tiny.sql.WalReader

1pub const Reader = struct {2    data: []const u8,3    salt: Salt,4    checksum: Checksum,5    offset: usize = header_size,6    index: usize = 0,7    stopped: bool = false,89    pub fn init(data: []const u8) ReadError!Reader {10        return initControlled(data, .{}) catch |err| switch (err) {11            error.Interrupted => unreachable,12            else => return @errorCast(err),13        };14    }1516    pub fn initControlled(data: []const u8, control: Control) ControlledReadError!Reader {17        try control.check();18        if (data.len < header_size) return error.InvalidWal;19        if (readU32(data[0..4]) != magic) return error.InvalidWal;20        if (readU32(data[4..8]) != format_version) return error.InvalidWal;21        if (readU32(data[8..12]) != page.size) return error.UnsupportedPageSize;22        var checksum: Checksum = .{};23        checksum.update(data[0..24]);24        if (readU32(data[24..28]) != checksum.first) return error.InvalidChecksum;25        if (readU32(data[28..32]) != checksum.second) return error.InvalidChecksum;26        try control.check();27        return .{28            .data = data,29            .salt = .{30                .first = readU32(data[16..20]),31                .second = readU32(data[20..24]),32            },33            .checksum = checksum,34        };35    }3637    pub fn next(self: *Reader) ReadError!?Frame {38        return self.nextControlled(.{}) catch |err| switch (err) {39            error.Interrupted => unreachable,40            else => return @errorCast(err),41        };42    }4344    pub fn nextControlled(self: *Reader, control: Control) ControlledReadError!?Frame {45        const phase = trace.scope("wal.next");46        defer phase.end();47        try control.check();48        if (self.stopped) return null;49        if (self.offset + frame_size > self.data.len) {50            self.stopped = true;51            return null;52        }5354        const frame_header = self.data[self.offset..][0..frame_header_size];55        const image = self.data[self.offset + frame_header_size ..][0..page.size];56        if (readU32(frame_header[8..12]) != self.salt.first or readU32(frame_header[12..16]) != self.salt.second) {57            self.stopped = true;58            return null;59        }6061        var checksum = self.checksum;62        checksum.update(frame_header[0..8]);63        checksum.update(image);64        if (readU32(frame_header[16..20]) != checksum.first or readU32(frame_header[20..24]) != checksum.second) {65            self.stopped = true;66            return null;67        }6869        try control.check();70        self.checksum = checksum;71        self.index += 1;72        self.offset += frame_size;73        return .{74            .index = self.index,75            .page_id = readU32(frame_header[0..4]),76            .db_page_count = readU32(frame_header[4..8]),77            .image = image,78        };79    }80};

1pub const WalReader = wal.Reader;