base58.c

/*
 * Copyright 2012-2014 Luke Dashjr
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the standard MIT license.  See COPYING for more details.
 */

#include <stddef.h>
#include <stdint.h>
#include <string.h>
#include <sys/types.h>
#include <stdio.h>
#include <inttypes.h>

const int8_t b58digits_map[] = {
	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
	-1,-1,-1,-1,-1,-1,-1,-1, -1,-1,-1,-1,-1,-1,-1,-1,
	-1, 0, 1, 2, 3, 4, 5, 6,  7, 8,-1,-1,-1,-1,-1,-1,
	-1, 9,10,11,12,13,14,15, 16,-1,17,18,19,20,21,-1,
	22,23,24,25,26,27,28,29, 30,31,32,-1,-1,-1,-1,-1,
	-1,33,34,35,36,37,38,39, 40,41,42,43,-1,44,45,46,
	47,48,49,50,51,52,53,54, 55,56,57,-1,-1,-1,-1,-1,
};

const char b58digits_ordered[] = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";

typedef uint64_t b58_maxint_t;
typedef uint32_t b58_almostmaxint_t;
#define b58_almostmaxint_bits (sizeof(b58_almostmaxint_t) * 8)
static const b58_almostmaxint_t b58_almostmaxint_mask = ((((b58_maxint_t)1) << b58_almostmaxint_bits) - 1);


// const char err_highbit[] = "High bit set on invalid digit";
// const char err_digit[] = "Invalid base58 digit";
			// Output number too big (carry to the next int32)
			// Output number too big (last int32 filled too far)

int b58tobin(void *bin, size_t *binszp, const char *b58, size_t b58sz)
{
	size_t binsz = *binszp;
	const unsigned char *b58u = (void*)b58;
	unsigned char *binu = bin;
	size_t outisz = (binsz + sizeof(b58_almostmaxint_t) - 1) / sizeof(b58_almostmaxint_t);
	b58_almostmaxint_t outi[outisz];
	b58_maxint_t t;
	b58_almostmaxint_t c;
	size_t i, j;
	uint8_t bytesleft = binsz % sizeof(b58_almostmaxint_t);
	b58_almostmaxint_t zeromask = bytesleft ? (b58_almostmaxint_mask << (bytesleft * 8)) : 0;
	unsigned zerocount = 0;
	
	if (!b58sz)
		b58sz = strlen(b58);
	
	for (i = 0; i < outisz; ++i) {
		outi[i] = 0;
	}
	
	// Leading zeros, just count
	for (i = 0; i < b58sz && b58u[i] == '1'; ++i)
		++zerocount;
	
	for ( ; i < b58sz; ++i)
	{
		if (b58u[i] & 0x80)
			// High-bit set on invalid digit
			return 0;
		if (b58digits_map[b58u[i]] == -1)
			// Invalid base58 digit
			return 0;
		c = (unsigned)b58digits_map[b58u[i]];
		for (j = outisz; j--; )
		{
			t = ((b58_maxint_t)outi[j]) * 58 + c;
			c = t >> b58_almostmaxint_bits;
			outi[j] = t & b58_almostmaxint_mask;
		}
		if (c)
			// Output number too big (carry to the next int32)
			return 0;
		if (outi[0] & zeromask)
			// Output number too big (last int32 filled too far)
			return 0;
	}
	
	j = 0;
	if (bytesleft) {
		for (i = bytesleft; i > 0; --i) {
			*(binu++) = (outi[0] >> (8 * (i - 1))) & 0xff;
		}
		++j;
	}
	
	for (; j < outisz; ++j)
	{
		for (i = sizeof(*outi); i > 0; --i) {
			*(binu++) = (outi[j] >> (8 * (i - 1))) & 0xff;
		}
	}
	
	// Count canonical base58 byte count
	binu = bin;
	for (i = 0; i < binsz; ++i)
	{
		if (binu[i])
			break;
		--*binszp;
	}
	*binszp += zerocount;
	
	return 1;
}

int b58enc(char *b58, size_t *b58sz, const void *data, size_t binsz)
{
	const uint8_t *bin = data;
	int carry;
	size_t i, j, high, zcount = 0;
	size_t size;
	
	while (zcount < binsz && !bin[zcount])
		++zcount;
	
	size = (binsz - zcount) * 138 / 100 + 1;
	uint8_t buf[size];
	memset(buf, 0, size);
	
	for (i = zcount, high = size - 1; i < binsz; ++i, high = j)
	{
		for (carry = bin[i], j = size - 1; (j > high) || carry; --j)
		{
			carry += 256 * buf[j];
			buf[j] = carry % 58;
			carry /= 58;
			if (!j) {
				// Otherwise j wraps to maxint which is > high
				break;
			}
		}
	}
	
	for (j = 0; j < size && !buf[j]; ++j);
	
	if (*b58sz <= zcount + size - j)
	{
		*b58sz = zcount + size - j + 1;
		return 0;
	}
	
	if (zcount)
		memset(b58, '1', zcount);
	for (i = zcount; j < size; ++i, ++j)
		b58[i] = b58digits_ordered[buf[j]];
	b58[i] = '\0';
	*b58sz = i + 1;
	
	return 1;
}