base64

[Niels Möller]

I've reorganized the base64 code again. The goal has been to support
*both* simple "one-shot" encoding, and streamed operation. The
declarations from the new base64.h are included below. For the actual
code, see the cvs repository
(http://cvs.lysator.liu.se/viewcvs/viewcvs.cgi/lsh/src/nettle/?cvsroot=lsh).

Comments are welcome.
/Niels


#define BASE64_BINARY_BLOCK_SIZE 3
#define BASE64_TEXT_BLOCK_SIZE 4

/* Base64 encoding */

/* Maximum length of output for base64_encode_update. NOTE: Doesn't
 * include any padding that base64_encode_final may add. */
/* We have at most 4 buffered bits, and a total of (4 + length * 8) bits. */
#define BASE64_ENCODE_LENGTH(length) (((length) * 8 + 4)/6)

/* Maximum lengbth of output generated by base64_encode_final. */
#define BASE64_ENCODE_FINAL_LENGTH 3

/* Exact length of output generated by base64_encode_raw, including
 * padding. */
#define BASE64_ENCODE_RAW_LENGTH(length) ((((length) + 2)/3)*4)

struct base64_encode_ctx
{
  unsigned word;   /* Leftover bits */
  unsigned bits;  /* Number of bits, always 0, 2, or 4. */
};

void
base64_encode_init(struct base64_encode_ctx *ctx);

/* Encodes a single byte. Returns amoutn of output (always 1 or 2). */
unsigned
base64_encode_single(struct base64_encode_ctx *ctx,
		     uint8_t *dst,
		     uint8_t src);

/* Returns the number of output characters. DST should point to an
 * area of size at least BASE64_ENCODE_LENGTH(length). */
unsigned
base64_encode_update(struct base64_encode_ctx *ctx,
		     uint8_t *dst,
		     unsigned length,
		     const uint8_t *src);

/* DST should point to an area of size at least
 * BASE64_ENCODE_FINAL_SIZE */
unsigned
base64_encode_final(struct base64_encode_ctx *ctx,
		    uint8_t *dst);

/* Lower level functions */

/* Encodes a string in one go, including any padding at the end.
 * Generates exactly BASE64_ENCODE_RAW_LENGTH(length) bytes of output.
 * Supports overlapped operation, if src <= dst. */
void
base64_encode_raw(uint8_t *dst, unsigned length, const uint8_t *src);

void
base64_encode_group(uint8_t *dst, uint32_t group);


/* Base64 decoding */

/* Maximum length of output for base64_decode_update. */
/* We have at most 6 buffered bits, and a total of (length + 1) * 6 bits. */
#define BASE64_DECODE_LENGTH(length) ((((length) + 1) * 6) / 8)

struct base64_decode_ctx
{
  enum
    {
      BASE64_DECODE_OK,
      BASE64_DECODE_ERROR,
      BASE64_DECODE_END
    } status; 
  unsigned word;   /* Leftover bits */
  unsigned bits;   /* Number buffered bits */
};

void
base64_decode_init(struct base64_decode_ctx *ctx);

/* Returns the number of output characters. DST should point to an
 * area of size at least BASE64_DECODE_LENGTH(length). */
unsigned
base64_decode_update(struct base64_decode_ctx *ctx,
		     uint8_t *dst,
		     unsigned length,
		     const uint8_t *src);

/* Returns 1 on success. */
int
base64_decode_status(struct base64_decode_ctx *ctx);

#endif /* NETTLE_BASE64_H_INCLUDED */