trezor-firmware/monero/serialize.c

//
// Created by Dusan Klinec on 02/05/2018.
//

#include "serialize.h"

int xmr_size_varint(uint64_t num){
	int ctr = 1;
	while (num >= 0x80) {
		++ctr;
		num >>= 7;
	}
	return ctr;
}

int xmr_write_varint(uint8_t * buff, size_t buff_size, uint64_t num){
	unsigned ctr = 0;
	while (num >= 0x80 && ctr < buff_size) {
		*buff = (uint8_t) (((num) & 0x7f) | 0x80);
		++buff;
		++ctr;
		num >>= 7;
	}

	/* writes the last one to dest */
	if (ctr < buff_size) {
		*buff = (uint8_t) num;
		++ctr;
	}
	return ctr <= buff_size ? (int)ctr : -1;
}

int xmr_read_varint(uint8_t * buff, size_t buff_size, uint64_t *val) {
	unsigned read = 0;
	int finished_ok = 0;
	*val = 0;

	for (int shift = 0; read < buff_size; shift += 7, ++read) {
		uint8_t byte = buff[read];
		if (byte == 0 && shift != 0) {
			return -1;
		}

		*val |= (uint64_t)(byte & 0x7f) << shift;

		/* If there is no next */
		if ((byte & 0x80) == 0) {
			finished_ok = 1;
			break;
		}
	}
	return finished_ok ? (int)read + 1 : -2;
}