Out-of-process rebuild: Add Shared/IPCProtocol.h — message definitions for parent↔helper IPC

Source/Shared/IPCProtocol.h

@@ -0,0 +1,98 @@
+#pragma once
+
+#include <string>
+#include <cstdint>
+
+// IPC Protocol between PluginBridge (parent) and PluginBridgeHelper (child)
+// Transport: Unix domain socket, newline-delimited JSON messages
+// 
+// Flow:
+//   Parent → Helper: commands (load plugin, get/set params, show GUI, quit)
+//   Helper → Parent: responses + notifications (param changes from GUI, crash)
+
+namespace IPC {
+
+// Socket path (unique per instance using PID)
+inline std::string getSocketPath(int parentPid)
+{
+    return "/tmp/pluginbridge_" + std::to_string(parentPid) + ".sock";
+}
+
+// Shared memory name (unique per instance)
+inline std::string getShmName(int parentPid)
+{
+    return "pluginbridge_audio_" + std::to_string(parentPid);
+}
+
+// Semaphore names
+inline std::string getInputSemName(int parentPid)
+{
+    return "pb_input_" + std::to_string(parentPid);
+}
+
+inline std::string getOutputSemName(int parentPid)
+{
+    return "pb_output_" + std::to_string(parentPid);
+}
+
+// --- Message Types (Parent → Helper) ---
+
+// Load a plugin by file path
+// {"cmd":"load","path":"/Library/Audio/Plug-Ins/VST3/Pro-Q 4.vst3"}
+// Response: {"ok":true,"name":"Pro-Q 4","params":737} or {"ok":false,"error":"..."}
+
+// Unload current plugin
+// {"cmd":"unload"}
+// Response: {"ok":true}
+
+// Search parameters by keyword
+// {"cmd":"search_param","keyword":"gain"}
+// Response: {"ok":true,"results":[{"i":12,"n":"Band 1 Gain","v":0.5,"t":"0.0 dB"},...]}
+
+// Get parameter values by index
+// {"cmd":"get_params","ids":[12,13,14]}
+// Response: {"ok":true,"values":{"12":0.5,"13":0.7,"14":0.0}}
+
+// Set parameter values
+// {"cmd":"set_params","values":{"12":0.75,"13":0.3}}
+// Response: {"ok":true}
+
+// Show/hide plugin GUI
+// {"cmd":"show_gui"}
+// {"cmd":"hide_gui"}
+// Response: {"ok":true}
+
+// Get plugin state (for save)
+// {"cmd":"get_state"}
+// Response: {"ok":true,"state":"<base64-encoded state>"}
+
+// Set plugin state (for restore)
+// {"cmd":"set_state","state":"<base64-encoded state>"}
+// Response: {"ok":true}
+
+// Configure audio
+// {"cmd":"configure","sampleRate":44100,"blockSize":512,"channels":2}
+// Response: {"ok":true}
+
+// Quit helper
+// {"cmd":"quit"}
+// No response (process exits)
+
+// --- Message Types (Helper → Parent, unsolicited notifications) ---
+
+// Parameter changed from GUI interaction
+// {"notify":"param_changed","index":12,"value":0.75}
+
+// Plugin crashed (sent if helper catches it before dying)
+// {"notify":"crashed","error":"..."}
+
+// Helper ready (sent after startup)
+// {"notify":"ready"}
+
+// --- Constants ---
+
+static constexpr int kMaxMessageSize = 65536;  // 64KB max for state blobs
+static constexpr int kHelperTimeoutMs = 5000;   // 5s to start up
+static constexpr int kProcessBlockTimeoutMs = 50; // 50ms max wait in processBlock
+
+} // namespace IPC