# Gavin Andresen
# 2011-12-13 16:05:42
# https://bitcointalk.org/index.php?topic=54451.msg649253#msg649253

Here's how to figure it out from the Satoshi client code: @p{par}

The IMPLEMENT_SERIALIZE macro is used to both store transactions on disk and to serialize them into a byte-array that can be hashed. @p{par}

For class CTransaction, that looks like: @p{brk}

Code:
    IMPLEMENT_SERIALIZE @p{brk}
    ( @p{brk}
        READWRITE(this-@s{gt}nVersion); @p{brk}
        nVersion = this-@s{gt}nVersion; @p{brk}
        READWRITE(vin); @p{brk}
        READWRITE(vout); @p{brk}
        READWRITE(nLockTime); @p{brk}
    ) @p{brk}

 @p{brk}
READWRITE is a wrapper that is overloaded to Do The Right Thing for all the types bitcoin deals with; for complex types like CTxOut, IMPLEMENT_SERIALIZE is (essentially) called recursively. @p{par}

Expand out all of the types and, assuming I didn't screw up (always an iffy assumption), it looks like a CTransaction is serialized as: @p{par}


Code:
nVersion @p{brk}
vin.size  (vectors are serialized as a compressed count immediately followed by their contents) @p{brk}
 vin[].prevout    (vin-@s{gt}prevout-@s{gt}hash followed immediately by vin-@s{gt}prevout-@s{gt}n, as 36 bytes) @p{brk}
 vin[].scriptSig   (CScripts are serialized as a vector of bytes) @p{brk}
 vin[].nSequence @p{brk}
 ... repeated for each vin @p{brk}
vout.size @p{brk}
 vout[].nValue @p{brk}
 vout[].scriptPubKey @p{brk}
 ... repeated for each vout @p{brk}
nLockTime @p{brk}

 @p{brk}
String all those bytes together, SHA256 them twice, and you should get the transaction hash for the merkle chain. @p{par}