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'use strict'
const {
wellknownHeaderNames,
headerNameLowerCasedRecord
} = require('./constants')
class TstNode {
/** @type {any} */
value = null
/** @type {null | TstNode} */
left = null
/** @type {null | TstNode} */
middle = null
/** @type {null | TstNode} */
right = null
/** @type {number} */
code
/**
* @param {string} key
* @param {any} value
* @param {number} index
*/
constructor (key, value, index) {
if (index === undefined || index >= key.length) {
throw new TypeError('Unreachable')
}
const code = this.code = key.charCodeAt(index)
// check code is ascii string
if (code > 0x7F) {
throw new TypeError('key must be ascii string')
}
if (key.length !== ++index) {
this.middle = new TstNode(key, value, index)
} else {
this.value = value
}
}
/**
* @param {string} key
* @param {any} value
* @returns {void}
*/
add (key, value) {
const length = key.length
if (length === 0) {
throw new TypeError('Unreachable')
}
let index = 0
/**
* @type {TstNode}
*/
let node = this
while (true) {
const code = key.charCodeAt(index)
// check code is ascii string
if (code > 0x7F) {
throw new TypeError('key must be ascii string')
}
if (node.code === code) {
if (length === ++index) {
node.value = value
break
} else if (node.middle !== null) {
node = node.middle
} else {
node.middle = new TstNode(key, value, index)
break
}
} else if (node.code < code) {
if (node.left !== null) {
node = node.left
} else {
node.left = new TstNode(key, value, index)
break
}
} else if (node.right !== null) {
node = node.right
} else {
node.right = new TstNode(key, value, index)
break
}
}
}
/**
* @param {Uint8Array} key
* @returns {TstNode | null}
*/
search (key) {
const keylength = key.length
let index = 0
/**
* @type {TstNode|null}
*/
let node = this
while (node !== null && index < keylength) {
let code = key[index]
// A-Z
// First check if it is bigger than 0x5a.
// Lowercase letters have higher char codes than uppercase ones.
// Also we assume that headers will mostly contain lowercase characters.
if (code <= 0x5a && code >= 0x41) {
// Lowercase for uppercase.
code |= 32
}
while (node !== null) {
if (code === node.code) {
if (keylength === ++index) {
// Returns Node since it is the last key.
return node
}
node = node.middle
break
}
node = node.code < code ? node.left : node.right
}
}
return null
}
}
class TernarySearchTree {
/** @type {TstNode | null} */
node = null
/**
* @param {string} key
* @param {any} value
* @returns {void}
* */
insert (key, value) {
if (this.node === null) {
this.node = new TstNode(key, value, 0)
} else {
this.node.add(key, value)
}
}
/**
* @param {Uint8Array} key
* @returns {any}
*/
lookup (key) {
return this.node?.search(key)?.value ?? null
}
}
const tree = new TernarySearchTree()
for (let i = 0; i < wellknownHeaderNames.length; ++i) {
const key = headerNameLowerCasedRecord[wellknownHeaderNames[i]]
tree.insert(key, key)
}
module.exports = {
TernarySearchTree,
tree
}
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