Merge branch 'charlesmchen/utiTypeForFileExtension'

src/Util/MIMETypeUtil.h

@@ -42,8 +42,9 @@ extern NSString *const OWSMimeTypeUnknownForTests;
 + (NSSet<NSString *> *)supportedImageUTITypes;
 + (NSSet<NSString *> *)supportedAnimatedImageUTITypes;
 
-+ (NSString *)utiTypeForMIMEType:(NSString *)mimeType;
-+ (NSString *)fileExtensionForUTIType:(NSString *)utiType;
-+ (NSString *)fileExtensionForMIMEType:(NSString *)mimeType;
++ (nullable NSString *)utiTypeForMIMEType:(NSString *)mimeType;
++ (nullable NSString *)utiTypeForFileExtension:(NSString *)fileExtension;
++ (nullable NSString *)fileExtensionForUTIType:(NSString *)utiType;
++ (nullable NSString *)fileExtensionForMIMEType:(NSString *)mimeType;
 
 @end

src/Util/MIMETypeUtil.m

@@ -1571,4 +1571,13 @@ NSString *const OWSMimeTypeUnknownForTests = @"unknown/mimetype";
     return fileExtension;
 }
 
++ (NSString *)utiTypeForFileExtension:(NSString *)fileExtension
+{
+    OWSAssert(fileExtension.length > 0);
+
+    NSString *utiType = (__bridge_transfer NSString *)UTTypeCreatePreferredIdentifierForTag(
+        kUTTagClassFilenameExtension, (__bridge CFStringRef)fileExtension, NULL);
+    return utiType;
+}
+
 @end