What does this syntax mean?
It's C++ for "set the scriptSig of the first input in the first transaction in this block to have the same contents as a script with the encoded nTime followed by the encoded nExtraNone".
Exactly what elements does the script sig contain and in what order?
It contains the block's
nTime, followed by by the
How is the extra nonce formatted?
An example from this time period would be in the scriptSig from the coinbase transaction of block #185000:
If we parse this script sig, it is:
04 -- Number of bytes in group of data
d508de4f -- 4 bytes. The little endian timestamp.
02 -- Number of bytes in group of data
e82d -- the little endian extranonce
Notice when you reverse the bytes in
d508de4f, you get
4fde08d5, which when you convert it to a timestamp is
Sun Jun 17 2012 12:41:57 GMT-0400 (EDT). When you byte-reverse
e82d (reversed is
2de8), and decode an integer from the hex, you get 11,752 for an extranonce value.