Simple IPC for external control (#3345)

* add simple IPC protocol

to allow communication via stdin/stdout

* ipc: add PATCH_MEMORY command

enables patches & cheates

src/core/ipc/ipc.cpp

@@ -0,0 +1,113 @@
+//  SPDX-FileCopyrightText: Copyright 2024 shadPS4 Emulator Project
+//  SPDX-License-Identifier: GPL-2.0-or-later
+
+#include "ipc.h"
+
+#include <iostream>
+#include <string>
+
+#include "common/memory_patcher.h"
+#include "common/thread.h"
+#include "common/types.h"
+
+/**
+ * Protocol summary:
+ * - IPC is enabled by setting the SHADPS4_ENABLE_IPC environment variable to "true"
+ * - Input will be stdin & output stderr
+ * - Strings are sent as UTF8
+ * - Each communication line is terminated by a newline character ('\n')
+ * - Each command parameter will be separated by a newline character ('\n'),
+ *   variadic commands will start sending the number of parameters after the cmd word.
+ *   Any ('\n') in the parameter must be escaped by a backslash ('\\n')
+ * - Numbers can be sent with any base. Must prefix the number with '0x' for hex,
+ *   '0b' for binary, or '0' for octal. Decimal numbers
+ *   will be sent without any prefix.
+ * - Output will be started by (';')
+ * - The IPC server(this) will send a block started by
+ *   #IPC_ENABLED
+ *   and ended by
+ *   #IPC_END
+ *   In between, it will send the current capabilities and commands before the emulator start
+ * - The IPC client(e.g., launcher) will send RUN then START to conintue the execution
+ **/
+
+/**
+ * Command list:
+ * - CAPABILITIES:
+ *   - ENABLE_MEMORY_PATCH: enables PATCH_MEMORY command
+ * - INPUT CMD:
+ *   - RUN: start the emulator execution
+ *   - START: start the game execution
+ *   - PATCH_MEMORY(
+ *       modName: str, offset: str, value: str,
+ *       target: str, size: str, isOffset: number, littleEndian: number,
+ *       patchMask: number, maskOffset: number
+ *     ): add a memory patch, check @ref MemoryPatcher::PatchMemory for details
+ * - OUTPUT CMD:
+ *   - N/A
+ **/
+
+void IPC::Init() {
+    const char* enabledEnv = std::getenv("SHADPS4_ENABLE_IPC");
+    enabled = enabledEnv && strcmp(enabledEnv, "true") == 0;
+    if (!enabled) {
+        return;
+    }
+
+    input_thread = std::jthread([this] {
+        Common::SetCurrentThreadName("IPC Read thread");
+        this->InputLoop();
+    });
+
+    std::cerr << ";#IPC_ENABLED\n";
+    std::cerr << ";ENABLE_MEMORY_PATCH\n";
+    std::cerr << ";#IPC_END\n";
+    std::cerr.flush();
+
+    const auto ok = run_semaphore.try_acquire_for(std::chrono::seconds(5));
+    if (!ok) {
+        std::cerr << "IPC: Failed to acquire run semaphore, closing process.\n";
+        exit(1);
+    }
+}
+
+void IPC::InputLoop() {
+    auto next_str = [&] -> const std::string& {
+        static std::string line_buffer;
+        do {
+            std::getline(std::cin, line_buffer, '\n');
+        } while (!line_buffer.empty() && line_buffer.back() == '\\');
+        return line_buffer;
+    };
+    auto next_u64 = [&] -> u64 {
+        auto& str = next_str();
+        return std::stoull(str, nullptr, 0);
+    };
+
+    while (true) {
+        auto& cmd = next_str();
+        if (cmd.empty()) {
+            continue;
+        }
+        if (cmd == "RUN") {
+            run_semaphore.release();
+        } else if (cmd == "START") {
+            start_semaphore.release();
+        } else if (cmd == "PATCH_MEMORY") {
+            MemoryPatcher::patchInfo entry;
+            entry.gameSerial = "*";
+            entry.modNameStr = next_str();
+            entry.offsetStr = next_str();
+            entry.valueStr = next_str();
+            entry.targetStr = next_str();
+            entry.sizeStr = next_str();
+            entry.isOffset = next_u64() != 0;
+            entry.littleEndian = next_u64() != 0;
+            entry.patchMask = static_cast<MemoryPatcher::PatchMask>(next_u64());
+            entry.maskOffset = static_cast<int>(next_u64());
+            MemoryPatcher::AddPatchToQueue(entry);
+        } else {
+            std::cerr << "UNKNOWN CMD: " << cmd << std::endl;
+        }
+    }
+}