Enum PagerError 

#[non_exhaustive]
pub enum PagerError {
    ZeroSize,
    SizeOverflow,
    Map(i32),
    Protect(i32),
    NotWritable,
    OutOfBounds {
        offset: usize,
        len: usize,
        region_len: usize,
    },
}

The reason a Region operation failed.

The variants separate the three places things go wrong: a request that does not describe a valid region (ZeroSize, SizeOverflow), the operating system refusing a call (Map, Protect), and a write that does not fit the region as it currently stands (NotWritable, OutOfBounds). The OS-level variants carry the raw error code — errno on Unix, GetLastError on Windows — so the underlying cause is not lost.

The set is #[non_exhaustive]: future platforms or features may add variants, so a match on this type must include a wildcard arm.

Examples

use pager_lang::{PagerError, Region};

// A region must be at least one page; zero bytes is rejected up front.
assert!(matches!(Region::new(0), Err(PagerError::ZeroSize)));

Variants (Non-exhaustive)

Non-exhaustive enums could have additional variants added in future. Therefore, when matching against variants of non-exhaustive enums, an extra wildcard arm must be added to account for any future variants.

ZeroSize

A region of zero bytes was requested. A region must span at least one page; ask for the number of bytes you need and the request is rounded up to whole pages.

SizeOverflow

Rounding the request up to whole pages, or adding the guard pages, overflowed usize. The requested size is too large to represent, let alone map.

Map(i32)

The operating system refused to map the region. The wrapped value is the OS error code (errno / GetLastError); the usual cause is exhausted address space or memory.

Protect(i32)

The operating system refused to change the region’s protection. The wrapped value is the OS error code. A frequent cause is a platform that forbids writable-and-executable pages, which rejects Protection::ReadWriteExecute.

NotWritable

A write was attempted on a region whose current protection does not permit writing. Flip it to Protection::ReadWrite with Region::protect first.

OutOfBounds

A write would have fallen outside the region: offset + len exceeded the region’s length. The fields report what was attempted against the region that exists.

Fields

offset: usize

The offset, in bytes, the write started at.

len: usize

The number of bytes the write would have copied.

region_len: usize

The length of the region, in bytes.

Trait Implementations

impl Clone for PagerError

fn clone(&self) -> PagerError

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for PagerError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for PagerError

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Display for PagerError

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Eq for PagerError

impl Error for PagerError

fn source(&self) -> Option<&(dyn Error + 'static)>

Returns the lower-level source of this error, if any.

fn description(&self) -> &str

👎Deprecated since 1.42.0:

use the Display impl or to_string()

fn cause(&self) -> Option<&dyn Error>

👎Deprecated since 1.33.0:

replaced by Error::source, which can support downcasting

fn provide<'a>(&'a self, request: &mut Request<'a>)

🔬This is a nightly-only experimental API. (error_generic_member_access)

Provides type-based access to context intended for error reports.

impl PartialEq for PagerError

fn eq(&self, other: &PagerError) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for PagerError

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl StructuralPartialEq for PagerError