bpo-40280: Add limited Emscripten REPL (GH-32284)

Co-authored-by: Katie Bell <katie@katharos.id.au>

1 files changed, 87 insertions, 0 deletions

diff --git a/Tools/wasm/python.worker.js b/Tools/wasm/python.worker.js
new file mode 100644
index 0000000..c3a8bdf
--- /dev/null
+++ b/Tools/wasm/python.worker.js
@@ -0,0 +1,87 @@
+class StdinBuffer {
+    constructor() {
+        this.sab = new SharedArrayBuffer(128 * Int32Array.BYTES_PER_ELEMENT)
+        this.buffer = new Int32Array(this.sab)
+        this.readIndex = 1;
+        this.numberOfCharacters = 0;
+        this.sentNull = true
+    }
+
+    prompt() {
+        this.readIndex = 1
+        Atomics.store(this.buffer, 0, -1)
+        postMessage({
+            type: 'stdin',
+            buffer: this.sab
+        })
+        Atomics.wait(this.buffer, 0, -1)
+        this.numberOfCharacters = this.buffer[0]
+    }
+
+    stdin = () => {
+        if (this.numberOfCharacters + 1 === this.readIndex) {
+            if (!this.sentNull) {
+                // Must return null once to indicate we're done for now.
+                this.sentNull = true
+                return null
+            }
+            this.sentNull = false
+            this.prompt()
+        }
+        const char = this.buffer[this.readIndex]
+        this.readIndex += 1
+        // How do I send an EOF??
+        return char
+    }
+}
+
+const stdoutBufSize = 128;
+const stdoutBuf = new Int32Array()
+let index = 0;
+
+const stdout = (charCode) => {
+    if (charCode) {
+        postMessage({
+            type: 'stdout',
+            stdout: String.fromCharCode(charCode),
+        })
+    } else {
+        console.log(typeof charCode, charCode)
+    }
+}
+
+const stderr = (charCode) => {
+    if (charCode) {
+        postMessage({
+            type: 'stderr',
+            stderr: String.fromCharCode(charCode),
+        })
+    } else {
+        console.log(typeof charCode, charCode)
+    }
+}
+
+const stdinBuffer = new StdinBuffer()
+
+var Module = {
+    noInitialRun: true,
+    stdin: stdinBuffer.stdin,
+    stdout: stdout,
+    stderr: stderr,
+    onRuntimeInitialized: () => {
+        postMessage({type: 'ready', stdinBuffer: stdinBuffer.sab})
+    }
+}
+
+onmessage = (event) => {
+    if (event.data.type === 'run') {
+        // TODO: Set up files from event.data.files
+        const ret = callMain(event.data.args)
+        postMessage({
+            type: 'finished',
+            returnCode: ret
+        })
+    }
+}
+
+importScripts('python.js')