silk/standard_streams

Complete-message standard-output and standard-error writes through a replaceable service.

When to use

Use StandardStreams for complete byte messages to stdout or stderr; structured logging belongs in silk.logger.

Details

StandardStreams is an ordinary source-declared service. Its requirement remains in an Effect until a caller supplies a provider, so tests and applications can replace the process-backed implementation lexically. Stream failure is typed as StreamWriteError.

Examples

Write one complete standard-output message

import silk.effect { Effect }

import silk.standard_streams { StandardStreams }

effect fn writeMessage() -> ()
! StandardStreams.StreamWriteError {
  let mut streams = StandardStreams.nativeStandardStreamProvider()
  return run StandardStreams.send(StandardStreams.stdout(), b"Silk\n")
    |> Effect.provideMut<StandardStreams>(&mut streams)
}

effect fn ignoreWriteFailure(error: StandardStreams.StreamWriteError) -> () {
  return ()
}

pub fn main() -> i32 {
  let completed = run Effect.catchAll(writeMessage(), ignoreWriteFailure)
  return 42
}

Import as StandardStreams with import silk.standard_streams.

Public declarations: 7.

StreamWriteError

pub struct StreamWriteError

A failure to commit one complete standard-stream message.

StandardStreams

pub service StandardStreams

A mutable service that writes complete messages to standard output or standard error.

Operation writeAll

effect fn writeAll(destination: bool, bytes: &[u8]) -> () ! StreamWriteError ? &mut StandardStreams

Writes a complete immutable byte sequence to the selected standard-stream destination.

Gotchas

A failure means that the service did not commit the complete message.

NativeStandardStreams

pub struct NativeStandardStreams

A process-backed provider for StandardStreams.

stdout

pub fn stdout() -> bool

Returns the destination value that selects process standard output.

stderr

pub fn stderr() -> bool

Returns the destination value that selects process standard error.

nativeStandardStreamProvider

pub fn nativeStandardStreamProvider() -> NativeStandardStreams

Creates a process-backed standard-stream provider.

Implementation StandardStreams for NativeStandardStreams

impl StandardStreams for NativeStandardStreams

Operation writeAll

writeAll = NativeStandardStreams.nativeWriteAll

send

pub effect fn send(destination: bool, bytes: &[u8]) -> () ! StreamWriteError ? &mut StandardStreams

Writes one complete immutable byte sequence to a selected standard stream.

Details

The returned Effect requires a mutable StandardStreams provider. Use stdout or stderr for destination.