The Ion 1.1 Draft Specification

NOPs

A NOP (short for "no-operation") is the binary equivalent of whitespace. NOP bytes have no meaning, but can be used as padding to achieve a desired alignment.

An opcode of 0xEC indicates a single-byte NOP pad. An opcode of 0xED indicates that a FlexUInt follows that represents the number of additional bytes to skip.

It is legal for a NOP to appear anywhere that a value can be encoded. It is not legal for a NOP to appear in annotation sequences or struct field names. If a NOP appears in place of a struct field value, then the associated field name is ignored; the NOP is immediately followed by the next field name, if any.

Encoding of a 1-byte NOP

┌──── The opcode `0xEC` represents a 1-byte NOP pad
│
EC

Encoding of a 3-byte NOP

┌──── The opcode `0xED` represents a variable-length NOP pad; a FlexUInt length follows
│  ┌──── Length: FlexUInt 2; two more bytes of NOP follow
│  │
ED 05 93 C6
      └─┬─┘
NOP bytes, values ignored