Struct Reader 

pub struct Reader { /* private fields */ }

Zero-copy reader for accessing region data from memory-mapped storage.

Holds a lock on the memory map and a snapshot of region metadata. The metadata is cloned at reader creation time, providing snapshot isolation and avoiding lock ordering deadlocks with writers.

Important: Lock Duration

Drop this reader as soon as possible. While held, this blocks:

• set_min_len (file growth)
• compact / punch_holes (final sync phase)

Long-lived readers can cause other operations to hang waiting for the lock. If you need to keep data around, copy it out of the reader first.

The Reader owns references to the Database and Region to ensure the underlying data structures remain valid for the lifetime of the guards.

Implementations

impl Reader

pub fn unchecked_read(&self, offset: usize, len: usize) -> &[u8]

Reads data from the region without bounds checking.

Safety

The caller must ensure offset + len is within the region’s length. Reading beyond the region’s bounds is undefined behavior.

pub fn read(&self, offset: usize, len: usize) -> &[u8]

Reads a slice of data from the region at the given offset.

Panics

Panics if offset + len exceeds the region’s length.

pub fn len(&self) -> usize

Returns the length of data in the region.

pub fn is_empty(&self) -> bool

Returns true if the region is empty.

pub fn read_all(&self) -> &[u8]

Returns a slice containing all data in the region.

pub fn prefixed(&self, offset: usize) -> &[u8]

Returns a slice from the offset to the end of the mmap.

This allows reading beyond the region boundary for performance-critical sequential access patterns, but the offset must still be within the region.

Panics

Panics if the offset exceeds the region’s length.