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base32.c
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base32.c
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/*
* libbase32 version 1.0
* Copyright (C) 2015 Trustifier Inc.
* Copyright (C) 2015 Ahmed Masud
* All rights reserved.
* Created by Ahmed Masud on 6/15/15.
*/
#include <string.h>
#include <stdint.h>
#include "base32.h"
static int encode_block(char *dest, const void *_src);
static const char base32_encoding[] = {
'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', /* 10 */
'A', 'B', 'C', 'D', 'E', 'F', 'G', 'H', /* 18 */
'J', 'K', /* 20 */
'M', 'N', /* 22 */
'P', 'Q', 'R', 'S', 'T', /* 27 */
'V', 'W', 'X', 'Y', 'Z' /* 32 */
};
static const char padding = '=';
/*
* 11111111 10101010 10110011 10111100 10010100
*-> 11111 11110 10101 01011 00111 01111 00100 10100
*/
static int encode_block(char *dest, const void *_src)
{
const unsigned char *src = _src; /* cast it to a unsigned char */
dest[0] = base32_encoding[(src[0] >> 3) & 0x1F]; /* first 5 bits */
dest[1] = base32_encoding[(src[0] << 2) & 0x1C | ((src[1] >> 6) & 0x3)]; /* last 3 bits + next 2 bits */
dest[2] = base32_encoding[(src[1] >> 1) & 0x1F]; /* next 5 bits (tail has 1 bit) */
dest[3] = base32_encoding[(src[1] << 4) & 0x10 | ((src[2] >> 4) & 0xF)]; /* last bit + next four bits */
dest[4] = base32_encoding[(src[2] << 1) & 0x1E | ((src[3] >> 7) & 0x1)];
dest[5] = base32_encoding[(src[3] >> 2) & 0x1F];
dest[6] = base32_encoding[(src[3] << 3) & 0x18 | ((src[4] >> 5) & 0x7)];
dest[7] = base32_encoding[(src[4] & 0x1F)];
return 0;
}
static int encode_tail(char *dest, const void *_src, size_t len)
{
int k;
const unsigned char *src = _src;
if(len < 1 || len > 5)
return -1;
for(k = 0 ; k < 8; k++ )
dest[k] = padding;
switch(len) {
case 5:
dest[7] = base32_encoding[(src[4]) & 0x1F];
case 4:
dest[6] = base32_encoding[(src[3] << 3) & 0x18 | (dest[7] != padding ? (src[4] >> 5) & 0x7 : 0)];
dest[5] = base32_encoding[(src[3] >> 2) & 0x1F];
case 3:
dest[4] = base32_encoding[(src[2] << 1) & 0x1E | (dest[5] != padding ? (src[3] >> 7) & 0x1 : 0)];
case 2:
dest[3] = base32_encoding[(src[1] << 4) & 0x10 | (dest[4] != padding ? (src[2] >> 4) & 0xF : 0)];
dest[2] = base32_encoding[(src[1] >> 1) & 0x1F];
case 1:
dest[1] = base32_encoding[(src[0] << 2) & 0x1C | (dest[2] != padding ? (src[1] >> 6 & 0x3) : 0)];
dest[0] = base32_encoding[(src[0] >> 3) & 0x1F];
break;
default:
die(127, "Internal error, length passed to encode_tail MUST BE between 1 and 5\n");
break;
}
return 0;
}
size_t base32enc(char *dest, const void *_src, size_t ssize)
{
int dk = 0, sk = 0, k;
const unsigned char *src = _src;
if ( ssize > 0 && ssize <= 5 ) {
encode_tail(dest, src, ssize);
dk = 8;
goto out;
}
ssize -= 5;
for(dk = 0, sk = 0; sk <= ssize; sk+=5, dk+=8) {
encode_block(&dest[dk], &src[sk]);
}
ssize += 5;
if (ssize > sk) {
encode_tail(&dest[dk], &src[sk], ssize - sk);
dk += 8;
}
out:
dest[dk] = 0;
while(dest[dk-1] == 0 )
dk--;
while(dest[dk-1] == padding) {
dest[dk-1] = 0;
dk--;
}
return dk;
}
static uint8_t index_of(char c)
{
int idx;
if (!c)
die(128, "Encountered null character in encoded string, bad format\n");
if(c >= '0' && c <= '9')
idx = c - '0';
else if (c >= 'A' && c <= 'H')
idx = c - 'A' + 10; /* no I */
else if (c >= 'J' && c <= 'K') /* no L */
idx = c - 'J' + 18;
else if (c >= 'M' && c <= 'N') /* no O */
idx = c - 'M' + 20;
else if (c >= 'P' && c <= 'T') /* no U */
idx = c - 'P' + 22;
else if (c >= 'V' && c <= 'Z')
idx = c - 'V' + 27;
else if (c == '=')
idx = 0;
else
die(128, "character [%d] out of bounds\n", c);
#if defined(DEBUG)
fprintf(stderr, "I think that index_of(%c) == %d whereas base32_encoding[%d] = %c\n", c, idx, idx, base32_encoding[idx]);
#endif
return idx;
}
static int decode_block(unsigned char *dest, const void *_src)
{
uint8_t idx[8] = {};
const unsigned char * src = _src;
int k;
int end = 0;
for (k = 0; k < 8; k++) {
if (src[k] == 0 || src[k] == padding) {
end = 1;
break;
}
idx[k] = index_of(src[k]);
}
dest[0] = (uint8_t)(((idx[0] << 3) & 0xF8) | ((idx[1] >> 2) & 0x7));
dest[1] = (uint8_t)(((idx[1] << 6) & 0xC0) | ((idx[2] << 1) & 0x3E) | ((idx[3] >> 4) & 0x1));
dest[2] = (uint8_t)(((idx[3] << 4) & 0xF0) | ((idx[4] >> 1) & 0xF));
dest[3] = (uint8_t)(((idx[4] << 7) & 0x80) | ((idx[5] << 2) & 0x7C) | ((idx[6] >> 3) & 0x3));
dest[4] = (uint8_t)(((idx[6] << 5) & 0xE0) | ((idx[7] & 0x1F)));
if (end) {
switch(k) {
case 0:
end = ((idx[0] << 3) & 0xF8) ? 1 : 0;
break;
case 1:
end = ((idx[1] << 6) & 0xC0) ? 2 : 1;
break;
case 2:
end = 2;
break;
case 3:
end = ((idx[3] << 4) & 0xF0 ) ? 3 : 2;
break;
case 4:
end = ((idx[4] << 7) & 0x80 ) ? 4 : 3;
break;
case 5:
end = 4;
break;
case 6:
end = ((idx[6] << 5) & 0xE0 ) ? 5 : 4;
break;
case 7:
end = 5;
break;
}
}
return end;
}
size_t base32dec(void *dest, size_t buf_size, const char * src) {
int sk, dk;
size_t src_len;
src_len = strlen(src);
if(buf_size <= 5) {
char small_buf[5]; /* small buffer for 1-5 bytes stuff */
decode_block(small_buf, src);
memcpy(dest, small_buf, buf_size);
return 0;
}
for(sk=0, dk=0; sk < src_len; sk+=8, dk+=5) {
int end = decode_block((unsigned char *)dest+dk, &src[sk]);
if ( end ) {
dk += end - 1;
break;
}
}
return dk;
}
size_t base32encsize(size_t count)
{
size_t size = -1;
size = count << 3; /* multiply by 8 */
if ( size % 5 == 0 )
return size/5;
else
return 1+size/5;
}
size_t base32decsize(size_t count)
{
size_t size = -1;
size = count * 5;
return (size >> 3) + (size % 8) ? 1 : 0;
}