unsigned 64-bit int / signed 64-bit int

[No Such Luck]

It seems as though java does not have the ability to read or handle
unsigned 64-bit integers. Correct me if I am wrong. I am trying to
develop an algorithm to bypass this limitation.

Suppose I have the usigned 64-bit int "18438013886959845375". This
number falls between (2 ^ 64) - 1 and (2 ^ 63) - 1, meaning it is a
valid unsigned 64-bit integer, but higher than what java can handle.

All I need are the appropriate bits in this number, not the number
itself. I can read "18438013886959845375" in as a string correctly. Can
anyone help with an algorithm to convert an unsigned 64-bit integer
represented as a string, into a signed 64-bit integer (2's compliment)
with the exact same bit pattern, so that java can ingest it properly
and read the bits.

Example:

input "18438013886959845375" (a string)
Output X (where X is a number java can handle, and X and
18438013886959845375 have the exact same bit sequence)

Thanks in advance.

[Raymond DeCampo]

No Such Luck wrote:

It seems as though java does not have the ability to read or handle
unsigned 64-bit integers. Correct me if I am wrong. I am trying to
develop an algorithm to bypass this limitation.

Suppose I have the usigned 64-bit int "18438013886959845375". This
number falls between (2 ^ 64) - 1 and (2 ^ 63) - 1, meaning it is a
valid unsigned 64-bit integer, but higher than what java can handle.

All I need are the appropriate bits in this number, not the number
itself. I can read "18438013886959845375" in as a string correctly. Can
anyone help with an algorithm to convert an unsigned 64-bit integer
represented as a string, into a signed 64-bit integer (2's compliment)
with the exact same bit pattern, so that java can ingest it properly
and read the bits.

Example:

input "18438013886959845375" (a string)
Output X (where X is a number java can handle, and X and
18438013886959845375 have the exact same bit sequence)

This may not be exactly what you want but you may want to look at
java.math.BigInteger, specifically the method toByteArray().

HTH,
Ray

--
XML is the programmer's duct tape.