Calculating jmp's from one segment to another in windows PE files - x86-64

Question

Assume I have a binary on my disk that I load into memory using VirtualAlloc and ReadFile.
If I want to follow a jmp instruction from one section to another, what do I need to add/subtract to get the destination address.
In other words, I want to know how IDA calculates the loc_140845BB8 from jmp loc_140845BB8
Example:
.text:000000014005D74E jmp loc_140845BB8
Jumps to the section seg007
seg007:0000000140845BB8 ; seg007:0000000140845BC4↓j
seg007:0000000140845BB8 and rbx, r14
PE info (seg007 is the section named "")

Answer 1

Segments are arbitary, it jumps where it jumps, without regard for segments. Jump location is calculated as the signed 32-bit value following the 0xE9 JMP opcode, added to the the address of where the next instruction would be (i.e. the location of JMP + 5 bytes).
def GetInsnLen(ea):
insn = ida_ua.insn_t()
return ida_ua.decode_insn(insn, ea)
def MakeSigned(number, size):
number = number & (1<<size) - 1
return number if number < 1<<size - 1 else - (1<<size) - (~number + 1)
def GetRawJumpTarget(ea):
if ea is None:
return None
insnlen = GetInsnLen(ea)
if not insnlen:
return None
result = MakeSigned(idc.get_wide_dword(ea + insnlen - 4), 32) + ea + insnlen
if ida_ida.cvar.inf.min_ea <= result < ida_ida.cvar.inf.max_ea:
return result
return None