#include "rsa.h"

void array_set_random_bytes(uint32_t *n, size_t size) {
	int fd = open("/dev/urandom", O_RDONLY);
	read(fd, n, size);
}

void array_set_msb_and_lsb_to_one(uint32_t *n, size_t size) {
	n[0] |= 1;
	n[size / sizeof(uint32_t) - 1] |= 1 << 31;
}

void array_bitwise_right_shift(uint32_t *a, size_t len) {
	size_t size = sizeof(uint32_t) * 8 - 1;
	for (size_t n = 0; n < len - 1; n++) {
		a[n] = a[n] >> 1 | (a[n + 1] & 1) << size;
	}
	a[len - 1] >>= 1;
}

void array_bitwise_left_shift(uint32_t *a, size_t len) {
	size_t size = sizeof(uint32_t) * 8 - 1;
	for (size_t n = len - 1; n > 0; n--) {
		a[n] = a[n] << 1 | ((a[n - 1] & (1 << size)) >> size);
	}
	a[0] <<= 1;
}

// Will underflow
void array_decrement(uint32_t *a, size_t len) {
	size_t cursor = 0;
	size_t size = sizeof(uint32_t) * 8;
	while (cursor < size * len) {
		a[cursor / size] = a[cursor / size] ^ (1 << (cursor % size));
		if (((a[cursor / size] >> (cursor % size)) & 1) == 0) {
			return;
		}
		cursor += 1;
	}
}