Validation

Validation with expect

Use expect to validate format constraints at parse time:

header: Header
expect header.magic == 0x42494E44
expect header.version >= 1
expect header.version <= 3
expect header.entry_size == sizeof(DataEntry)

If an expect condition evaluates to zero (false), the SDDL engine reports a data error and parsing fails.

Common Patterns

Magic number validation:

header: FileHeader
expect header.signature == 0x4D42  # "BM" for BMP files

Size consistency checks:

header: Header
expect header.entry_size == sizeof(Row)

Range validation:

header: Header
expect header.count >= 0
expect header.count <= 1000000

Combined conditions:

expect header.version >= 1 && header.version <= 3