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use nix;
use std::error;
use std::fmt;
use std::io;
use std::num;
/// This module implements a simple error type to match the errors that can be thrown from the C
/// functions as well as some extra errors resulting from internal validations.
///
/// As this crate exposes an opinionated API to the POSIX queues certain errors have been
/// ignored:
///
/// * ETIMEDOUT: The low-level timed functions are not exported and this error can not occur.
/// * EAGAIN: Non-blocking queue calls are not supported.
/// * EINVAL: Same reason as ETIMEDOUT
/// * EMSGSIZE: The message size is immutable after queue creation and this crate checks it.
/// * ENAMETOOLONG: This crate performs name validation
///
/// If an unexpected error is encountered it will be wrapped appropriately and should be reported
/// as a bug on https://github.com/aprilabank/posix_mq.rs
#[derive(Debug)]
pub enum Error {
// These errors are raised inside of the library
InvalidQueueName(&'static str),
ValueReadingError(io::Error),
MessageSizeExceeded(),
MaximumMessageSizeExceeded(),
MaximumMessageCountExceeded(),
// These errors match what is described in the man pages (from mq_overview(7) onwards).
PermissionDenied(),
InvalidQueueDescriptor(),
QueueCallInterrupted(),
QueueAlreadyExists(),
QueueNotFound(),
InsufficientMemory(),
InsufficientSpace(),
// These two are (hopefully) unlikely in modern systems
ProcessFileDescriptorLimitReached(),
SystemFileDescriptorLimitReached(),
// If an unhandled / unknown / unexpected error occurs this error will be used.
// In those cases bug reports would be welcome!
UnknownForeignError(nix::errno::Errno),
// Some other unexpected / unknown error occured. This is probably an error from
// the nix crate. Bug reports also welcome for this!
UnknownInternalError(Option<nix::Error>),
}
impl error::Error for Error {
fn description(&self) -> &str {
use Error::*;
match *self {
// This error contains more sensible description strings already
InvalidQueueName(e) => e,
ValueReadingError(_) => "error reading system configuration for message queues",
MessageSizeExceeded() => "message is larger than maximum size for specified queue",
MaximumMessageSizeExceeded() => "specified queue message size exceeds system maximum",
MaximumMessageCountExceeded() => "specified queue message count exceeds system maximum",
PermissionDenied() => "permission to the specified queue was denied",
InvalidQueueDescriptor() => "the internal queue descriptor was invalid",
QueueCallInterrupted() => "queue method interrupted by signal",
QueueAlreadyExists() => "the specified queue already exists",
QueueNotFound() => "the specified queue could not be found",
InsufficientMemory() => "insufficient memory to call queue method",
InsufficientSpace() => "insufficient space to call queue method",
ProcessFileDescriptorLimitReached() =>
"maximum number of process file descriptors reached",
SystemFileDescriptorLimitReached() =>
"maximum number of system file descriptors reached",
UnknownForeignError(_) => "unknown foreign error occured: please report a bug!",
UnknownInternalError(_) => "unknown internal error occured: please report a bug!",
}
}
}
impl fmt::Display for Error {
fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
// Explicitly import this to gain access to Error::description()
use std::error::Error;
f.write_str(self.description())
}
}
/// This from implementation is used to translate errors from the lower-level
/// C-calls into sensible Rust errors.
impl From<nix::Error> for Error {
fn from(e: nix::Error) -> Self {
match e {
nix::Error::Sys(e) => match_errno(e),
_ => Error::UnknownInternalError(Some(e)),
}
}
}
// This implementation is used when reading system queue settings.
impl From<io::Error> for Error {
fn from(e: io::Error) -> Self {
Error::ValueReadingError(e)
}
}
// This implementation is used when parsing system queue settings. The unknown error is returned
// here because the system is probably seriously broken if those files don't contain numbers.
impl From<num::ParseIntError> for Error {
fn from(_: num::ParseIntError) -> Self {
Error::UnknownInternalError(None)
}
}
fn match_errno(err: nix::errno::Errno) -> Error {
use nix::errno::Errno::*;
match err {
EACCES => Error::PermissionDenied(),
EBADF => Error::InvalidQueueDescriptor(),
EINTR => Error::QueueCallInterrupted(),
EEXIST => Error::QueueAlreadyExists(),
EMFILE => Error::ProcessFileDescriptorLimitReached(),
ENFILE => Error::SystemFileDescriptorLimitReached(),
ENOENT => Error::QueueNotFound(),
ENOMEM => Error::InsufficientMemory(),
ENOSPC => Error::InsufficientSpace(),
_ => Error::UnknownForeignError(err),
}
}
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