Release version 2.1.1.

[mLib] / base32.c

/* -*-c-*-
 *
 * $Id$
 *
 * Base32 encoding and decoding.
 *
 * (c) 1997 Straylight/Edgeware
 */

/*----- Licensing notice --------------------------------------------------*
 *
 * This file is part of the mLib utilities library.
 *
 * mLib is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Library General Public License as
 * published by the Free Software Foundation; either version 2 of the
 * License, or (at your option) any later version.
 *
 * mLib 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 Library General Public License for more details.
 *
 * You should have received a copy of the GNU Library General Public
 * License along with mLib; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */

/*----- Header files ------------------------------------------------------*/

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#include "base32.h"
#include "dstr.h"

/*----- Important tables --------------------------------------------------*/

static const char encodemap[] = { "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567" };

static const signed char decodemap[] = {
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  /* 0x */
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  /* 1x */
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,  /* 2x */
  -1, -1, 26, 27, 28, 29, 30, 31, -1, -1, -1, -1, -1, -1, -1, -1,  /* 3x */
  -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,  /* 4x */
  15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,  /* 5x */
  -1,  0,  1,  2,  3,  4,  5,  6,  7,  8,  9, 10, 11, 12, 13, 14,  /* 6x */
  15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,  /* 7x */
};

/*----- Main code ---------------------------------------------------------*/

/* --- @base32_encode@ --- *
 *
 * Arguments:	@base32_ctx *ctx@ = pointer to a context block
 *		@const void *p@ = pointer to a source buffer
 *		@size_t sz@ = size of the source buffer
 *		@dstr *d@ = pointer to destination string
 *
 * Returns:	---
 *
 * Use:		Encodes a binary string in base32.  To flush out the final
 *		few characters (if necessary), pass a null source pointer.
 */

void base32_encode(base32_ctx *ctx,
		   const void *p, size_t sz,
		   dstr *d)
{
  if (p) {
    unsigned long accl = ctx->accl, acch = ctx->acch;
    unsigned qsz = ctx->qsz;
    const unsigned char *src = p;

    while (sz) {
      acch = (acch << 8) | ((accl >> 24) & 0xff);
      accl = (accl << 8) | *src++;
      qsz++;
      sz--;
      if (qsz == 5) {
	DPUTC(d, encodemap[(acch >> 3) & 0x1f]);
	DPUTC(d, encodemap[((acch << 2) & 0x1c) | ((accl >> 30) & 0x03)]);
	DPUTC(d, encodemap[(accl >> 25) & 0x1f]);
	DPUTC(d, encodemap[(accl >> 20) & 0x1f]);
	DPUTC(d, encodemap[(accl >> 15) & 0x1f]);
	DPUTC(d, encodemap[(accl >> 10) & 0x1f]);
	DPUTC(d, encodemap[(accl >>  5) & 0x1f]);
	DPUTC(d, encodemap[(accl >>  0) & 0x1f]);
	ctx->lnlen += 8;
	if (ctx->maxline && ctx->lnlen >= ctx->maxline) {
	  dstr_puts(d, ctx->indent);
	  ctx->lnlen = 0;
	}
	qsz = 0;
	accl = acch = 0;
      }
    }

    ctx->acch = acch; ctx->accl = accl;
    ctx->qsz = qsz;
  } else {
    unsigned long accl = ctx->accl, acch = ctx->acch;
    unsigned qsz = ctx->qsz;

    if (qsz) {
      unsigned pad = 5 - qsz;
      if (pad > 3) {
	acch = accl << (pad * 8 - 32);
	accl = 0;
      } else {
	acch = (acch << (8 * pad)) | ((accl & 0xffffffff) >> (32 - 8 * pad));
	accl = accl << (8 * pad);
      }
      qsz = 40;
      pad *= 8;
      while (qsz > pad) {
	DPUTC(d, encodemap[(acch >> 3) & 0x1f]);
	acch = (acch << 5) | ((accl >> 27) & 0x1f);
	accl = (accl << 5);
	qsz -= 5;
      }
      while (qsz) {
	DPUTC(d, '=');
	qsz -= 5;
      }
      ctx->lnlen += 8;
    }
    ctx->qsz = 0;
    ctx->acch = ctx->accl = 0;
  }
}

/* --- @base32_decode@ --- *
 *
 * Arguments:	@base32_ctx *ctx@ = pointer to a context block
 *		@const void *p@ = pointer to a source buffer
 *		@size_t sz@ = size of the source buffer
 *		@dstr *d@ = pointer to destination string
 *
 * Returns:	---
 *
 * Use:		Decodes a binary string in base32.  To flush out the final
 *		few characters (if necessary), pass a null source pointer.
 */

void base32_decode(base32_ctx *ctx,
		   const void *p, size_t sz,
		   dstr *d)
{
  if (p) {
    unsigned long accl = ctx->accl, acch = ctx->acch;
    unsigned qsz = ctx->qsz;
    const char *src = p;
    int ch;

    while (sz) {

      /* --- Get the next character and convert it --- */

      ch = *src++;
      if (ch >= 128 || ch < 0)
	ch = -1;
      else
	ch = decodemap[ch];
      sz--;
      if (ch == -1)
	continue;

      /* --- Bung it in the accumulator --- */

      acch = (acch << 5) | ((accl >> 27) & 0x1f);
      accl = (accl << 5) | ch;
      qsz++;

      /* --- Maybe write out a completed triplet --- */

      if (qsz == 8) {
	DPUTC(d, (acch >>  0) & 0xff);
	DPUTC(d, (accl >> 24) & 0xff);
	DPUTC(d, (accl >> 16) & 0xff);
	DPUTC(d, (accl >>  8) & 0xff);
	DPUTC(d, (accl >>  0) & 0xff);
	acch = accl = 0;
	qsz = 0;
      }
    }

    ctx->acch = acch; ctx->accl = accl;
    ctx->qsz = qsz;
  } else {

    /* --- Notes about the tail-end bits --- *
     *
     * I'll use the queue size to work out how many tail-end bytes I ought to
     * write.  This isn't strictly right, but it's easier.
     */

    unsigned long acch = ctx->acch, accl = ctx->accl;
    unsigned qsz = ctx->qsz;

    /* --- Now fiddle with everything else --- *
     *
     * There's a bodge here for invalid encodings which have a funny number
     * of quintets in the final group.  I'm not sure this is really worth
     * having, but it might save some unexpected behaviour.  (Not that you
     * won't still get unexpected behaviour if the stream is completely
     * empty, of course.)
     */

    if (qsz) {
      unsigned pad = 8 - qsz;
      if (pad > 6) {
	acch = accl << (5 * pad - 32);
	accl = 0;
      } else {
	acch = (acch << (5 * pad)) | ((accl & 0xffffffff) >> (32 - 5 * pad));
	accl = accl << (5 * pad);
      }

      qsz *= 5;
      while (qsz >= 8) {
	DPUTC(d, acch & 0xff);
	acch = accl >> 24;
	accl <<= 8;
	qsz -= 8;
      }
    }

    /* --- That seems to be good enough --- */

    ctx->qsz = 0;
    ctx->acch = ctx->accl = 0;
  }
}

/* --- @base32_init@ --- *
 *
 * Arguments:	@base32_ctx *ctx@ = pointer to context block to initialize
 *
 * Returns:	---
 *
 * Use:		Initializes a base32 context properly.
 */

void base32_init(base32_ctx *ctx)
{
  ctx->accl = ctx->acch = 0;
  ctx->qsz = 0;
  ctx->lnlen = 0;
  ctx->indent = "\n";
  ctx->maxline = 72;
}

/*----- Test driver code --------------------------------------------------*/

#ifdef TEST_RIG

int main(int argc, char *argv[])
{
  unsigned char buf[BUFSIZ];
  dstr d = DSTR_INIT;
  base32_ctx ctx;
  void (*proc)(base32_ctx *, const void *, size_t, dstr *);
  size_t sz;

  base32_init(&ctx);

  if (argc > 1 && strcmp(argv[1], "-d") == 0)
    proc = base32_decode;
  else {
    proc = base32_encode;
    putchar('\t');
    ctx.indent = "\n\t";
    ctx.maxline = 32;
  }

  do {
    sz = fread(buf, 1, sizeof(buf), stdin);
    if (sz) {
      proc(&ctx, buf, sz, &d);
      dstr_write(&d, stdout);
      dstr_destroy(&d);
    }
  } while (sz == sizeof(buf));

  proc(&ctx, 0, 0, &d);
  dstr_write(&d, stdout);

  if (proc == base32_encode)
    putchar('\n');

  return (0);
}

#endif

/*----- That's all, folks -------------------------------------------------*/