75 lines
2.8 KiB
Zig
75 lines
2.8 KiB
Zig
const std = @import("std");
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const assert = std.debug.assert;
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const segfault = true;
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pub const JournalHeader = packed struct {
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hash_chain_root: u128 = undefined,
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prev_hash_chain_root: u128,
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checksum: u128 = undefined,
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magic: u64,
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command: u32,
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size: u32,
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pub fn calculate_checksum(self: *const JournalHeader, entry: []const u8) u128 {
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assert(entry.len >= @sizeOf(JournalHeader));
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assert(entry.len == self.size);
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const checksum_offset = @offsetOf(JournalHeader, "checksum");
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const checksum_size = @sizeOf(@TypeOf(self.checksum));
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assert(checksum_offset == 0 + 16 + 16);
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assert(checksum_size == 16);
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var target: [32]u8 = undefined;
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std.crypto.hash.Blake3.hash(entry[checksum_offset + checksum_size ..], target[0..], .{});
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return @bitCast(u128, target[0..checksum_size].*);
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}
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pub fn calculate_hash_chain_root(self: *const JournalHeader) u128 {
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const hash_chain_root_size = @sizeOf(@TypeOf(self.hash_chain_root));
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assert(hash_chain_root_size == 16);
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const prev_hash_chain_root_offset = @offsetOf(JournalHeader, "prev_hash_chain_root");
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const prev_hash_chain_root_size = @sizeOf(@TypeOf(self.prev_hash_chain_root));
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assert(prev_hash_chain_root_offset == 0 + 16);
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assert(prev_hash_chain_root_size == 16);
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const checksum_offset = @offsetOf(JournalHeader, "checksum");
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const checksum_size = @sizeOf(@TypeOf(self.checksum));
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assert(checksum_offset == 0 + 16 + 16);
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assert(checksum_size == 16);
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assert(prev_hash_chain_root_offset + prev_hash_chain_root_size == checksum_offset);
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const header = @bitCast([@sizeOf(JournalHeader)]u8, self.*);
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const source = header[prev_hash_chain_root_offset .. checksum_offset + checksum_size];
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assert(source.len == prev_hash_chain_root_size + checksum_size);
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var target: [32]u8 = undefined;
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std.crypto.hash.Blake3.hash(source, target[0..], .{});
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if (segfault) {
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return @bitCast(u128, target[0..hash_chain_root_size].*);
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} else {
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var array = target[0..hash_chain_root_size].*;
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return @bitCast(u128, array);
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}
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}
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pub fn set_checksum_and_hash_chain_root(self: *JournalHeader, entry: []const u8) void {
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self.checksum = self.calculate_checksum(entry);
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self.hash_chain_root = self.calculate_hash_chain_root();
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}
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};
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test "fixed" {
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var buffer = [_]u8{0} ** 65536;
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var entry = std.mem.bytesAsValue(JournalHeader, buffer[0..@sizeOf(JournalHeader)]);
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entry.* = .{
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.prev_hash_chain_root = 0,
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.magic = 0,
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.command = 0,
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.size = 64 + 128,
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};
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entry.set_checksum_and_hash_chain_root(buffer[0..entry.size]);
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try std.io.null_writer.print("{}\n", .{entry});
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}
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