Allow UTF-16 surrogate pairs in Base64 decoded strings

[dchristensen]

Pull request type

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• Bugfix
• New feature or enhancement
• UI change (please include screenshot!)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no api changes)
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What is the current behavior?

Base64 decoding fails with <Invalid Base64> when UTF-16 surrogate pairs are encountered. Surrogate pairs allow the Unicode encoding to encode characters with codepoints greater than 0xFFFF in UTF-16. In the linked issue the the example document includes the key emoji (🗝️) which is represented in UTF-16 as \ud83d\udddd.

Issue Number: DevToys-app/DevToys#1461

What is the new behavior?

• Expand the allowed character ranges to include the UTF-16 surrogate pair ranges
  • U+D800—U+DBFF (high surrogates)
  • U+DC00—U+DFFF (low surrogates)
• Removed an invalid range check. Previously the code was attempting to check for codepoints greater than 0xFFFF, but used a 32-bit integer value.

Other information

Unicode documentation for UTF-16 surrogate pairs

Quality check

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