Fix parse_hex algorithm

[compmaniak]

Current parse_hex implementation doesn't work at the extreme case when input is "fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff...". The function consumes all of such chars but returns maximum value for the specified type. This happens because of bounds checking via integer overflow.

[codecov]

Codecov Report

Merging #1267 into develop will decrease coverage by <.01%.
The diff coverage is 90%.

@@             Coverage Diff             @@
##           develop    #1267      +/-   ##
===========================================
- Coverage    95.43%   95.43%   -0.01%     
===========================================
  Files          112      112              
  Lines        11072    11074       +2     
===========================================
+ Hits         10567    10568       +1     
- Misses         505      506       +1

Impacted Files	Coverage Δ
include/boost/beast/http/detail/basic_parser.hpp	89.88% <90%> (-0.23%)	⬇️

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[vinniefalco]

Good find! I will add a test to confirm. Can you please give me more details? What is the exact string, is it "fffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffffff"? How many f are in there? And what is the "specified type" you are using?

[vinniefalco]

I understand the problem now. Good work