Difference between revisions of "Protocols/OSCAR/TLV"
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| Numeric type or "tag" of the data, possible values are defined in the TLV class for the group of TLVs | | Numeric type or "tag" of the data, possible values are defined in the TLV class for the group of TLVs | ||
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Revision as of 04:07, 17 March 2020
| OSCAR Protocol |
| Introduction • Terms • Clients |
| Basic |
| Datatypes • FLAP • SNAC • TLV |
| UUIDs • Errors • Tool IDs |
| Host Interaction |
| Rate Limits • Migration • Messages |
| Other Services |
| ADMIN • ADVERT • ALERT |
| BART • BOS • BUCP • CHAT |
| CHAT_NAV |
| Tutorials |
| Sign On • BART • Rendezvous |
| ICBM • Locate • Buddies |
| Foodgroups |
| OSERVICE (0x0001) |
| LOCATE (0x0002) |
| BUDDY (0x0003) |
| ICBM (0x0004) |
| ADVERT (0x0005) |
| INVITE (0x0006) |
| ADMIN (0x0007) |
| POPUP (0x0008) |
| PD (0x0009) |
| USER_LOOKUP (0x000A) |
| STATS (0x000B) |
| TRANSLATE (0x000C) |
| CHAT_NAV (0x000D) |
| CHAT (0x000E) |
| ODIR (0x000F) |
| BART (0x0010) |
| FEEDBAG (0x0013) |
| ICQ (0x0015) |
| BUCP (0x0017) |
| ALERT (0x0018) |
| PLUGIN (0x0022) |
| UNNAMED_FG_24 (0x0024) |
| MDIR (0x0025) |
| ARS (0x044A) |
TLVs are a very common structure used in the OSCAR protocol to represent dynamically typed data. Parsers should always ignore unknown tags as to not break old clients when new protocol items are added. Possible values for tags are determined by where the TLV is in the protocol; these possible values belong to a TLV class. In the wild, the term type is sometimes used interchangeably with tag, however this document uses tag to reference the integer value associated with the TLV and type as the datatype associated with that tag.
| Name | Size | Notes |
|---|---|---|
| Type | uint16 (word) | Numeric type or "tag" of the data, possible values are defined in the TLV class for the group of TLVs |
| Length | uint16 (word) | Length in bytes of the variable data |
| Value | blob | The data inside the TLV of len length; usually another datatype is used to represent the data - this is described in the TLV class |
TLVs are usually used in an array of TLV form, allowing the protocol to easily be expanded. Having just one TLV without an array does not gain much since it only allows one item to be described. There are two common methods for adding an array of TLVs to datatypes and SNACs. An additional method also exists to add an array of TLVs to SNACs.
The most common is a tlvBlock which is a u16 number of TLVs followed by that many TLVs. The less common is a tlvLBlock which instead of counting the number of TLVs, counts the size of all the TLVs. The third, which is only available in SNACs, is the tlvRestBlock which says any remaining bytes in the SNAC are TLVs.
| Name | Size | Notes |
|---|---|---|
| tlvBlock | uint16 (word) + data | Two byte number of elements, followed by that many elements |
| tlvLBlock | uint16 (word) + data | Two byte length of elements, followed by that many bytes of elements |
