REBOL [
    Title: "The PIPE function"
    File: %pipe.r
    Purpose: {
        Defines the PIPE function that works as a pipe between two ports, streaming data
        from the first to the second.
    }
    Author: "Gabriele Santilli"
    License: {
        =================================
        A message from Qtask about this source code:

        We have selected the MIT license (as of 2010-Jan-1) because
        it is the closest “standard” license to our intent.  If we had our way,
        we would declare this source as public domain, with absolutely no
        strings attached, not even the string that says you have to have
        strings.  We want to help people, so please feel free to contact us
        at API@Qtask.com if you have questions.
         

        (you only need to include the standard license text below in your
        homage to this source code)
        =================================

        Copyright 2008 Qtask, Inc.

        Permission is hereby granted, free of charge, to any person obtaining
        a copy of this software and associated documentation files
        (the "Software"), to deal in the Software without restriction, including
        without limitation the rights to use, copy, modify, merge, publish,
        distribute, sublicense, and/or sell copies of the Software, and to
        permit persons to whom the Software is furnished to do so, subject
        to the following conditions:

        The above copyright notice and this permission notice shall be included
        in all copies or substantial portions of the Software.

        THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
        OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
        FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
        THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR
        OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
        ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
        OTHER DEALINGS IN THE SOFTWARE.
    }
    Version: 1.0.0
]

pipe: func [
    {Create a pipe between two ports and stream all data from source to dest} [catch] 
    source [port! file! url!] 
    dest [port! file! url!] 
    /thru filter [port! url!] 
    /part size [integer!] 
    /with chunk-size [integer!] 
    /local 
    condition body 
    close-source? close-dest? close-filter? 
    data filtered
] [
    chunk-size: any [chunk-size 256 * 1024] 
    unless any [not size size > 0] [throw make error! compose [script invalid-arg (join size " (size must be greater than zero)")]] 
    unless chunk-size > 0 [throw make error! compose [script invalid-arg (join chunk-size " (chunk-size must be greater than zero)")]] 
    unless port? source [
        source: open/binary/direct/read source 
        close-source?: yes
    ] 
    unless port? dest [
        dest: open/binary/direct/write/new dest 
        close-dest?: yes
    ] 
    if url? filter [
        filter: open/binary filter 
        close-filter?: yes
    ] 
    condition: either size [[size > 0]] [[data: copy/part source chunk-size]] 
    body: compose [(either size [[
                    data: copy/part source min size chunk-size 
                    either data [size: size - length? data] [break]
                ]] [[]]) (either filter [[
                    if filtered: copy filter [insert dest filtered] 
                    insert filter data
                ]] [[
                    insert dest data
                ]])] 
    while condition body 
    if filter [
        update filter 
        if data: copy filter [insert dest data]
    ] 
    attempt [update dest] 
    case/all [
        close-source? [close source] 
        close-dest? [close dest] 
        close-filter? [close filter]
    ]
]