FormatHashBlocks: blocks = 1 + ((len + 8) / 64); // should be len + 9 #599

FormatHashBlocks: int blocks = 1 + ((len + 8) / 64);

I think this should be len+9, because 64 bits are used for the bit count, and then assuming the input's length is in whole bytes, you will need one more byte in front of the length bytes to place the 0x80. Note this does not effect current versions of bitcoin, but maybe in the future if the length of the block's hash input changed, this could be a problem.

Cheers, Dean

This is correct; SHA256 can hash up to 55 bytes in one block, not 56.

Actually... that means the formula is correct; closing...