wallet/slash6.h

#pragma once
// Converts a bit buffer, arbitrarily positioned with respect to byte boundaries, into a
//	base sixty four numeral.	In release mode, returns without doing anything if the output
//	string buffer is too small.
//	In debug mode, halts execution with an assert.   Should throw, need to put in and
//	unit test.
void bits2base64(
	const uint8_t * bitBuffer,
	unsigned int start,
	unsigned int length,
	std::span<char>base64Numerals
	);

//	Converts a base64 numeral into a bit buffer.  The input string is terminated by the first
//	non base64 character, normally a space or null, or terminated when the bit buffer is full.
//	A correct length base64 numeral does not need a terminating space or null.
//	If successful, returns a length equal to the bit buffer length.  If the input string is too
//	short, returns a length shorter than the bit buffer.  If the bit buffer is not a multiple of six bits, and the last base64 numeral of the bit buffer has trailing binary ones, returns a length greater than the size of the bitbuffer, without writing the trailing binary bits into the bit buffer.
unsigned int base64_to_bits(
	uint8_t* bitBuffer,
	unsigned int start,
	unsigned int length,
	const char* base64Numerals
	);

/* Expects pointer to byte buffer and pointer to string.
	Expects a string of exactly the correct number of numerals,
	terminated by a non base64 character, such as null.
	Throws exception if that is not what it gets.
	Fills the byte buffer exactly.
	Returns a uint8_t containing the excess bits of the last numeral in its low order part.*/
uint8_t base64_to_bytes(
	uint8_t* byteBuffer,
	uint_fast32_t byteCount,
	const char* base64Numerals
	);

/* Expects reference to a range object over bytes and pointer to string.
	Expects a string of exactly the correct number of numerals,
	terminated by a non base64 character, such as null.
	Throws exception if that is not what it gets.
	Fills the byte buffer exactly.
	Returns a uint8_t containing the excess bits of the last numeral in its low order part.*/
template < typename T>
std::enable_if_t<
	!std::is_pointer<T>::value &&
	sizeof(std::declval<T>()[0]) == 1,
	uint8_t
>base64_to_bytes( T& byteRange, const char* base64Numerals) {
	return base64_to_bytes(
		static_cast<std::nullptr_t>(&byteRange[0]),
		static_cast<uint_fast32_t>(std::size(byteRange)), base64Numerals);
}