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UTF-8 Validator for Lua

This is an example of the "branchy" algorithm in Lua as described in Daniel Lemire's paper on Validating UTF-8 In Less Than One Instruction Per Byte.

I needed a fast UTF-8 validator that portably works in all versions of Lua. Since I don't have access to SIMD instructions using plain Lua, the "branchy" algorithm described in the paper was used.

The standard Lua (and Teal) versions in the repo will work in Lua 5.1-5.4 and LuaJIT 2.0/2.1. There are some notes below regarding potential optimizations for Lua 5.2+

Notes

This code will mark the UTF-16 surrogates (U+D800 through U+DFFF) as invalid. If you are using Lua 5.3+'s utf8.len for validation, it will mark these as valid.

Potential Optimizations

Examples of both optimizations are commented in the utf8validator.lua file.

find in the right spot

After nil/range checking the second/third/fourth bytes, a find() pattern match can offload some processing to C for all the ASCII characters in regular Lua. This drastically improves the speed of validation and still passes all the tests (tests run in 52% of the original time)

_, i=input:find(".*", i)
i=i+1

Note: This slows down LuaJIT (tests run in 160% of the time without it)

Adding goto for a small speedup

A simple speedup in Lua 5.2+ is just adding labels to the nil checks on the bytes after the branches. The tests run in 88% of the original time.

::fourth::iffourth==nilorfourth<128orfourth>191thenreturnfalse, code_pointsend::third::ifthird==nilorthird<128orthird>191thenreturnfalse, code_pointsend::second::ifsecond==nilorsecond<128orsecond>191thenreturnfalse, code_pointsend::none::

and then adding the goto in the respective byte checks:

ifbyte<=127theni=i+1gotononeelseifbyte>=194andbyte<=223thensecond=sbyte(input, i+1)
i=i+2gotosecond-- you can see all the goto's commented in utf8validator.lua/tl

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A fast Lua UTF-8 validation function

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luatealutf-8

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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

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UTF-8 Validator for Lua
This is an example of the "branchy" algorithm in Lua as described in Daniel Lemire's paper on Validating UTF-8 In Less Than One Instruction Per Byte.
I needed a fast UTF-8 validator that portably works in all versions of Lua. Since I don't have access to SIMD instructions using plain Lua, the "branchy" algorithm described in the paper was used.
The standard Lua (and Teal) versions in the repo will work in Lua 5.1-5.4 and LuaJIT 2.0/2.1. There are some notes below regarding potential optimizations for Lua 5.2+
Notes
This code will mark the UTF-16 surrogates (U+D800 through U+DFFF) as invalid. If you are using Lua 5.3+'s utf8.len for validation, it will mark these as valid.
Potential Optimizations
Examples of both optimizations are commented in the utf8validator.lua file.
find in the right spot
After nil/range checking the second/third/fourth bytes, a find() pattern match can offload some processing to C for all the ASCII characters in regular Lua. This drastically improves the speed of validation and still passes all the tests (tests run in 52% of the original time)
_, i=input:find(".*", i)
i=i+1
Note: This slows down LuaJIT (tests run in 160% of the time without it)
Adding goto for a small speedup
A simple speedup in Lua 5.2+ is just adding labels to the nil checks on the bytes after the branches. The tests run in 88% of the original time.
::fourth::iffourth==nilorfourth<128orfourth>191thenreturnfalse, code_pointsend::third::ifthird==nilorthird<128orthird>191thenreturnfalse, code_pointsend::second::ifsecond==nilorsecond<128orsecond>191thenreturnfalse, code_pointsend::none::
and then adding the goto in the respective byte checks:
ifbyte<=127theni=i+1gotononeelseifbyte>=194andbyte<=223thensecond=sbyte(input, i+1)
i=i+2gotosecond-- you can see all the goto's commented in utf8validator.lua/tl
Licenses
About
A fast Lua UTF-8 validation function
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luatealutf-8
Resources
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1 watching
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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UTF-8 Validator for Lua
This is an example of the "branchy" algorithm in Lua as described in Daniel Lemire's paper on Validating UTF-8 In Less Than One Instruction Per Byte.
I needed a fast UTF-8 validator that portably works in all versions of Lua. Since I don't have access to SIMD instructions using plain Lua, the "branchy" algorithm described in the paper was used.
The standard Lua (and Teal) versions in the repo will work in Lua 5.1-5.4 and LuaJIT 2.0/2.1. There are some notes below regarding potential optimizations for Lua 5.2+
Notes
This code will mark the UTF-16 surrogates (U+D800 through U+DFFF) as invalid. If you are using Lua 5.3+'s utf8.len for validation, it will mark these as valid.
Potential Optimizations
Examples of both optimizations are commented in the utf8validator.lua file.
find in the right spot
After nil/range checking the second/third/fourth bytes, a find() pattern match can offload some processing to C for all the ASCII characters in regular Lua. This drastically improves the speed of validation and still passes all the tests (tests run in 52% of the original time)
_, i=input:find(".*", i)
i=i+1
Note: This slows down LuaJIT (tests run in 160% of the time without it)
Adding goto for a small speedup
A simple speedup in Lua 5.2+ is just adding labels to the nil checks on the bytes after the branches. The tests run in 88% of the original time.
::fourth::iffourth==nilorfourth<128orfourth>191thenreturnfalse, code_pointsend::third::ifthird==nilorthird<128orthird>191thenreturnfalse, code_pointsend::second::ifsecond==nilorsecond<128orsecond>191thenreturnfalse, code_pointsend::none::
and then adding the goto in the respective byte checks:
ifbyte<=127theni=i+1gotononeelseifbyte>=194andbyte<=223thensecond=sbyte(input, i+1)
i=i+2gotosecond-- you can see all the goto's commented in utf8validator.lua/tl
Licenses
About
A fast Lua UTF-8 validation function
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luatealutf-8
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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UTF-8 Validator for Lua
This is an example of the "branchy" algorithm in Lua as described in Daniel Lemire's paper on Validating UTF-8 In Less Than One Instruction Per Byte.
I needed a fast UTF-8 validator that portably works in all versions of Lua. Since I don't have access to SIMD instructions using plain Lua, the "branchy" algorithm described in the paper was used.
The standard Lua (and Teal) versions in the repo will work in Lua 5.1-5.4 and LuaJIT 2.0/2.1. There are some notes below regarding potential optimizations for Lua 5.2+
Notes
This code will mark the UTF-16 surrogates (U+D800 through U+DFFF) as invalid. If you are using Lua 5.3+'s utf8.len for validation, it will mark these as valid.
Potential Optimizations
Examples of both optimizations are commented in the utf8validator.lua file.
find in the right spot
After nil/range checking the second/third/fourth bytes, a find() pattern match can offload some processing to C for all the ASCII characters in regular Lua. This drastically improves the speed of validation and still passes all the tests (tests run in 52% of the original time)
_, i=input:find(".*", i)
i=i+1
Note: This slows down LuaJIT (tests run in 160% of the time without it)
Adding goto for a small speedup
A simple speedup in Lua 5.2+ is just adding labels to the nil checks on the bytes after the branches. The tests run in 88% of the original time.
::fourth::iffourth==nilorfourth<128orfourth>191thenreturnfalse, code_pointsend::third::ifthird==nilorthird<128orthird>191thenreturnfalse, code_pointsend::second::ifsecond==nilorsecond<128orsecond>191thenreturnfalse, code_pointsend::none::
and then adding the goto in the respective byte checks:
ifbyte<=127theni=i+1gotononeelseifbyte>=194andbyte<=223thensecond=sbyte(input, i+1)
i=i+2gotosecond-- you can see all the goto's commented in utf8validator.lua/tl
Licenses
About
A fast Lua UTF-8 validation function
Topics
luatealutf-8
Resources
Readme
Activity
Stars
0 stars
Watchers
1 watching
Forks
0 forks
Report repository
Contributors
Languages

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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UTF-8 Validator for Lua
This is an example of the "branchy" algorithm in Lua as described in Daniel Lemire's paper on Validating UTF-8 In Less Than One Instruction Per Byte.
I needed a fast UTF-8 validator that portably works in all versions of Lua. Since I don't have access to SIMD instructions using plain Lua, the "branchy" algorithm described in the paper was used.
The standard Lua (and Teal) versions in the repo will work in Lua 5.1-5.4 and LuaJIT 2.0/2.1. There are some notes below regarding potential optimizations for Lua 5.2+
Notes
This code will mark the UTF-16 surrogates (U+D800 through U+DFFF) as invalid. If you are using Lua 5.3+'s utf8.len for validation, it will mark these as valid.
Potential Optimizations
Examples of both optimizations are commented in the utf8validator.lua file.
find in the right spot
After nil/range checking the second/third/fourth bytes, a find() pattern match can offload some processing to C for all the ASCII characters in regular Lua. This drastically improves the speed of validation and still passes all the tests (tests run in 52% of the original time)
_, i=input:find(".*", i)
i=i+1
Note: This slows down LuaJIT (tests run in 160% of the time without it)
Adding goto for a small speedup
A simple speedup in Lua 5.2+ is just adding labels to the nil checks on the bytes after the branches. The tests run in 88% of the original time.
::fourth::iffourth==nilorfourth<128orfourth>191thenreturnfalse, code_pointsend::third::ifthird==nilorthird<128orthird>191thenreturnfalse, code_pointsend::second::ifsecond==nilorsecond<128orsecond>191thenreturnfalse, code_pointsend::none::
and then adding the goto in the respective byte checks:
ifbyte<=127theni=i+1gotononeelseifbyte>=194andbyte<=223thensecond=sbyte(input, i+1)
i=i+2gotosecond-- you can see all the goto's commented in utf8validator.lua/tl
Licenses
About
A fast Lua UTF-8 validation function
Topics
luatealutf-8
Resources
Readme
Activity
Stars
0 stars
Watchers
1 watching
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0 forks
Report repository
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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UTF-8 Validator for Lua
This is an example of the "branchy" algorithm in Lua as described in Daniel Lemire's paper on Validating UTF-8 In Less Than One Instruction Per Byte.
I needed a fast UTF-8 validator that portably works in all versions of Lua. Since I don't have access to SIMD instructions using plain Lua, the "branchy" algorithm described in the paper was used.
The standard Lua (and Teal) versions in the repo will work in Lua 5.1-5.4 and LuaJIT 2.0/2.1. There are some notes below regarding potential optimizations for Lua 5.2+
Notes
This code will mark the UTF-16 surrogates (U+D800 through U+DFFF) as invalid. If you are using Lua 5.3+'s utf8.len for validation, it will mark these as valid.
Potential Optimizations
Examples of both optimizations are commented in the utf8validator.lua file.
find in the right spot
After nil/range checking the second/third/fourth bytes, a find() pattern match can offload some processing to C for all the ASCII characters in regular Lua. This drastically improves the speed of validation and still passes all the tests (tests run in 52% of the original time)
_, i=input:find(".*", i)
i=i+1
Note: This slows down LuaJIT (tests run in 160% of the time without it)
Adding goto for a small speedup
A simple speedup in Lua 5.2+ is just adding labels to the nil checks on the bytes after the branches. The tests run in 88% of the original time.
::fourth::iffourth==nilorfourth<128orfourth>191thenreturnfalse, code_pointsend::third::ifthird==nilorthird<128orthird>191thenreturnfalse, code_pointsend::second::ifsecond==nilorsecond<128orsecond>191thenreturnfalse, code_pointsend::none::
and then adding the goto in the respective byte checks:
ifbyte<=127theni=i+1gotononeelseifbyte>=194andbyte<=223thensecond=sbyte(input, i+1)
i=i+2gotosecond-- you can see all the goto's commented in utf8validator.lua/tl
Licenses
About
A fast Lua UTF-8 validation function
Topics
luatealutf-8
Resources
Readme
Activity
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1 watching
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0 forks
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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UTF-8 Validator for Lua
This is an example of the "branchy" algorithm in Lua as described in Daniel Lemire's paper on Validating UTF-8 In Less Than One Instruction Per Byte.
I needed a fast UTF-8 validator that portably works in all versions of Lua. Since I don't have access to SIMD instructions using plain Lua, the "branchy" algorithm described in the paper was used.
The standard Lua (and Teal) versions in the repo will work in Lua 5.1-5.4 and LuaJIT 2.0/2.1. There are some notes below regarding potential optimizations for Lua 5.2+
Notes
This code will mark the UTF-16 surrogates (U+D800 through U+DFFF) as invalid. If you are using Lua 5.3+'s utf8.len for validation, it will mark these as valid.
Potential Optimizations
Examples of both optimizations are commented in the utf8validator.lua file.
find in the right spot
After nil/range checking the second/third/fourth bytes, a find() pattern match can offload some processing to C for all the ASCII characters in regular Lua. This drastically improves the speed of validation and still passes all the tests (tests run in 52% of the original time)
_, i=input:find(".*", i)
i=i+1
Note: This slows down LuaJIT (tests run in 160% of the time without it)
Adding goto for a small speedup
A simple speedup in Lua 5.2+ is just adding labels to the nil checks on the bytes after the branches. The tests run in 88% of the original time.
::fourth::iffourth==nilorfourth<128orfourth>191thenreturnfalse, code_pointsend::third::ifthird==nilorthird<128orthird>191thenreturnfalse, code_pointsend::second::ifsecond==nilorsecond<128orsecond>191thenreturnfalse, code_pointsend::none::
and then adding the goto in the respective byte checks:
ifbyte<=127theni=i+1gotononeelseifbyte>=194andbyte<=223thensecond=sbyte(input, i+1)
i=i+2gotosecond-- you can see all the goto's commented in utf8validator.lua/tl
Licenses
About
A fast Lua UTF-8 validation function
Topics
luatealutf-8
Resources
Readme
Activity
Stars
0 stars
Watchers
1 watching
Forks
0 forks
Report repository
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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UTF-8 Validator for Lua
This is an example of the "branchy" algorithm in Lua as described in Daniel Lemire's paper on Validating UTF-8 In Less Than One Instruction Per Byte.
I needed a fast UTF-8 validator that portably works in all versions of Lua. Since I don't have access to SIMD instructions using plain Lua, the "branchy" algorithm described in the paper was used.
The standard Lua (and Teal) versions in the repo will work in Lua 5.1-5.4 and LuaJIT 2.0/2.1. There are some notes below regarding potential optimizations for Lua 5.2+
Notes
This code will mark the UTF-16 surrogates (U+D800 through U+DFFF) as invalid. If you are using Lua 5.3+'s utf8.len for validation, it will mark these as valid.
Potential Optimizations
Examples of both optimizations are commented in the utf8validator.lua file.
find in the right spot
After nil/range checking the second/third/fourth bytes, a find() pattern match can offload some processing to C for all the ASCII characters in regular Lua. This drastically improves the speed of validation and still passes all the tests (tests run in 52% of the original time)
_, i=input:find(".*", i)
i=i+1
Note: This slows down LuaJIT (tests run in 160% of the time without it)
Adding goto for a small speedup
A simple speedup in Lua 5.2+ is just adding labels to the nil checks on the bytes after the branches. The tests run in 88% of the original time.
::fourth::iffourth==nilorfourth<128orfourth>191thenreturnfalse, code_pointsend::third::ifthird==nilorthird<128orthird>191thenreturnfalse, code_pointsend::second::ifsecond==nilorsecond<128orsecond>191thenreturnfalse, code_pointsend::none::
and then adding the goto in the respective byte checks:
ifbyte<=127theni=i+1gotononeelseifbyte>=194andbyte<=223thensecond=sbyte(input, i+1)
i=i+2gotosecond-- you can see all the goto's commented in utf8validator.lua/tl
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A fast Lua UTF-8 validation function
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