1 files changed, 27 insertions, 0 deletions
diff --git a/source/blender/blenlib/intern/fileops.c b/source/blender/blenlib/intern/fileops.c
index 6fc2222241b..31825c69737 100644
--- a/source/blender/blenlib/intern/fileops.c
+++ b/source/blender/blenlib/intern/fileops.c
@@ -262,6 +262,33 @@ bool BLI_file_magic_is_gzip(const char header[4])
   return header[0] == 0x1f && header[1] == 0x8b && header[2] == 0x08;
 }
 
+bool BLI_file_magic_is_zstd(const char header[4])
+{
+  /* ZSTD files consist of concatenated frames, each either a Zstd frame or a skippable frame.
+   * Both types of frames start with a magic number: 0xFD2FB528 for Zstd frames and 0x184D2A5*
+   * for skippable frames, with the * being anything from 0 to F.
+   *
+   * To check whether a file is Zstd-compressed, we just check whether the first frame matches
+   * either. Seeking through the file until a Zstd frame is found would make things more
+   * complicated and the probability of a false positive is rather low anyways.
+   *
+   * Note that LZ4 uses a compatible format, so even though its compressed frames have a
+   * different magic number, a valid LZ4 file might also start with a skippable frame matching
+   * the second check here.
+   *
+   * For more details, see https://github.com/facebook/zstd/blob/dev/doc/zstd_compression_format.md
+   */
+
+  uint32_t magic = *((uint32_t *)header);
+  if (magic == 0xFD2FB528) {
+    return true;
+  }
+  if ((magic >> 4) == 0x184D2A5) {
+    return true;
+  }
+  return false;
+}
+
 /**
  * Returns true if the file with the specified name can be written.
  * This implementation uses access(2), which makes the check according