retroforth/literate/Unu.md

Unu

unu
(verb) (-hia) pull out, withdraw, draw out, extract.

Unu is a tool for extracting fenced code blocks from Markdown documents.

I always found documenting my projects to be annoying. Eventually I decided to start mixing the code into the commentary using Markdown. Unu is the tool I use to extract the sources from the original files. I've found that this makes it easier for me to keep the commentary up to date.

The Code

Headers

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

I use this for readability purposes.

#define KiB * 1024

read_line(FILE *file, char *line_buffer)

void read_line(FILE *file, char *line_buffer) {
  int ch, count;

  if (file == NULL || line_buffer == NULL)
  {
    printf("Error: file or line buffer pointer is null.");
    exit(1);
  }

  ch = getc(file);
  count = 0;

  while ((ch != '\n') && (ch != EOF)) {
    line_buffer[count] = ch;
    count++;
    ch = getc(file);
  }

  line_buffer[count] = '\0';
}

extract(char *fname)

The line buffer needs to be big enough for the longest lines in your source files. Here it's capped at 16KiB, which is sufficient for everything I've used Unu with so far.

char source[16 KiB];

int fenced(char *s)
{
  int a = strcmp(s, "```");
  int b = strcmp(s, "~~~");
  if (a == 0) return 1;
  if (b == 0) return 1;
              return 0;
}

void extract(char *fname) {
  char *buffer = (char *)source;
  char fence[4];
  FILE *fp;
  int inBlock;
  inBlock = 0;
  fp = fopen(fname, "r");
  if (fp == NULL)
    return;
  while (!feof(fp)) {
    read_line(fp, buffer);
    strncpy(fence, buffer, 3);
    fence[3] = '\0';
    if (fenced(fence)) {
      if (inBlock == 0)
        inBlock = 1;
      else
        inBlock = 0;
    } else {
      if ((inBlock == 1) && (strlen(buffer) != 0))
        printf("%s\n", buffer);
    }
  }
  fclose(fp);
}

main(int argc, char **argv)

int main(int argc, char **argv) {
  int i = 1;
  if (argc > 1) {
    while (i < argc) {
      extract(argv[i++]);
    }
  }
  else
    printf("unu\n(c) 2013-2017 charles childers\n\nTry:\n  %s filename\n", argv[0]);
  return 0;
}