MimeDetector: new class to resolve file extensions

Author: pschatzmann

src/AudioTools/CoreAudio/AudioMetaData.h

@@ -1,2 +1,4 @@
 #pragma once
 #include "AudioTools/CoreAudio/AudioMetaData/MetaData.h"
+#include "AudioTools/CoreAudio/AudioMetaData/MimeDetector.h"
+#include "AudioTools/CoreAudio/AudioMetaData/MimeResolver.h"

src/AudioTools/CoreAudio/AudioMetaData/MimeResolver.h

@@ -0,0 +1,123 @@
+#pragma once
+
+#include <ctype.h>
+#include <stddef.h>
+
+#include "AudioTools/CoreAudio/AudioBasic/Collections/Vector.h"
+#include "AudioTools/CoreAudio/AudioBasic/StrView.h"
+
+namespace audio_tools {
+
+/// extension to mime table (sorted alphabetically)
+struct MimeEntry {
+  const char* ext;
+  const char* mime;
+};
+/// Default mime table (sorted alphabetically) stored in program memory
+static const MimeEntry mime_table[] = {
+    {"aac", "audio/aac"},
+    {"ac3", "audio/ac3"},
+    {"aiff", "audio/aiff"},
+    {"aif", "audio/aiff"},
+    {"aifc", "audio/aiff"},
+    {"alac", "audio/alac"},
+    {"amr", "audio/amr"},
+    {"au", "audio/basic"},
+    {"caf", "audio/x-caf"},
+    {"dts", "audio/vnd.dts"},
+    {"flac", "audio/flac"},
+    {"m3u", "audio/x-mpegurl"},
+    {"m3u8", "application/vnd.apple.mpegurl"},
+    {"m4a", "audio/m4a"},
+    {"mid", "audio/midi"},
+    {"midi", "audio/midi"},
+    {"mka", "audio/x-matroska"},
+    {"mkv", "video/x-matroska"},
+    {"mp2", "audio/mpeg"},
+    {"mp2t", "video/MP2T"},
+    {"mp3", "audio/mpeg"},
+    {"mp4", "video/mp4"},
+    {"mpeg", "audio/mpeg"},
+    {"oga", "audio/ogg"},
+    {"ogg", "audio/ogg"},
+    {"ogv", "video/ogg"},
+    {"opus", "audio/ogg; codecs=opus"},
+    {"sid", "audio/prs.sid"},
+    {"spx", "audio/ogg; codecs=spx"},
+    {"ts", "video/MP2T"},
+    {"vorbis", "audio/ogg; codec=vorbis"},
+    {"wave", "audio/vnd.wave"},
+    {"wav", "audio/vnd.wave"},
+    {"webm", "video/webm"},
+    {"wma", "audio/x-ms-wma"},
+    {nullptr, nullptr}};
+
+/**
+ * @class MimeResolver
+ * @brief Lookup MIME types by file extension.
+ *
+ * Small, header-only helper that maps file name extensions (for example
+ * "mp3" or ".wav") to standardized MIME type strings (for example
+ * "audio/mpeg" or "audio/vnd.wave"). The resolver performs a
+ * case-insensitive match and accepts extensions with or without a
+ * leading '.'.
+ *
+ * Behavior:
+ * - The lookup table is a fixed, const array (`mime_table`) declared above
+ *   the class. Modify that table to add or change mappings.
+ * - Lookup returns a pointer to a constant string from the table. The
+ *   returned pointer is valid for the lifetime of the program. If no
+ *   mapping is found, the methods return nullptr.
+ * - Thread-safety: read-only operations are safe for concurrent use.
+ *
+ * @ingroup codecs
+ * @ingroup decoder
+ * @author Phil Schatzmann
+ * @copyright GPLv3
+ */
+class MimeResolver {
+ public:
+  /// Return MIME for a filename (looks up extension). Returns nullptr if
+  /// unknown.
+  const char* fromFilename(const char* filename) {
+    if (!filename) return nullptr;
+    const char* dot = strrchr(filename, '.');
+    if (!dot || *(dot + 1) == '\0') return nullptr;
+    return fromExtension(dot + 1);
+  }
+
+  /// Return MIME for an extension (case-insensitive). Returns nullptr if
+  /// unknown.
+  const char* fromExtension(const char* extension) {
+    if (!extension) return nullptr;
+    // skip leading dot if provided
+    if (extension[0] == '.') extension++;
+    StrView extView(extension);
+
+    // search in custom table first
+    for (size_t i = 0; i < custom_mime_table.size(); i++) {
+      if (extView.equalsIgnoreCase(custom_mime_table[i].ext))
+        return custom_mime_table[i].mime;
+    }
+
+    // search in default table
+    for (size_t i = 0; mime_table[i].ext != nullptr; i++) {
+      if (extView.equalsIgnoreCase(mime_table[i].ext))
+        return mime_table[i].mime;
+    }
+    return nullptr;
+  }
+
+  /// Add custom mime entry (overrides default entries)
+  void addMimeEntry(const char* ext, const char* mime) {
+    MimeEntry entry;
+    entry.ext = ext;
+    entry.mime = mime;
+    custom_mime_table.push_back(entry);
+  }
+
+ protected:
+  Vector<MimeEntry> custom_mime_table;
+};
+
+}  // namespace audio_tools