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Module sui::bcs

This module implements BCS (de)serialization in Move.
Full specification can be found here: https://github.com/diem/bcs

Short summary (for Move-supported types):

  • address - sequence of X bytes
  • bool - byte with 0 or 1
  • u8 - a single u8 byte
  • u16 / u32 / u64 / u128 / u256 - LE bytes
  • vector - ULEB128 length + LEN elements
  • option - first byte bool: None (0) or Some (1), then value

Usage example:

/// This function reads u8 and u64 value from the input
/// and returns the rest of the bytes.
fun deserialize(bytes: vector<u8>): (u8, u64, vector<u8>) {
use sui::bcs::\{Self, BCS\};

let prepared: BCS = bcs::new(bytes);
let (u8_value, u64_value) = (
prepared.peel_u8(),
prepared.peel_u64()
);

// unpack bcs struct
let leftovers = prepared.into_remainder_bytes();

(u8_value, u64_value, leftovers)
}
use std::ascii;
use std::bcs;
use std::option;
use std::string;
use std::vector;
use sui::address;
use sui::hex;

Struct BCS​

A helper struct that saves resources on operations. For better vector performance, it stores reversed bytes of the BCS and enables use of vector::pop_back.

public struct BCS has copy, drop, store
Click to open
Fields
bytes: vector<u8>

Constants​

For when bytes length is less than required for deserialization.

const EOutOfRange: u64 = 0;

For when the boolean value different than 0 or 1.

const ENotBool: u64 = 1;

For when ULEB byte is out of range (or not found).

const ELenOutOfRange: u64 = 2;

Function to_bytes​

Get BCS serialized bytes for any value.
Re-exports stdlib bcs::to_bytes.

public fun to_bytes<T>(value: &T): vector<u8>

Function new​

Creates a new instance of BCS wrapper that holds inversed bytes for better performance.

public fun new(bytes: vector<u8>): sui::bcs::BCS

Function into_remainder_bytes​

Unpack the BCS struct returning the leftover bytes.
Useful for passing the data further after partial deserialization.

public fun into_remainder_bytes(bcs: sui::bcs::BCS): vector<u8>

Function peel_address​

Read address from the bcs-serialized bytes.

public fun peel_address(bcs: &mut sui::bcs::BCS): address

Function peel_bool​

Read a bool value from bcs-serialized bytes.

public fun peel_bool(bcs: &mut sui::bcs::BCS): bool

Function peel_u8​

Read u8 value from bcs-serialized bytes.

public fun peel_u8(bcs: &mut sui::bcs::BCS): u8

Macro function peel_num​

macro fun peel_num<$I, $T>($bcs: &mut sui::bcs::BCS, $len: u64, $bits: $I): $T

Function peel_u16​

Read u16 value from bcs-serialized bytes.

public fun peel_u16(bcs: &mut sui::bcs::BCS): u16

Function peel_u32​

Read u32 value from bcs-serialized bytes.

public fun peel_u32(bcs: &mut sui::bcs::BCS): u32

Function peel_u64​

Read u64 value from bcs-serialized bytes.

public fun peel_u64(bcs: &mut sui::bcs::BCS): u64

Function peel_u128​

Read u128 value from bcs-serialized bytes.

public fun peel_u128(bcs: &mut sui::bcs::BCS): u128

Function peel_u256​

Read u256 value from bcs-serialized bytes.

public fun peel_u256(bcs: &mut sui::bcs::BCS): u256

Function peel_vec_length​

Read ULEB bytes expecting a vector length. Result should then be used to perform peel_* operation LEN times.

In BCS vector length is implemented with ULEB128;
See more here: https://en.wikipedia.org/wiki/LEB128

public fun peel_vec_length(bcs: &mut sui::bcs::BCS): u64

Macro function peel_vec​

Peel vector<T&gt;</span> from serialized bytes, where <span class="code-inline">peel: |&mut BCS| -> $T gives the functionality of peeling each value.

public macro fun peel_vec<$T>($bcs: &mut sui::bcs::BCS, $peel: |&mut sui::bcs::BCS| -> $T): vector<$T>

Function peel_vec_address​

Peel a vector of address from serialized bytes.

public fun peel_vec_address(bcs: &mut sui::bcs::BCS): vector<address>

Function peel_vec_bool​

Peel a vector of address from serialized bytes.

public fun peel_vec_bool(bcs: &mut sui::bcs::BCS): vector<bool>

Function peel_vec_u8​

Peel a vector of u8 (eg string) from serialized bytes.

public fun peel_vec_u8(bcs: &mut sui::bcs::BCS): vector<u8>

Function peel_vec_vec_u8​

Peel a vector<vector<u8>> (eg vec of string) from serialized bytes.

public fun peel_vec_vec_u8(bcs: &mut sui::bcs::BCS): vector<vector<u8>>

Function peel_vec_u16​

Peel a vector of u16 from serialized bytes.

public fun peel_vec_u16(bcs: &mut sui::bcs::BCS): vector<u16>

Function peel_vec_u32​

Peel a vector of u32 from serialized bytes.

public fun peel_vec_u32(bcs: &mut sui::bcs::BCS): vector<u32>

Function peel_vec_u64​

Peel a vector of u64 from serialized bytes.

public fun peel_vec_u64(bcs: &mut sui::bcs::BCS): vector<u64>

Function peel_vec_u128​

Peel a vector of u128 from serialized bytes.

public fun peel_vec_u128(bcs: &mut sui::bcs::BCS): vector<u128>

Function peel_vec_u256​

Peel a vector of u256 from serialized bytes.

public fun peel_vec_u256(bcs: &mut sui::bcs::BCS): vector<u256>

Function peel_enum_tag​

Peel enum from serialized bytes, where $f takes a tag value and returns the corresponding enum variant. Move enums are limited to 127 variants, however the tag can be any u32 value.

Example:

let my_enum = match (bcs.peel_enum_tag()) \{
0 => Enum::Empty,
1 => Enum::U8(bcs.peel_u8()),
2 => Enum::U16(bcs.peel_u16()),
3 => Enum::Struct { a: bcs.peel_address(), b: bcs.peel_u8() \},
_ => abort,
};
public fun peel_enum_tag(bcs: &mut sui::bcs::BCS): u32

Macro function peel_option​

Peel Option<T&gt;</span> from serialized bytes, where <span class="code-inline">peel: |&mut BCS| -> $T gives the functionality of peeling the inner value.

public macro fun peel_option<$T>($bcs: &mut sui::bcs::BCS, $peel: |&mut sui::bcs::BCS| -> $T): std::option::Option<$T>

Function peel_option_address​

Peel Option<address> from serialized bytes.

public fun peel_option_address(bcs: &mut sui::bcs::BCS): std::option::Option<address>

Function peel_option_bool​

Peel Option<bool> from serialized bytes.

public fun peel_option_bool(bcs: &mut sui::bcs::BCS): std::option::Option<bool>

Function peel_option_u8​

Peel Option<u8> from serialized bytes.

public fun peel_option_u8(bcs: &mut sui::bcs::BCS): std::option::Option<u8>

Function peel_option_u16​

Peel Option<u16> from serialized bytes.

public fun peel_option_u16(bcs: &mut sui::bcs::BCS): std::option::Option<u16>

Function peel_option_u32​

Peel Option<u32> from serialized bytes.

public fun peel_option_u32(bcs: &mut sui::bcs::BCS): std::option::Option<u32>

Function peel_option_u64​

Peel Option<u64> from serialized bytes.

public fun peel_option_u64(bcs: &mut sui::bcs::BCS): std::option::Option<u64>

Function peel_option_u128​

Peel Option<u128> from serialized bytes.

public fun peel_option_u128(bcs: &mut sui::bcs::BCS): std::option::Option<u128>

Function peel_option_u256​

Peel Option<u256> from serialized bytes.

public fun peel_option_u256(bcs: &mut sui::bcs::BCS): std::option::Option<u256>