Struct YcdIndex 

pub struct YcdIndex { /* private fields */ }

An in-memory index over a contiguous set of YCD files.

Building the index reads every file’s header once and stores the resulting metadata. Subsequent read_digits calls use binary search to locate the relevant file(s) and seek directly to the target block, skipping every other file entirely.

Stale-index detection

Each time a file is actually read, its current file_size and last-modified time are compared against the snapshot taken at build time. If any difference is detected, read_digits returns io::ErrorKind::InvalidData with an explicit “stale index” message. There is no silent fallback to a full-scan path.

Example

use std::io;
use ycd_reader::YcdIndex;

fn main() -> io::Result<()> {
    let files = [
        "Pi - Dec - Chudnovsky - 0.ycd",
        "Pi - Dec - Chudnovsky - 1.ycd",
    ];

    // Build the index once (reads all headers).
    let index = YcdIndex::build(&files)?;

    // Fast random-access — only the relevant file(s) are opened.
    let digits = index.read_digits(999_995, 20)?;
    assert_eq!(digits, "45815130927562832084");

    Ok(())
}

Implementations

impl YcdIndex

pub fn build<P: AsRef<Path>>(files: &[P]) -> Result<Self>

Build an index from an ordered, contiguous slice of YCD file paths.

Every file’s header is read and validated (base-10 constraint, contiguity, no duplicates, no gaps). On success the index is ready for read_digits calls.

Errors

Returns the same errors as YcdFileUtil::read_digits for header and continuity problems. Additionally returns InvalidInput when files is empty.

pub fn rebuild<P: AsRef<Path>>(&mut self, files: &[P]) -> Result<()>

Discard the current index and rebuild it from a new file list.

On success self is replaced with the freshly built index. If the rebuild fails, self is left unchanged.

pub fn len(&self) -> usize

Returns the number of YCD files in the index.

pub fn is_empty(&self) -> bool

Returns true if the index contains no files.

pub fn entries(&self) -> &[YcdIndexEntry]

Returns a slice of all index entries in digit order.

pub fn read_digits( &self, one_based_start_position: usize, length: usize, ) -> Result<String>

Read exactly length decimal digits starting at 1-based position one_based_start_position.

Binary search locates the first file that contains the start position. Only the file(s) actually needed are opened; all other files are skipped entirely.

Before reading each file, its current file_size and last-modified time are compared against the index snapshot. A mismatch returns io::ErrorKind::InvalidData with an “index is stale” message.

Errors

Condition	io::ErrorKind
Index is empty, position 0, or length 0	InvalidInput
Start or end position outside the indexed range	InvalidInput
start + length overflows usize	InvalidData
File size or mtime differs from index snapshot	InvalidData
File does not exist	NotFound
Payload truncated within logical range	UnexpectedEof
Output string pre-allocation failure	Other

Trait Implementations

impl Clone for YcdIndex

fn clone(&self) -> YcdIndex

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for YcdIndex

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

Formats the value using the given formatter.