vfat-rs 0.1.1

A no_std-compatible FAT32/VFAT filesystem implementation in Rust for custom kernels
Documentation 
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pub(crate) use fat_entry::*;
pub(crate) use fat_reader::*;
pub(crate) use fat_writer::*;

use crate::VfatRsError::CheckedMulFailed;
use crate::cache::CachedPartition;
use crate::formats::cluster_id::ClusterId;
use crate::{SectorId, error};

mod fat_entry;
mod fat_reader;
mod fat_writer;

/// Given a cluster_id, returns the sector id to read to get the FAT table entry for
/// this cluster id.
fn get_params(device: &CachedPartition, cluster_id: ClusterId) -> error::Result<(SectorId, usize)> {
    // this should be 512 / 32 = 18
    let fat_entries_per_sector = device.sector_size / FAT_ENTRY_SIZE;
    // In which sector is this cid contained? Cid: 222 / 18 = 12

    let cluster_id_val = u32::from(cluster_id);
    let containing_sector = cluster_id_val / fat_entries_per_sector as u32;
    // The sector is 12, now let's calculate the offset in that sector: 222 % 18 = 6.

    let offset_in_sector = ((cluster_id_val % fat_entries_per_sector as u32) as usize)
        .checked_mul(FAT_ENTRY_SIZE)
        .ok_or(CheckedMulFailed)?;

    let sector = device.fat_start_sector + containing_sector;

    Ok((sector, offset_in_sector))
}