Export block and object layout constants from Rtrace (#1572)

Author: dcodeIO

lib/rtrace/index.d.ts

@@ -27,6 +27,13 @@ export declare interface RtraceOptions {
   getMemory(): WebAssembly.Memory;
 }
 
+/** Overhead between a pointer to a block and its unmanaged data. */
+export declare const BLOCK_OVERHEAD;
+/** Overhead between a pointer to a block's unmanaged data to its managed data. */
+export declare const OBJECT_OVERHEAD;
+/** Overhead between a pointer to a block and its managed data. */
+export declare const TOTAL_OVERHEAD;
+
 export declare class Rtrace {
   [key: string]: unknown; // can be used as a Wasm import
 

lib/rtrace/index.js

@@ -9,7 +9,9 @@ const PTR_SIZE = 1 << PTR_SIZE_BITS;
 const PTR_MASK = PTR_SIZE - 1;
 const PTR_VIEW = Uint32Array;
 
-const BLOCK_OVERHEAD = PTR_SIZE;
+export const BLOCK_OVERHEAD = PTR_SIZE;
+export const OBJECT_OVERHEAD = 16;
+export const TOTAL_OVERHEAD = BLOCK_OVERHEAD + OBJECT_OVERHEAD;
 
 const RT_TLSF = "~lib/rt/tlsf/";
 

lib/rtrace/umd/index.js

@@ -5,7 +5,7 @@ var rtrace = (function(exports) {
   Object.defineProperty(exports, "__esModule", {
     value: true
   });
-  exports.default = exports.Rtrace = void 0;
+  exports.default = exports.Rtrace = exports.TOTAL_OVERHEAD = exports.OBJECT_OVERHEAD = exports.BLOCK_OVERHEAD = void 0;
   // WebAssembly pages are 65536 kb
   const PAGE_SIZE_BITS = 16;
   const PAGE_SIZE = 1 << PAGE_SIZE_BITS;
@@ -16,6 +16,11 @@ var rtrace = (function(exports) {
   const PTR_MASK = PTR_SIZE - 1;
   const PTR_VIEW = Uint32Array;
   const BLOCK_OVERHEAD = PTR_SIZE;
+  exports.BLOCK_OVERHEAD = BLOCK_OVERHEAD;
+  const OBJECT_OVERHEAD = 16;
+  exports.OBJECT_OVERHEAD = OBJECT_OVERHEAD;
+  const TOTAL_OVERHEAD = BLOCK_OVERHEAD + OBJECT_OVERHEAD;
+  exports.TOTAL_OVERHEAD = TOTAL_OVERHEAD;
   const RT_TLSF = "~lib/rt/tlsf/";
 
   function assert(x) {