refactor(struct): 10% performance improvement

apps/demo/src/pages/logcat.tsx

@@ -54,6 +54,7 @@ const state = makeAutoObservable({
     logcat: undefined as Logcat | undefined,
     running: false,
     buffer: [] as LogRow[],
+    flushRequested: false,
     list: [] as LogRow[],
     count: 0,
     stream: undefined as ReadableStream<LogMessage> | undefined,
@@ -73,21 +74,20 @@ const state = makeAutoObservable({
                 new WritableStream({
                     write: (chunk) => {
                         this.buffer.push(chunk);
+                        if (!this.flushRequested) {
+                            this.flushRequested = true;
+                            requestAnimationFrame(this.flush);
+                        }
                     },
                 }),
                 { signal: this.stopSignal.signal }
             )
             .catch(() => { });
-        this.flush();
     },
     flush() {
-        if (this.buffer.length) {
         this.list.push(...this.buffer);
         this.buffer = [];
-        }
-        if (this.running) {
-            requestAnimationFrame(this.flush);
-        }
+        this.flushRequested = false;
     },
     stop() {
         this.running = false;

libraries/adb/src/commands/sync/stat.ts

@@ -34,7 +34,8 @@ export const AdbSyncLstatResponse =
             get permission() { return this.mode & 0b00001111_11111111; },
         })
         .postDeserialize((object) => {
-            if (object.mode === 0 &&
+            if (
+                object.mode === 0 &&
                 object.size === 0 &&
                 object.mtime === 0
             ) {

libraries/adb/src/stream/buffered.ts

@@ -26,38 +26,25 @@ export class BufferedStream {
         this.reader = stream.getReader();
     }
 
-    /**
-     *
-     * @param length
-     * @returns
-     */
-    public async read(length: number): Promise<Uint8Array> {
-        let result: Uint8Array;
-        let index: number;
-
-        if (this.buffered) {
-            let array = this.buffered;
-            const offset = this.bufferedOffset;
-            if (this.bufferedLength > length) {
-                // PERF: `subarray` is slow
-                // don't use it until absolutely necessary
-                this.bufferedOffset += length;
-                this.bufferedLength -= length;
-                return array.subarray(offset, offset + length);
-            }
-
-            this.buffered = undefined;
-            array = array.subarray(offset);
-            result = new Uint8Array(length);
-            result.set(array);
-            index = this.bufferedLength;
-            length -= this.bufferedLength;
-        } else {
-            const { done, value: array } = await this.reader.read();
+    private async readSource() {
+        const { done, value } = await this.reader.read();
         if (done) {
             throw new BufferedStreamEndedError();
         }
+        return value;
+    }
 
+    private async readAsync(length: number, initial?: Uint8Array) {
+        let result: Uint8Array;
+        let index: number;
+
+        if (initial) {
+            result = new Uint8Array(length);
+            result.set(initial);
+            index = initial.byteLength;
+            length -= initial.byteLength;
+        } else {
+            const array = await this.readSource();
             if (array.byteLength === length) {
                 return array;
             }
@@ -76,11 +63,7 @@ export class BufferedStream {
         }
 
         while (length > 0) {
-            const { done, value: array } = await this.reader.read();
-            if (done) {
-                throw new BufferedStreamEndedError();
-            }
-
+            const array = await this.readSource();
             if (array.byteLength === length) {
                 result.set(array, index);
                 return result;
@@ -102,6 +85,31 @@ export class BufferedStream {
         return result;
     }
 
+    /**
+     *
+     * @param length
+     * @returns
+     */
+    public read(length: number): Uint8Array | Promise<Uint8Array> {
+        // PERF: Add a synchronous path for reading from internal buffer
+        if (this.buffered) {
+            const array = this.buffered;
+            const offset = this.bufferedOffset;
+            if (this.bufferedLength > length) {
+                // PERF: `subarray` is slow
+                // don't use it until absolutely necessary
+                this.bufferedOffset += length;
+                this.bufferedLength -= length;
+                return array.subarray(offset, offset + length);
+            }
+
+            this.buffered = undefined;
+            return this.readAsync(length, array.subarray(offset));
+        }
+
+        return this.readAsync(length);
+    }
+
     /**
      * Return a readable stream with unconsumed data (if any) and
      * all data from the wrapped stream.

libraries/struct/README.md

@@ -645,13 +645,11 @@ struct.field(
 
 ### Relationship between types
 
-A `Struct` is a map between keys and `StructFieldDefinition`s.
-
-A `StructValue` is a map between keys and `StructFieldValue`s.
-
-A `Struct` can create (deserialize) multiple `StructValue`s with same field definitions.
-
-Each time a `Struct` deserialize, each `StructFieldDefinition` in it creates exactly one `StructFieldValue` to be put into the `StructValue`.
+* `StructFieldValue`: Contains value of a field, with optional metadata and accessor methods.
+* `StructFieldDefinition`: Definition of a field, can deserialize `StructFieldValue`s from a stream or create them from exist values.
+* `StructValue`: A map between field names and `StructFieldValue`s.
+* `Struct`: Definiton of a struct, a map between field names and `StructFieldDefintion`s. May contain extra metadata.
+* Result of `Struct#deserialize()`: A map between field names and results of `StructFieldValue#get()`.
 
 ### `StructFieldDefinition`
 

libraries/struct/src/basic/field-value.ts

@@ -20,6 +20,11 @@ export abstract class StructFieldValue<
     /** Gets the associated `Struct` instance */
     public readonly struct: StructValue;
 
+    public get hasCustomAccessors(): boolean {
+        return this.get !== StructFieldValue.prototype.get ||
+            this.set !== StructFieldValue.prototype.set;
+    }
+
     protected value: TDefinition['TValue'];
 
     public constructor(

libraries/struct/src/basic/stream.ts

@@ -1,3 +1,5 @@
+import type { ValueOrPromise } from "../utils.js";
+
 export interface StructDeserializeStream {
     /**
      * Read data from the underlying data source.
@@ -15,5 +17,5 @@ export interface StructAsyncDeserializeStream {
      * The stream must return exactly `length` bytes or data. If that's not possible
      * (due to end of file or other error condition), it must throw an error.
      */
-    read(length: number): Promise<Uint8Array>;
+    read(length: number): ValueOrPromise<Uint8Array>;
 }

libraries/struct/src/basic/struct-value.ts

@@ -1,4 +1,4 @@
-import { StructFieldValue } from "./field-value.js";
+import type { StructFieldValue } from "./field-value.js";
 
 export const STRUCT_VALUE_SYMBOL = Symbol("struct-value");
 
@@ -11,9 +11,15 @@ export class StructValue {
     /**
      * Gets the result struct value object
      */
-    public readonly value: Record<PropertyKey, unknown> = {};
+    public readonly value: Record<PropertyKey, unknown>;
 
-    public constructor() {
+    public constructor(prototype: any) {
+        // PERF: `Object.create(extra)` is 50% faster
+        // than `Object.defineProperties(this.value, extra)`
+        this.value = Object.create(prototype);
+
+        // PERF: `Object.defineProperty` is slow
+        // but we need it to be non-enumerable
         Object.defineProperty(
             this.value,
             STRUCT_VALUE_SYMBOL,
@@ -31,8 +37,8 @@ export class StructValue {
         this.fieldValues[name] = fieldValue;
 
         // PERF: `Object.defineProperty` is slow
-        if (fieldValue.get !== StructFieldValue.prototype.get ||
-            fieldValue.set !== StructFieldValue.prototype.set) {
+        // use normal property when possible
+        if (fieldValue.hasCustomAccessors) {
             Object.defineProperty(this.value, name, {
                 configurable: true,
                 enumerable: true,

libraries/struct/src/struct.ts

@@ -490,7 +490,10 @@ export class Struct<
         Overwrite<TExtra, T>,
         TPostDeserialized
     > {
-        Object.assign(this._extra, Object.getOwnPropertyDescriptors(value));
+        Object.defineProperties(
+            this._extra,
+            Object.getOwnPropertyDescriptors(value)
+        );
         return this as any;
     }
 
@@ -540,14 +543,12 @@ export class Struct<
     public deserialize(
         stream: StructDeserializeStream | StructAsyncDeserializeStream,
     ): ValueOrPromise<StructDeserializedResult<TFields, TExtra, TPostDeserialized>> {
-        const structValue = new StructValue();
-        Object.defineProperties(structValue.value, this._extra);
+        const structValue = new StructValue(this._extra);
+
+        let promise = SyncPromise.resolve();
 
-        return SyncPromise
-            .try(() => {
-                let result = SyncPromise.resolve();
         for (const [name, definition] of this._fields) {
-                    result = result
+            promise = promise
                 .then(() =>
                     definition.deserialize(this.options, stream as any, structValue)
                 )
@@ -555,8 +556,8 @@ export class Struct<
                     structValue.set(name, fieldValue);
                 });
         }
-                return result;
-            })
+
+        return promise
             .then(() => {
                 const object = structValue.value;
 
@@ -588,7 +589,7 @@ export class Struct<
                 }
             }
         } else {
-            structValue = new StructValue();
+            structValue = new StructValue({});
             for (const [name, definition] of this._fields) {
                 const fieldValue = definition.create(
                     this.options,

libraries/struct/src/sync-promise.ts

@@ -1,185 +1,106 @@
-enum State {
-    Pending,
-    Fulfilled,
-    Rejected,
+export interface SyncPromise<T> {
+    then<TResult1 = T, TResult2 = never>(
+        onfulfilled?: ((value: T) => TResult1 | PromiseLike<TResult1>) | null | undefined,
+        onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null | undefined
+    ): SyncPromise<TResult1 | TResult2>;
+
+    valueOrPromise(): T | PromiseLike<T>;
 }
 
-function fulfilledThen<T, TResult1 = T>(
-    this: SyncPromise<T>,
-    onfulfilled?: ((value: T) => TResult1 | PromiseLike<TResult1>) | undefined | null,
-): SyncPromise<TResult1> {
-    if (onfulfilled) {
-        return SyncPromise.try(() => onfulfilled(this.result as T));
-    }
-    return this as unknown as SyncPromise<TResult1>;
+interface SyncPromiseStatic {
+    reject<T = never>(reason?: any): SyncPromise<T>;
+
+    resolve(): SyncPromise<void>;
+    resolve<T>(value: T | PromiseLike<T>): SyncPromise<T>;
+
+    try<T>(executor: () => T | PromiseLike<T>): SyncPromise<T>;
 }
 
-function rejectedThen<T, TResult1 = T, TResult2 = never>(
-    this: SyncPromise<T>,
-    onfulfilled?: ((value: T) => TResult1 | PromiseLike<TResult1>) | undefined | null,
-    onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | undefined | null
-): SyncPromise<TResult2> {
-    if (onrejected) {
-        return SyncPromise.try(() => onrejected(this.result));
+export const SyncPromise: SyncPromiseStatic = {
+    reject<T = never>(reason?: any): SyncPromise<T> {
+        return new RejectedSyncPromise(reason);
+    },
+    resolve<T>(value?: T | PromiseLike<T>): SyncPromise<T> {
+        if (
+            typeof value === 'object' &&
+            value !== null &&
+            typeof (value as PromiseLike<T>).then === 'function'
+        ) {
+            return new PendingSyncPromise(value as PromiseLike<T>);
+        } else {
+            return new ResolvedSyncPromise(value as T);
         }
-    return this as unknown as SyncPromise<TResult2>;
-}
-
-function fulfilledValue<T>(
-    this: SyncPromise<T>,
-) {
-    return this.result as T;
-}
-
-function rejectedValue<T>(
-    this: SyncPromise<T>,
-): never {
-    throw this.result;
-}
-
-const INTERNAL_CREATED = Symbol('internal-created') as any;
-
-export class SyncPromise<T> implements PromiseLike<T> {
-    public static reject<T = never>(reason?: any): SyncPromise<T> {
-        const promise = new SyncPromise<T>(INTERNAL_CREATED);
-        promise.handleReject(reason);
-        return promise;
-    }
-
-    public static resolve(): SyncPromise<void>;
-    public static resolve<T>(value: T | PromiseLike<T>): SyncPromise<T>;
-    public static resolve<T>(value?: T | PromiseLike<T>): SyncPromise<T> {
-        if (value instanceof SyncPromise) {
-            return value;
-        }
-
-        const promise = new SyncPromise<T>(INTERNAL_CREATED);
-        promise.handleResolve(value!);
-        return promise;
-    }
-
-    public static try<T>(executor: () => T | PromiseLike<T>): SyncPromise<T> {
+    },
+    try<T>(executor: () => T | PromiseLike<T>): SyncPromise<T> {
         try {
             return SyncPromise.resolve(executor());
         } catch (e) {
             return SyncPromise.reject(e);
         }
     }
+};
 
-    public state: State = State.Pending;
-    public result: unknown;
-    public promise: PromiseLike<T> | undefined;
+class PendingSyncPromise<T> implements SyncPromise<T> {
+    private promise: PromiseLike<T>;
 
-    public constructor(executor: (resolve: (value: T | PromiseLike<T>) => void, reject: (reason?: any) => void) => void) {
-        if (executor === INTERNAL_CREATED) {
-            return;
+    public constructor(promise: PromiseLike<T>) {
+        this.promise = promise;
     }
 
-        let promiseResolve: (value: T | PromiseLike<T>) => void;
-        let promiseReject: (reason?: any) => void;
-
-        let settled = false;
-        let sync = true;
-
-        const handleReject = (reason?: any) => {
-            if (settled) { return; }
-            settled = true;
-
-            if (!sync) {
-                promiseReject(reason);
-                return;
-            }
-
-            this.handleReject(reason);
-        };
-
-        try {
-            executor(
-                (value: T | PromiseLike<T>) => {
-                    if (settled) { return; }
-                    settled = true;
-
-                    if (!sync) {
-                        promiseResolve(value);
-                        return;
-                    }
-
-                    this.handleResolve(value);
-                },
-                handleReject
-            );
-        } catch (e) {
-            handleReject(e);
-        }
-
-        if (this.state === State.Pending && !this.promise) {
-            this.promise = new Promise<T>((resolve, reject) => {
-                promiseResolve = resolve;
-                promiseReject = reject;
-            });
-        }
-
-        sync = false;
-    }
-
-    private handleResolveValue(value: T) {
-        this.state = State.Fulfilled;
-        this.result = value;
-        this.then = fulfilledThen;
-        this.valueOrPromise = fulfilledValue;
-    };
-
-    private handleResolve(value: T | PromiseLike<T>) {
-        if (typeof value === 'object' &&
-            value !== null &&
-            'then' in value &&
-            typeof value.then === 'function'
-        ) {
-            if (value instanceof SyncPromise) {
-                switch (value.state) {
-                    case State.Fulfilled:
-                        this.handleResolveValue(value.result as T);
-                        return;
-                    case State.Rejected:
-                        this.handleReject(value.result);
-                        return;
-                }
-            }
-
-            this.promise = value as PromiseLike<T>;
-        } else {
-            this.handleResolveValue(value as T);
-        }
-    }
-
-    private handleReject(reason?: any) {
-        this.state = State.Rejected;
-        this.result = reason;
-        this.then = rejectedThen;
-        this.valueOrPromise = rejectedValue;
-    };
-
     public then<TResult1 = T, TResult2 = never>(
         onfulfilled?: ((value: T) => TResult1 | PromiseLike<TResult1>) | null | undefined,
         onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null | undefined
-    ): SyncPromise<TResult1 | TResult2> {
-        // The result promise isn't really a `SyncPromise`,
-        // but we attach a `valueOrPromise` to it,
-        // so it's compatible with `SyncPromise`.
-        // PERF: it's 230% faster than creating a real `SyncPromise` instance.
-        const promise =
-            this.promise!.then(onfulfilled, onrejected) as unknown as SyncPromise<TResult1 | TResult2>;
-        promise.valueOrPromise = this.valueOrPromise as unknown as () => TResult1 | TResult2 | PromiseLike<TResult1 | TResult2>;
-        return promise;
-    }
-
-    public catch<TResult = never>(
-        onrejected?: ((reason: any) => TResult | PromiseLike<TResult>) | null | undefined
-    ): SyncPromise<T | TResult> {
-        return this.then(undefined, onrejected);
+    ) {
+        return new PendingSyncPromise<TResult1 | TResult2>(
+            this.promise.then(onfulfilled, onrejected)
+        );
     }
 
     public valueOrPromise(): T | PromiseLike<T> {
-        return this;
+        return this.promise;
+    }
+}
+
+class ResolvedSyncPromise<T> implements SyncPromise<T> {
+    private value: T;
+
+    public constructor(value: T) {
+        this.value = value;
+    }
+
+    public then<TResult1 = T, TResult2 = never>(
+        onfulfilled?: ((value: T) => TResult1 | PromiseLike<TResult1>) | null | undefined,
+        onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null | undefined
+    ) {
+        if (!onfulfilled) {
+            return this as any;
+        }
+        return SyncPromise.try(() => onfulfilled(this.value));
+    }
+
+    public valueOrPromise(): T | PromiseLike<T> {
+        return this.value;
+    }
+}
+
+class RejectedSyncPromise<T> implements SyncPromise<T> {
+    private reason: any;
+
+    public constructor(reason: any) {
+        this.reason = reason;
+    }
+
+    public then<TResult1 = T, TResult2 = never>(
+        onfulfilled?: ((value: T) => TResult1 | PromiseLike<TResult1>) | null | undefined,
+        onrejected?: ((reason: any) => TResult2 | PromiseLike<TResult2>) | null | undefined
+    ) {
+        if (!onrejected) {
+            return this as any;
+        }
+        return SyncPromise.try(() => onrejected(this.reason));
+    }
+
+    public valueOrPromise(): T | PromiseLike<T> {
+        throw this.reason;
     }
 }