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PITO MDdocs

Try it locally

The repository carries two small programs built on the library: get, a downloader with a progress line, and serve, a local file server with Range support at a set speed. Everything below runs on Linux, macOS or WSL, with no network beyond 127.0.0.1.

Build them

Section titled “Build them”
Terminal window
git clone https://github.com/gmrdad82/pito-fetch && cd pito-fetch
cargo build --release --examples
export PATH="$PWD/target/release/examples:$PATH"

serve

Section titled “serve”
usage: serve <DIR> <PORT> [BYTES_PER_SECOND]

It serves the files in DIR on 127.0.0.1:PORT, answers Range requests with 206, and sends at most BYTES_PER_SECOND when given, so a download lasts long enough to stop it. Make a file and start it in the background:

Terminal window
mkdir -p tmp/files && head -c 50000000 /dev/urandom > tmp/files/demo.bin
serve tmp/files 8471 10000000 &
sum=$(sha256sum tmp/files/demo.bin | cut -d' ' -f1)   # macOS: shasum -a 256
cd tmp

get

Section titled “get”
usage: get <URL> <SHA256> <DEST>

It downloads URL to DEST, pinned to SHA256, and prints the path on success. On a terminal it draws a progress line on stderr; piped, it prints only the result. It exits 0 on success, 1 when the download fails and 2 on wrong arguments.

Terminal window
$ get http://127.0.0.1:8471/demo.bin $sum models/demo.bin
models/demo.bin

Things to try

Section titled “Things to try”

Stop and resume. Press Ctrl-C halfway, look at ls models (a demo.bin.part), and run the same line again: the bar picks up where it stopped. Resume and verify explains it.

A wrong sum. Any other 64 hex characters:

Terminal window
$ get http://127.0.0.1:8471/demo.bin $(printf '0%.0s' $(seq 64)) models/copy.bin
get: checksum mismatch: expected 0000000000000000000000000000000000000000000000000000000000000000, got adfffd73f4828f23fcc2dd03f8a91eca4f332e554b0dd8706afbd5cfb77a6295
$ echo $?
1

Your got differs: the file is random. ls models shows no copy.bin and no part file.

A missing file and a dead server.

Terminal window
$ get http://127.0.0.1:8471/nope.bin $sum models/x.bin
get: http 404 from http://127.0.0.1:8471/nope.bin
$ get http://127.0.0.1:8479/demo.bin $sum models/x.bin
get: offline: could not reach http://127.0.0.1:8479/demo.bin

Two at once. Remove models/demo.bin and start two downloads of it together; both print the path, and there is one verified file (Two downloads of one file):

Terminal window
$ rm models/demo.bin
$ ( get http://127.0.0.1:8471/demo.bin $sum models/demo.bin & get http://127.0.0.1:8471/demo.bin $sum models/demo.bin; wait )
models/demo.bin
models/demo.bin

Stop the server mid-download. While get runs, stop serve from another terminal (pkill -f 'serve tmp/files'). The broken connection is retried after a second, the server is gone, and get fails, keeping the part file:

get: offline: could not reach http://127.0.0.1:8471/demo.bin

Start serve again and rerun get to finish from where it stopped.

When you’re done, kill %1 stops the server.