/* ----------------------------------------------------------------------------- 
 * encoding.c
 *
 *     This file implements a number of filters for encoding and decoding data
 *     in various formats including URL encoding and Base 64.
 * 
 * Author(s) : David Beazley (beazley@cs.uchicago.edu)
 *             Mike Sliczniak (mzsliczn@midway.uchicago.edu)
 *
 * Copyright (C) 1999-2000.  The University of Chicago
 * See the file LICENSE for information on usage and redistribution.	
 * ----------------------------------------------------------------------------- */

static char cvsroot[] = "$Header: /home/pastacvs/cvs-rep/vermicelli/tot/src/SWILL-0.1/Source/SWILL/encoding.c,v 1.1 2005/01/27 08:46:25 dillema Exp $";

#include "swillint.h"

/* -----------------------------------------------------------------------------
 * swill_url_decode()
 *
 * Decodes a url-encoded string.  '+' characters are converted into spaces
 * and '%xx' sequences are converted into their character equivalent.
 *
 *     in    Is any file-like object supporting a Getc method.
 *     out   Is any file-like object supporting a Putc method.
 *
 * ----------------------------------------------------------------------------- */

void 
swill_url_decode(DOH *in, DOH *out) {
  int  ch, nch;
  int  state,i;
  while (1) {
    ch = Getc(in);
    if (ch == EOF) return;
    if (ch == '+') {
      Putc(' ',out);
    } else {
      if (ch == '%') {
	nch = 0;
	for (i = 0; i < 2; i++) {
	  nch = nch << 4;
	  ch = Getc(in);
	  if (ch == EOF) {
	    Putc(ch,out);
	    return;
	  } 
	  if (isxdigit(ch)) {
	    if (isdigit(ch)) {
	      nch += (ch - '0');
	    } else {
	      nch += (tolower(ch) - 'a') + 10;
	    }
	  }
	}
	Putc(nch,out);
      } else {
	Putc(ch,out);
      }
    }
  }
}

/* -----------------------------------------------------------------------------
 * swill_url_encode()
 *
 * Encodes a string. Spaces are converted into '+' and all other non-valid
 * characters are converted into a '%xx' sequence.
 * ----------------------------------------------------------------------------- */

void 
swill_url_encode(DOH *in, DOH *out) {
  int  ch, nch;
  int  state,i;
  char *trans = "0123456789abcdef";
  while (1) {
    ch = Getc(in);
    if (ch == EOF) return;
    if (ch == ' ') {
      Putc('+',out);
    } else if (isalnum(ch) || (ch == '_')) {
      Putc(ch,out);
    } else {
      int i;
      Putc('%',out);
      i = (ch & 0xf0) >> 4;
      Putc(trans[i],out);
      i = (ch & 0x0f);
      Putc(trans[i],out);
    }
  }
}

/* ----------------------------------------------------------------------------- 
 * swill_url_encoder()
 *
 * Function given to DohEncoder for printf conversions.
 * ----------------------------------------------------------------------------- */

DOH *
swill_url_encoder(DOH *s) {
  DOH *ns = NewString("");
  swill_url_encode(s,ns);
  return ns;
}

/* -----------------------------------------------------------------------------
 * swill_pre_encode()
 *
 * Take a piece of text and perform a few character substitutions for HTML.
 * ----------------------------------------------------------------------------- */

void 
swill_pre_encode(DOH *in, DOH *out) {
  int ch;
  while (1) {
    ch = Getc(in);
    if (ch == EOF) return;
    else if (ch == '<') Write(out,"&lt;",4);
    else if (ch == '>') Write(out,"&gt;",4);
    else if (ch == '&') Write(out,"&amp;",5);
    else Putc(ch,out);
  }
}

/* -----------------------------------------------------------------------------
 * swill_pre_encoder()
 *
 * Encoder function registered with Printf
 * ----------------------------------------------------------------------------- */
 
DOH *
swill_pre_encoder(DOH *s) {
  DOH *ns = NewString("");
  int ch;
  while (1) {
    ch = Getc(s);
    if (ch == EOF) return ns;
    else if (ch == '<') Write(ns,"&lt;",4);
    else if (ch == '>') Write(ns,"&gt;",4);
    else if (ch == '&') Write(ns,"&amp;",5);
    else Putc(ch,ns);
  }
}

/* -----------------------------------------------------------------------------
 * Base64 decoding
 * ----------------------------------------------------------------------------- */

static char *base64chars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";
static unsigned char base64map[256];
static int  base64init = 0;

static void init_base64() {
   int i;
   for (i = 0; i < 256; i++) {
     base64map[i] = 255;
   }
   for (i = 0; i < strlen(base64chars); i++) {
     base64map[base64chars[i]] = i;
   }
   
}

/* -----------------------------------------------------------------------------
 * swill_base64_decode()
 * 
 * Decode a base64 encoded data stream.
 *
 *   in   - Any file-like object with a Getc method.  The base64 input stream.
 *   out  - Any file-like object with a Putc method.  The base64 output stream.
 *
 * This function is primarily used to decode passwords.
 * ----------------------------------------------------------------------------- */

void
swill_base64_decode(DOH *in, DOH *out) {
  char group[4], decode[3];
  int grpi;
  int i,ch;
  int nbytes;
  if (!base64init) {
    init_base64();
    base64init = 1;
  }
  while (1) {
    /* Read in a triplet */
    for (i = 0; i < 4; i++) {
    l1:
      ch = Getc(in);
      if (ch == EOF) break;
      if (base64map[ch] == 255) goto l1;
      group[i] = ch;
    } 
    /* Pad out to a multiple of four */
    while (i < 4) {
      group[i] = '=';
      i++;
    }
    /* Figure out how many bytes are to be read */
    nbytes = 3;
    for (i = 4; i > 0; i--) {
      if (group[i-1] != '=') break;
      nbytes--;
    }

    /* Decode the string */
    grpi = 0;
    for (i = 0; i < 4; i++) {
      grpi = grpi << 6;
      grpi = grpi + ((base64map[group[i]]) & 63);
    }
    
    if (nbytes >= 1) {
      Putc((grpi >> 16) & 0xff, out);
    }
    if (nbytes >= 2) {
      Putc((grpi >> 8) & 0xff, out);
    }
    if (nbytes >= 3) {
      Putc(grpi & 0xff, out);
    }
    if ((ch == EOF) || (nbytes < 3)) return;
  }
}