Struct NullIoProvider 

pub struct NullIoProvider;

A no-op I/O provider that silently discards all output and returns IoErrorKind::Unsupported for reads.

Useful as a default when no I/O back-end is configured.

Trait Implementations

impl IoProvider for NullIoProvider

fn read_char(&mut self, _port: PortId) -> Result<char, IoErrorKind>

Read a single character from the specified input port.

fn peek_char(&mut self, _port: PortId) -> Result<char, IoErrorKind>

Peek at the next character without consuming it.

fn char_ready(&mut self, _port: PortId) -> Result<bool, IoErrorKind>

Return true if a character is ready on the input port.

fn write_char(&mut self, _port: PortId, _c: char) -> Result<(), IoErrorKind>

Write a single character to the specified output port.

fn write_str(&mut self, _port: PortId, _s: &str) -> Result<(), IoErrorKind>

Write a string slice to the specified output port.

fn flush(&mut self, _port: PortId) -> Result<(), IoErrorKind>

Flush the specified output port.

fn close_port(&mut self, _port: PortId) -> Result<(), IoErrorKind>

Close the specified port.

fn is_input_port(&self, _port: PortId) -> bool

Return true if the port is an input port.

fn is_output_port(&self, _port: PortId) -> bool

Return true if the port is an output port.

fn is_port_open(&self, _port: PortId) -> bool

Return true if the port is still open. Default: returns true (assumes ports are open unless overridden).

fn is_textual_port(&self, port: PortId) -> bool

Return true if the port is a textual port. Default: returns true for any valid input or output port.

fn is_binary_port(&self, _port: PortId) -> bool

Return true if the port is a binary port. Default: returns false (all ports are textual by default).

fn open_input_string(&mut self, _s: &str) -> Result<PortId, IoErrorKind>

Open an input port that reads from the given string.

fn open_output_string(&mut self) -> Result<PortId, IoErrorKind>

Open an output port that accumulates characters into a string buffer.

fn get_output_string(&self, _port: PortId) -> Result<&str, IoErrorKind>

Retrieve the accumulated string from an output string port.

fn file_exists(&self, _path: &str) -> Result<bool, IoErrorKind>

Check whether a file exists at the given path. Default: returns IoErrorKind::Unsupported.

fn delete_file(&mut self, _path: &str) -> Result<(), IoErrorKind>

Delete the file at the given path. Default: returns IoErrorKind::Unsupported.

fn read_file(&mut self, _path: &str) -> Result<&str, IoErrorKind>

Read the entire contents of a file as a string. Default: returns IoErrorKind::Unsupported.

fn command_line_count(&self) -> Result<usize, IoErrorKind>

Return the number of command-line arguments. Default: returns IoErrorKind::Unsupported.

fn command_line_arg(&self, _index: usize) -> Result<&str, IoErrorKind>

Return the command-line argument at the given index. Default: returns IoErrorKind::Unsupported.

fn get_environment_variable( &mut self, _name: &str, ) -> Result<Option<&str>, IoErrorKind>

Retrieve the value of an environment variable by name. Returns Ok(Some(value)) if found, Ok(None) if not set. Default: returns IoErrorKind::Unsupported.

fn environment_variables_count(&mut self) -> Result<usize, IoErrorKind>

Return the number of environment variables. Must be called before environment_variable_at to snapshot the current environment. Default: returns IoErrorKind::Unsupported.

fn environment_variable_at( &self, _index: usize, ) -> Result<(&str, &str), IoErrorKind>

Return the environment variable name and value at the given index. environment_variables_count must be called first to snapshot the environment. Default: returns IoErrorKind::Unsupported.

fn exit_process(&mut self, _code: i32) -> Result<(), IoErrorKind>

Exit the process with the given status code. Default: returns IoErrorKind::Unsupported.

fn emergency_exit_process(&mut self, _code: i32) -> Result<(), IoErrorKind>

Emergency exit the process (no cleanup) with the given status code. Default: returns IoErrorKind::Unsupported.