feat: base64

[peter-jerry-ye]

No description provided.

[peter-jerry-ye-code-review]

Potential buffer overflow in base64_decode function

Category
Correctness
Code Snippet
let output = FixedArray::make(input.length() * 3 / 4, b'\x00')
let len = decoder.decode_to(input, output, url_safe~)
Recommendation
Add bounds checking or use a more precise size calculation. The current formula input.length() * 3 / 4 may be insufficient when input contains padding characters or whitespace, potentially causing buffer overflow in decode_to.
Reasoning
Base64 encoded strings can have padding characters ('=') that don't contribute to output bytes, and the current size calculation doesn't account for this. A safer approach would be to calculate the exact output size or add bounds checking in decode_to.

Magic numbers and bit manipulation patterns should be documented

Category
Maintainability
Code Snippet
self.buffer = (byte & 0b11) << 4
self.buffer = (byte & 0b1111) << 2
self.buffer = (idx & 0b11) << 6
Recommendation
Add inline comments explaining the bit manipulation logic and consider extracting magic numbers as named constants like let MASK_2_BITS = 0b11 and let MASK_4_BITS = 0b1111.
Reasoning
The bit manipulation logic is complex and crucial for correctness. Clear documentation and named constants would improve code readability and maintainability, making it easier for future developers to understand and modify the encoding/decoding logic.

Redundant modulo operation in decode loop

Category
Performance
Code Snippet
for ch in input {
match self.i % 4 {
0 => { ... self.i = 1 }
1 => { ... self.i = 2 }
2 => { ... self.i = 3 }
3 => { ... self.i = 0 }
}
Recommendation
Since self.i is manually managed and cycles through 0-3, replace self.i % 4 with direct self.i matching and ensure self.i wraps around properly: self.i = (self.i + 1) % 4 or use explicit reset to 0.
Reasoning
The modulo operation is unnecessary since self.i is already constrained to 0-3 range by the code logic. Removing this redundant operation will improve performance in the decode loop, which processes each character of the input.

[tonyfettes]

Make base64 as a separate package.