Add usb gadget support

src/util.cpp

@@ -1,49 +1,43 @@
+#include <array>
+#include <cstdio>
+#include <dirent.h>
 #include <fcntl.h>
+#include <fstream>
+#include <memory>
 #include <mntent.h>
+#include <sstream>
 #include <stdio.h>
 #include <string.h>
 #include <sys/stat.h>
 #include <unistd.h>
-#include <fstream>
-#include <sstream>
-#include <array>
-#include <memory>
-#include <cstdio>
-#include <dirent.h>
 
-char* fs_mount_point(char *filesystem_type)
-{
+char *fs_mount_point(char *filesystem_type) {
   struct mntent *ent;
   FILE *mounts;
   char *mount_point = nullptr;
 
   mounts = setmntent("/proc/mounts", "r");
 
-  while (nullptr != (ent = getmntent(mounts)))
-  {
-    if (strcmp(ent->mnt_fsname, filesystem_type) == 0)
-    {
+  while (nullptr != (ent = getmntent(mounts))) {
+    if (strcmp(ent->mnt_fsname, filesystem_type) == 0) {
       mount_point = ent->mnt_dir;
       break;
     }
   }
 
   // Alternate search location on Android
-  if (mount_point == nullptr)
-  {
+  if (mount_point == nullptr) {
     const char *alt_usb_gadget = "/config/usb_gadget";
-    DIR *dir                   = opendir(alt_usb_gadget);
+    DIR *dir = opendir(alt_usb_gadget);
 
-    if (dir)
-    {
+    if (dir) {
       mount_point = (char *)"/config";
     }
   }
   return mount_point;
 }
 
-char* strjin(char *w1, char *w2)
-{
+char *strjin(char *w1, char *w2) {
   char *s = new char[strlen(w1) + strlen(w2) + 1];
 
   strcpy(s, w1);
@@ -51,38 +45,42 @@ char* strjin(char *w1, char *w2)
   return s;
 }
 
-bool isdir(char *path)
-{
+bool isdir(char *path) {
   struct stat sb;
 
   if (stat(path, &sb) == 0)
-    return true;
+    return S_ISDIR(sb.st_mode);
   else
     return false;
 }
 
-void sysfs_write(char *path, char *content)
-{
+bool isfile(char *path) {
+  struct stat sb;
+
+  if (stat(path, &sb) == 0)
+    return S_ISREG(sb.st_mode);
+  else
+    return false;
+}
+
+void sysfs_write(char *path, char *content) {
   printf("Write: %s -> %s\n", content, path);
   std::ofstream sysfsFile(path);
   sysfsFile << content << std::endl;
   sysfsFile.close();
 }
 
-char* sysfs_read(char *path)
-{
-  std::string   value;
+char *sysfs_read(char *path) {
+  std::string value;
   std::ifstream sysfsFile(path);
 
-  if (!sysfsFile.is_open())
-  {
+  if (!sysfsFile.is_open()) {
     return nullptr;
   }
   sysfsFile >> value;
   sysfsFile.close();
 
-  if (value.empty())
-  {
+  if (value.empty()) {
     return nullptr;
   }
   char *result = new char[value.length() + 1];