, i, 2))}' > "$iothrottleso"
    echo "$iothrottleso"
}

# Default values for input and output limits
INPUT_LIMIT=""
OUTPUT_LIMIT=""

# Parse command-line arguments
while [[ $# -gt 0 ]]; do
    case "$1" in
        -i)
            INPUT_LIMIT="$2"
            shift 2
            ;;
        -o)
            OUTPUT_LIMIT="$2"
            shift 2
            ;;
        *)
            break
            ;;
    esac
done

# Convert limits to bytes
convert_to_bytes() {
    local value="$1"
    if [[ "$value" =~ ^[0-9]+K$ ]]; then
        value=$(( ${value%K*} * 1024 ))
    fi
    if [[ "$value" =~ ^[0-9]+k$ ]]; then
        value=$(( ${value%k*} * 1000 ))
    fi
    if [[ "$value" =~ ^[0-9]+M$ ]]; then
        value=$(( ${value%M*} * 1024 * 1024 ))
    fi
    if [[ "$value" =~ ^[0-9]+m$ ]]; then
        value=$(( ${value%m*} * 1000 * 1000 ))
    fi
    echo "$value"
}

IOTHROTTLE_READ=$(convert_to_bytes "$INPUT_LIMIT")
IOTHROTTLE_WRITE=$(convert_to_bytes "$OUTPUT_LIMIT")

# Export environment variables
export IOTHROTTLE_READ=${IOTHROTTLE_READ:-0}
export IOTHROTTLE_WRITE=${IOTHROTTLE_WRITE:-0}

# Preload the library and execute the remaining command
_so=$(_iothrottle.so)
if [ IOTHROTTLE_DEBUG = 1 ] ; then
    echo LD_PRELOAD=$_so
    LD_PRELOAD=$_so "$@"
else
    LD_PRELOAD=$_so "$@"
    rm $_so
fi