reading keyboard input without "consuming" it in x86 assembly
- by Bob
Ok so here the deal:
I have an assignment regarding DOS and interrupts:
I need to write a sort of key-logger function that can be called from C code.
what it means is a c program would call an assembly function called startlog that would indicate to start logging the keys pressed until a function called endlog is called. the logging should work like this: write the ascii value of any key pressed without disturbing the C code between startlog and endlog, meaning that if the C code also needs to read the input (let's say by scanf, it would work ok).
I managed to write the logger by changing the interrupt vector 9th entry (interrupt for keyboard press) to a function I wrote that writes the values to a file, and it works fine. however the C code does not get the input.
Basically what i did is read the key pressed using int 21h, however after reading the ascii value it is "consumed" so I need a way to either simulate the key press again or read the value without "consuming" it so next time a key is read it reads the same key.
(I described the code in english because it is long and clumsy assembly code)
