Add some definisions and constants for Buffer

assembly/buffer/index.ts

@@ -2,6 +2,14 @@ import { BLOCK_MAXSIZE, BLOCK, BLOCK_OVERHEAD } from "rt/common";
 import { E_INVALIDLENGTH, E_INDEXOUTOFRANGE } from "util/error";
 import { Uint8Array } from "typedarray";
 
+export const kMaxLength       = constants.MAX_LENGTH;
+export const kMaxStringLength = constants.MAX_STRING_LENGTH;
+
+export namespace constants {
+  export const MAX_LENGTH        = i32.MAX_VALUE; // (2 ^ 31) - 1 (~2GB)
+  export const MAX_STRING_LENGTH = BLOCK_MAXSIZE >>> alignof<u16>();
+}
+
 export class Buffer extends Uint8Array {
   constructor(size: i32) {
     super(size);
@@ -250,7 +258,7 @@ export class Buffer extends Uint8Array {
     }
     return this;
   }
-  
+
   swap32(): Buffer {
     let dataLength = this.dataLength;
     // Make sure dataLength is divisible by 4
@@ -263,7 +271,7 @@ export class Buffer extends Uint8Array {
     }
     return this;
   }
-  
+
   swap64(): Buffer {
     let dataLength = this.dataLength;
     // Make sure dataLength is divisible by 8

assembly/node.d.ts

@@ -95,3 +95,19 @@ declare namespace Buffer {
     export function decodeUnsafe(ptr: usize, byteLength: i32): string;
   }
 }
+
+declare module "buffer" {
+  export type TranscodeEncoding = "ascii" | "utf8" | "utf16le" | "ucs2" | "latin1" | "binary";
+
+  export const kMaxLength: i32;
+  export const kStringMaxLength: i32;
+
+  export const constants: {
+    MAX_LENGTH: i32;
+    MAX_STRING_LENGTH: i32;
+  };
+
+  // To export the buffer, we must obtain the `typeof Buffer`
+  const BuffType: typeof Buffer;
+  export { BuffType as Buffer };
+}