mirror of
https://github.com/harivansh-afk/url-shortner.git
synced 2026-04-15 08:03:46 +00:00
52 lines
1.3 KiB
Python
52 lines
1.3 KiB
Python
"""
|
|
Base62 encoding for short URL generation.
|
|
|
|
- Uses 0-9, A-Z, a-z (62 characters)
|
|
- URL-safe (no special characters)
|
|
- More compact than hex (base16) or base64
|
|
|
|
Length vs Capacity:
|
|
- 6 chars: 62^6 = 56.8 billion unique URLs
|
|
- 7 chars: 62^7 = 3.5 trillion unique URLs
|
|
"""
|
|
|
|
CHARSET = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"
|
|
BASE = len(CHARSET) # 62
|
|
|
|
|
|
def base62_encode(num: int) -> str:
|
|
"""
|
|
Encode an integer to a base62 string.
|
|
"""
|
|
if num < 0:
|
|
raise ValueError("Cannot encode negative numbers")
|
|
if num == 0:
|
|
return CHARSET[0]
|
|
|
|
result = []
|
|
while num:
|
|
result.append(CHARSET[num % BASE])
|
|
num //= BASE
|
|
|
|
return "".join(reversed(result))
|
|
|
|
|
|
def base62_decode(encoded: str) -> int:
|
|
"""
|
|
Decode a base62 string back to an integer.
|
|
"""
|
|
if not encoded:
|
|
raise ValueError("Cannot decode empty string")
|
|
|
|
num = 0
|
|
for char in encoded:
|
|
if char not in CHARSET:
|
|
raise ValueError(f"Invalid character: {char}")
|
|
num = num * BASE + CHARSET.index(char)
|
|
|
|
return num
|
|
|
|
|
|
def pad_to_length(encoded: str, length: int = 7) -> str:
|
|
"""Pad encoded string to minimum length with leading zeros."""
|
|
return encoded.zfill(length)[-length:] if len(encoded) < length else encoded
|