[Info-ingres] Convert hex string to an integer

[Martin Bowes]

Hi All,

There has got to be an easier  way....

Given a string which represents a hex value, convert it to an integer of a given size.

The only solution I've come up with is by making an OME function. See attached.

Here is how I would describe that function...
hex2int(hexString, integerSize)
Convert the indicated hex string into a signed integer of the given size. Case is ignored.

Two's complement is respected and hence when converting to integer1 the string 'FF' becomes -1. However the same string converted to integer2 becomes 255.

The hex string may be prefixed with '0x', '+0x', or '-0x'. But in the case of '-0x' there is the possibility of a double negative if the string converts to a negative integer.

And here is some sample output...
select hex2int('FFFD', 8)\g
┌──────────────────────┐
│col1                  │
├──────────────────────┤
│                 65533│
└──────────────────────┘
(1 row)

select hex2int('FFFD', 22)\g
E_OME001 hex2int(): Invalid size '22' specified. It must be one of 1, 2,
    4, 8
    (Tue Aug 10 14:47:58 2021)

select hex2int('FFFD', 2)\g

┌──────┐
│col1  │
├──────┤
│    -3│
└──────┘
(1 row)

select hex2int('garbage', 8)\g
Executing . . .

E_OME001 hex2int(): Non hex character 'g' found in string.
    (Wed Aug 11 14:08:29 2021)

So the questions are:

1.       Can anyone do this in simple SQL? If so, how?

2.       Could people have a quick look over the C code and give me some feedback please. I'm not a C coder and after compiling with no errors I'm not too sure what more I have to do.

Thanks,

Marty
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