Problem in Existing Implementation

Oct 13, 2025 by leolavanderia.com.br 145 views

Issue Summary

The existing Bit Vector implementation in the dot/parachain/types package uses []bool as the underlying storage of bits, which consumes 8x more memory than necessary. This is because bool consumes 1 byte to store the value, and a vector of 8 bits will consume 8 bytes. To address this issue, we propose using []byte as the underlying storage of bits to store 8 bits per byte.

Problem in Existing Implementation

The current Bit Vector implementation in dot/parachain/types uses []bool to store individual bits. This approach has several drawbacks:

Inefficient memory usage: As mentioned earlier, using []bool consumes 8x more memory than necessary. This is because each bool value requires 1 byte of storage, resulting in a total of 8 bytes for a vector of 8 bits.
Limited scalability: The current implementation may not be suitable for large-scale applications that require efficient memory management.

Proposed Solution

To address the issues mentioned above, we propose using []byte as the underlying storage of bits. This approach has several advantages:

Compact storage: By storing 8 bits per byte, we can reduce memory usage by a factor of 8.
Improved scalability: The new implementation can handle large-scale applications with efficient memory management.

Implementation Details

To implement the efficient BitVector data structure, we need to follow these steps:

Step 1: Define the BitVec struct

type BitVec struct {
    bits []byte  // Underlying storage
    len  int     // Number of bits
}

Step 2: Implement bit manipulation operations

We need to implement the following bit manipulation operations:

Get: Retrieves the value of a specific bit at the given index.
Set: Sets the value of a specific bit at the given index.
Push: Adds a new bit to the end of the BitVector.

Step 3: Implement SCALE codec encoding/decoding

We need to implement SCALE codec encoding and decoding for network serialization.

Step 4: Optimize memory allocation strategy

We need to optimize the memory allocation strategy for dynamic growth.

Bit Manipulation Operations

To implement the bit manipulation operations, we can use the following functions:

Get

func (bv *BitVec) Get(index int) bool {
    byteIndex := index / 8
    bitIndex := index % 8
    return (bv.bits[byteIndex] >> bitIndex) & 1 == 1
}

Set

func (bv *BitVec) Set(index int, value bool) {
    byteIndex := index / 8
    bitIndex := index % 8
    if value {
        bv.bits[byteIndex] |= 1 << bitIndex
    } else {
        bv.bits[byteIndex] &= ^(1 << bitIndex)
    }
}

Push

func (bv *BitVec) Push(value bool) {
    byteIndex := bv.len / 8
    if byteIndex >= len(bv.bits) {
        bv.bits = append(bv.bits, 0)
    }
    if value {
        bv.bits[byteIndex] |= 1 << (bv.len % 8)
    } else {
        bv.bits[byteIndex] &= ^(1 << (bv.len % 8))
    }
    bv.len++
}

SCALE Codec Encoding/Decoding

To implement SCALE codec encoding and decoding, we can use the following functions:

Encode

func (bv *BitVec) Encode(w io.Writer) error {
    // Implement SCALE codec encoding logic here
}

Decode

func (bv *BitVec) Decode(r io.Reader) error {
    // Implement SCALE codec decoding logic here
}

Optimizing Memory Allocation Strategy

To optimize the memory allocation strategy for dynamic growth, we can use the following approach:

Use a dynamic array: Instead of using a fixed-size array, we can use a dynamic array that can grow or shrink as needed.
Use a buffer: We can use a buffer to store the new bits and then append them to the underlying storage array.

Acceptance Criteria

To ensure that the new implementation meets the requirements, we need to test the following acceptance criteria:

Implementation uses []byte as the underlying storage: The new implementation should use []byte as the underlying storage of bits.
All existing functionality is preserved: The new implementation should preserve all existing functionality, including getting and setting individual bits, push operations, length calculations, and SCALE encoding and decoding.
All existing tests pass with the new implementation: The new implementation should pass all existing tests.
Documentation on how to use bit vector: The new implementation should include documentation on how to use the bit vector.

Q: What is the main issue with the existing Bit Vector implementation in the `dot/parachain/types` package?

A: The main issue with the existing Bit Vector implementation is that it uses []bool as the underlying storage of bits, which consumes 8x more memory than necessary. This is because bool consumes 1 byte to store the value, and a vector of 8 bits will consume 8 bytes.

Q: Why is it necessary to use `[]byte` as the underlying storage of bits?

A: Using []byte as the underlying storage of bits is necessary to reduce memory usage and improve scalability. By storing 8 bits per byte, we can reduce memory usage by a factor of 8 and make the implementation more efficient.

Q: What are the advantages of using `[]byte` as the underlying storage of bits?

A: The advantages of using []byte as the underlying storage of bits include:

Compact storage: By storing 8 bits per byte, we can reduce memory usage by a factor of 8.
Improved scalability: The new implementation can handle large-scale applications with efficient memory management.

Q: How does the new implementation handle bit manipulation operations?

A: The new implementation handles bit manipulation operations using the following functions:

Get: Retrieves the value of a specific bit at the given index.
Set: Sets the value of a specific bit at the given index.
Push: Adds a new bit to the end of the BitVector.

Q: How does the new implementation handle SCALE codec encoding and decoding?

A: The new implementation handles SCALE codec encoding and decoding using the following functions:

Encode: Encodes the BitVector using the SCALE codec.
Decode: Decodes the BitVector using the SCALE codec.

Q: How does the new implementation optimize memory allocation strategy?

A: The new implementation optimizes memory allocation strategy by using a dynamic array and a buffer to store new bits.

Q: What are the acceptance criteria for the new implementation?

A: The acceptance criteria for the new implementation include:

Implementation uses []byte as the underlying storage: The new implementation should use []byte as the underlying storage of bits.
All existing functionality is preserved: The new implementation should preserve all existing functionality, including getting and setting individual bits, push operations, length calculations, and SCALE encoding and decoding.
All existing tests pass with the new implementation: The new implementation should pass all existing tests.
Documentation on how to use bit vector: The new implementation should include documentation on how to use the bit vector.

Q: What are the benefits of implementing the efficient BitVector data structure?

A: The benefits of implementing the efficient BitVector data structure include:

Improved memory usage: The new implementation reduces memory usage by a factor of 8.
Improved scalability: The new implementation can handle large-scale applications with efficient memory management.
Preserved functionality: The new implementation preserves all existing functionality.

Q: How can I get started with implementing the efficient BitVector data structure?

A: To get started with implementing the efficient BitVector data structure, follow these steps:

Review the existing implementation: Review the existing Bit Vector implementation in the dot/parachain/types package.
Understand the requirements: Understand the requirements for the new implementation, including the need to use []byte as the underlying storage of bits.
Implement the new data structure: Implement the new BitVector data structure using []byte as the underlying storage of bits.
Implement bit manipulation operations: Implement the bit manipulation operations, including getting and setting individual bits, push operations, and length calculations.
Implement SCALE codec encoding and decoding: Implement SCALE codec encoding and decoding.
Optimize memory allocation strategy: Optimize memory allocation strategy using a dynamic array and a buffer.
Test the new implementation: Test the new implementation to ensure that it meets the acceptance criteria.

By following these steps and implementing the efficient BitVector data structure, you can improve the memory usage and scalability of the Substrate framework.