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| 1 | const std = @import("std"); |
| 2 | const assert = std.debug.assert; |
| 3 | |
| 4 | const segfault = true; |
| 5 | |
| 6 | pub const JournalHeader = packed struct { |
| 7 | hash_chain_root: u128 = undefined, |
| 8 | prev_hash_chain_root: u128, |
| 9 | checksum: u128 = undefined, |
| 10 | magic: u64, |
| 11 | command: u32, |
| 12 | size: u32, |
| 13 | |
| 14 | pub fn calculate_checksum(self: *const JournalHeader, entry: []const u8) u128 { |
| 15 | assert(entry.len >= @sizeOf(JournalHeader)); |
| 16 | assert(entry.len == self.size); |
| 17 | |
| 18 | const checksum_offset = @byteOffsetOf(JournalHeader, "checksum"); |
| 19 | const checksum_size = @sizeOf(@TypeOf(self.checksum)); |
| 20 | assert(checksum_offset == 0 + 16 + 16); |
| 21 | assert(checksum_size == 16); |
| 22 | |
| 23 | var target: [32]u8 = undefined; |
| 24 | std.crypto.hash.Blake3.hash(entry[checksum_offset + checksum_size ..], target[0..], .{}); |
| 25 | return @bitCast(u128, target[0..checksum_size].*); |
| 26 | } |
| 27 | |
| 28 | pub fn calculate_hash_chain_root(self: *const JournalHeader) u128 { |
| 29 | const hash_chain_root_size = @sizeOf(@TypeOf(self.hash_chain_root)); |
| 30 | assert(hash_chain_root_size == 16); |
| 31 | |
| 32 | const prev_hash_chain_root_offset = @byteOffsetOf(JournalHeader, "prev_hash_chain_root"); |
| 33 | const prev_hash_chain_root_size = @sizeOf(@TypeOf(self.prev_hash_chain_root)); |
| 34 | assert(prev_hash_chain_root_offset == 0 + 16); |
| 35 | assert(prev_hash_chain_root_size == 16); |
| 36 | |
| 37 | const checksum_offset = @byteOffsetOf(JournalHeader, "checksum"); |
| 38 | const checksum_size = @sizeOf(@TypeOf(self.checksum)); |
| 39 | assert(checksum_offset == 0 + 16 + 16); |
| 40 | assert(checksum_size == 16); |
| 41 | |
| 42 | assert(prev_hash_chain_root_offset + prev_hash_chain_root_size == checksum_offset); |
| 43 | |
| 44 | const header = @bitCast([@sizeOf(JournalHeader)]u8, self.*); |
| 45 | const source = header[prev_hash_chain_root_offset .. checksum_offset + checksum_size]; |
| 46 | assert(source.len == prev_hash_chain_root_size + checksum_size); |
| 47 | var target: [32]u8 = undefined; |
| 48 | std.crypto.hash.Blake3.hash(source, target[0..], .{}); |
| 49 | if (segfault) { |
| 50 | return @bitCast(u128, target[0..hash_chain_root_size].*); |
| 51 | } else { |
| 52 | var array = target[0..hash_chain_root_size].*; |
| 53 | return @bitCast(u128, array); |
| 54 | } |
| 55 | } |
| 56 | |
| 57 | pub fn set_checksum_and_hash_chain_root(self: *JournalHeader, entry: []const u8) void { |
| 58 | self.checksum = self.calculate_checksum(entry); |
| 59 | self.hash_chain_root = self.calculate_hash_chain_root(); |
| 60 | } |
| 61 | }; |
| 62 | |
| 63 | test "fixed" { |
| 64 | var buffer = [_]u8{0} ** 65536; |
| 65 | var entry = std.mem.bytesAsValue(JournalHeader, buffer[0..@sizeOf(JournalHeader)]); |
| 66 | entry.* = .{ |
| 67 | .prev_hash_chain_root = 0, |
| 68 | .magic = 0, |
| 69 | .command = 0, |
| 70 | .size = 64 + 128, |
| 71 | }; |
| 72 | entry.set_checksum_and_hash_chain_root(buffer[0..entry.size]); |
| 73 | try std.io.null_writer.print("{}\n", .{entry}); |
| 74 | } |
Andrew Kelley <andrew@ziglang.org> 2020-10-26 13:18:44-07:00
test