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//! Hikari GPT Parser
const efi = @import("../../efi/efi.zig");
const constants = @import("constants.zig");
const types = @import("types.zig");
pub const ParseError = error{
read_failed,
invalid_protective_mbr,
invalid_signature,
invalid_revision,
invalid_header_size,
invalid_header_crc,
invalid_entries_crc,
no_partitions,
partition_not_found,
};
pub const Parser = struct {
block_io: *efi.protocols.BlockIoProtocol,
block_size: u32,
header: types.Header,
entries_buffer: [*]u8,
entries_count: u32,
entry_size: u32,
pub fn initialize(block_io: *efi.protocols.BlockIoProtocol, boot_services: *efi.services.BootServices) ParseError!Parser {
const block_size = block_io.media.block_size;
var header_buffer: [512]u8 align(8) = undefined;
const header_read_status = block_io.read_blocks(
block_io,
block_io.media.media_id,
constants.header_lba,
block_size,
&header_buffer,
);
if (efi.types.is_error(header_read_status)) {
return ParseError.read_failed;
}
const header: *const types.Header = @ptrCast(@alignCast(&header_buffer));
if (header.signature != constants.signature) {
return ParseError.invalid_signature;
}
if (header.revision < constants.revision_1_0) {
return ParseError.invalid_revision;
}
if (header.header_size < constants.header_size_minimum) {
return ParseError.invalid_header_size;
}
const stored_header_crc = header.header_crc32;
var header_for_crc = header_buffer;
const header_ptr: *types.Header = @ptrCast(@alignCast(&header_for_crc));
header_ptr.header_crc32 = 0;
const calculated_header_crc = calculate_crc32(header_for_crc[0..header.header_size]);
if (calculated_header_crc != stored_header_crc) {
return ParseError.invalid_header_crc;
}
if (header.partition_entries_count == 0) {
return ParseError.no_partitions;
}
const entries_total_size = header.partition_entries_count * header.partition_entry_size;
const entries_blocks = (entries_total_size + block_size - 1) / block_size;
const entries_buffer_size = entries_blocks * block_size;
var entries_buffer: [*]align(8) u8 = undefined;
const alloc_status = boot_services.allocate_pool(
.loader_data,
entries_buffer_size,
&entries_buffer,
);
if (efi.types.is_error(alloc_status)) {
return ParseError.read_failed;
}
const entries_read_status = block_io.read_blocks(
block_io,
block_io.media.media_id,
header.partition_entries_lba,
entries_buffer_size,
entries_buffer,
);
if (efi.types.is_error(entries_read_status)) {
return ParseError.read_failed;
}
const calculated_entries_crc = calculate_crc32(entries_buffer[0..entries_total_size]);
if (calculated_entries_crc != header.partition_entries_crc32) {
return ParseError.invalid_entries_crc;
}
return Parser{
.block_io = block_io,
.block_size = block_size,
.header = header.*,
.entries_buffer = entries_buffer,
.entries_count = header.partition_entries_count,
.entry_size = header.partition_entry_size,
};
}
pub fn find_partition_by_type(self: *const Parser, type_guid: efi.types.Guid) ?*const types.PartitionEntry {
var index: u32 = 0;
while (index < self.entries_count) : (index += 1) {
const entry = self.get_partition_entry(index);
if (entry.is_empty()) {
continue;
}
if (entry.is_type(type_guid)) {
return entry;
}
}
return null;
}
pub fn find_partition_by_index(self: *const Parser, index: u32) ?*const types.PartitionEntry {
if (index >= self.entries_count) {
return null;
}
const entry = self.get_partition_entry(index);
if (entry.is_empty()) {
return null;
}
return entry;
}
pub fn get_partition_entry(self: *const Parser, index: u32) *const types.PartitionEntry {
const offset = index * self.entry_size;
return @ptrCast(@alignCast(self.entries_buffer + offset));
}
pub fn count_valid_partitions(self: *const Parser) u32 {
var count: u32 = 0;
var index: u32 = 0;
while (index < self.entries_count) : (index += 1) {
const entry = self.get_partition_entry(index);
if (!entry.is_empty()) {
count += 1;
}
}
return count;
}
pub fn get_disk_guid(self: *const Parser) efi.types.Guid {
return self.header.disk_guid;
}
pub fn get_first_usable_lba(self: *const Parser) u64 {
return self.header.first_usable_lba;
}
pub fn get_last_usable_lba(self: *const Parser) u64 {
return self.header.last_usable_lba;
}
};
const crc32_table: [256]u32 = blk: {
@setEvalBranchQuota(10000);
break :blk generate_crc32_table();
};
fn generate_crc32_table() [256]u32 {
var table: [256]u32 = undefined;
var index: u32 = 0;
while (index < 256) : (index += 1) {
var crc: u32 = index;
var bit: u32 = 0;
while (bit < 8) : (bit += 1) {
if ((crc & 1) != 0) {
crc = (crc >> 1) ^ 0xEDB88320;
} else {
crc = crc >> 1;
}
}
table[index] = crc;
}
return table;
}
pub fn calculate_crc32(data: []const u8) u32 {
var crc: u32 = 0xFFFFFFFF;
for (data) |byte| {
const table_index = (crc ^ byte) & 0xFF;
crc = (crc >> 8) ^ crc32_table[table_index];
}
return crc ^ 0xFFFFFFFF;
}
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