ledit.asm

A 100% dependency-free terminal line editor, written in x86_64 assembly.

Highlights:

• Zero dependencies: Not even libc/standard library -- can be dropped into any project and work immediately
• Basic navigation functionality: Arrow keys, home/end keys (and Ctrl+A/Ctrl-E), backspace, and delete
• No dynamic memory allocation: Works with static buffers only
• Tiny: Static library is <2kb in size when stripped

Demo

Compiling and Running

ledit depends upon nasm. To compile and run the demo application, run:

 $ make demo
 $ ./demo

This will start the line editor. Press Enter to exit.

Using ledit as a readline-like Library

After compiling, the static library ledit.asm.o should be present. To compile a program with ledit, add this to the compiler's list of input files.

Important! Due to the way ledit is written (read: because I am an assembly newbie), any C code must be compiled with -static. For example:

 $ cc my_app.c ledit.asm.o -o my_app -static

To use ledit within C code, define the function ledit() as an extern and define your own syntax() function. The simplest usage is as follows:

#include <unistd.h>  // For write()

extern void ledit(); // Tell compiler to look in ledit.asm.o for ledit

void syntax(char *inp, int inp_len){ // Can be used for syntax highlighting and other text post-processing
  write(STDOUT_FILENO, inp, inp_len);
}

int main(){
  ledit();
  return 0;
}

Some Interesting Implementation Details

• I rolled my own itoa() in about 35 instructions for this project, see label itoa in ledit.asm for the annotated algorithm.
• ledit interfaces directly with termios (without the C standard library's tcgetattr() or tcsetattr()), see the beginning of labels ledit and shutdown.
• See ledit.h for the reference C implementation. Most features in the asm version are 1:1 with the C version, but there some changes (most notably, the lack of sscanf() and printf() in asm, which the C version uses very liberally).