How to convert string to integer in MASM

I want to simply get the user to input a number. I can get input (I think), but this is a string, and I need to conve开发者_如何学Pythonrt it to a number (DWORD). I couldn't find anything that worked in MASM. I tried the C functions strtol and atoi, but it couldn't find them. Is there some function that works in MASM? Or do I have to write my own conversion?

I tried several include files, but I couldn't get the C functions:

windows.inc

kernel32.inc

user32.inc

msvcrt.inc

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Its over 20 years since I used MASM so I'm a bit rusty. The algorithm is pretty straightforward though.

• Assuming your string is in ASCII
• Start at the end of the string
• You will need to split each character off the string and subtract 30H from it to give the digit
• store that digit in a register
• calculate your next power of ten
• Each time you move one character left and get that digit multiply by the next power of ten
• add to accumulator

E.g for an integer

31H 32H 33H

31h-30H = 1H 32H-30H = 2H * 10 33H-30H = 3H * 10 * 10

Bingo!

If the number represents a double you will need to cope with in a similar manner.

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I did atoi PROTO C strptr:DWORD and then I was able to call atoi.