Struct ReaderConfig 

#[non_exhaustive]
pub struct ReaderConfig {

    pub max_ifds: usize,
    pub max_ifd_entries: u64,
    pub snapshot_policy: SnapshotPolicy,
    pub max_metadata_bytes: u64,
    pub work_budget: WorkBudget,
    pub max_window_pixels: u64,
    pub max_window_bytes: u64,
    pub max_window_blocks: usize,
    pub max_decoded_block_bytes: u64,
    pub max_concurrent_reads: usize,
    pub read_limiter: Option<Arc<Semaphore>>,
    pub max_decode_tasks: usize,
    pub source_id: String,
    pub block_cache: Arc<BlockCache>,
    pub cpu_limiter: Option<CpuLimiter>,
    pub prefetch_ring: u8,
    /* private fields */
}

Runtime limits for a CogReader.

max_decode_tasks caps concurrent CPU-heavy decode/stitch jobs submitted through spawn_blocking. Waiting for a permit is async, so excess requests yield the Tokio worker instead of flooding the blocking pool.

#[non_exhaustive]: construct with ReaderConfig::default() and assign fields (or use struct-update syntax inside this crate). This lets new fields be added without breaking external callers.

Fields (Non-exhaustive)

Non-exhaustive structs could have additional fields added in future. Therefore, non-exhaustive structs cannot be constructed in external crates using the traditional Struct { .. } syntax; cannot be matched against without a wildcard ..; and struct update syntax will not work.

max_ifds: usize

Maximum IFDs accepted before upstream allocations; defaults to 256.

max_ifd_entries: u64

Maximum directory entries per IFD before upstream allocations; defaults to 4096. A zero limit rejects nonempty directories.

snapshot_policy: SnapshotPolicy

Strong validator required for managed sources by default. Opaque ObjectReader handles require explicit AssumeImmutable.

max_metadata_bytes: u64

Maximum cumulative metadata bytes fetched while opening (default: 8 MiB).

work_budget: WorkBudget

Shared active-work byte allowance; completed caller-owned images and resident caches have separate ownership/budgets.

max_window_pixels: u64

Maximum pixels in a single source window (default: 16 million).

max_window_bytes: u64

Maximum declared window data plus mask bytes, and compressed bytes per fetch batch (default: 256 MiB).

max_window_blocks: usize

Maximum blocks requested by one window (default: 4096).

max_decoded_block_bytes: u64

Maximum declared uncompressed bytes in any TIFF block (default: 64 MiB).

max_concurrent_reads: usize

Concurrent foreground windows per reader (default: 8), clamped to 1..=tokio::sync::Semaphore::MAX_PERMITS.

read_limiter: Option<Arc<Semaphore>>

Optional shared foreground read limiter, e.g. across a mosaic pool.

max_decode_tasks: usize

Capacity of the reader’s CPU limiter when cpu_limiter is None. Defaults to available parallelism (four if unavailable), clamped to 1..=tokio::sync::Semaphore::MAX_PERMITS. Ignored for an injected limiter.

source_id: String

Caller-supplied id for this logical source (same id ⇒ shared blocks).

block_cache: Arc<BlockCache>

Shared decoded-block cache injected by the caller.

cpu_limiter: Option<CpuLimiter>

Shared CPU-job limiter. When None, the reader builds its own sized to max_decode_tasks. Inject the same CpuLimiter into several readers (and their Tilers) to bound the whole process/mosaic to one CPU budget — see crate::blocking::CpuLimiter.

prefetch_ring: u8

Speculative block prefetch radius, in native COG blocks. After each read_window, the blocks in a ring of this width around the window are fetched + decoded into the shared block cache in the background — map-browsing patterns make those exactly the blocks the neighbouring XYZ tiles need next, turning their cold misses into warm hits.

0 (the default) disables prefetch. Each ring step issues extra object-store GETs, so leave it off for pay-per-request storage unless the latency win is worth it; 1 is the sweet spot for tile serving.

Trait Implementations

impl Clone for ReaderConfig

fn clone(&self) -> Self

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Default for ReaderConfig

fn default() -> Self

Returns the “default value” for a type.