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//! FAT32 Boot Sector (BPB)
const constants = @import("../constants/constants.zig");
pub const BootSector = extern struct {
jump_boot: [3]u8,
oem_name: [8]u8,
bytes_per_sector: u16 align(1),
sectors_per_cluster: u8,
reserved_sectors: u16 align(1),
fat_count: u8,
root_entry_count: u16 align(1), // Must be 0 for FAT32
total_sectors_16: u16 align(1), // Must be 0 for FAT32
media_type: u8,
fat_size_16: u16 align(1), // Must be 0 for FAT32
sectors_per_track: u16 align(1),
head_count: u16 align(1),
hidden_sectors: u32 align(1),
total_sectors_32: u32 align(1),
// FAT32 extended BPB
fat_size_32: u32 align(1),
ext_flags: u16 align(1),
fs_version: u16 align(1),
root_cluster: u32 align(1),
fsinfo_sector: u16 align(1),
backup_boot_sector: u16 align(1),
reserved: [12]u8,
drive_number: u8,
reserved1: u8,
boot_sig: u8,
volume_id: u32 align(1),
volume_label: [11]u8,
fs_type: [8]u8,
boot_code: [420]u8,
signature: u16 align(1),
pub fn is_valid(self: *const BootSector) bool {
if (self.signature != constants.boot_signature) {
return false;
}
if (self.bytes_per_sector < constants.sector_size_min or
self.bytes_per_sector > constants.sector_size_max)
{
return false;
}
if (self.sectors_per_cluster == 0) {
return false;
}
if (self.fat_count == 0) {
return false;
}
if (self.fat_size_32 == 0) {
return false;
}
return true;
}
pub fn get_fat_start_sector(self: *const BootSector) u32 {
return self.reserved_sectors;
}
pub fn get_data_start_sector(self: *const BootSector) u32 {
return self.reserved_sectors + (@as(u32, self.fat_count) * self.fat_size_32);
}
pub fn get_total_clusters(self: *const BootSector) u32 {
const data_sectors = self.total_sectors_32 - self.get_data_start_sector();
return data_sectors / self.sectors_per_cluster;
}
pub fn cluster_to_sector(self: *const BootSector, cluster: u32) u32 {
return self.get_data_start_sector() + ((cluster - 2) * self.sectors_per_cluster);
}
pub fn get_bytes_per_cluster(self: *const BootSector) u32 {
return @as(u32, self.bytes_per_sector) * self.sectors_per_cluster;
}
};
pub const FsInfo = extern struct {
signature_1: u32 align(1),
reserved_1: [480]u8,
signature_2: u32 align(1),
free_cluster_count: u32 align(1),
next_free_cluster: u32 align(1),
reserved_2: [12]u8,
signature_3: u32 align(1),
pub fn is_valid(self: *const FsInfo) bool {
return self.signature_1 == constants.fsinfo_sig1 and
self.signature_2 == constants.fsinfo_sig2 and
self.signature_3 == constants.fsinfo_sig3;
}
};
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