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/* base16.h
 *
 * Hex encoding and decoding, following spki conventions (i.e.
 * allowing whitespace between digits).
 */

/* nettle, low-level cryptographics library
 *
 * Copyright (C) 2002 Niels Möller
 *  
 * The nettle 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.
 * 
 * The nettle 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 the nettle library; see the file COPYING.LIB.  If not, write to
 * the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
 * MA 02111-1307, USA.
 */
 
#ifndef NETTLE_BASE16_H_INCLUDED
#define NETTLE_BASE16_H_INCLUDED

#include <inttypes.h>


/* Base16 encoding */

/* Maximum length of output for base16_encode_update. */
#define BASE16_ENCODE_LENGTH(length) ((length) * 2)

/* Encodes a single byte. Always stores two digits in dst[0] and dst[1]. */
void
base16_encode_single(uint8_t *dst,
		     uint8_t src);

/* Always stores BASE16_ENCODE_LENGTH(length) digits in dst. */
void
base16_encode_update(uint8_t *dst,
		     unsigned length,
		     const uint8_t *src);


/* Base16 decoding */

/* Maximum length of output for base16_decode_update. */
/* We have at most 4 buffered bits, and a total of (length + 1) * 4 bits. */
#define BASE16_DECODE_LENGTH(length) (((length) + 1) / 2)

struct base16_decode_ctx
{
  unsigned word;   /* Leftover bits */
  unsigned bits;   /* Number buffered bits */
};

void
base16_decode_init(struct base16_decode_ctx *ctx);

/* Decodes a single byte. Returns amount of output (0 or 1), or -1 on
 * errors. */
int
base16_decode_single(struct base16_decode_ctx *ctx,
		     uint8_t *dst,
		     uint8_t src);

/* Returns 1 on success, 0 on error. DST should point to an area of
 * size at least BASE16_DECODE_LENGTH(length), and for sanity
 * checking, *DST_LENGTH should be initialized to the size of that
 * area before the call. *DST_LENGTH is updated to the amount of
 * decoded output. */

/* FIXME: Currently results in an assertion failure if *DST_LENGTH is
 * too small. Return some error instead? */
int
base16_decode_update(struct base16_decode_ctx *ctx,
		     unsigned *dst_length,
		     uint8_t *dst,
		     unsigned src_length,
		     const uint8_t *src);

/* Returns 1 on success. */
int
base16_decode_final(struct base16_decode_ctx *ctx);

#endif /* NETTLE_BASE16_H_INCLUDED */