Changes to cpp_rpc to make it work on Android (+ Hexagon offloading) (a…

…pache#5535)

* Changes to cpp_rpc to make it work on Android (+ Hexagon offloading)

- Implement getNextString to break up std::string into words. stringstream
  just doesn't work on Android.
- string::find_last_of doesn't look for the last substring, but the
  last character from a given string.
- Use SIGTERM to terminate processes (this isn't necessary, but using
  SIGKILL is not a good practice).
- Convert "./rpc" to a full path. When a module is uploaded and offloaded
  to Hexagon, the dlopen on Hexagon needs an absolute path (or a path
  without directories).

* Only set the absolute patch on non-Windows platforms

Windows has different macros for the maximum path length.

apps/cpp_rpc/rpc_env.cc

@@ -67,7 +67,17 @@ namespace {
 namespace tvm {
 namespace runtime {
 RPCEnv::RPCEnv() {
+#ifndef _WIN32
+  char cwd[PATH_MAX];
+  if (char *rc = getcwd(cwd, sizeof(cwd))) {
+    base_ = std::string(cwd) + "/rpc";
+  } else {
+    base_ = "./rpc";
+  }
+#else
   base_ = "./rpc";
+#endif
+
   mkdir(base_.c_str(), 0777);
   TVM_REGISTER_GLOBAL("tvm.rpc.server.workpath").set_body([](TVMArgs args, TVMRetValue* rv) {
     static RPCEnv env;

apps/cpp_rpc/rpc_server.cc

@@ -66,6 +66,22 @@ static pid_t waitPidEintr(int* status) {
 }
 #endif
 
+#ifdef __ANDROID__
+static std::string getNextString(std::stringstream* iss) {
+  std::string str = iss->str();
+  size_t start = iss->tellg();
+  size_t len = str.size();
+  // Skip leading spaces.
+  while (start < len && isspace(str[start])) start++;
+
+  size_t end = start;
+  while (end < len && !isspace(str[end])) end++;
+
+  iss->seekg(end);
+  return str.substr(start, end-start);
+}
+#endif
+
 /*!
  * \brief RPCServer RPC Server class.
  * \param host The hostname of the server, Default=0.0.0.0
@@ -164,9 +180,9 @@ class RPCServer {
         int status = 0;
         const pid_t finished_first = waitPidEintr(&status);
         if (finished_first == timer_pid) {
-          kill(worker_pid, SIGKILL);
+          kill(worker_pid, SIGTERM);
         } else if (finished_first == worker_pid) {
-          kill(timer_pid, SIGKILL);
+          kill(timer_pid, SIGTERM);
         } else {
           LOG(INFO) << "Child pid=" << finished_first << " unexpected, but still continue.";
         }
@@ -260,7 +276,12 @@ class RPCServer {
 
       std::stringstream ssin(remote_key);
       std::string arg0;
+#ifndef __ANDROID__
       ssin >> arg0;
+#else
+      arg0 = getNextString(&ssin);
+#endif
+
       if (arg0 != expect_header) {
         code = kRPCMismatch;
         CHECK_EQ(conn.SendAll(&code, sizeof(code)), sizeof(code));
@@ -274,7 +295,11 @@ class RPCServer {
         CHECK_EQ(conn.SendAll(&keylen, sizeof(keylen)), sizeof(keylen));
         CHECK_EQ(conn.SendAll(server_key.c_str(), keylen), keylen);
         LOG(INFO) << "Connection success " << addr->AsString();
+#ifndef __ANDROID__
         ssin >> *opts;
+#else
+        *opts = getNextString(&ssin);
+#endif
         *conn_sock = conn;
         return;
       }
@@ -301,8 +326,9 @@ class RPCServer {
   int GetTimeOutFromOpts(const std::string& opts) const {
     const std::string option = "-timeout=";
 
-    if (opts.find(option) == 0) {
-      const std::string cmd = opts.substr(opts.find_last_of(option) + 1);
+    size_t pos = opts.rfind(option);
+    if (pos != std::string::npos) {
+      const std::string cmd = opts.substr(pos + option.size());
       CHECK(support::IsNumber(cmd)) << "Timeout is not valid";
       return std::stoi(cmd);
     }