wasm: close base64 encoder (#22)

Close the base64 encoder before returning the buffer. This ensures that
all the bytes are written to the buffer. Without this, the last few
bytes may be missing, resulting in a corrupted image. Usually, this
would only corrupt the checksum, and the image would still be displayed
fine. However, some applications do not like this (e.g., slack).

cmd/wasm/main.go

@@ -46,6 +46,10 @@ func yellerWrapper() js.Func {
 		if err := png.Encode(enc, yelledAt); err != nil {
 			return newError(fmt.Errorf("encoding image: %w", err))
 		}
+		if err := enc.Close(); err != nil {
+			return newError(fmt.Errorf("closing encoder: %w", err))
+		}
+
 		return map[string]any{
 			"result": buf.String(),
 		}

docs/wasm_exec.js

@@ -113,6 +113,10 @@
 				this.mem.setUint32(addr + 4, Math.floor(v / 4294967296), true);
 			}
 
+			const setInt32 = (addr, v) => {
+				this.mem.setUint32(addr + 0, v, true);
+			}
+
 			const getInt64 = (addr) => {
 				const low = this.mem.getUint32(addr + 0, true);
 				const high = this.mem.getInt32(addr + 4, true);
@@ -206,7 +210,10 @@
 
 			const timeOrigin = Date.now() - performance.now();
 			this.importObject = {
-				go: {
+				_gotest: {
+					add: (a, b) => a + b,
+				},
+				gojs: {
 					// Go's SP does not change as long as no Go code is running. Some operations (e.g. calls, getters and setters)
 					// may synchronously trigger a Go event handler. This makes Go code get executed in the middle of the imported
 					// function. A goroutine can switch to a new stack if the current stack is too small (see morestack function).
@@ -269,7 +276,7 @@
 									this._resume();
 								}
 							},
-							getInt64(sp + 8) + 1, // setTimeout has been seen to fire up to 1 millisecond early
+							getInt64(sp + 8),
 						));
 						this.mem.setInt32(sp + 16, id, true);
 					},
@@ -551,4 +558,4 @@
 			};
 		}
 	}
-})();
+})();