forked from NPM/numass-framework
31 lines
3.7 KiB
Markdown
31 lines
3.7 KiB
Markdown
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---
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content_type: "doc_shard"
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title: "Binary meta"
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chapter: envelope
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ordering: 50
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label: "binary_meta"
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published: false
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---
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Binary meta format is made to limit size and simplify parsing to automatic messages. The notation for the node looks the following way (all numeric values use BigEndian encoding):
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<br>
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All strings are encoded in a following way: 2 bytes for string length, byte array of given length representing UTF-8 encoded string.
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<br>
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1. Meta name as string.
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2. 2 bytes unsigned integer representing the number of values in the node. Could be zero.
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3. For each of values an encoded name of the value and then:
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* `0` for Null value.
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* `T` for `TIME` value, followed by two unsigned long values representing epoch second and nanosecond adjustment.
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* `S` for `STRING` value followed by encoded string.
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* `D` for double based `NUMBER` followed by double (double encoding specified by [Java serialization](https://docs.oracle.com/javase/8/docs/api/java/io/DataOutput.html#writeDouble-double-)).
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* `I` for integer based `NUMBER` followed by signed 4-bytes integer value.
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* `B` for [`BigDecimal`](https://docs.oracle.com/javase/8/docs/api/java/math/BigDecimal.html) based `NUMBER` followed by 2-byte unsigned integer defining the number of bytes in representation, bytes themselves and 4-byte scale factor.
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* `+` for boolean `true`.
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* `-` for boolean `false`.
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* `L` for list value and then 2-byte list size followed by sequence of values (as in item 3, but without a name).
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4. 2 bytes unsigned integer representing the number of child nodes in this node. Could be zero.
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5. For each of child nodes:
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* child node name,
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* 2-byte unsigned integer representing number of children with this name.
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* The sequence of nodes with given name encoding like the root node, but without name.
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