/*
    C playground by ChillerDragon
    File: test.c
*/
#include "stdio.h"
#include "string.h"

int char_allowed(unsigned char in)
{
  switch(in) {
    case '0': case '1': case '2': case '3': case '4':
    case '5': case '6': case '7': case '8': case '9':
    case 'a': case 'b': case 'c': case 'd': case 'e':
    case 'f': case 'g': case 'h': case 'i': case 'j':
    case 'k': case 'l': case 'm': case 'n': case 'o':
    case 'p': case 'q': case 'r': case 's': case 't':
    case 'u': case 'v': case 'w': case 'x': case 'y': case 'z':
    case 'A': case 'B': case 'C': case 'D': case 'E':
    case 'F': case 'G': case 'H': case 'I': case 'J':
    case 'K': case 'L': case 'M': case 'N': case 'O':
    case 'P': case 'Q': case 'R': case 'S': case 'T':
    case 'U': case 'V': case 'W': case 'X': case 'Y': case 'Z':
    case '-': case '.': case '_': case '~':
      return 1;
    default:
      break;
  }
  return 0;
}

void str_url_escape(const char *pSrc, char *pDst, int Size)
{
	int Index = 0;
	int Length = strlen(pSrc);
	while(Size-- && Length--)
	{
		unsigned char in = *pSrc;
		if(char_allowed(in))
			pDst[Index++] = in;
		else
		{
			snprintf(&pDst[Index], sizeof(pDst), "%%%02x", in);
			Index += 3;
		}
		pSrc++;
	}
	pDst[Index] = 0;
}

int main()
{
    char buf[16];
	char esc[16];

    strncpy(buf,"♪ x x", sizeof(buf));
    str_url_escape(buf, esc, sizeof(esc));
    printf("buf '%s'\n", buf);
    printf("esc '%s'\n", esc);

    strncpy(buf,"hello", sizeof(buf));
    str_url_escape(buf, esc, sizeof(esc));
    printf("buf '%s'\n", buf);
    printf("esc '%s'\n", esc);
}

/* $ gcc test.c && ./a.out
 *
 * buf 'x'
 * esc '%e2%99%aa%20x%20x'
 * buf 'hello'
 * esc 'hello'
 *
 */