BMParameter¶
BMParameter is a dynamically typed value wrapper used to carry arguments in BMInvoke RPC calls. Because the protocol must support passing arbitrary types (integers, strings, nested objects, etc.) as method arguments, each value is wrapped in a BMParameter that prefixes it with a type tag.
- Class ID: 3
Wire Format¶
After the object envelope, a BMParameter contains a single dynamically typed value serialized using BMEncoding.
The encoding consists of a type tag followed by the value:
| # | Field | Type | Description |
|---|---|---|---|
| 1 | tag |
UTF | A single-character type tag identifying the value type. |
| 2 | value |
(varies) | The serialized value, in the format dictated by the tag. |
Type Tags¶
| Tag | Value Type | Wire Format |
|---|---|---|
@ |
Object | Standard object envelope + class-specific payload. |
i |
Signed int | i32 (4 bytes) |
I |
Unsigned int | u32 (4 bytes) |
s |
Signed short | i16 (2 bytes) |
S |
Unsigned short | u16 (2 bytes) |
f |
Float | f32 (4 bytes, IEEE 754) |
d |
Double | f64 (8 bytes, IEEE 754) |
B |
Boolean | bool (1 byte) |
* |
String | UTF |
Total minimum size¶
5 (envelope) + 3 (tag as UTF) + 1 (smallest value: bool) = 9 bytes
Object Parameters¶
When the tag is @, the value is a nested Externalizable object. This results in two consecutive @ markers on the wire: one from the BMEncoding tag and one from the nested object's own envelope.
Relationship to BMInvoke¶
BMParameter objects appear exclusively as elements of the arguments array inside a BMInvoke. Each argument to an RPC call is individually wrapped in its own BMParameter.