/*
 * quoprint.c:  quoted-printable encoding and decoding functions
 *
 * ====================================================================
 * Copyright (c) 2000-2004 CollabNet.  All rights reserved.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution.  The terms
 * are also available at http://subversion.tigris.org/license-1.html.
 * If newer versions of this license are posted there, you may use a
 * newer version instead, at your option.
 *
 * This software consists of voluntary contributions made by many
 * individuals.  For exact contribution history, see the revision
 * history and logs, available at http://subversion.tigris.org/.
 * ====================================================================
 */



#include <string.h>

#include <apr.h>
#include <apr_pools.h>
#include <apr_general.h>        /* for APR_INLINE */

#include "svn_pools.h"
#include "svn_io.h"
#include "svn_error.h"
#include "svn_quoprint.h"


/* Caveats:

	(1) This code is for the encoding and decoding of binary data
	    only.  Thus, CRLF sequences are encoded as =0D=0A, and we
	    don't have to worry about tabs and spaces coming before
	    hard newlines, since there aren't any.

	(2) The decoder does no error reporting, and instead throws
	    away invalid sequences.  It also discards CRLF sequences,
	    since those can only appear in the encoding of text data.

	(3) The decoder does not strip whitespace at the end of a
	    line, so it is not actually compliant with RFC 2045.
	    (Such whitespace should never occur, even in the encoding
	    of text data, but RFC 2045 requires a decoder to detect
	    that a transport agent has added trailing whitespace).

	(4) The encoder is tailored to make output embeddable in XML,
	    which means it quotes <>'"& as well as the characters
	    required by RFC 2045.  */

#define QUOPRINT_LINELEN 76
#define VALID_LITERAL(c) ((c) == '\t' || ((c) >= ' ' && (c) <= '~' \
                                          && (c) != '='))
#define ENCODE_AS_LITERAL(c) (VALID_LITERAL(c) && (c) != '\t' && (c) != '<' \
                              && (c) != '>' && (c) != '\'' && (c) != '"' \
                              && (c) != '&')
static const char hextab[] = "0123456789ABCDEF";



/* Binary input --> quoted-printable-encoded output */

struct encode_baton {
  svn_stream_t *output;
  int linelen;                  /* Bytes output so far on this line */
  apr_pool_t *pool;
};


/* Quoted-printable-encode a byte string which may or may not be the
   totality of the data being encoded.  *LINELEN carries the length of
   the current output line; initialize it to 0.  Output will be
   appended to STR.  */
static void
encode_bytes (svn_stringbuf_t *str, const char *data, apr_size_t len,
              int *linelen)
{
  char buf[3];
  const char *p;

  /* Keep encoding three-byte groups until we run out.  */
  for (p = data; p < data + len; p++)
    {
      /* Encode this character.  */
      if (ENCODE_AS_LITERAL(*p))
        {
          svn_stringbuf_appendbytes (str, p, 1);
          (*linelen)++;
        }
      else
        {
          buf[0] = '=';
          buf[1] = hextab[(*p >> 4) & 0xf];
          buf[2] = hextab[*p & 0xf];
          svn_stringbuf_appendbytes (str, buf, 3);
          *linelen += 3;
        }

      /* Make sure our output lines don't exceed QUOPRINT_LINELEN.  */
      if (*linelen + 3 > QUOPRINT_LINELEN)
        {
          svn_stringbuf_appendcstr (str, "=\n");
          *linelen = 0;
        }
    }
}


/* Write handler for svn_quoprint_encode.  */
static svn_error_t *
encode_data (void *baton, const char *data, apr_size_t *len)
{
  struct encode_baton *eb = baton;
  apr_pool_t *subpool = svn_pool_create (eb->pool);
  svn_stringbuf_t *encoded = svn_stringbuf_create ("", subpool);
  apr_size_t enclen;
  svn_error_t *err = SVN_NO_ERROR;

  /* Encode this block of data and write it out.  */
  encode_bytes (encoded, data, *len, &eb->linelen);
  enclen = encoded->len;
  if (enclen != 0)
    err = svn_stream_write (eb->output, encoded->data, &enclen);
  svn_pool_destroy (subpool);
  return err;
}


/* Close handler for svn_quoprint_encode().  */
static svn_error_t *
finish_encoding_data (void *baton)
{
  struct encode_baton *eb = baton;
  svn_error_t *err = SVN_NO_ERROR;
  apr_size_t len;

  /* Terminate the current output line if it's not empty.  */
  if (eb->linelen > 0)
    {
      len = 2;
      err = svn_stream_write (eb->output, "=\n", &len);
    }

  /* Pass on the close request and clean up the baton.  */
  if (err == SVN_NO_ERROR)
    err = svn_stream_close (eb->output);
  svn_pool_destroy (eb->pool);
  return err;
}


svn_stream_t *
svn_quoprint_encode (svn_stream_t *output, apr_pool_t *pool)
{
  apr_pool_t *subpool = svn_pool_create (pool);
  struct encode_baton *eb = apr_palloc (subpool, sizeof (*eb));
  svn_stream_t *stream;

  eb->output = output;
  eb->linelen = 0;
  eb->pool = subpool;
  stream = svn_stream_create (eb, pool);
  svn_stream_set_write (stream, encode_data);
  svn_stream_set_close (stream, finish_encoding_data);
  return stream;
}


svn_stringbuf_t *
svn_quoprint_encode_string (svn_stringbuf_t *str, apr_pool_t *pool)
{
  svn_stringbuf_t *encoded = svn_stringbuf_create ("", pool);
  int linelen = 0;

  encode_bytes (encoded, str->data, str->len, &linelen);
  if (linelen > 0)
    svn_stringbuf_appendcstr (encoded, "=\n");
  return encoded;
}



/* Quoted-printable-encoded input --> binary output */

struct decode_baton {
  svn_stream_t *output;
  char buf[3];                  /* Bytes waiting to be decoded */
  int buflen;                   /* Number of bytes waiting */
  apr_pool_t *pool;
};


/* Decode a byte string which may or may not be the total amount of
   data being decoded.  INBUF and *INBUFLEN carry the leftover bytes
   from call to call.  Have room for four bytes in INBUF and
   initialize *INBUFLEN to 0 and *DONE to FALSE.  Output will be
   appended to STR.  */
static void
decode_bytes (svn_stringbuf_t *str, const char *data, apr_size_t len,
              char *inbuf, int *inbuflen)
{
  const char *p, *find1, *find2;
  char c;

  for (p = data; p <= data + len; p++)
    {
      /* Append this byte to the buffer and see what we have.  */
      inbuf[(*inbuflen)++] = *p;
      if (*inbuf != '=')
        {
          /* Literal character; append it if it's valid as such.  */
          if (VALID_LITERAL(*inbuf))
            svn_stringbuf_appendbytes (str, inbuf, 1);
          *inbuflen = 0;
        }
      else if (*inbuf == '=' && *inbuflen == 2 && inbuf[1] == '\n')
        {
          /* Soft newline; ignore.  */
          *inbuflen = 0;
        }
      else if (*inbuf == '=' && *inbuflen == 3)
        {
          /* Encoded character; decode it and append.  */
          find1 = strchr(hextab, inbuf[1]);
          find2 = strchr(hextab, inbuf[2]);
          if (find1 != NULL && find2 != NULL)
            {
              c = ((find1 - hextab) << 4) | (find2 - hextab);
              svn_stringbuf_appendbytes (str, &c, 1);
            }
          *inbuflen = 0;
        }
    }
}


/* Write handler for svn_quoprint_decode.  */
static svn_error_t *
decode_data (void *baton, const char *data, apr_size_t *len)
{
  struct decode_baton *db = baton;
  apr_pool_t *subpool;
  svn_stringbuf_t *decoded;
  apr_size_t declen;
  svn_error_t *err = SVN_NO_ERROR;

  /* Decode this block of data.  */
  subpool = svn_pool_create (db->pool);
  decoded = svn_stringbuf_create ("", subpool);
  decode_bytes (decoded, data, *len, db->buf, &db->buflen);

  /* Write the output, clean up, go home.  */
  declen = decoded->len;
  if (declen != 0)
    err = svn_stream_write (db->output, decoded->data, &declen);
  svn_pool_destroy (subpool);
  return err;
}


/* Close handler for svn_quoprint_decode().  */
static svn_error_t *
finish_decoding_data (void *baton)
{
  struct decode_baton *db = baton;
  svn_error_t *err;

  /* Pass on the close request and clean up the baton.  */
  err = svn_stream_close (db->output);
  svn_pool_destroy (db->pool);
  return err;
}


svn_stream_t *
svn_quoprint_decode (svn_stream_t *output, apr_pool_t *pool)
{
  apr_pool_t *subpool = svn_pool_create (pool);
  struct decode_baton *db = apr_palloc (subpool, sizeof (*db));
  svn_stream_t *stream;

  db->output = output;
  db->buflen = 0;
  db->pool = subpool;
  stream = svn_stream_create (db, pool);
  svn_stream_set_write (stream, decode_data);
  svn_stream_set_close (stream, finish_decoding_data);
  return stream;
}


svn_stringbuf_t *
svn_quoprint_decode_string (svn_stringbuf_t *str, apr_pool_t *pool)
{
  svn_stringbuf_t *decoded = svn_stringbuf_create ("", pool);
  char ingroup[4];
  int ingrouplen = 0;

  decode_bytes (decoded, str->data, str->len, ingroup, &ingrouplen);
  return decoded;
}
