Boolset Encoding and Decoding

Boolset is an encoding method used to represent a set of boolean values. It converts a set of boolean values into a string for easy storage and transmission. In Cloudreve's API, Boolset is typically used for permission settings, such as user group permissions and file permissions.

Internal Representation

The BooleanSet type is essentially a byte slice ([]byte). In this slice, each bit represents a boolean value (permission switch).

• The 0th flag bit corresponds to the 0th bit of the 0th byte in the byte slice.
• The 1st flag bit corresponds to the 1st bit of the 0th byte in the byte slice.
• ...
• The 7th flag bit corresponds to the 7th bit of the 0th byte in the byte slice.
• The 8th flag bit corresponds to the 0th bit of the 1st byte in the byte slice.
• And so on...

A bit value of 1 indicates the corresponding flag is true (enabled), while 0 indicates false (disabled).

Encoding Process

1. Determine Maximum Index: Find the maximum index max_n among all flags to be represented.
2. Calculate Byte Count: Determine the number of bytes required. At least floor(max_n / 8) + 1 bytes are needed to accommodate all flags.
3. Initialize Byte Sequence: Create a byte sequence with the required number of bytes, initializing all bytes to 0.
4. Set Flags: For each flag n that needs to be set to true:
   • Locate the byte_index = floor(n / 8)th byte in the byte sequence.
   • Calculate the bit index within that byte: bit_index = n % 8.
   • Set the bit_indexth bit of that byte to 1. This is typically done using a Bitwise OR operation: byte[byte_index] = byte[byte_index] | (1 << bit_index).
5. Base64 Encode: Encode the final byte sequence into a Base64 string.

Decoding Process

1. Base64 Decode: First, decode the Base64 string back into the original byte sequence.
2. Check Flag: To check the status (true or false) of a specific flag n:
   • Calculate the byte index: byte_index = floor(n / 8).
   • Boundary Check: Check if byte_index is within the valid range of the byte sequence. If it's out of range, the flag is implicitly false (because it was never set).
   • If byte_index is valid, locate the byte_indexth byte in the sequence.
   • Calculate the bit index: bit_index = n % 8.
   • Check the value of the bit_indexth bit of that byte. This is typically done using a Bitwise AND operation: is_set = (byte[byte_index] & (1 << bit_index)) != 0.
   • If the result is non-zero, flag n is true; otherwise, it is false.

Programming Language Implementation

Golang

boolset.go

// Load from string
bs, err := boolset.FromString("/f8B")
if err != nil {
	return nil, err
}

// Read the 5th flag bit
fmt.Println(bs.Enabled(5))

// Set the 1st flag bit
boolset.Set(1, true, bs)

// Save to string
encoded, err := bs.String()
if err != nil {
	return nil, err
}

TypeScript

boolset.ts

// Load from string
const bs = new Boolset("/f8B");

// Read the 5th flag bit
console.log(bs.enabled(5));

// Set the 1st flag bit
bs.set(1, true);

// Save to string
const encoded = bs.toString();

Flag Definition

User Group Permissions

Flag Bit	Description
0	Is administrator
1	Is anonymous user group
2	Can share files
3	Can access WebDAV
4	Can perform server-side batch download
5	Can execute archive compression tasks
6	Can enable WebDAV proxy
7	Can download shares from others
8	Can download shares for free
9	Can perform remote downloads
10	Can relocate storage policy
11	Use redirect direct link
12	Can use advanced delete options
13	Can select specific node to process tasks
14	Can set higher share permissions for anonymous users

File Permissions

Flag Bit	Description
0	Read
1	Update
2	Create
3	Delete

Node Functions

Flag Bit	Description
0	Reserved, do not use
1	Create compressed file
2	Decompress file
3	Remote download
4	Transfer storage policy