Multiple Huffman code tables

HPACK/QPACK uses only one static table of Huffman coding, but the
compression ratio can be improved by combining multiple tables. There is *no
overhead* in data size due to the combination. Theoretically, two code
tables can reduce the bit length of one code table by an average of one
bit, since the two code tables itself has one bit of information. *This
proposal especially reduces the token size increasing in recent years.* Let
me know the link to the conclusions if this approach has been considered.
The following is a comparison based on my proof of concept code. The
leftmost number is the reduced bit size.

'XPACK   comp. ratio request', 0.2533415841584158, 1.3393005138405436
'HPACK   comp. ratio request', 0.2471534653465347, 1.3282919612033537
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0, 'gzip, deflate, br'
0, 'accept-language'
0, 'ja,en-US;q=0.9,en;q=0.8'
0, 'cache-control'
0, 'max-age=0'
0, 'dnt'
0, '1'
0, 'sec-ch-ua'
-1, '"Google Chrome";v="117", "Not;A=Brand";v="8", "Chromium";v="117"'
0, 'sec-ch-ua-arch'
0, '"x86"'
0, 'sec-ch-ua-bitness'
0, '"64"'
0, 'sec-ch-ua-full-version'
0, '"117.0.5938.89"'
0, 'sec-ch-ua-full-version-list'
-1, '"Google Chrome";v="117.0.5938.89", "Not;A=Brand";v="8.0.0.0",
"Chromium";v="117.0.5938.89"'
0, 'sec-ch-ua-mobile'
0, '?0'
0, 'sec-ch-ua-model'
0, '""'
0, 'sec-ch-ua-platform'
0, '"Windows"'
0, 'sec-ch-ua-platform-version'
0, '"10.0.0"'
0, 'sec-ch-ua-wow64'
0, '?0'
0, 'sec-fetch-dest'
0, 'document'
0, 'sec-fetch-mode'
0, 'navigate'
0, 'sec-fetch-site'
0, 'same-origin'
0, 'sec-fetch-user'
0, '?1'
0, 'sec-gpc'
0, '1'
0, 'upgrade-insecure-requests'
0, '1'
0, 'user-agent'
-3, 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36
(KHTML, like Gecko) Chrome/117.0.0.0 Safari/537.36'
0, 'x-client-data'
-45, 'CKa1yQEIj7bJAQiltskBCKmdygEI5tTKAQieicsBCJahywEIhaDNAQjwsc0BCNy9zQEI38TNAQi1xc0BCLnKzQEI1dDNAQiR0s0BCIrTzQEIwtTNAQjJ1s0BCPnA1BUYwcvMARi4v80B'

'XPACK   comp. ratio response', 0.25389886578449905, 1.340300870942201
'HPACK   comp. ratio response', 0.24155245746691867, 1.3184827478775605
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-2, 'Sec-CH-UA-Arch'
0, 'accept-ch'
-2, 'Sec-CH-UA-Bitness'
0, 'accept-ch'
-2, 'Sec-CH-UA-Full-Version'
0, 'accept-ch'
-2, 'Sec-CH-UA-Full-Version-List'
0, 'accept-ch'
-2, 'Sec-CH-UA-Model'
0, 'accept-ch'
-2, 'Sec-CH-UA-Platform'
0, 'accept-ch'
-2, 'Sec-CH-UA-Platform-Version'
0, 'accept-ch'
-1, 'Sec-CH-UA-WoW64'
0, 'alt-svc'
0, 'h3=":443"; ma=2592000,h3-29=":443"; ma=2592000'
0, 'cache-control'
0, 'private, max-age=0'
0, 'content-encoding'
0, 'br'
0, 'content-length'
0, '54188'
0, 'content-security-policy-report-only'
-2, 'object-src 'none';base-uri 'self';script-src
'nonce-OqX2tRcsQ42YI77KwfGMfg' 'strict-dynamic' 'report-sample'
'unsafe-eval' 'unsafe-inline' https'
0, 'http:;report-uri https://csp.withgoogle.com/csp/gws/other-hp'
0, 'content-type'
-1, 'text/html; charset=UTF-8'
0, 'cross-origin-opener-policy'
0, 'same-origin-allow-popups; report-to="gws"'
0, 'date'
-2, 'Wed, 22 Nov 2023 18:46:19 GMT'
0, 'expires'
0, '-1'
0, 'origin-trial'
-50, 'Ap+qNlnLzJDKSmEHjzM5ilaa908GuehlLqGb6ezME5lkhelj20qVzfv06zPmQ3LodoeujZuphAolrnhnPA8w4AIAAABfeyJvcmlnaW4iOiJodHRwczovL3d3dy5nb29nbGUuY29tOjQ0MyIsImZlYXR1cmUiOiJQZXJtaXNzaW9uc1BvbGljeVVubG9hZCIsImV4cGlyeSI6MTY4NTY2Mzk5OX0='
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-83, 'AvudrjMZqL7335p1KLV2lHo1kxdMeIN0dUI15d0CPz9dovVLCcXk8OAqjho1DX4s6NbHbA/AGobuGvcZv0drGgQAAAB9eyJvcmlnaW4iOiJodHRwczovL3d3dy5nb29nbGUuY29tOjQ0MyIsImZlYXR1cmUiOiJCYWNrRm9yd2FyZENhY2hlTm90UmVzdG9yZWRSZWFzb25zIiwiZXhwaXJ5IjoxNjkxNTM5MTk5LCJpc1N1YmRvbWFpbiI6dHJ1ZX0='
0, 'p3p'
-2, 'CP="This is not a P3P policy! See g.co/p3phelp for more info."'
0, 'permissions-policy'
0, 'unload=()'
0, 'report-to'
0, '{"group":"gws","max_age":2592000,"endpoints":[{"url":"https://csp.withgoogle.com/csp/report-to/gws/other"}]}'
0, 'server'
0, 'gws'
0, 'set-cookie'
0, '1P_JAR=2023-11-22-18; expires=Fri, 22-Dec-2023 18:46:19 GMT;
path=/; domain=.google.com; Secure; SameSite=none'
0, 'set-cookie'
-23, 'AEC=Ackid1QH6gVXB6Rn68KWRmRtOGSW1unAfUHYsxuZh3Zs8cyWCZdKy8vrhQ;
expires=Mon, 20-May-2024 18:46:19 GMT; path=/; domain=.google.com;
Secure; HttpOnly; SameSite=lax'
0, 'set-cookie'
-19, 'NID=511=fx_DiN-XffVTX7QHZe7UgP5GQd0mx2HY9B0Hz6MgzEpOESnD8DldcSLyj-U6AHIo8t4-dcOKelciAyOK2j03GJE1r_31zKvXnECnKWvOQiFPO6mtTTaCZWqtn2x8m5lnzbB_CyUA-HzXz-Vw3TXC0eeW_AQlcu8CybBgyxtW5Kc;
expires=Thu, 23-May-2024 18:46:19 GMT; path=/; domain=.google.com;
Secure; HttpOnly; SameSite=none'
0, 'strict-transport-security'
0, 'max-age=31536000'
0, 'x-frame-options'
-12, 'SAMEORIGIN'
0, 'x-xss-protection'
0, '0'

https://github.com/falsandtru/spica/blob/master/src/ascii.xpack.ts