Directives
Directives are system values that modify the encoding context.
note
This chapter focuses on the binary encoding of directives. The Directives section explains what they are and how they are used.
The binary encoding of directives is a specialized delimited container.
Directives are opened using opcodes 0xE1 through 0xE8.
They may contain any number of tagged values, and they are closed with the end-container opcode (0xEF).
Directives may only occur at the top level of a stream and may not be annotated.
Directive Opcodes
| Opcode | Directive |
|---|---|
0xE1 | set_symbols |
0xE2 | add_symbols |
0xE3 | set_macros |
0xE4 | add_macros |
0xE5 | use |
0xE6 | module |
0xE7 | import |
0xE8 | encoding |
Examples
Encoding of (:$ion set_symbols "foo" "bar")
┌──── Opcode 0xE1 indicates a set_symbols directive
│ ┌─── String "foo"
│ │ ┌─── String "bar"
│ │ │ ┌─── End of directive
E1 93 66 6F 6F 93 62 61 72 EF
Encoding of (:$ion add_symbols "baz")
┌──── Opcode 0xE2 indicates an add_symbols directive
│ ┌─── String "baz"
│ │ ┌─── End of directive
E2 93 62 61 7A EF
Encoding of (:$ion module foo "com.amazon.Bar" 1)
┌──── Opcode 0xE6 indicates a module directive
│ ┌─── Symbol "foo" (assuming SID 10)
│ │ ┌─── String "com.amazon.Bar"
│ │ │ ┌─── Integer 1
│ │ │ │ ┌─── End of directive
E6 50 15 9E 63 6F 6D 2E 61 6D 61 7A 6F 6E 2E 42 61 72 61 01 EF