pub fn frame_header_size(src: &[u8]) -> Result<usize, ReadFrameHeaderError>Expand description
Length in bytes of the frame header at the start of src, including the
4-byte magic number (the offset at which the first block begins). Backs the
C ZSTD_frameHeaderSize.
Only the magic number and the descriptor byte are needed: the length
follows from the descriptor alone, so a caller holding just that five-byte
prefix learns how much of the header is still to read. Upstream’s
ZSTD_frameHeaderSize measures it the same way
(zstd_decompress.c:416-429), without looking at the descriptor’s other
bits, so a header this library refuses to decode is still measured. With
the legacy feature a v0.5-v0.7 header is measured by its own format’s
size fields, as LegacyVersion::header_size does.
§Errors
ReadFrameHeaderError when src is shorter
than five bytes, has a bad magic number, or is a skippable frame.
use structured_zstd::decoding::frame_header_size;
// Magic number and a descriptor announcing a window byte only.
assert_eq!(frame_header_size(&[0x28, 0xB5, 0x2F, 0xFD, 0x00]).unwrap(), 6);