Update the GetFilePaths function to recursively add only JPEG file paths (#42)

[ROCm/rocjpeg commit: a5b31eec78]

projects/rocjpeg/samples/rocjpeg_samples_utils.h

@@ -32,8 +32,10 @@ THE SOFTWARE.
 #include <mutex>
 #if __cplusplus >= 201703L && __has_include(<filesystem>)
     #include <filesystem>
+    namespace fs = std::filesystem;
 #else
     #include <experimental/filesystem>
+    namespace fs = std::experimental::filesystem;
 #endif
 #include <chrono>
 #include "rocjpeg.h"
@@ -168,6 +170,27 @@ public:
         }
     }
 
+    /**
+     * Checks if a file is a JPEG file.
+     *
+     * @param filePath The path to the file to be checked.
+     * @return True if the file is a JPEG file, false otherwise.
+     */
+    static bool IsJPEG(const std::string& filePath) {
+        std::ifstream file(filePath, std::ios::binary);
+        if (!file.is_open()) {
+            std::cerr << "Failed to open file: " << filePath << std::endl;
+            return false;
+        }
+
+        unsigned char buffer[2];
+        file.read(reinterpret_cast<char*>(buffer), 2);
+        file.close();
+
+        // The first two bytes of every JPEG stream are always 0xFFD8, which represents the Start of Image (SOI) marker.
+        return buffer[0] == 0xFF && buffer[1] == 0xD8;
+    }
+
     /**
      * @brief Gets the file paths.
      *
@@ -180,24 +203,22 @@ public:
      * @return True if successful, false otherwise.
      */
     static bool GetFilePaths(std::string &input_path, std::vector<std::string> &file_paths, bool &is_dir, bool &is_file) {
-    #if __cplusplus >= 201703L && __has_include(<filesystem>)
-        is_dir = std::filesystem::is_directory(input_path);
-        is_file = std::filesystem::is_regular_file(input_path);
-    #else
-        is_dir = std::experimental::filesystem::is_directory(input_path);
-        is_file = std::experimental::filesystem::is_regular_file(input_path);
-    #endif
+        if (!fs::exists(input_path)) {
+            std::cerr << "ERROR: the input path does not exist!" << std::endl;
+            return false;
+        }
+        is_dir = fs::is_directory(input_path);
+        is_file = fs::is_regular_file(input_path);
         if (is_dir) {
-    #if __cplusplus >= 201703L && __has_include(<filesystem>)
-            for (const auto &entry : std::filesystem::directory_iterator(input_path))
-    #else
-            for (const auto &entry : std::experimental::filesystem::directory_iterator(input_path))
-    #endif
-                file_paths.push_back(entry.path());
-        } else if (is_file) {
+            for (const auto &entry : fs::recursive_directory_iterator(input_path)) {
+                if (fs::is_regular_file(entry) && IsJPEG(entry.path().string())) {
+                    file_paths.push_back(entry.path().string());
+                }
+            }
+        } else if (is_file && IsJPEG(input_path)) {
             file_paths.push_back(input_path);
         } else {
-            std::cerr << "ERROR: the input path is not valid!" << std::endl;
+            std::cerr << "ERROR: the input path does not contain JPEG files!" << std::endl;
             return false;
         }
         return true;
@@ -612,7 +633,7 @@ private:
         "-be    [backend] - select rocJPEG backend (0 for hardware-accelerated JPEG decoding using VCN,\n"
         "                                           1 for hybrid JPEG decoding using CPU and GPU HIP kernels (currently not supported)) [optional - default: 0]\n"
         "-fmt   [output format] - select rocJPEG output format for decoding, one of the [native, yuv, y, rgb, rgb_planar] - [optional - default: native]\n"
-        "-o     [output path] - path to an output file or a path to a directory - write decoded images to a file or directory based on selected output format - [optional]\n"
+        "-o     [output path] - path to an output file or a path to an existing directory - write decoded images to a file or an existing directory based on selected output format - [optional]\n"
         "-crop  -crop [crop rectangle] - crop rectangle for output in a comma-separated format: left,top,right,bottom - [optional]\n"
         "-d     [device id] - specify the GPU device id for the desired device (use 0 for the first device, 1 for the second device, and so on) [optional - default: 0]\n";
         if (show_threads) {