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//! FAT32 Cluster Operations
const constants = @import("../constants/constants.zig");
const types = @import("../types/types.zig");
const BootSector = types.BootSector;
pub const ClusterError = error{
InvalidCluster,
BadCluster,
ReadFailed,
};
/// Check if cluster number is valid data cluster
pub fn is_valid_cluster(cluster: u32) bool {
return cluster >= constants.cluster_data_start and
cluster < constants.cluster_eoc_start and
cluster != constants.cluster_bad;
}
/// Check if cluster marks end of chain
pub fn is_end_of_chain(cluster: u32) bool {
return (cluster & constants.cluster_mask) >= constants.cluster_eoc_start;
}
/// Calculate FAT sector and offset for a cluster
pub fn get_fat_position(cluster: u32, bytes_per_sector: u32) struct { sector: u32, offset: u32 } {
const fat_offset = cluster * 4;
return .{
.sector = fat_offset / bytes_per_sector,
.offset = fat_offset % bytes_per_sector,
};
}
/// Calculate LBA for a cluster's data
pub fn cluster_to_lba(
cluster: u32,
data_start_lba: u64,
sectors_per_cluster: u32,
) u64 {
return data_start_lba + (@as(u64, cluster - 2) * sectors_per_cluster);
}
/// Read next cluster from FAT entry
pub fn parse_fat_entry(entry: u32) ClusterError!?u32 {
const next = entry & constants.cluster_mask;
if (is_end_of_chain(next)) {
return null;
}
if (next == constants.cluster_bad) {
return ClusterError.BadCluster;
}
if (next < constants.cluster_data_start) {
return ClusterError.InvalidCluster;
}
return next;
}
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