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Calypso Container File Format (CCFF)

This is a semi-normative specification of the Calypso Container File Format (CCFF), used within Calypso and SaturnVM. Assume all multi-byte fields are little-endian, unless otherwise specified. No padding is present between fields.

The beginning of a CCFF file must contain four big-endian bytes: 0x43434646 (CCFF in ASCII encoding). This is the magic number of the CCFF file, and must be present for a CCFF file to be valid.

The next part of the file must contain an instance of a file header (Hdr). The rest of the file after this header is section data.

File Header (Hdr)

The offsets provided in this table are from the start of the Hdr. No padding is present and multi-byte fields are little-endian.

Offset (bytes) Size (bytes) Name Type Description
0x00 0x02 abiver u16 A user-defined ABI version.
0x02 0x01 filety u8 A user-defined file type.
0x03 0x01 len(sections) u8 The number of sections in this container file.
0x04 dynamic sections [SectionHdr] An array (consecutive memory with no padding) of section headers len(sections) long. Note that because SectionHdr contains a dynamic-length field, accessing a section is O(n), so implementations should ideally store sections in a HashMap (or some other near-O(1) lookup complexity data structure) from section name (or some other unique identifier) to the section's metadata and/or data.

Section Header (SectionHdr)

The offsets provided in this table are from the start of the SectionHdr. No padding is present and multi-byte fields are little-endian.

Offset (bytes) Size (bytes) Name Type Description
0x00 0x01 type u8 A user-defined section type.
0x01 0x04 flags u32 User-defined section bitflags.
0x05 0x04 offset u32 The byte offset of this section's data from the start of the file, including the magic bytes.
0x09 0x04 size u32 The byte size of this section's data.
0x0d 0x01 sizeof(name) u8 The byte size of the section name.
0x0e sizeof(name) name str ASCII-encoded section name. This name must be unique throughout the entire file and must consist of only characters between 0x21 (!) up to and including 0x7E (~), i.e. non-control, non-whitespace characters.