The Ion 1.1 Draft Specification

Strings

If the high nibble of the opcode is 0x9_, it represents a string. The low nibble of the opcode indicates how many UTF-8 bytes follow. Opcode 0x90 represents a string with empty text ("").

Strings longer than 15 bytes can be encoded with the F9 opcode, which takes a FlexUInt-encoded length after the opcode.

0xEB x05 represents null.string.

Encoding of the empty string, ""

┌──── Opcode in range 90-9F indicates a string
│┌─── Low nibble 0 indicates that no UTF-8 bytes follow
90

Encoding of a 14-byte string

┌──── Opcode in range 90-9F indicates a string
│┌─── Low nibble E indicates that 14 UTF-8 bytes follow
││  f  o  u  r  t  e  e  n     b  y  t  e  s
9E 66 6F 75 72 74 65 65 6E 20 62 79 74 65 73
   └──────────────────┬────────────────────┘
                 UTF-8 bytes

Encoding of a 24-byte string

┌──── Opcode F9 indicates a variable-length string
│  ┌─── Length: FlexUInt 24
│  │   v  a  r  i  a  b  l  e     l  e  n  g  t  h     e  n  c  o  d  i  n  g
F9 31 76 61 72 69 61 62 6C 65 20 6C 65 6E 67 74 68 20 65 6E 63 6f 64 69 6E 67
      └────────────────────────────────┬────────────────────────────────────┘
                                  UTF-8 bytes

Encoding of null.string

┌──── Opcode 0xEB indicates a typed null; a byte follows specifying the type
│  ┌─── Null type: string
│  │
EB 05