Wasmex.Pipe (wasmex v0.9.2)

A Pipe is a memory buffer that can be used in exchange for a Wasm file.

Pipes have a read and write position which can be set using seek/2.

Example

Pipes can be written to and read from:

iex> {:ok, pipe} = Wasmex.Pipe.new()
iex> Wasmex.Pipe.write(pipe, "hello")
{:ok, 5}
iex> Wasmex.Pipe.seek(pipe, 0)
iex> Wasmex.Pipe.read(pipe)
"hello"

They can be used to capture stdout/stdin/stderr of WASI programs:

iex> {:ok, stdin} = Wasmex.Pipe.new()
iex> {:ok, stdout} = Wasmex.Pipe.new()
iex> {:ok, stderr} = Wasmex.Pipe.new()
iex> Wasmex.Store.new_wasi(%Wasmex.Wasi.WasiOptions{
...>   stdin: stdin,
...>   stdout: stdout,
...>   stderr: stderr,
...> })

Summary

Functions

new()

Creates and returns a new Pipe.

read(pipe)

Reads all available bytes from the Pipe and returns them as a binary.

seek(pipe, pos_from_start)

Sets the read/write position of the Pipe to the given position.

size(pipe)

Returns the current size of the Pipe in bytes.

write(pipe, binary)

Writes the given binary into the pipe.

Types

t()

@type t() :: %Wasmex.Pipe{reference: reference(), resource: binary()}

Functions

new()

@spec new() :: {:error, reason :: binary()} | {:ok, t()}

Creates and returns a new Pipe.

Example

iex> {:ok, %Pipe{}} = Wasmex.Pipe.new()

read(pipe)

@spec read(t()) :: binary()

Reads all available bytes from the Pipe and returns them as a binary.

This function does not block if there are no bytes available. Reading starts at the current read position, see seek/2, and forwards the read position to the end of the Pipe. The read bytes are not erased and can be read again after seeking back.

Example

iex> {:ok, pipe} = Wasmex.Pipe.new()
iex> Wasmex.Pipe.write(pipe, "hello")
iex> Wasmex.Pipe.read(pipe) # current position is at EOL, nothing more to read
""
iex> Wasmex.Pipe.seek(pipe, 0)
iex> Wasmex.Pipe.read(pipe)
"hello"
iex> Wasmex.Pipe.seek(pipe, 3)
iex> Wasmex.Pipe.read(pipe)
"lo"
iex> Wasmex.Pipe.read(pipe)
""

seek(pipe, pos_from_start)

@spec seek(t(), integer()) :: :ok | :error

Sets the read/write position of the Pipe to the given position.

The position is given as a number of bytes from the start of the Pipe.

Example

iex> {:ok, pipe} = Wasmex.Pipe.new()
iex> Wasmex.Pipe.write(pipe, "hello")
iex> Wasmex.Pipe.seek(pipe, 0)
:ok
iex> Wasmex.Pipe.read(pipe)
"hello"

size(pipe)

@spec size(t()) :: integer()

Returns the current size of the Pipe in bytes.

Example

iex> {:ok, pipe} = Wasmex.Pipe.new()
iex> Wasmex.Pipe.size(pipe)
0
iex> Wasmex.Pipe.write(pipe, "hello")
iex> Wasmex.Pipe.size(pipe)
5

write(pipe, binary)

@spec write(t(), binary()) :: {:ok, integer()} | :error

Writes the given binary into the pipe.

Writing starts at the current write position, see seek/2, and forwards it.

Example

iex> {:ok, pipe} = Wasmex.Pipe.new()
iex> Wasmex.Pipe.write(pipe, "hello")
{:ok, 5}
iex> Wasmex.Pipe.seek(pipe, 0)
iex> Wasmex.Pipe.read(pipe)
"hello"