Crate rsynko_download 

rsynko-download

This crate specifies one-resource download meaning independently of HTTP and filesystems.

Capabilities

FetchStreamAlg denotes incremental retrieval as a carrier and a step, so an interpreter chooses whether stepping reads memory, walks a manifest, or waits on a network. AtomicPublishAlg denotes publication without an observable partial destination: an unpublished carrier is written, then committed or abandoned. DownloadObservationAlg defines the progress and terminal observations, and DownloadProgressAlg and DownloadReportAlg emit them.

An interpreter chooses the stream, the unpublished carrier, and the observation carriers; a reference interpreter reifying the observations lives in rsynko-memory.

The derived program

DownloadExt::download_resource derives the complete operation from exactly those capabilities: it fetches into an unpublished carrier, commits it atomically at the final path, and emits exactly one terminal observation. A caller composes it further without acquiring anything new:

use alux_ext::ext;
use rsynko_download::{
    AtomicPublishAlg, DownloadError, DownloadExt, DownloadObservationAlg, DownloadProgressAlg,
    DownloadReportAlg, FetchStreamAlg,
};
use std::fmt::Display;
use std::path::Path;

#[ext(name = DownloadBatchExt)]
impl<This, Source, FetchError, Stream, PublishError, Event, Progress> This
where
    Source: ?Sized,
    This: FetchStreamAlg<Source, Error = FetchError, Stream = Stream>
        + AtomicPublishAlg<Error = PublishError>
        + DownloadObservationAlg<Event = Event, Progress = Progress>
        + DownloadProgressAlg<Progress = Progress>
        + DownloadReportAlg<Event = Event>,
    FetchError: Display,
    PublishError: Display,
{
    /// Publishes several resources in declaration order and stops at the first failure.
    fn download_resources<'a>(
        &self,
        requests: impl IntoIterator<Item = (&'a Source, &'a Path)>,
    ) -> Result<u64, DownloadError<FetchError, PublishError>>
    where
        Source: 'a,
    {
        let mut published = 0;
        for (source, destination) in requests {
            published += self.download_resource(source, destination)?;
        }
        Ok(published)
    }
}

Observation operations

DownloadObservationOp reifies progress and terminal reports as inspectable stream elements, and DownloadObservationInterpreter interprets one element without choosing a channel or owning a consumption loop. Both are generated from the observation vocabulary, so an interpreter states what an observation means and never restates its shape.

Laws

• progress begins at zero and retrieved byte counts are monotonic;
• successful publication preserves the fetched bytes exactly;
• the final path never denotes partial bytes;
• every execution emits exactly one terminal event;
• success is reported only after atomic publication succeeds.

Macros

ambassador_impl_AtomicPublishAlg

A macro to be used by ambassador::Delegate to delegate AtomicPublishAlg

ambassador_impl_DownloadObservationAlg

A macro to be used by ambassador::Delegate to delegate DownloadObservationAlg

ambassador_impl_DownloadProgressAlg

A macro to be used by ambassador::Delegate to delegate DownloadProgressAlg

ambassador_impl_DownloadReportAlg

A macro to be used by ambassador::Delegate to delegate DownloadReportAlg

ambassador_impl_FetchStreamAlg

A macro to be used by ambassador::Delegate to delegate FetchStreamAlg

Structs

FetchStream

Denotes an opened resource stream and its expected byte count when known.

Enums

DownloadError

Denotes failure to fetch or atomically publish one resource.

Traits

AtomicPublishAlg

Specifies atomic publication at a final path.

DownloadExt

Derives complete one-resource download meaning from three primitive capabilities.

DownloadLawFixture

Supplies the retrieval state and recorded trace a download scenario cannot author for itself.

DownloadLaws

Authors the one-resource download laws.

DownloadObservationAlg

Provides the carriers and constructors for download observations.

DownloadProgressAlg

Specifies observation of non-terminal download progress.

DownloadReportAlg

Specifies observation of terminal download events.

FetchStreamAlg

Specifies incremental retrieval of one resource: a byte-stream coalgebra of carrier and step.