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/* frames/pem.c
*
* PEM64 encoding for framing.
*
* Copyright 2009 Simtec Electronics
*
* For licence terms refer to the COPYING file.
*/
#include "pem.h"
#ifdef TEST_PEM
#include <stdio.h>
#include <assert.h>
#include <string.h>
#include <stdlib.h>
#endif
static const char *dictionary =
"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
static int inverse_dictionary[128] =
{ -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 0 -- 9 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 10 -- 19 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 20 -- 29 */
-1, -1, -1, -1, -1, -1, -1, -1, -1, -1, /* 30 -- 39 */
-1, -1, -1, 62, -1, -1, -1, 63, 52, 53, /* 40 -- 49 */
54, 55, 56, 57, 58, 59, 60, 61, -1, -1, /* 50 -- 59 */
-1, 0, -1, -1, -1, 0, 1, 2, 3, 4, /* 60 -- 69 */
5, 6, 7, 8, 9, 10, 11, 12, 13, 14, /* 70 -- 79 */
15, 16, 17, 18, 19, 20, 21, 22, 23, 24, /* 80 -- 89 */
25, -1, -1, -1, -1, -1, -1, 26, 27, 28, /* 90 -- 99 */
29, 30, 31, 32, 33, 34, 35, 36, 37, 38, /* 100--109 */
39, 40, 41, 42, 43, 44, 45, 46, 47, 48, /* 110--119 */
49, 50, 51, -1, -1, -1, -1, -1 }; /* 120--127 */
#define FILLERCHAR ('=')
/* exported interface documented in pem.h */
int
pem64_encode_bytes_length(int nbytes)
{
return ((nbytes + 2) / 3) * 4;
}
int pem64_encode_bytes(const unsigned char *inbytes,
int nbytes,
char *outtext)
{
int filledcount = 0;
while (nbytes >= 3) {
int
c1 = inbytes[0],
c2 = inbytes[1],
c3 = inbytes[2];
*(outtext++) = dictionary[c1 >> 2];
*(outtext++) = dictionary[((c1 & 0x3) << 4) | (c2 >> 4)];
*(outtext++) = dictionary[((c2 & 0xf) << 2) | (c3 >> 6)];
*(outtext++) = dictionary[c3 & 0x3f];
filledcount += 4;
nbytes -= 3;
inbytes += 3;
}
if (nbytes == 2) {
int
c1 = inbytes[0],
c2 = inbytes[1];
*(outtext++) = dictionary[c1 >> 2];
*(outtext++) = dictionary[((c1 & 0x3) << 4) | (c2 >> 4)];
*(outtext++) = dictionary[((c2 & 0xf) << 2)];
*(outtext++) = FILLERCHAR;
filledcount += 4;
} else if (nbytes == 1) {
int
c1 = inbytes[0];
*(outtext++) = dictionary[c1 >> 2];
*(outtext++) = dictionary[((c1 & 0x3) << 4)];
*(outtext++) = FILLERCHAR;
*(outtext++) = FILLERCHAR;
filledcount += 4;
}
return filledcount;
}
int pem64_decode_bytes(const char *intext,
int nchars,
unsigned char *outbytes)
{
unsigned char *outbcopy = outbytes;
while (nchars >= 4) {
int
c1 = intext[0],
c2 = intext[1],
c3 = intext[2],
c4 = intext[3];
int
b1 = inverse_dictionary[c1],
b2 = inverse_dictionary[c2],
b3 = inverse_dictionary[c3],
b4 = inverse_dictionary[c4];
if ((b1 == -1) || (b2 == -1) || (b3 == -1) || (b4 == -1))
return outbytes - outbcopy;
*(outbytes++) = (b1 << 2) | (b2 >> 4);
if (c3 != FILLERCHAR)
*(outbytes++) = ((b2 & 0xf) << 4) | (b3 >> 2);
if (c4 != FILLERCHAR)
*(outbytes++) = ((b3 & 0x3) << 6) | b4;
nchars -= 4;
intext += 4;
}
return outbytes - outbcopy;
}
void
pem64_encode_12bits(const short value, char *outtext)
{
*(outtext++) = dictionary[value & 0x3f];
*(outtext++) = dictionary[(value >> 6) & 0x3f];
}
short
pem64_decode_12bits(const char *intext)
{
int
b1 = inverse_dictionary[(int) intext[0]],
b2 = inverse_dictionary[(int) intext[1]];
if ((b1 == -1) || (b2 == -1))
return 0;
return (b1 | (b2 << 6));
}
#ifdef TEST_PEM
static char pem_buffer[4096];
static void
run_single_test(const unsigned char *buffer,
const int buflen)
{
unsigned char *bcopy = calloc(buflen, 1);
int pemchars = pem64_encode_bytes(buffer, buflen, pem_buffer);
int pembytes = pem64_decode_bytes(pem_buffer, pemchars, bcopy);
assert((pemchars % 4) == 0);
assert(pembytes == buflen);
assert(memcmp(bcopy, buffer, pembytes) == 0);
free(bcopy);
}
#define R(S) run_single_test(S, sizeof(S) - 1)
int
main(int argc, char **argv)
{
R("123");
R("\1\2\3");
R("\1\2");
R("1234");
R("12345");
R("123456");
return 0;
}
#endif
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