Add 100MB limit to parsed characters cache

src/util.js

@@ -670,3 +670,182 @@ export function isValidUrl(url) {
         return false;
     }
 }
+
+/**
+ * LimitedMap class that limits the memory usage of string values.
+ */
+export class LimitedMap {
+    /**
+     * Creates an instance of LimitedMap.
+     * @param {number} maxMemoryInBytes - The maximum allowed memory in bytes for string values.
+     */
+    constructor(maxMemoryInBytes) {
+        if (typeof maxMemoryInBytes !== 'number' || maxMemoryInBytes <= 0) {
+            throw new Error('maxMemoryInBytes must be a positive number');
+        }
+        this.maxMemory = maxMemoryInBytes;
+        this.currentMemory = 0;
+        this.map = new Map();
+        this.queue = [];
+    }
+
+    /**
+     * Estimates the memory usage of a string in bytes.
+     * Assumes each character occupies 2 bytes (UTF-16).
+     * @param {string} str
+     * @returns {number}
+     */
+    static estimateStringSize(str) {
+        return str.length * 2;
+    }
+
+    /**
+     * Adds or updates a key-value pair in the map.
+     * If adding the new value exceeds the memory limit, evicts oldest entries.
+     * @param {string} key
+     * @param {string} value
+     */
+    set(key, value) {
+        if (typeof key !== 'string' || typeof value !== 'string') {
+            return;
+        }
+
+        const newValueSize = LimitedMap.estimateStringSize(value);
+
+        // If the new value itself exceeds the max memory, reject it
+        if (newValueSize > this.maxMemory) {
+            return;
+        }
+
+        // Check if the key already exists to adjust memory accordingly
+        if (this.map.has(key)) {
+            const oldValue = this.map.get(key);
+            const oldValueSize = LimitedMap.estimateStringSize(oldValue);
+            this.currentMemory -= oldValueSize;
+            // Remove the key from its current position in the queue
+            const index = this.queue.indexOf(key);
+            if (index > -1) {
+                this.queue.splice(index, 1);
+            }
+        }
+
+        // Evict oldest entries until there's enough space
+        while (this.currentMemory + newValueSize > this.maxMemory && this.queue.length > 0) {
+            const oldestKey = this.queue.shift();
+            const oldestValue = this.map.get(oldestKey);
+            const oldestValueSize = LimitedMap.estimateStringSize(oldestValue);
+            this.map.delete(oldestKey);
+            this.currentMemory -= oldestValueSize;
+        }
+
+        // After eviction, check again if there's enough space
+        if (this.currentMemory + newValueSize > this.maxMemory) {
+            return;
+        }
+
+        // Add the new key-value pair
+        this.map.set(key, value);
+        this.queue.push(key);
+        this.currentMemory += newValueSize;
+    }
+
+    /**
+     * Retrieves the value associated with the given key.
+     * @param {string} key
+     * @returns {string | undefined}
+     */
+    get(key) {
+        return this.map.get(key);
+    }
+
+    /**
+     * Checks if the map contains the given key.
+     * @param {string} key
+     * @returns {boolean}
+     */
+    has(key) {
+        return this.map.has(key);
+    }
+
+    /**
+     * Deletes the key-value pair associated with the given key.
+     * @param {string} key
+     * @returns {boolean} - Returns true if the key was found and deleted, else false.
+     */
+    delete(key) {
+        if (!this.map.has(key)) {
+            return false;
+        }
+        const value = this.map.get(key);
+        const valueSize = LimitedMap.estimateStringSize(value);
+        this.map.delete(key);
+        this.currentMemory -= valueSize;
+
+        // Remove the key from the queue
+        const index = this.queue.indexOf(key);
+        if (index > -1) {
+            this.queue.splice(index, 1);
+        }
+
+        return true;
+    }
+
+    /**
+     * Clears all entries from the map.
+     */
+    clear() {
+        this.map.clear();
+        this.queue = [];
+        this.currentMemory = 0;
+    }
+
+    /**
+     * Returns the number of key-value pairs in the map.
+     * @returns {number}
+     */
+    size() {
+        return this.map.size;
+    }
+
+    /**
+     * Returns the current memory usage in bytes.
+     * @returns {number}
+     */
+    totalMemory() {
+        return this.currentMemory;
+    }
+
+    /**
+     * Returns an iterator over the keys in the map.
+     * @returns {IterableIterator<string>}
+     */
+    keys() {
+        return this.map.keys();
+    }
+
+    /**
+     * Returns an iterator over the values in the map.
+     * @returns {IterableIterator<string>}
+     */
+    values() {
+        return this.map.values();
+    }
+
+    /**
+     * Iterates over the map in insertion order.
+     * @param {Function} callback - Function to execute for each element.
+     */
+    forEach(callback) {
+        this.map.forEach((value, key) => {
+            callback(value, key, this);
+        });
+    }
+
+    /**
+     * Makes the LimitedMap iterable.
+     * @returns {Iterator} - Iterator over [key, value] pairs.
+     */
+    [Symbol.iterator]() {
+        return this.map[Symbol.iterator]();
+    }
+}