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util: create hex style cache and fast path #62999

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3c455e0
util: create hex style cache and fast path
araujogui Apr 28, 2026
10facb7
util: skip getHexStyle() when colorization is disabled
araujogui Apr 28, 2026
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67 changes: 46 additions & 21 deletions lib/util.js
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Original file line number Diff line number Diff line change
Expand Up @@ -114,7 +114,11 @@ const kEscapeEnd = 'm';
const kDimCode = 2;
const kBoldCode = 1;

// Close sequence for 24-bit foreground colors (reset to default foreground)
const kHexCloseSeq = kEscape + '39' + kEscapeEnd;

let styleCache;
const hexStyleCache = { __proto__: null };
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@Renegade334 Renegade334 Apr 29, 2026 •
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I note the benchmarks are all repeating the same lookup – I imagine that using a plain object as the map here could end up deoptimising if the cache miss rate is high, eg. colours being randomised by the user? Appreciate this is probably quite niche in reality, but might be worth a benchmark case to see how something like a SafeMap would compare.


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@ljharb ljharb Apr 28, 2026

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isn't the maximum possible permutations here 16,781,312 - is the memory size of 17 million key/value pairs a massive concern?

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@araujogui araujogui Apr 28, 2026

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Great point, altought a LRU doesn't seem a bad idea

function getStyleCache() {
if (styleCache === undefined) {
Expand All @@ -137,6 +141,25 @@ function getStyleCache() {
return styleCache;
}

/**
* Returns the cached ANSI escape sequences for a hex color.
* Computes and caches on first use to avoid repeated Buffer allocations.
* @param {string} hex A valid hex color string (#RGB or #RRGGBB)
* @returns {{openSeq: string, closeSeq: string}}
*/
function getHexStyle(hex) {
const cached = hexStyleCache[hex];
if (cached !== undefined) return cached;
const { 0: r, 1: g, 2: b } = hexToRgb(hex);
const style = {
__proto__: null,
openSeq: kEscape + rgbToAnsi24Bit(r, g, b) + kEscapeEnd,
closeSeq: kHexCloseSeq,
};
hexStyleCache[hex] = style;
return style;
}

function replaceCloseCode(str, closeSeq, openSeq, keepClose) {
const closeLen = closeSeq.length;
let index = str.indexOf(closeSeq);
Expand All @@ -163,15 +186,6 @@ function replaceCloseCode(str, closeSeq, openSeq, keepClose) {
// Matches #RGB or #RRGGBB
const hexColorRegExp = /^#(?:[0-9a-fA-F]{3}|[0-9a-fA-F]{6})$/;

/**
* Validates whether a string is a valid hex color code.
* @param {string} hex The hex string to validate (e.g., '#fff' or '#ffffff')
* @returns {boolean} True if valid hex color, false otherwise
*/
function isValidHexColor(hex) {
return typeof hex === 'string' && RegExpPrototypeExec(hexColorRegExp, hex) !== null;
}

/**
* Parses a hex color string into RGB components.
* Supports both 3-digit (#RGB) and 6-digit (#RRGGBB) formats.
Expand Down Expand Up @@ -225,6 +239,17 @@ function styleText(format, text, options) {
const processed = replaceCloseCode(text, style.closeSeq, style.openSeq, style.keepClose);
return style.openSeq + processed + style.closeSeq;
}

if (format[0] === '#') {
let hexStyle = hexStyleCache[format];
if (hexStyle === undefined && RegExpPrototypeExec(hexColorRegExp, format) !== null) {
hexStyle = getHexStyle(format);
}
if (hexStyle !== undefined) {
const processed = replaceCloseCode(text, hexStyle.closeSeq, hexStyle.openSeq, false);
return hexStyle.openSeq + processed + hexStyle.closeSeq;
}
}
}

validateString(text, 'text');
Expand Down Expand Up @@ -255,24 +280,24 @@ function styleText(format, text, options) {
for (const key of formatArray) {
if (key === 'none') continue;

if (isValidHexColor(key)) {
if (typeof key === 'string' && key[0] === '#') {
let hexStyle = hexStyleCache[key];
if (hexStyle === undefined) {
if (RegExpPrototypeExec(hexColorRegExp, key) === null) {
throw new ERR_INVALID_ARG_VALUE('format', key,
'must be a valid hex color (#RGB or #RRGGBB)');
}
hexStyle = getHexStyle(key);
}
if (skipColorize) continue;
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const { 0: r, 1: g, 2: b } = hexToRgb(key);
const openSeq = kEscape + rgbToAnsi24Bit(r, g, b) + kEscapeEnd;
const closeSeq = kEscape + '39' + kEscapeEnd;
openCodes += openSeq;
closeCodes = closeSeq + closeCodes;
processedText = replaceCloseCode(processedText, closeSeq, openSeq, false);
openCodes += hexStyle.openSeq;
closeCodes = hexStyle.closeSeq + closeCodes;
processedText = replaceCloseCode(processedText, hexStyle.closeSeq, hexStyle.openSeq, false);
continue;
}

const style = cache[key];
if (style === undefined) {
// Check if it looks like an invalid hex color (starts with #)
if (typeof key === 'string' && key[0] === '#') {
throw new ERR_INVALID_ARG_VALUE('format', key,
'must be a valid hex color (#RGB or #RRGGBB)');
}
validateOneOf(key, 'format', ObjectGetOwnPropertyNames(inspect.colors));
}
openCodes += style.openSeq;
Expand Down
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