Printf implementation

Shortened Assembly printf library implementation for Windows.

Motivation

The idea is to understand how printf works from the inside and understand the intricacies of writing applications for the Windows system in NASM using the Windows API.

What printf specifiers are available?

There are %%, %c, %s, %d, %x, %o, %b (%b stands for "convert number to binary format") specifiers.

Program architecture

Description of libraries

1. Strlib contains btoa, printString, PrintChar, itoa, memset.
2. Winlib contains macroses-wrappers for Windows API: GetStdHandle, WriteFile, ExitProcess.
3. Printflib contains only _myPrintf implementation.

Implementation details

1. switch is implemented via jump table.
2. itoa is implemented with the faster division if the given base (radix) is a power of two.
3. GetNextPrintfArgument function gets each new unproceed printf argument using global variable (it is assumed that the number of arguments passed after format string is not less than the number of specifiers in it).

Compiling && Running

Compile, link and run examples:

cd examples
nasm.exe -f win32 ownPrintf.asm -o ownPrintf.obj
gcc.exe -m32 -o ownPrintf
.\ownPrintf.exe

Compile printflib.asm , link and run with another program (e.g. with C program)

cd examples
<path_to_nasm_assembler>\nasm.exe -f win32 ..\lib\printflib.asm
<path_to_mingw32_gcc>\gcc.exe -c test.c -o test.o
<path_to_mingw32_gcc>\gcc.exe test.o ..\lib\printflib.obj -o test.exe
.\test.exe