Add draft for when wasm is supported

wasm-encode.js

@@ -0,0 +1,78 @@
+#!/usr/bin/env node
+
+/**
+ * Cleaned version of:
+ * <https://merckx.dev/notes/embedding-binary-data-in-wasm.html>.
+ *
+ * To do: when Node supports WASM imports, we can drop `fs` and start using
+ * this.
+ *
+ * In the future, when importing WASM is supported in Node, we can use this.
+ * This little script takes an input file path and an output file path as
+ * arguments and generates a WASM file from the former to the latter.
+ * The data from the WASM can then be accessed with:
+ *
+ * ```js
+ * import {data} from './output.wasm'
+ * const u8 = data.buffer
+ * ```
+ */
+
+import {Buffer} from 'node:buffer'
+import fs from 'node:fs/promises'
+import process from 'node:process'
+// @ts-expect-error: untyped.
+import {unsigned, signed} from 'leb128'
+
+const data = await fs.readFile(process.argv[2])
+
+/** @type {Buffer} */
+const size = unsigned.encode(data.length)
+/** @type {Buffer} */
+const length = signed.encode(data.length)
+/** @type {Buffer} */
+const globalL = unsigned.encode(5 + length.length)
+/** @type {Buffer} */
+const dataL = unsigned.encode(5 + size.length + data.length)
+/** @type {Buffer} */
+const memoryPages = unsigned.encode(Math.ceil(data.length / 65_536))
+/** @type {Buffer} */
+const memoryL = unsigned.encode(2 + memoryPages.length)
+
+await fs.writeFile(
+  process.argv[3],
+  bin`
+  00 61 73 6d                                         // WASM_BINARY_MAGIC
+  01 00 00 00                                         // WASM_BINARY_VERSION
+  05 ${memoryL} 01                                    // section "Memory" (5)
+  00 ${memoryPages}                                   // memory 0
+  06 ${globalL} 01 7f 00 41 ${length} 0b              // section "Global" (6)
+  07 11 02 04 6461 7461 02 00 06 6c65 6e67 7468 03 00 // section "Export" (7)
+  0b ${dataL} 01                                      // section "Data" (11)
+  00 41 00 0b ${size}                                 // data segment header 0
+  ${data}                                             // data
+  `
+)
+
+/**
+ *
+ * @param {TemplateStringsArray} values
+ * @param  {...Buffer} inserts
+ * @returns {Buffer}
+ */
+function bin(values, ...inserts) {
+  /** @type {Array<Buffer>} */
+  const result = []
+  let index = -1
+
+  while (++index < values.length) {
+    const bytes = values[index].replace(/\/\/(.*?)\n/g, '').replace(/\s+/g, '')
+    result.push(Buffer.from(bytes, 'hex'))
+
+    if (index < inserts.length) {
+      result.push(inserts[index])
+    }
+  }
+
+  return Buffer.concat(result)
+}