TagBuf is a network data exchange format.
- tagBuf: tag + data
- tagBuffer: N tagBufs
Tag contains much information about data. TagBuf writes or reads from blob data to build a tagBuffer by tagBuf and build a tagBuf by tag.
Tag takes up 4 bytes. And tag will make the best of each bit.
| Range of Bits | Note |
|---|---|
| 31~13 | field number |
| 12~08 | tagBuf reserved |
| 07~04 | tagBuf internal-tag |
| 03~00 | tagBuf write type |
| No. | Write Type | Note |
|---|---|---|
| 0 | VarintFixed | kinds of Integers, zigzag-int, zigzag-int64. Above also support unsinged type. double value, 8 bytes, float value, 4 bytes. And about bool value, specially it only takes up 1 bit. |
| 1 | Container | NSArray on iOS platform(Objective-C), List on Android(Java), vector<T> on C++ |
| 2 | Blob Stream | such as NSString, NSData/String/string |
| 3 | Object | An Object |
Especially, if [07] eaquals to 0 represents there is an object at next tagBuf, 1 represents not.
- Write type is VarintFixed.
| Internal-Tag value | Meaning |
|---|---|
| 0 | 8 bits integer, such as char |
| 1 | 16 bits integer, such as short |
| 2 | 32 bits integer, such as int |
| 3 | 64 bits integer, such as long/long long |
| 4 | 32 bits float |
| 5 | 64 bits double |
| 6 | 1 bits value: bool |
| 7 | Indicate object is nil/null if this is a number(NSNumber/Number) object |
- Write type is Container
| Internal-Tag value | Meaning |
|---|---|
| 0 | Indicate non-contain, such as a array contain 0 element. |
| 1 | Contains string |
| 2 | Contains data(NSData) |
| 3 | Contains an object |
| 4 | Contains containers |
| 7 | Indicate object is nil/null/NULL |
You may have a question: where is integer. We think it is an object in container's integer(include C++). We will check type of container's element and store it to builtin structure in runtime. Defaultly, contain-type is 32 bits intger if the type is like integer(include float and double).
- Write type is Blob Stream
| Internal-Tag value | Meaning |
|---|---|
| 0 | Represents NSString/String/string |
| 1 | Represents NSData |
| 7 | Indicate object is nil/null/NULL |
- Write type is Blob Stream
| Internal-Tag value | Meaning |
|---|---|
| 7 | Indicate object is nil/null/NULL |
| Bits | Meaning |
|---|---|
| 08~10 | Represents the length of zigzag |
| 11 | 1 represents that the bytes of string or data's length has been compressed by zigzag. |
| 12 | 1 represents that there store a bool [true] value, 0 represents [false] value when write tpye is VarintFixed and internal-tag is varint_bool(6). And 1 represents that container contains number value(bool, 8~64bits, values by VarintFixed's internal values). |
Above is overall design idea.