src/basenc.c

/* Base64, base32, and similar encoding/decoding strings or files.
   Copyright (C) 2004-2025 Free Software Foundation, Inc.

   This program is free software: you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation, either version 3 of the License, or
   (at your option) any later version.

   This program 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 General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <https://www.gnu.org/licenses/>. */

/* Written by Simon Josefsson <simon@josefsson.org>.  */

#include <config.h>

#include <stdio.h>
#include <getopt.h>
#include <sys/types.h>
#include <gmp.h>

#include "system.h"
#include "assure.h"
#include "c-ctype.h"
#include "fadvise.h"
#include "quote.h"
#include "xstrtol.h"
#include "xdectoint.h"
#include "xbinary-io.h"

#if BASE_TYPE == 42
# define AUTHORS \
  proper_name ("Simon Josefsson"), \
  proper_name ("Assaf Gordon")
#else
# define AUTHORS proper_name ("Simon Josefsson")
#endif

#if BASE_TYPE == 32
# include "base32.h"
# define PROGRAM_NAME "base32"
#elif BASE_TYPE == 64
# include "base64.h"
# define PROGRAM_NAME "base64"
#elif BASE_TYPE == 42
# include "base32.h"
# include "base64.h"
# include "assure.h"
# define PROGRAM_NAME "basenc"
#else
# error missing/invalid BASE_TYPE definition
#endif



#if BASE_TYPE == 42
enum
{
  BASE64_OPTION = CHAR_MAX + 1,
  BASE64URL_OPTION,
  BASE58_OPTION,
  BASE32_OPTION,
  BASE32HEX_OPTION,
  BASE16_OPTION,
  BASE2MSBF_OPTION,
  BASE2LSBF_OPTION,
  Z85_OPTION
};
#endif

static struct option const long_options[] =
{
  {"decode", no_argument, 0, 'd'},
  {"wrap", required_argument, 0, 'w'},
  {"ignore-garbage", no_argument, 0, 'i'},
#if BASE_TYPE == 42
  {"base64",    no_argument, 0, BASE64_OPTION},
  {"base64url", no_argument, 0, BASE64URL_OPTION},
  {"base58",    no_argument, 0, BASE58_OPTION},
  {"base32",    no_argument, 0, BASE32_OPTION},
  {"base32hex", no_argument, 0, BASE32HEX_OPTION},
  {"base16",    no_argument, 0, BASE16_OPTION},
  {"base2msbf", no_argument, 0, BASE2MSBF_OPTION},
  {"base2lsbf", no_argument, 0, BASE2LSBF_OPTION},
  {"z85",       no_argument, 0, Z85_OPTION},
#endif
  {GETOPT_HELP_OPTION_DECL},
  {GETOPT_VERSION_OPTION_DECL},
  {nullptr, 0, nullptr, 0}
};

void
usage (int status)
{
  if (status != EXIT_SUCCESS)
    emit_try_help ();
  else
    {
      printf (_("\
Usage: %s [OPTION]... [FILE]\n\
"), program_name);

#if BASE_TYPE == 42
      fputs (_("\
basenc encode or decode FILE, or standard input, to standard output.\n\
"), stdout);
#else
      printf (_("\
Base%d encode or decode FILE, or standard input, to standard output.\n\
"), BASE_TYPE);
#endif

      emit_stdin_note ();
      emit_mandatory_arg_note ();
#if BASE_TYPE == 42
      fputs (_("\
      --base64          same as 'base64' program (RFC4648 section 4)\n\
"), stdout);
      fputs (_("\
      --base64url       file- and url-safe base64 (RFC4648 section 5)\n\
"), stdout);
      fputs (_("\
      --base58          visually unambiguous base58 encoding\n\
"), stdout);
      fputs (_("\
      --base32          same as 'base32' program (RFC4648 section 6)\n\
"), stdout);
      fputs (_("\
      --base32hex       extended hex alphabet base32 (RFC4648 section 7)\n\
"), stdout);
      fputs (_("\
      --base16          hex encoding (RFC4648 section 8)\n\
"), stdout);
      fputs (_("\
      --base2msbf       bit string with most significant bit (msb) first\n\
"), stdout);
      fputs (_("\
      --base2lsbf       bit string with least significant bit (lsb) first\n\
"), stdout);
#endif
      fputs (_("\
  -d, --decode          decode data\n\
  -i, --ignore-garbage  when decoding, ignore non-alphabet characters\n\
  -w, --wrap=COLS       wrap encoded lines after COLS character (default 76).\n\
                          Use 0 to disable line wrapping\n\
"), stdout);
#if BASE_TYPE == 42
      fputs (_("\
      --z85             ascii85-like encoding (ZeroMQ spec:32/Z85);\n\
                        when encoding, input length must be a multiple of 4;\n\
                        when decoding, input length must be a multiple of 5\n\
"), stdout);
#endif
      fputs (HELP_OPTION_DESCRIPTION, stdout);
      fputs (VERSION_OPTION_DESCRIPTION, stdout);
#if BASE_TYPE == 42
      fputs (_("\
\n\
When decoding, the input may contain newlines in addition to the bytes of\n\
the formal alphabet.  Use --ignore-garbage to attempt to recover\n\
from any other non-alphabet bytes in the encoded stream.\n\
"), stdout);
#else
      printf (_("\
\n\
The data are encoded as described for the %s alphabet in RFC 4648.\n\
When decoding, the input may contain newlines in addition to the bytes of\n\
the formal %s alphabet.  Use --ignore-garbage to attempt to recover\n\
from any other non-alphabet bytes in the encoded stream.\n"),
              PROGRAM_NAME, PROGRAM_NAME);
#endif
      emit_ancillary_info (PROGRAM_NAME);
    }

  exit (status);
}

#if BASE_TYPE != 64
static int
base32_required_padding (int len)
{
  int partial = len % 8;
  return partial ? 8 - partial : 0;
}
#endif

#if BASE_TYPE != 32
static int
base64_required_padding (int len)
{
  int partial = len % 4;
  return partial ? 4 - partial : 0;
}
#endif

#if BASE_TYPE == 42
static int
no_required_padding (MAYBE_UNUSED int len)
{
  return 0;
}
#endif

#define ENC_BLOCKSIZE (1024 * 3 * 10)

#if BASE_TYPE == 32
# define BASE_LENGTH BASE32_LENGTH
# define REQUIRED_PADDING base32_required_padding
/* Note that increasing this may decrease performance if --ignore-garbage
   is used, because of the memmove operation below.  */
# define DEC_BLOCKSIZE (1024 * 5)

/* Ensure that BLOCKSIZE is a multiple of 5 and 8.  */
static_assert (ENC_BLOCKSIZE % 40 == 0); /* Padding chars only on last block. */
static_assert (DEC_BLOCKSIZE % 40 == 0); /* Complete encoded blocks are used. */

# define base_encode base32_encode
# define base_decode_context base32_decode_context
# define base_decode_ctx_init base32_decode_ctx_init
# define base_decode_ctx base32_decode_ctx
# define base_decode_ctx_finalize decode_ctx_finalize
# define isubase isubase32
#elif BASE_TYPE == 64
# define BASE_LENGTH BASE64_LENGTH
# define REQUIRED_PADDING base64_required_padding
/* Note that increasing this may decrease performance if --ignore-garbage
   is used, because of the memmove operation below.  */
# define DEC_BLOCKSIZE (1024 * 3)

/* Ensure that BLOCKSIZE is a multiple of 3 and 4.  */
static_assert (ENC_BLOCKSIZE % 12 == 0); /* Padding chars only on last block. */
static_assert (DEC_BLOCKSIZE % 12 == 0); /* Complete encoded blocks are used. */

# define base_encode base64_encode
# define base_decode_context base64_decode_context
# define base_decode_ctx_init base64_decode_ctx_init
# define base_decode_ctx base64_decode_ctx
# define base_decode_ctx_finalize decode_ctx_finalize
# define isubase isubase64
#elif BASE_TYPE == 42


# define BASE_LENGTH base_length
# define REQUIRED_PADDING required_padding

/* Note that increasing this may decrease performance if --ignore-garbage
   is used, because of the memmove operation below.  */
# define DEC_BLOCKSIZE (4200)
static_assert (DEC_BLOCKSIZE % 40 == 0); /* complete encoded blocks for base32*/
static_assert (DEC_BLOCKSIZE % 12 == 0); /* complete encoded blocks for base64*/

static idx_t (*base_length) (idx_t len);
static int (*required_padding) (int i);
static bool (*isubase) (unsigned char ch);
static void (*base_encode) (char const *restrict in, idx_t inlen,
                            char *restrict out, idx_t outlen);

struct base16_decode_context
{
  /* Either a 4-bit nibble, or negative if we have no nibble.  */
  signed char nibble;
};

struct z85_decode_context
{
  int i;
  unsigned char octets[5];
};

struct base58_context
{
  unsigned char *buf;
  idx_t size;
  idx_t capacity;
};

struct base2_decode_context
{
  unsigned char octet;
  int bit_pos;
};

struct base_decode_context
{
  union {
    struct base64_decode_context base64;
    struct base32_decode_context base32;
    struct base16_decode_context base16;
    struct base2_decode_context base2;
    struct z85_decode_context z85;
    struct base58_context base58;
  } ctx;
  char *inbuf;
  idx_t bufsize;
};
static void (*base_decode_ctx_init) (struct base_decode_context *ctx);
static bool (*base_decode_ctx) (struct base_decode_context *ctx,
                                char const *restrict in, idx_t inlen,
                                char *restrict out, idx_t *outlen);
static bool (*base_decode_ctx_finalize) (struct base_decode_context *ctx,
                                         char *restrict *out, idx_t *outlen);

struct base_encode_context
{
  union {
    struct base58_context base58;
  } ctx;
};

static void (*base_encode_ctx_init) (struct base_encode_context *ctx);
static bool (*base_encode_ctx) (struct base_encode_context *ctx,
                                char const *restrict in, idx_t inlen,
                                char *restrict out, idx_t *outlen);
static bool (*base_encode_ctx_finalize) (struct base_encode_context *ctx,
                                         char *restrict *out, idx_t *outlen);

static bool
no_padding (MAYBE_UNUSED struct base_decode_context *ctx)
{
  return false;
}

static int
no_pending_length (MAYBE_UNUSED struct base_decode_context *ctx)
{
  return 0;
}
#endif

#if BASE_TYPE == 42
static bool (*has_padding) (struct base_decode_context *ctx);
static int (*get_pending_length) (struct base_decode_context *ctx);

static bool
base64_ctx_has_padding (struct base_decode_context *ctx)
{
  return ctx->ctx.base64.i && ctx->ctx.base64.buf[ctx->ctx.base64.i - 1] == '=';
}

static bool
base32_ctx_has_padding (struct base_decode_context *ctx)
{
  return ctx->ctx.base32.i && ctx->ctx.base32.buf[ctx->ctx.base32.i - 1] == '=';
}

static int
base64_ctx_get_pending_length (struct base_decode_context *ctx)
{
  return ctx->ctx.base64.i;
}

static int
base32_ctx_get_pending_length (struct base_decode_context *ctx)
{
  return ctx->ctx.base32.i;
}

static int
base16_ctx_get_pending_length (MAYBE_UNUSED struct base_decode_context *ctx)
{
  return 1; /* Always check nibble state.  */
}

static int
z85_ctx_get_pending_length (struct base_decode_context *ctx)
{
  return ctx->ctx.z85.i;
}

static int
base2_ctx_get_pending_length (struct base_decode_context *ctx)
{
  return ctx->ctx.base2.bit_pos;
}
#else
static bool
has_padding (struct base_decode_context *ctx)
{
  return ctx->i && ctx->buf[ctx->i - 1] == '=';
}

static int
get_pending_length (struct base_decode_context *ctx)
{
  return ctx->i;
}
#endif


/* Process any pending data in CTX, while auto padding if appropriate.
   Return TRUE on success, FALSE on failure.  */

static bool
decode_ctx_finalize (struct base_decode_context *ctx,
                     char *restrict *out, idx_t *outlen)
{
  if (get_pending_length (ctx) == 0)
    {
      *outlen = 0;
      return true;
    }

  /* Auto-pad input and flush the context */
  char padbuf[8] ATTRIBUTE_NONSTRING = "========";
  idx_t pending_len = get_pending_length (ctx);
  idx_t auto_padding = REQUIRED_PADDING (pending_len);
  idx_t n = *outlen;
  bool result;

  if (auto_padding && ! has_padding (ctx))
    {
      affirm (auto_padding <= sizeof (padbuf));
      result = base_decode_ctx (ctx, padbuf, auto_padding, *out, &n);
    }
  else
    {
      result = base_decode_ctx (ctx, "", 0, *out, &n);
    }

  *outlen = n;
  return result;
}

#if BASE_TYPE == 42

static idx_t
base64_length_wrapper (idx_t len)
{
  return BASE64_LENGTH (len);
}

static void
base64_decode_ctx_init_wrapper (struct base_decode_context *ctx)
{
  base64_decode_ctx_init (&ctx->ctx.base64);
}

static bool
base64_decode_ctx_wrapper (struct base_decode_context *ctx,
                           char const *restrict in, idx_t inlen,
                           char *restrict out, idx_t *outlen)
{
  return base64_decode_ctx (&ctx->ctx.base64, in, inlen, out, outlen);
}

static void
init_inbuf (struct base_decode_context *ctx)
{
  ctx->bufsize = DEC_BLOCKSIZE;
  ctx->inbuf = xcharalloc (ctx->bufsize);
}

static void
prepare_inbuf (struct base_decode_context *ctx, idx_t inlen)
{
  if (ctx->bufsize < inlen)
    ctx->inbuf = xpalloc (ctx->inbuf, &ctx->bufsize,
                          inlen - ctx->bufsize, -1, sizeof *ctx->inbuf);
}


static void
base64url_encode (char const *restrict in, idx_t inlen,
                  char *restrict out, idx_t outlen)
{
  base64_encode (in, inlen, out, outlen);
  /* translate 62nd and 63rd characters */
  char *p = out;
  while (outlen--)
    {
      if (*p == '+')
        *p = '-';
      else if (*p == '/')
        *p = '_';
      ++p;
    }
}

static bool
isubase64url (unsigned char ch)
{
  return (ch == '-' || ch == '_'
          || (ch != '+' && ch != '/' && isubase64 (ch)));
}

static void
base64url_decode_ctx_init_wrapper (struct base_decode_context *ctx)
{
  base64_decode_ctx_init (&ctx->ctx.base64);
  init_inbuf (ctx);
}


static bool
base64url_decode_ctx_wrapper (struct base_decode_context *ctx,
                              char const *restrict in, idx_t inlen,
                              char *restrict out, idx_t *outlen)
{
  prepare_inbuf (ctx, inlen);
  memcpy (ctx->inbuf, in, inlen);

  /* translate 62nd and 63rd characters */
  idx_t i = inlen;
  char *p = ctx->inbuf;
  while (i--)
    {
      if (*p == '+' || *p == '/')
        {
          *outlen = 0;
          return false; /* reject base64 input */
        }
      else if (*p == '-')
        *p = '+';
      else if (*p == '_')
        *p = '/';
      ++p;
    }

  return base64_decode_ctx (&ctx->ctx.base64, ctx->inbuf, inlen,
                            out, outlen);
}



static idx_t
base32_length_wrapper (idx_t len)
{
  return BASE32_LENGTH (len);
}

static void
base32_decode_ctx_init_wrapper (struct base_decode_context *ctx)
{
  base32_decode_ctx_init (&ctx->ctx.base32);
}

static bool
base32_decode_ctx_wrapper (struct base_decode_context *ctx,
                           char const *restrict in, idx_t inlen,
                           char *restrict out, idx_t *outlen)
{
  return base32_decode_ctx (&ctx->ctx.base32, in, inlen, out, outlen);
}

/* ABCDEFGHIJKLMNOPQRSTUVWXYZ234567
     to
   0123456789ABCDEFGHIJKLMNOPQRSTUV */
static const char base32_norm_to_hex[32 + 9] = {
/*0x32, 0x33, 0x34, 0x35, 0x36, 0x37, */
  'Q',  'R',  'S',  'T',  'U',  'V',

  0x38, 0x39, 0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x40,

/*0x41, 0x42, 0x43, 0x44, 0x45, 0x46, 0x47, 0x48, */
  '0',  '1',  '2',  '3',  '4',  '5',  '6',  '7',

/*0x49, 0x4a, 0x4b, 0x4c, 0x4d, 0x4e, 0x4f, 0x50, */
  '8',  '9',  'A',  'B',  'C',  'D',  'E',  'F',

/*0x51, 0x52, 0x53, 0x54, 0x55, 0x56, 0x57, 0x58, */
  'G',  'H',  'I',  'J',  'K',  'L',  'M',  'N',

/*0x59, 0x5a, */
  'O',  'P',
};

/* 0123456789ABCDEFGHIJKLMNOPQRSTUV
     to
   ABCDEFGHIJKLMNOPQRSTUVWXYZ234567 */
static const char base32_hex_to_norm[32 + 9] = {
  /* from: 0x30 .. 0x39 ('0' to '9') */
  /* to:*/ 'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', 'I', 'J',

  0x3a, 0x3b, 0x3c, 0x3d, 0x3e, 0x3f, 0x40,

  /* from: 0x41 .. 0x4A ('A' to 'J') */
  /* to:*/ 'K', 'L', 'M', 'N', 'O', 'P', 'Q', 'R', 'S', 'T',

  /* from: 0x4B .. 0x54 ('K' to 'T') */
  /* to:*/ 'U', 'V', 'W', 'X', 'Y', 'Z', '2', '3', '4', '5',

  /* from: 0x55 .. 0x56 ('U' to 'V') */
  /* to:*/ '6', '7'
};


inline static bool
isubase32hex (unsigned char ch)
{
  return ('0' <= ch && ch <= '9') || ('A' <= ch && ch <= 'V');
}


static void
base32hex_encode (char const *restrict in, idx_t inlen,
                  char *restrict out, idx_t outlen)
{
  base32_encode (in, inlen, out, outlen);

  for (char *p = out; outlen--; p++)
    {
      affirm (0x32 <= *p && *p <= 0x5a);          /* LCOV_EXCL_LINE */
      *p = base32_norm_to_hex[*p - 0x32];
    }
}


static void
base32hex_decode_ctx_init_wrapper (struct base_decode_context *ctx)
{
  base32_decode_ctx_init (&ctx->ctx.base32);
  init_inbuf (ctx);
}


static bool
base32hex_decode_ctx_wrapper (struct base_decode_context *ctx,
                              char const *restrict in, idx_t inlen,
                              char *restrict out, idx_t *outlen)
{
  prepare_inbuf (ctx, inlen);

  idx_t i = inlen;
  char *p = ctx->inbuf;
  while (i--)
    {
      if (isubase32hex (*in))
        *p = base32_hex_to_norm[*in - 0x30];
      else
        *p = *in;
      ++p;
      ++in;
    }

  return base32_decode_ctx (&ctx->ctx.base32, ctx->inbuf, inlen,
                            out, outlen);
}
/* With this approach this file works independent of the charset used
   (think EBCDIC).  However, it does assume that the characters in the
   Base32 alphabet (A-Z2-7) are encoded in 0..255.  POSIX
   1003.1-2001 require that char and unsigned char are 8-bit
   quantities, though, taking care of that problem.  But this may be a
   potential problem on non-POSIX C99 platforms.

   IBM C V6 for AIX mishandles "#define B32(x) ...'x'...", so use "_"
   as the formal parameter rather than "x".  */
# define B16(_)                                 \
  ((_) == '0' ? 0                               \
   : (_) == '1' ? 1                             \
   : (_) == '2' ? 2                             \
   : (_) == '3' ? 3                             \
   : (_) == '4' ? 4                             \
   : (_) == '5' ? 5                             \
   : (_) == '6' ? 6                             \
   : (_) == '7' ? 7                             \
   : (_) == '8' ? 8                             \
   : (_) == '9' ? 9                             \
   : (_) == 'A' || (_) == 'a' ? 10              \
   : (_) == 'B' || (_) == 'b' ? 11              \
   : (_) == 'C' || (_) == 'c' ? 12              \
   : (_) == 'D' || (_) == 'd' ? 13              \
   : (_) == 'E' || (_) == 'e' ? 14              \
   : (_) == 'F' || (_) == 'f' ? 15              \
   : -1)

static signed char const base16_to_int[256] = {
  B16 (0), B16 (1), B16 (2), B16 (3),
  B16 (4), B16 (5), B16 (6), B16 (7),
  B16 (8), B16 (9), B16 (10), B16 (11),
  B16 (12), B16 (13), B16 (14), B16 (15),
  B16 (16), B16 (17), B16 (18), B16 (19),
  B16 (20), B16 (21), B16 (22), B16 (23),
  B16 (24), B16 (25), B16 (26), B16 (27),
  B16 (28), B16 (29), B16 (30), B16 (31),
  B16 (32), B16 (33), B16 (34), B16 (35),
  B16 (36), B16 (37), B16 (38), B16 (39),
  B16 (40), B16 (41), B16 (42), B16 (43),
  B16 (44), B16 (45), B16 (46), B16 (47),
  B16 (48), B16 (49), B16 (50), B16 (51),
  B16 (52), B16 (53), B16 (54), B16 (55),
  B16 (56), B16 (57), B16 (58), B16 (59),
  B16 (60), B16 (61), B16 (62), B16 (63),
  B16 (32), B16 (65), B16 (66), B16 (67),
  B16 (68), B16 (69), B16 (70), B16 (71),
  B16 (72), B16 (73), B16 (74), B16 (75),
  B16 (76), B16 (77), B16 (78), B16 (79),
  B16 (80), B16 (81), B16 (82), B16 (83),
  B16 (84), B16 (85), B16 (86), B16 (87),
  B16 (88), B16 (89), B16 (90), B16 (91),
  B16 (92), B16 (93), B16 (94), B16 (95),
  B16 (96), B16 (97), B16 (98), B16 (99),
  B16 (100), B16 (101), B16 (102), B16 (103),
  B16 (104), B16 (105), B16 (106), B16 (107),
  B16 (108), B16 (109), B16 (110), B16 (111),
  B16 (112), B16 (113), B16 (114), B16 (115),
  B16 (116), B16 (117), B16 (118), B16 (119),
  B16 (120), B16 (121), B16 (122), B16 (123),
  B16 (124), B16 (125), B16 (126), B16 (127),
  B16 (128), B16 (129), B16 (130), B16 (131),
  B16 (132), B16 (133), B16 (134), B16 (135),
  B16 (136), B16 (137), B16 (138), B16 (139),
  B16 (140), B16 (141), B16 (142), B16 (143),
  B16 (144), B16 (145), B16 (146), B16 (147),
  B16 (148), B16 (149), B16 (150), B16 (151),
  B16 (152), B16 (153), B16 (154), B16 (155),
  B16 (156), B16 (157), B16 (158), B16 (159),
  B16 (160), B16 (161), B16 (162), B16 (163),
  B16 (132), B16 (165), B16 (166), B16 (167),
  B16 (168), B16 (169), B16 (170), B16 (171),
  B16 (172), B16 (173), B16 (174), B16 (175),
  B16 (176), B16 (177), B16 (178), B16 (179),
  B16 (180), B16 (181), B16 (182), B16 (183),
  B16 (184), B16 (185), B16 (186), B16 (187),
  B16 (188), B16 (189), B16 (190), B16 (191),
  B16 (192), B16 (193), B16 (194), B16 (195),
  B16 (196), B16 (197), B16 (198), B16 (199),
  B16 (200), B16 (201), B16 (202), B16 (203),
  B16 (204), B16 (205), B16 (206), B16 (207),
  B16 (208), B16 (209), B16 (210), B16 (211),
  B16 (212), B16 (213), B16 (214), B16 (215),
  B16 (216), B16 (217), B16 (218), B16 (219),
  B16 (220), B16 (221), B16 (222), B16 (223),
  B16 (224), B16 (225), B16 (226), B16 (227),
  B16 (228), B16 (229), B16 (230), B16 (231),
  B16 (232), B16 (233), B16 (234), B16 (235),
  B16 (236), B16 (237), B16 (238), B16 (239),
  B16 (240), B16 (241), B16 (242), B16 (243),
  B16 (244), B16 (245), B16 (246), B16 (247),
  B16 (248), B16 (249), B16 (250), B16 (251),
  B16 (252), B16 (253), B16 (254), B16 (255)
};

static bool
isubase16 (unsigned char ch)
{
  return ch < sizeof base16_to_int && 0 <= base16_to_int[ch];
}

static idx_t
base16_length (idx_t len)
{
  return len * 2;
}


static void
base16_encode (char const *restrict in, idx_t inlen,
               char *restrict out, idx_t outlen)
{
  static const char base16[16] ATTRIBUTE_NONSTRING = "0123456789ABCDEF";

  while (inlen && outlen)
    {
      unsigned char c = *in;
      *out++ = base16[c >> 4];
      *out++ = base16[c & 0x0F];
      ++in;
      inlen--;
      outlen -= 2;
    }
}


static void
base16_decode_ctx_init (struct base_decode_context *ctx)
{
  init_inbuf (ctx);
  ctx->ctx.base16.nibble = -1;
}


static bool
base16_decode_ctx (struct base_decode_context *ctx,
                   char const *restrict in, idx_t inlen,
                   char *restrict out, idx_t *outlen)
{
  bool ignore_lines = true;  /* for now, always ignore them */
  char *out0 = out;
  signed char nibble = ctx->ctx.base16.nibble;

  /* inlen==0 is request to flush output.
     if there is a dangling high nibble - we are missing the low nibble,
     so return false - indicating an invalid input.  */
  if (inlen == 0)
    {
      *outlen = 0;
      return nibble < 0;
    }

  while (inlen--)
    {
      unsigned char c = *in++;
      if (ignore_lines && c == '\n')
        continue;

      if (sizeof base16_to_int <= c || base16_to_int[c] < 0)
        {
          *outlen = out - out0;
          return false; /* garbage - return false */
        }

      if (nibble < 0)
        nibble = base16_to_int[c];
      else
        {
          /* have both nibbles, write octet */
          *out++ = (nibble << 4) + base16_to_int[c];
          nibble = -1;
        }
    }

  ctx->ctx.base16.nibble = nibble;
  *outlen = out - out0;
  return true;
}



ATTRIBUTE_PURE
static idx_t
z85_length (idx_t len)
{
  /* Z85 does not allow padding, so no need to round to highest integer.  */
  idx_t z85_len = (len * 5) / 4;
  affirm (0 <= z85_len);
  return z85_len;
}

static bool
isuz85 (unsigned char ch)
{
  return c_isalnum (ch) || strchr (".-:+=^!/*?&<>()[]{}@%$#", ch) != nullptr;
}

static char const z85_encoding[85] ATTRIBUTE_NONSTRING =
  "0123456789"
  "abcdefghijklmnopqrstuvwxyz"
  "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
  ".-:+=^!/*?&<>()[]{}@%$#";

static void
z85_encode (char const *restrict in, idx_t inlen,
            char *restrict out, idx_t outlen)
{
  int i = 0;
  unsigned char quad[4];
  idx_t outidx = 0;

  while (true)
    {
      if (inlen == 0)
        {
          /* no more input, exactly on 4 octet boundary. */
          if (i == 0)
            return;

          /* currently, there's no way to return an error in encoding.  */
          error (EXIT_FAILURE, 0,
                 _("invalid input (length must be multiple of 4 characters)"));
        }
      else
        {
          quad[i++] = *in++;
          --inlen;
        }

      /* Got a quad, encode it */
      if (i == 4)
        {
          int_fast64_t val = quad[0];
          val = (val << 24) + (quad[1] << 16) + (quad[2] << 8) + quad[3];

          for (int j = 4; j >= 0; --j)
            {
              int c = val % 85;
              val /= 85;

              /* NOTE: if there is padding (which is trimmed by z85
                 before outputting the result), the output buffer 'out'
                 might not include enough allocated bytes for the padding,
                 so don't store them. */
              if (outidx + j < outlen)
                out[j] = z85_encoding[c];
            }
          out += 5;
          outidx += 5;
          i = 0;
        }
    }
}

static void
z85_decode_ctx_init (struct base_decode_context *ctx)
{
  init_inbuf (ctx);
  ctx->ctx.z85.i = 0;
}


# define Z85_LO_CTX_TO_32BIT_VAL(ctx) \
  (((ctx)->ctx.z85.octets[1] * 85 * 85 * 85) +      \
   ((ctx)->ctx.z85.octets[2] * 85 * 85) +	    \
   ((ctx)->ctx.z85.octets[3] * 85) +		    \
   ((ctx)->ctx.z85.octets[4]))


# define Z85_HI_CTX_TO_32BIT_VAL(ctx) \
  ((int_fast64_t) (ctx)->ctx.z85.octets[0] * 85 * 85 * 85 * 85 )

/*
 0 -  9:  0 1 2 3 4 5 6 7 8 9
 10 - 19:  a b c d e f g h i j
 20 - 29:  k l m n o p q r s t
 30 - 39:  u v w x y z A B C D
 40 - 49:  E F G H I J K L M N
 50 - 59:  O P Q R S T U V W X
 60 - 69:  Y Z . - : + = ^ ! /   #dummy comment to workaround syntax-check
 70 - 79:  * ? & < > ( ) [ ] {
 80 - 84:  } @ % $ #
*/
static signed char const z85_decoding[93] = {
  68, -1,  84,  83, 82,  72, -1,               /* ! " # $ % & ' */
  75, 76,  70,  65, -1,  63, 62, 69,           /* ( ) * + , - . / */
  0,  1,   2,   3,  4,   5,  6,   7,  8,  9,   /* '0' to '9' */
  64, -1,  73,  66, 74,  71, 81,               /* : ; < =  > ? @ */
  36, 37,  38,  39, 40,  41, 42,  43, 44, 45,  /* 'A' to 'J' */
  46, 47,  48,  49, 50,  51, 52,  53, 54, 55,  /* 'K' to 'T' */
  56, 57,  58,  59, 60,  61,                   /* 'U' to 'Z' */
  77,  -1, 78,  67,  -1,  -1,                  /* [ \ ] ^ _ ` */
  10, 11,  12,  13, 14,  15, 16,  17, 18, 19,  /* 'a' to 'j' */
  20, 21,  22,  23, 24,  25, 26,  27, 28, 29,  /* 'k' to 't' */
  30, 31,  32,  33, 34,  35,                   /* 'u' to 'z' */
  79, -1,  80                                  /* { | } */
};

static bool
z85_decode_ctx (struct base_decode_context *ctx,
                char const *restrict in, idx_t inlen,
                char *restrict out, idx_t *outlen)
{
  bool ignore_lines = true;  /* for now, always ignore them */

  *outlen = 0;

  /* inlen==0 is request to flush output.
     if there are dangling values - we are missing entries,
     so return false - indicating an invalid input.  */
  if (inlen == 0)
    {
      if (ctx->ctx.z85.i > 0)
        {
          /* Z85 variant does not allow padding - input must
             be a multiple of 5 - so return error.  */
          return false;
        }
      return true;
    }

  while (inlen--)
    {
      if (ignore_lines && *in == '\n')
        {
          ++in;
          continue;
        }

      /* z85 decoding */
      unsigned char c = *in;

      if (c >= 33 && c <= 125)
        {
          signed char ch = z85_decoding[c - 33];
          if (ch < 0)
            return false; /* garbage - return false */
          c = ch;
        }
      else
        return false; /* garbage - return false */

      ++in;

      ctx->ctx.z85.octets[ctx->ctx.z85.i++] = c;
      if (ctx->ctx.z85.i == 5)
        {
          /* decode the lowest 4 octets, then check for overflows.  */
          int_fast64_t val = Z85_LO_CTX_TO_32BIT_VAL (ctx);

          /* The Z85 spec and the reference implementation say nothing
             about overflows. To be on the safe side, reject them.  */

          val += Z85_HI_CTX_TO_32BIT_VAL (ctx);
          if ((val >> 24) & ~0xFF)
            return false;

          *out++ = val >> 24;
          *out++ = (val >> 16) & 0xFF;
          *out++ = (val >> 8) & 0xFF;
          *out++ = val & 0xFF;

          *outlen += 4;

          ctx->ctx.z85.i = 0;
        }
    }
  return true;
}


inline static bool
isubase2 (unsigned char ch)
{
  return ch == '0' || ch == '1';
}

static idx_t
base2_length (idx_t len)
{
  return len * 8;
}


inline static void
base2msbf_encode (char const *restrict in, idx_t inlen,
                  char *restrict out, idx_t outlen)
{
  while (inlen && outlen)
    {
      unsigned char c = *in;
      for (int i = 0; i < 8; i++)
        {
          *out++ = c & 0x80 ? '1' : '0';
          c <<= 1;
        }
      inlen--;
      outlen -= 8;
      ++in;
    }
}

inline static void
base2lsbf_encode (char const *restrict in, idx_t inlen,
                  char *restrict out, idx_t outlen)
{
  while (inlen && outlen)
    {
      unsigned char c = *in;
      for (int i = 0; i < 8; i++)
        {
          *out++ = c & 0x01 ? '1' : '0';
          c >>= 1;
        }
      inlen--;
      outlen -= 8;
      ++in;
    }
}


static void
base2_decode_ctx_init (struct base_decode_context *ctx)
{
  init_inbuf (ctx);
  ctx->ctx.base2.octet = 0;
  ctx->ctx.base2.bit_pos = 0;
}


static bool
base2lsbf_decode_ctx (struct base_decode_context *ctx,
                      char const *restrict in, idx_t inlen,
                      char *restrict out, idx_t *outlen)
{
  bool ignore_lines = true;  /* for now, always ignore them */

  *outlen = 0;

  /* inlen==0 is request to flush output.
     if there is a dangling bit - we are missing some bits,
     so return false - indicating an invalid input.  */
  if (inlen == 0)
    return ctx->ctx.base2.bit_pos == 0;

  while (inlen--)
    {
      if (ignore_lines && *in == '\n')
        {
          ++in;
          continue;
        }

      if (!isubase2 (*in))
        return false;

      bool bit = (*in == '1');
      ctx->ctx.base2.octet |= bit << ctx->ctx.base2.bit_pos;
      ++ctx->ctx.base2.bit_pos;

      if (ctx->ctx.base2.bit_pos == 8)
        {
          *out++ = ctx->ctx.base2.octet;
          ctx->ctx.base2.octet = 0;
          ++*outlen;
          ctx->ctx.base2.bit_pos = 0;
        }

      ++in;
    }

  return true;
}

static bool
base2msbf_decode_ctx (struct base_decode_context *ctx,
                      char const *restrict in, idx_t inlen,
                      char *restrict out, idx_t *outlen)
{
  bool ignore_lines = true;  /* for now, always ignore them */

  *outlen = 0;

  /* inlen==0 is request to flush output.
     if there is a dangling bit - we are missing some bits,
     so return false - indicating an invalid input.  */
  if (inlen == 0)
    return ctx->ctx.base2.bit_pos == 0;

  while (inlen--)
    {
      if (ignore_lines && *in == '\n')
        {
          ++in;
          continue;
        }

      if (!isubase2 (*in))
        return false;

      bool bit = (*in == '1');
      if (ctx->ctx.base2.bit_pos == 0)
        ctx->ctx.base2.bit_pos = 8;
      --ctx->ctx.base2.bit_pos;
      ctx->ctx.base2.octet |= bit << ctx->ctx.base2.bit_pos;

      if (ctx->ctx.base2.bit_pos == 0)
        {
          *out++ = ctx->ctx.base2.octet;
          ctx->ctx.base2.octet = 0;
          ++*outlen;
        }

      ++in;
    }

  return true;
}

/* Map from GMP (up to base 62):
   "0123456789 ABCDEFGHIJKLMNOPQRSTUVWXYZ abcdefghijklmnopqrstuv";
   to base 58:
   "123456789A BCDEFGHJKLMNPQRSTUVWXYZabc defghijkmnopqrstuvwxyz";  */
static signed char const gmp_to_base58[256] = {
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  '1','2','3','4','5','6','7','8','9','A',-1, -1, -1, -1, -1, -1,
  -1, 'B','C','D','E','F','G','H','J','K','L','M','N','P','Q','R',
  'S','T','U','V','W','X','Y','Z','a','b','c',-1, -1, -1, -1, -1,
  -1, 'd','e','f','g','h','i','j','k','m','n','o','p','q','r','s',
  't','u','v','w','x','y','z',-1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
};

static signed char const base58_to_gmp[256] = {
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, '0','1','2','3','4','5','6','7','8',-1, -1, -1, -1, -1, -1,
  -1, '9','A','B','C','D','E','F','G', -1,'H','I','J','K','L',-1,
  'M','N','O','P','Q','R','S','T','U','V','W',-1, -1, -1, -1, -1,
  -1, 'X','Y','Z','a','b','c','d','e','f','g','h',-1, 'i','j','k',
  'l','m','n','o','p','q','r','s','t','u','v',-1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1
};

static bool
isubase58 (unsigned char ch)
{
  return ch < sizeof base58_to_gmp && 0 <= base58_to_gmp[ch];
}


ATTRIBUTE_PURE
static idx_t
base58_length (idx_t len)
{
  /* Base58 output length is approximately log(256)/log(58),
     which is approximately len * 138 / 100,
     which is at most ((len + 100 - 1) / 100) * 138
     +1 to ensure we've enough place for NUL  */
  idx_t base58_len = ((len + 99) / 100) * 138 + 1;
  affirm (0 < base58_len);
  return base58_len;
}


static void
base58_encode_ctx_init (struct base_encode_context *ctx)
{
  ctx->ctx.base58.buf = nullptr;
  ctx->ctx.base58.size = 0;
  ctx->ctx.base58.capacity = 0;
}


static bool
base58_encode_ctx (struct base_encode_context *ctx,
                   char const *restrict in, idx_t inlen,
                   MAYBE_UNUSED char *restrict out, idx_t *outlen)
{
  *outlen = 0;   /* Only accumulate input in this function.  */

  if (inlen == 0)
    return true;

  idx_t free_space = ctx->ctx.base58.capacity - ctx->ctx.base58.size;
  if (free_space < inlen)
    {
      ctx->ctx.base58.buf = xpalloc (ctx->ctx.base58.buf,
                                     &ctx->ctx.base58.capacity,
                                     inlen - free_space,
                                     -1, sizeof *ctx->ctx.base58.buf);
    }

  memcpy (ctx->ctx.base58.buf + ctx->ctx.base58.size, in, inlen);
  ctx->ctx.base58.size += inlen;

  return true;
}

static void
base58_encode (char const* data, size_t data_len,
               char *out, idx_t *outlen)
{
  affirm (base_length (data_len) <= *outlen);

  size_t zeros = 0;
  while (zeros < data_len && data[zeros] == 0)
    zeros++;

  memset (out, '1', zeros);
  char *p = out + zeros;

  /* Use GMP to convert from base 256 to base 58.  */
  mpz_t num;
  mpz_init (num);
  if (data_len - zeros)
    {
      mpz_import (num, data_len - zeros, 1, 1, 0, 0, data + zeros);
      affirm (mpz_sizeinbase (num, 58) + 1 <= *outlen);
      for (p = mpz_get_str (p, 58, num); *p; p++)
        *p = gmp_to_base58[to_uchar (*p)];
    }
  mpz_clear (num);

  *outlen = p - out;
}


static bool
base58_encode_ctx_finalize (struct base_encode_context *ctx,
                            char *restrict *out, idx_t *outlen)
{
  /* Ensure output buffer is large enough.  */
  idx_t max_outlen = base_length (ctx->ctx.base58.size);
  if (max_outlen > *outlen)
    {
      *out = xrealloc (*out, max_outlen);
      *outlen = max_outlen;
    }

  base58_encode ((char *)ctx->ctx.base58.buf, ctx->ctx.base58.size,
                 *out, outlen);

  free (ctx->ctx.base58.buf);
  ctx->ctx.base58.buf = nullptr;

  return true;
}


static void
base58_decode_ctx_init (struct base_decode_context *ctx)
{
  ctx->ctx.base58.size = 0;
  ctx->ctx.base58.capacity = 0;
  ctx->ctx.base58.buf = nullptr;
}

static bool
base58_decode_ctx (struct base_decode_context *ctx,
                   char const *restrict in, idx_t inlen,
                   MAYBE_UNUSED char *restrict out, idx_t *outlen)
{
  bool ignore_lines = true;  /* for now, always ignore them */

  *outlen = 0;   /* Only accumulate input in this function.  */

  if (inlen == 0)
    return true;

  idx_t free_space = ctx->ctx.base58.capacity - ctx->ctx.base58.size;
  free_space -= 1;  /* Ensure we leave space for NUL (for mpz_set_str).  */
  if (free_space < inlen)
    {
      ctx->ctx.base58.buf = xpalloc (ctx->ctx.base58.buf,
                                     &ctx->ctx.base58.capacity,
                                     inlen - free_space,
                                     -1, sizeof *ctx->ctx.base58.buf);
    }

  /* Accumulate all valid input characters in our buffer.
     Note we don't rely on mpz_set_str() for validation
     as that allows (skips) all whitespace.  */
  for (idx_t i = 0; i < inlen; i++)
    {
      unsigned char c = in[i];

      if (ignore_lines && c == '\n')
        continue;

      if (!isubase58 (c))
        return false;

      ctx->ctx.base58.buf[ctx->ctx.base58.size++] = base58_to_gmp[to_uchar (c)];
    }

  return true;
}


static bool
base58_decode (char const *data, size_t data_len,
               char *restrict out, idx_t *outlen)
{
  affirm (data_len <= *outlen);

  size_t ones = 0;
  while (ones < data_len && data[ones] == base58_to_gmp['1'])
    ones++;

  memset (out, 0, ones);

  /* Use GMP to convert from base 58 to base 256.  */
  mpz_t num;
  mpz_init (num);

  if ((data_len - ones) && mpz_set_str (num, data + ones, 58) != 0)
    {
      mpz_clear (num);
      *outlen = 0;
      return false;
    }

  size_t exported_size = 0;
  if (data_len - ones)
    {
      size_t binary_size = (mpz_sizeinbase (num, 2) + 7) / 8;
      affirm (*outlen - ones >= binary_size);
      mpz_export (out + ones, &exported_size, 1, 1, 0, 0, num);
    }

  mpz_clear (num);
  *outlen = ones + exported_size;
  return true;
}


static bool
base58_decode_ctx_finalize (struct base_decode_context *ctx,
                            char *restrict *out, idx_t *outlen)
{
  /* Ensure output buffer is large enough.
     Worst case is input is all '1's.  */
  idx_t max_outlen = ctx->ctx.base58.size;
  if (max_outlen > *outlen)
    {
      *out = xrealloc (*out, max_outlen);
      *outlen = max_outlen;
    }

  /* Ensure input buffer is NUL terminated (for mpz_get_str).  */
  if (ctx->ctx.base58.size)
    ctx->ctx.base58.buf[ctx->ctx.base58.size] = '\0';

  bool ret = base58_decode ((char *)ctx->ctx.base58.buf, ctx->ctx.base58.size,
                            *out, outlen);

  free (ctx->ctx.base58.buf);
  ctx->ctx.base58.buf = nullptr;

  return ret;
}

#endif /* BASE_TYPE == 42, i.e., "basenc"*/



static void
wrap_write (char const *buffer, idx_t len,
            idx_t wrap_column, idx_t *current_column, FILE *out)
{
  if (wrap_column == 0)
    {
      /* Simple write. */
      if (fwrite (buffer, 1, len, stdout) < len)
        write_error ();
    }
  else
    for (idx_t written = 0; written < len; )
      {
        idx_t to_write = MIN (wrap_column - *current_column, len - written);

        if (to_write == 0)
          {
            if (fputc ('\n', out) == EOF)
              write_error ();
            *current_column = 0;
          }
        else
          {
            if (fwrite (buffer + written, 1, to_write, stdout) < to_write)
              write_error ();
            *current_column += to_write;
            written += to_write;
          }
      }
}

static _Noreturn void
finish_and_exit (FILE *in, char const *infile)
{
  if (fclose (in) != 0)
    {
      if (streq (infile, "-"))
        error (EXIT_FAILURE, errno, _("closing standard input"));
      else
        error (EXIT_FAILURE, errno, "%s", quotef (infile));
    }

  exit (EXIT_SUCCESS);
}

static _Noreturn void
do_encode (FILE *in, char const *infile, FILE *out, idx_t wrap_column)
{
  idx_t current_column = 0;
  char *inbuf, *outbuf;
  idx_t sum;

  inbuf = xmalloc (ENC_BLOCKSIZE);
  outbuf = xmalloc (BASE_LENGTH (ENC_BLOCKSIZE));

#if BASE_TYPE == 42
  /* Initialize encoding context if needed (for base58) */
  struct base_encode_context encode_ctx;
  bool use_ctx = (base_encode_ctx_init != nullptr);
  if (use_ctx)
    base_encode_ctx_init (&encode_ctx);
#endif

  do
    {
      idx_t n;

      sum = 0;
      do
        {
          n = fread (inbuf + sum, 1, ENC_BLOCKSIZE - sum, in);
          sum += n;
        }
      while (!feof (in) && !ferror (in) && sum < ENC_BLOCKSIZE);

      if (sum > 0)
        {
#if BASE_TYPE == 42
          if (use_ctx)
            {
              idx_t outlen = 0;
              base_encode_ctx (&encode_ctx, inbuf, sum, outbuf, &outlen);

              wrap_write (outbuf, outlen, wrap_column, &current_column, out);
            }
          else
#endif
            {
              /* Process input one block at a time.  Note that ENC_BLOCKSIZE
                 is sized so that no pad chars will appear in output. */
              base_encode (inbuf, sum, outbuf, BASE_LENGTH (sum));

              wrap_write (outbuf, BASE_LENGTH (sum), wrap_column,
                          &current_column, out);
            }
        }
    }
  while (!feof (in) && !ferror (in) && sum == ENC_BLOCKSIZE);

#if BASE_TYPE == 42
  if (use_ctx && base_encode_ctx_finalize)
    {
      idx_t outlen = BASE_LENGTH (ENC_BLOCKSIZE);
      base_encode_ctx_finalize (&encode_ctx, &outbuf, &outlen);

      wrap_write (outbuf, outlen, wrap_column, &current_column, out);
    }
#endif

  /* When wrapping, terminate last line. */
  if (wrap_column && current_column > 0 && fputc ('\n', out) == EOF)
    write_error ();

  if (ferror (in))
    error (EXIT_FAILURE, errno, _("read error"));

  finish_and_exit (in, infile);
}

static _Noreturn void
do_decode (FILE *in, char const *infile, FILE *out, bool ignore_garbage)
{
  char *inbuf, *outbuf;
  idx_t sum;
  struct base_decode_context ctx;

  inbuf = xmalloc (BASE_LENGTH (DEC_BLOCKSIZE));
  outbuf = xmalloc (DEC_BLOCKSIZE);

#if BASE_TYPE == 42
  ctx.inbuf = nullptr;
#endif
  base_decode_ctx_init (&ctx);

  do
    {
      bool ok;

      sum = 0;
      do
        {
          idx_t n = fread (inbuf + sum,
                           1, BASE_LENGTH (DEC_BLOCKSIZE) - sum, in);

          if (ignore_garbage)
            {
              for (idx_t i = 0; n > 0 && i < n;)
                {
                  if (isubase (inbuf[sum + i])
                      || (REQUIRED_PADDING (1) && inbuf[sum + i] == '='))
                    i++;
                  else
                    memmove (inbuf + sum + i, inbuf + sum + i + 1, --n - i);
                }
            }

          sum += n;

          if (ferror (in))
            error (EXIT_FAILURE, errno, _("read error"));
        }
      while (sum < BASE_LENGTH (DEC_BLOCKSIZE) && !feof (in));

      while (sum || feof (in))
        {
          idx_t n = DEC_BLOCKSIZE;
          if (sum)
            ok = base_decode_ctx (&ctx, inbuf, sum, outbuf, &n);
          else
            ok = base_decode_ctx_finalize (&ctx, &outbuf, &n);

          if (fwrite (outbuf, 1, n, out) < n)
            write_error ();

          if (! ok)
            error (EXIT_FAILURE, 0, _("invalid input"));

          if (sum == 0)
            break;
          sum = 0;
        }
    }
  while (!feof (in));

  finish_and_exit (in, infile);
}

int
main (int argc, char **argv)
{
  int opt;
  FILE *input_fh;
  char const *infile;

  /* True if --decode has been given and we should decode data. */
  bool decode = false;
  /* True if we should ignore non-base-alphabetic characters. */
  bool ignore_garbage = false;
  /* Wrap encoded data around the 76th column, by default. */
  idx_t wrap_column = 76;

#if BASE_TYPE == 42
  int base_type = 0;
#endif

  initialize_main (&argc, &argv);
  set_program_name (argv[0]);
  setlocale (LC_ALL, "");
  bindtextdomain (PACKAGE, LOCALEDIR);
  textdomain (PACKAGE);

  atexit (close_stdout);

  while ((opt = getopt_long (argc, argv, "diw:", long_options, nullptr)) != -1)
    switch (opt)
      {
      case 'd':
        decode = true;
        break;

      case 'w':
        {
          intmax_t w;
          strtol_error s_err = xstrtoimax (optarg, nullptr, 10, &w, "");
          if (LONGINT_OVERFLOW < s_err || w < 0)
            error (EXIT_FAILURE, 0, "%s: %s",
                   _("invalid wrap size"), quote (optarg));
          wrap_column = s_err == LONGINT_OVERFLOW || IDX_MAX < w ? 0 : w;
        }
        break;

      case 'i':
        ignore_garbage = true;
        break;

#if BASE_TYPE == 42
      case BASE64_OPTION:
      case BASE64URL_OPTION:
      case BASE32_OPTION:
      case BASE32HEX_OPTION:
      case BASE16_OPTION:
      case BASE2MSBF_OPTION:
      case BASE2LSBF_OPTION:
      case Z85_OPTION:
      case BASE58_OPTION:
        base_type = opt;
        break;
#endif

      case_GETOPT_HELP_CHAR;

      case_GETOPT_VERSION_CHAR (PROGRAM_NAME, AUTHORS);

      default:
        usage (EXIT_FAILURE);
        break;
      }

#if BASE_TYPE == 42
  required_padding = no_required_padding;
  has_padding = no_padding;
  get_pending_length = no_pending_length;
  base_decode_ctx_finalize = decode_ctx_finalize;

  switch (base_type)
    {
    case BASE64_OPTION:
      base_length = base64_length_wrapper;
      required_padding = base64_required_padding;
      has_padding = base64_ctx_has_padding;
      get_pending_length = base64_ctx_get_pending_length;
      isubase = isubase64;
      base_encode = base64_encode;
      base_decode_ctx_init = base64_decode_ctx_init_wrapper;
      base_decode_ctx = base64_decode_ctx_wrapper;
      break;

    case BASE64URL_OPTION:
      base_length = base64_length_wrapper;
      required_padding = base64_required_padding;
      has_padding = base64_ctx_has_padding;
      get_pending_length = base64_ctx_get_pending_length;
      isubase = isubase64url;
      base_encode = base64url_encode;
      base_decode_ctx_init = base64url_decode_ctx_init_wrapper;
      base_decode_ctx = base64url_decode_ctx_wrapper;
      break;

    case BASE32_OPTION:
      base_length = base32_length_wrapper;
      required_padding = base32_required_padding;
      has_padding = base32_ctx_has_padding;
      get_pending_length = base32_ctx_get_pending_length;
      isubase = isubase32;
      base_encode = base32_encode;
      base_decode_ctx_init = base32_decode_ctx_init_wrapper;
      base_decode_ctx = base32_decode_ctx_wrapper;
      break;

    case BASE32HEX_OPTION:
      base_length = base32_length_wrapper;
      required_padding = base32_required_padding;
      has_padding = base32_ctx_has_padding;
      get_pending_length = base32_ctx_get_pending_length;
      isubase = isubase32hex;
      base_encode = base32hex_encode;
      base_decode_ctx_init = base32hex_decode_ctx_init_wrapper;
      base_decode_ctx = base32hex_decode_ctx_wrapper;
      break;

    case BASE16_OPTION:
      base_length = base16_length;
      get_pending_length = base16_ctx_get_pending_length;
      isubase = isubase16;
      base_encode = base16_encode;
      base_decode_ctx_init = base16_decode_ctx_init;
      base_decode_ctx = base16_decode_ctx;
      break;

    case BASE2MSBF_OPTION:
      base_length = base2_length;
      get_pending_length = base2_ctx_get_pending_length;
      isubase = isubase2;
      base_encode = base2msbf_encode;
      base_decode_ctx_init = base2_decode_ctx_init;
      base_decode_ctx = base2msbf_decode_ctx;
      break;

    case BASE2LSBF_OPTION:
      base_length = base2_length;
      get_pending_length = base2_ctx_get_pending_length;
      isubase = isubase2;
      base_encode = base2lsbf_encode;
      base_decode_ctx_init = base2_decode_ctx_init;
      base_decode_ctx = base2lsbf_decode_ctx;
      break;

    case Z85_OPTION:
      base_length = z85_length;
      get_pending_length = z85_ctx_get_pending_length;
      isubase = isuz85;
      base_encode = z85_encode;
      base_decode_ctx_init = z85_decode_ctx_init;
      base_decode_ctx = z85_decode_ctx;
      break;

    case BASE58_OPTION:
      base_length = base58_length;
      isubase = isubase58;
      base_encode_ctx_init = base58_encode_ctx_init;
      base_encode_ctx = base58_encode_ctx;
      base_encode_ctx_finalize = base58_encode_ctx_finalize;
      base_decode_ctx_init = base58_decode_ctx_init;
      base_decode_ctx = base58_decode_ctx;
      base_decode_ctx_finalize = base58_decode_ctx_finalize;
      break;

    default:
      error (0, 0, _("missing encoding type"));
      usage (EXIT_FAILURE);
    }
#endif

  if (argc - optind > 1)
    {
      error (0, 0, _("extra operand %s"), quote (argv[optind + 1]));
      usage (EXIT_FAILURE);
    }

  if (optind < argc)
    infile = argv[optind];
  else
    infile = "-";

  if (streq (infile, "-"))
    {
      xset_binary_mode (STDIN_FILENO, O_BINARY);
      input_fh = stdin;
    }
  else
    {
      input_fh = fopen (infile, "rb");
      if (input_fh == nullptr)
        error (EXIT_FAILURE, errno, "%s", quotef (infile));
    }

  fadvise (input_fh, FADVISE_SEQUENTIAL);

  if (decode)
    do_decode (input_fh, infile, stdout, ignore_garbage);
  else
    do_encode (input_fh, infile, stdout, wrap_column);
}