Handling the frame itself

You are reaching the end of the frame parsing! It is time to put the various bits together.

Building the type

✅ Make the frame::ZstandardFrame structure contain three fields: the frame header, a vector of blocks, and an optional checksum (a u32).

Parsing

✅ Implement ZstandardFrame::parse() and call it from Frame::parse() in the presence of a Zstandard frame.

This method will need to:

• parse the header;
• parse the blocks (there is at least one), and continue doing so as long as the parsed block is not the last one;
• parse the checksum (a 32 bit little-endian value) if it is present according to the frame header descriptor.

The RFC limits the size of a block to the smallest of the window size and 128 KiB. You may want to pass this maximum block size to Block::parse() so that it can reject oversized blocks early with a dedicated error, before attempting to read a huge slice from the input.

Decoding

✅ Implement ZstandardFrame::decode() and call it from Frame::decode() in the presence of a Zstandard frame.

Decoding a frame means decoding each block in turn and concatenating the results. Return an error first if the frame header carries a dictionary ID, as dictionaries are not supported. The checksum will be verified later, once compressed blocks are handled.