Implement all Expr unmarshalling (untested). Put wordsize logic in constants.ts. Some README additions.

src/runtime/javascript/constants.ts

@@ -0,0 +1,39 @@
+// Untested!
+import os from 'os'
+
+export const BE: boolean = os.endianness() === 'BE'
+
+export let WORDSIZE_BITS: number
+switch (process.arch) {
+  case 'arm':
+  case 'ia32':
+  case 'ppc':
+  case 's390':
+  case 'x32':
+    WORDSIZE_BITS = 32
+    break
+
+  case 'arm64':
+  case 'mips':
+  case 'mipsel':
+  case 'ppc64':
+  case 's390x':
+  case 'x64':
+    WORDSIZE_BITS = 64
+    break
+
+  default:
+    throw Error(`Unknown architecture: ${process.arch}`)
+}
+
+export const WORDSIZE_BYTES = WORDSIZE_BITS / 8
+
+export let LINT_BASE: bigint
+
+switch (WORDSIZE_BITS) {
+  case 64: LINT_BASE = BigInt('10000000000000000000'); break
+  case 32: LINT_BASE = BigInt('1000000000'); break
+  case 16: LINT_BASE = BigInt('10000'); break
+  case 8: LINT_BASE = BigInt('100'); break
+  default: throw Error(`Unsupported word size: ${WORDSIZE_BITS}`)
+}