/* gbase64.c - Base64 encoding/decoding
 *
 *  Copyright (C) 2006 Alexander Larsson <alexl@redhat.com>
 *  Copyright (C) 2000-2003 Ximian Inc.
 *
 * SPDX-License-Identifier: LGPL-2.1-or-later
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, see <http://www.gnu.org/licenses/>.
 *
 * This is based on code in camel, written by:
 *    Michael Zucchi <notzed@ximian.com>
 *    Jeffrey Stedfast <fejj@ximian.com>
 */

#include "config.h"

#include <string.h>

#include "gbase64.h"
#include "gtestutils.h"
#include "glibintl.h"


/**
 * SECTION:base64
 * @title: Base64 Encoding
 * @short_description: encodes and decodes data in Base64 format
 *
 * Base64 is an encoding that allows a sequence of arbitrary bytes to be
 * encoded as a sequence of printable ASCII characters. For the definition
 * of Base64, see 
 * [RFC 1421](http://www.ietf.org/rfc/rfc1421.txt)
 * or
 * [RFC 2045](http://www.ietf.org/rfc/rfc2045.txt).
 * Base64 is most commonly used as a MIME transfer encoding
 * for email.
 *
 * GLib supports incremental encoding using g_base64_encode_step() and
 * g_base64_encode_close(). Incremental decoding can be done with
 * g_base64_decode_step(). To encode or decode data in one go, use
 * g_base64_encode() or g_base64_decode(). To avoid memory allocation when
 * decoding, you can use g_base64_decode_inplace().
 *
 * Support for Base64 encoding has been added in GLib 2.12.
 */

static const char base64_alphabet[] =
        "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";

/**
 * g_base64_encode_step:
 * @in: (array length=len) (element-type guint8): the binary data to encode
 * @len: the length of @in
 * @break_lines: whether to break long lines
 * @out: (out) (array) (element-type guint8): pointer to destination buffer
 * @state: (inout): Saved state between steps, initialize to 0
 * @save: (inout): Saved state between steps, initialize to 0
 *
 * Incrementally encode a sequence of binary data into its Base-64 stringified
 * representation. By calling this function multiple times you can convert
 * data in chunks to avoid having to have the full encoded data in memory.
 *
 * When all of the data has been converted you must call
 * g_base64_encode_close() to flush the saved state.
 *
 * The output buffer must be large enough to fit all the data that will
 * be written to it. Due to the way base64 encodes you will need
 * at least: (@len / 3 + 1) * 4 + 4 bytes (+ 4 may be needed in case of
 * non-zero state). If you enable line-breaking you will need at least:
 * ((@len / 3 + 1) * 4 + 4) / 76 + 1 bytes of extra space.
 *
 * @break_lines is typically used when putting base64-encoded data in emails.
 * It breaks the lines at 76 columns instead of putting all of the text on
 * the same line. This avoids problems with long lines in the email system.
 * Note however that it breaks the lines with `LF` characters, not
 * `CR LF` sequences, so the result cannot be passed directly to SMTP
 * or certain other protocols.
 *
 * Returns: The number of bytes of output that was written
 *
 * Since: 2.12
 */
gsize
g_base64_encode_step (const guchar *in,
                      gsize         len,
                      gboolean      break_lines,
                      gchar        *out,
                      gint         *state,
                      gint         *save)
{
  char *outptr;
  const guchar *inptr;

  g_return_val_if_fail (in != NULL || len == 0, 0);
  g_return_val_if_fail (out != NULL, 0);
  g_return_val_if_fail (state != NULL, 0);
  g_return_val_if_fail (save != NULL, 0);

  if (len == 0)
    return 0;

  inptr = in;
  outptr = out;

  if (len + ((char *) save) [0] > 2)
    {
      const guchar *inend = in+len-2;
      int c1, c2, c3;
      int already;

      already = *state;

      switch (((char *) save) [0])
        {
        case 1:
          c1 = ((unsigned char *) save) [1];
          goto skip1;
        case 2:
          c1 = ((unsigned char *) save) [1];
          c2 = ((unsigned char *) save) [2];
          goto skip2;
        }

      /*
       * yes, we jump into the loop, no i'm not going to change it,
       * it's beautiful!
       */
      while (inptr < inend)
        {
          c1 = *inptr++;
        skip1:
          c2 = *inptr++;
        skip2:
          c3 = *inptr++;
          *outptr++ = base64_alphabet [ c1 >> 2 ];
          *outptr++ = base64_alphabet [ c2 >> 4 |
                                        ((c1&0x3) << 4) ];
          *outptr++ = base64_alphabet [ ((c2 &0x0f) << 2) |
                                        (c3 >> 6) ];
          *outptr++ = base64_alphabet [ c3 & 0x3f ];
          /* this is a bit ugly ... */
          if (break_lines && (++already) >= 19)
            {
              *outptr++ = '\n';
              already = 0;
            }
        }

      ((char *)save)[0] = 0;
      len = 2 - (inptr - inend);
      *state = already;
    }

  g_assert (len == 0 || len == 1 || len == 2);

    {
      char *saveout;

      /* points to the slot for the next char to save */
      saveout = & (((char *)save)[1]) + ((char *)save)[0];

      /* len can only be 0 1 or 2 */
      switch(len)
        {
        case 2:
          *saveout++ = *inptr++;
          G_GNUC_FALLTHROUGH;
        case 1:
          *saveout++ = *inptr++;
        }
      ((char *)save)[0] += len;
    }

  return outptr - out;
}

/**
 * g_base64_encode_close:
 * @break_lines: whether to break long lines
 * @out: (out) (array) (element-type guint8): pointer to destination buffer
 * @state: (inout): Saved state from g_base64_encode_step()
 * @save: (inout): Saved state from g_base64_encode_step()
 *
 * Flush the status from a sequence of calls to g_base64_encode_step().
 *
 * The output buffer must be large enough to fit all the data that will
 * be written to it. It will need up to 4 bytes, or up to 5 bytes if
 * line-breaking is enabled.
 *
 * The @out array will not be automatically nul-terminated.
 *
 * Returns: The number of bytes of output that was written
 *
 * Since: 2.12
 */
gsize
g_base64_encode_close (gboolean  break_lines,
                       gchar    *out,
                       gint     *state,
                       gint     *save)
{
  int c1, c2;
  char *outptr = out;

  g_return_val_if_fail (out != NULL, 0);
  g_return_val_if_fail (state != NULL, 0);
  g_return_val_if_fail (save != NULL, 0);

  c1 = ((unsigned char *) save) [1];
  c2 = ((unsigned char *) save) [2];

  switch (((char *) save) [0])
    {
    case 2:
      outptr [2] = base64_alphabet[ ( (c2 &0x0f) << 2 ) ];
      g_assert (outptr [2] != 0);
      goto skip;
    case 1:
      outptr[2] = '=';
      c2 = 0;  /* saved state here is not relevant */
    skip:
      outptr [0] = base64_alphabet [ c1 >> 2 ];
      outptr [1] = base64_alphabet [ c2 >> 4 | ( (c1&0x3) << 4 )];
      outptr [3] = '=';
      outptr += 4;
      break;
    }
  if (break_lines)
    *outptr++ = '\n';

  *save = 0;
  *state = 0;

  return outptr - out;
}

/**
 * g_base64_encode:
 * @data: (array length=len) (element-type guint8) (nullable): the binary data to encode
 * @len: the length of @data
 *
 * Encode a sequence of binary data into its Base-64 stringified
 * representation.
 *
 * Returns: (transfer full): a newly allocated, zero-terminated Base-64
 *               encoded string representing @data. The returned string must
 *               be freed with g_free().
 *
 * Since: 2.12
 */
gchar *
g_base64_encode (const guchar *data,
                 gsize         len)
{
  gchar *out;
  gint state = 0, outlen;
  gint save = 0;

  g_return_val_if_fail (data != NULL || len == 0, NULL);

  /* We can use a smaller limit here, since we know the saved state is 0,
     +1 is needed for trailing \0, also check for unlikely integer overflow */
  g_return_val_if_fail (len < ((G_MAXSIZE - 1) / 4 - 1) * 3, NULL);

  out = g_malloc ((len / 3 + 1) * 4 + 1);

  outlen = g_base64_encode_step (data, len, FALSE, out, &state, &save);
  outlen += g_base64_encode_close (FALSE, out + outlen, &state, &save);
  out[outlen] = '\0';

  return (gchar *) out;
}

static const unsigned char mime_base64_rank[256] = {
  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  255,255,255,255,255,255,255,255,255,255,255, 62,255,255,255, 63,
   52, 53, 54, 55, 56, 57, 58, 59, 60, 61,255,255,255,  0,255,255,
  255,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,
   15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,255,255,255,255,255,
  255, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
   41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51,255,255,255,255,255,
  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
  255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,255,
};

/**
 * g_base64_decode_step: (skip)
 * @in: (array length=len) (element-type guint8): binary input data
 * @len: max length of @in data to decode
 * @out: (out caller-allocates) (array) (element-type guint8): output buffer
 * @state: (inout): Saved state between steps, initialize to 0
 * @save: (inout): Saved state between steps, initialize to 0
 *
 * Incrementally decode a sequence of binary data from its Base-64 stringified
 * representation. By calling this function multiple times you can convert
 * data in chunks to avoid having to have the full encoded data in memory.
 *
 * The output buffer must be large enough to fit all the data that will
 * be written to it. Since base64 encodes 3 bytes in 4 chars you need
 * at least: (@len / 4) * 3 + 3 bytes (+ 3 may be needed in case of non-zero
 * state).
 *
 * Returns: The number of bytes of output that was written
 *
 * Since: 2.12
 **/
gsize
g_base64_decode_step (const gchar  *in,
                      gsize         len,
                      guchar       *out,
                      gint         *state,
                      guint        *save)
{
  const guchar *inptr;
  guchar *outptr;
  const guchar *inend;
  guchar c, rank;
  guchar last[2];
  unsigned int v;
  int i;

  g_return_val_if_fail (in != NULL || len == 0, 0);
  g_return_val_if_fail (out != NULL, 0);
  g_return_val_if_fail (state != NULL, 0);
  g_return_val_if_fail (save != NULL, 0);

  if (len == 0)
    return 0;

  inend = (const guchar *)in+len;
  outptr = out;

  /* convert 4 base64 bytes to 3 normal bytes */
  v=*save;
  i=*state;

  last[0] = last[1] = 0;

  /* we use the sign in the state to determine if we got a padding character
     in the previous sequence */
  if (i < 0)
    {
      i = -i;
      last[0] = '=';
    }

  inptr = (const guchar *)in;
  while (inptr < inend)
    {
      c = *inptr++;
      rank = mime_base64_rank [c];
      if (rank != 0xff)
        {
          last[1] = last[0];
          last[0] = c;
          v = (v<<6) | rank;
          i++;
          if (i==4)
            {
              *outptr++ = v>>16;
              if (last[1] != '=')
                *outptr++ = v>>8;
              if (last[0] != '=')
                *outptr++ = v;
              i=0;
            }
        }
    }

  *save = v;
  *state = last[0] == '=' ? -i : i;

  return outptr - out;
}

/**
 * g_base64_decode:
 * @text: (not nullable): zero-terminated string with base64 text to decode
 * @out_len: (out): The length of the decoded data is written here
 *
 * Decode a sequence of Base-64 encoded text into binary data.  Note
 * that the returned binary data is not necessarily zero-terminated,
 * so it should not be used as a character string.
 *
 * Returns: (transfer full) (array length=out_len) (element-type guint8):
 *               newly allocated buffer containing the binary data
 *               that @text represents. The returned buffer must
 *               be freed with g_free().
 *
 * Since: 2.12
 */
guchar *
g_base64_decode (const gchar *text,
                 gsize       *out_len)
{
  guchar *ret;
  gsize input_length;
  gint state = 0;
  guint save = 0;

  g_return_val_if_fail (text != NULL, NULL);
  g_return_val_if_fail (out_len != NULL, NULL);

  input_length = strlen (text);

  /* We can use a smaller limit here, since we know the saved state is 0,
     +1 used to avoid calling g_malloc0(0), and hence returning NULL */
  ret = g_malloc0 ((input_length / 4) * 3 + 1);

  *out_len = g_base64_decode_step (text, input_length, ret, &state, &save);

  return ret;
}

/**
 * g_base64_decode_inplace:
 * @text: (inout) (array length=out_len) (element-type guint8): zero-terminated
 *        string with base64 text to decode
 * @out_len: (inout): The length of the decoded data is written here
 *
 * Decode a sequence of Base-64 encoded text into binary data
 * by overwriting the input data.
 *
 * Returns: (transfer none): The binary data that @text responds. This pointer
 *               is the same as the input @text.
 *
 * Since: 2.20
 */
guchar *
g_base64_decode_inplace (gchar *text,
                         gsize *out_len)
{
  gint input_length, state = 0;
  guint save = 0;

  g_return_val_if_fail (text != NULL, NULL);
  g_return_val_if_fail (out_len != NULL, NULL);

  input_length = strlen (text);

  g_return_val_if_fail (input_length > 1, NULL);

  *out_len = g_base64_decode_step (text, input_length, (guchar *) text, &state, &save);

  return (guchar *) text;
}
