+
---
@@ -168,7 +168,7 @@ fn main() {
```rust
use parity_scale_codec::{ Encode };
@@ -96,8 +96,8 @@ fn main() {
7
```
-
-pba-col center style="margin-left: 10px;">
+
+
```rust
use serde::{ Serialize };
@@ -125,8 +125,8 @@ fn main() {
42
```
-
-
+
+
+
+| `0b00` | `0b01` | `0b10` | `0b11` |
+| ------ | ------ | ------ | ------ |
+| single-byte mode; upper six bits are the LE encoding of the value. Valid only for values of `0` through `63`.
+| two-byte mode: upper six bits and the following byte is the LE encoding of the value. Valid only for values `64` through `(2^14 - 1)`.
+| four-byte mode: upper six bits and the following three bytes are the LE encoding of the value. Valid only for values `(2^14)` through `(2^30 - 1)`.
+| Big-integer mode: The upper six bits are the number of bytes following, plus four. The value is contained, LE encoded, in the bytes following. The final (most significant) byte must be non-zero. Valid only for values `(2^30)` through `(2^536 - 1)`.
+|
+
+
+
+Compact/general integers are encoded with the two least significant **bits** denoting the mode.
-- `0b00`: single-byte mode; upper six bits are the LE encoding of the value. Valid only for values of `0` through `63`.
-- `0b01`: two-byte mode: upper six bits and the following byte is the LE encoding of the value. Valid only for values `64` through `(2^14 - 1)`.
-- `0b10`: four-byte mode: upper six bits and the following three bytes are the LE encoding of the value. Valid only for values `(2^14)` through `(2^30 - 1)`.
-- `0b11`: Big-integer mode: The upper six bits are the number of bytes following, plus four. The value is contained, LE encoded, in the bytes following. The final (most significant) byte must be non-zero. Valid only for values `(2^30)` through `(2^536 - 1)`.
---
@@ -390,6 +398,7 @@ fn main() {
println!("{:02x?}", [0u8, 1u8, 2u8, 3u8, 4u8].encode());
println!("{:02x?}", vec![0u8, 1u8, 2u8, 3u8, 4u8].encode());
println!("{:02x?}", "hello".encode());
+ println!("{:02x?}", vec![0u8; 1024].encode());
}
```
@@ -397,8 +406,13 @@ fn main() {
[00, 01, 02, 03, 04]
[14, 00, 01, 02, 03, 04]
[14, 68, 65, 6c, 6c, 6f]
+[01, 10, 00, 00, ... snip ... , 00]
```
+Notes:
+
+Note that the length prefix can be multiple bytes, like the last example.
+
---
### Tuple and Struct
@@ -437,6 +451,38 @@ Note that tuple and struct encode the same, even though struct has named fields.
---
+## Embedded Compact
+
+```rust
+use parity_scale_codec::Encode;
+
+#[derive(Encode)]
+struct Example {
+ number: u64,
+ #[codec(compact)]
+ compact_number: u64,
+}
+
+#[derive(Encode)]
+enum Choices {
+ One(u64, #[codec(compact)] u64),
+}
+
+fn main() {
+ let my_struct = Example { number: 42, compact_number: 1337 };
+ let my_choice = Choices::One(42, 1337);
+ println!("{:02x?}", my_struct.encode());
+ println!("{:02x?}", my_choice.encode());
+}
+```
+
+```bash
+[2a, 00, 00, 00, 00, 00, 00, 00, e5, 14]
+[00, 2a, 00, 00, 00, 00, 00, 00, 00, e5, 14]
+```
+
+---
+
### Enum
Prefix with index (`u8`), then the value, if any.
@@ -603,4 +649,12 @@ SCALE Codec has been implemented in other languages, including:
---
+## Missing Some Metadata?
+
+To make SCALE useful as an encoding format within the Substrate and Polkadot ecosystem, we need to figure out a way to provide **metadata** about all the types we will expect, and when we will expect them.
+
+HINT: We do.
+
+---
+
### Remember, in the end of the day, everything is just 0's and 1's.