Initial commit

1 files changed, 447 insertions, 0 deletions

diff --git a/intmath.c b/intmath.c
new file mode 100644
index 0000000..cba66a9
--- /dev/null
+++ b/intmath.c
@@ -0,0 +1,447 @@
+
+#include <stdlib.h>
+#include <string.h>
+
+#include "minitest.h"
+#include "intmath.h"
+
+int int_pown(unsigned int base, unsigned int exp) {
+	int res = 1;
+	while (exp > 0) {
+		res *= base;
+		exp--;
+	}
+	return res;
+}
+
+int int_pow10(unsigned int exp) {
+	return int_pown(10, exp);
+}
+
+int int_floor(int x, int precision) {
+	int sign = (x < 0) * -2 + 1;
+	x *= sign;
+
+	int iterations = 0;
+	while (x > int_pow10(precision)) {
+		x /= 10;
+		iterations++;
+	}
+
+	return (x + (sign == -1))
+		* int_pow10(iterations)
+		* sign;
+}
+
+int int_ceil(int x, int precision) {
+	return -int_floor(-x, precision);
+}
+
+int int_min(int a, int b) {
+	return (a < b) * a + (b <= a) * b;
+}
+
+int int_max(int a, int b) {
+	return (a > b) * a + (b >= a) * b;
+}
+
+/* Returns `int x` floored to `unsigned int precision` as an `exp_notated`
+ * value with given `unsigned int base`.
+ *
+ * `unsigned int base` affects the precision.
+ */
+exp_notated int_floored_exponent_notation_base
+(
+	int x,
+	unsigned int precision,
+	unsigned int base
+) {
+	int original = x;
+	int sign = (x < 0) * -2 + 1;
+	x *= sign;
+
+	int i = 0;
+	while (x >= int_pown(base, precision)) {
+		x /= base;
+		i++;
+	}
+	x += (sign == -1) && (original != -x * int_pown(base, i)); 
+	if (x >= int_pown(base, precision)) {
+		x /= base;
+		i++;
+	}
+	x *= sign;
+
+	exp_notated res = {
+		.mantissa = x,
+		.exponent = i,
+		.base = base
+	};
+	return res;
+}
+
+exp_notated int_floored_exponent_notation(int x, unsigned int precision) {
+	return int_floored_exponent_notation_base(x, precision, 10);
+}
+
+exp_notated int_ceiled_exponent_notation_base(
+	int x,
+	unsigned int precision,
+	unsigned int base
+) {
+	exp_notated res = int_floored_exponent_notation_base(-x, precision, base);
+	res.mantissa = -res.mantissa;
+	return res;
+}
+
+exp_notated int_ceiled_exponent_notation(int x, unsigned int precision) {
+	return int_ceiled_exponent_notation_base(x, precision, 10);
+}
+
+int exp_notated_to_int(exp_notated x) {
+	return x.mantissa * int_pown(x.base, x.exponent);
+}
+
+/* Returns the appropriate binary prefix for `exp_notated x`. `x` must have
+ * `1024` as its base, it should not be greater than `1023*1024^10` and it
+ * should be floored/ceiled (ie. the mantissa should not be further away from
+ * zero than `1023`). Failing to meet these conditions results in the function
+ * returning `NULL`.
+ */
+const char* binary_prefix(exp_notated x) {
+	if (
+		(x.base != 1024) ||
+		(x.exponent > 10) ||
+		(x.mantissa > 1023) ||
+		(x.mantissa < -1023)
+	) {
+		return NULL;
+	}
+
+	switch (x.exponent) {
+		case 0:
+			return "";
+		case 1:
+			return "Ki";
+		case 2:
+			return "Mi";
+		case 3:
+			return "Gi";
+		case 4:
+			return "Ti";
+		case 5:
+			return "Pi";
+		case 6:
+			return "Ei";
+		case 7:
+			return "Zi";
+		case 8:
+			return "Yi";
+		case 9:
+			return "Ri";
+		default:
+			return "Qi";
+	}
+}
+
+/* Returns the a string describing the argument `int x` floored to the
+ * appropriate multiple of 1024 followed with a binary prefix (Ki, Mi, Gi...).
+ * The string is dynamically allocated and should be free'd.
+ *
+ * Returns NULL on malloc error.
+ */
+char* int_floored_with_binary_prefix(int x) {
+	exp_notated x_exp = int_floored_exponent_notation_base(x, 1, 1024);
+	if (x_exp.exponent > 10) /* quebi-=1024^10 greatest defined prefix */
+		x_exp.mantissa *= int_pow10(x_exp.exponent - 10);
+
+	const char* prefix = binary_prefix(x_exp);
+
+	size_t bufsize =
+		5 + /* len("-1024") */
+		int_max(0, x_exp.exponent - 10) + /* length of possible zeros */
+		4;  /* len(" Gi\0") */
+	char* res = malloc(bufsize);
+	if (res == NULL) return NULL;
+	sprintf(res, "%d", x_exp.mantissa);
+	if (strcmp(prefix, "") != 0)
+		strcat(res, " ");
+	strcat(res, prefix);
+
+	return res;
+}
+
+char* test_pown() {
+	mt_assert_eq(int_pown(2, 5), 32);
+	mt_assert_eq(int_pown(3, 3), 27);
+	mt_assert_eq(int_pown(9, 0), 1);
+	return 0;
+}
+
+char* test_pow10() {
+	mt_assert_eq(int_pow10(3), 1000);
+	mt_assert_eq(int_pow10(0), 1);
+	return 0;
+}
+
+char* test_floor() {
+	mt_assert_eq(int_floor(34128, 2), 34000);
+	mt_assert_eq(int_floor(-34128, 3), -34200);
+	mt_assert_eq(int_floor(-9999, 3), -10000);
+	mt_assert_eq(int_floor(9999, 3), 9990);
+	mt_assert_eq(int_floor(0, 1), 0);
+	return 0;
+}
+
+char* test_ceil() {
+	mt_assert_eq(int_ceil(44212, 3), 44300);
+	mt_assert_eq(int_ceil(-44212, 3), -44200);
+	mt_assert_eq(int_ceil(-9999, 3), -9990);
+	mt_assert_eq(int_ceil(9999, 3), 10000);
+	mt_assert_eq(int_ceil(0, 1), 0);
+	return 0;
+}
+
+char* test_min() {
+	mt_assert_eq(int_min(2, 6), 2);
+	mt_assert_eq(int_min(4, 1), 1);
+	mt_assert_eq(int_min(10, 10), 1);
+	return 0;
+}
+
+char* test_max() {
+	mt_assert_eq(int_max(3, 7), 7);
+	mt_assert_eq(int_min(4, 1), 4);
+	mt_assert_eq(int_min(10, 10), 10);
+	return 0;
+}
+
+char* test_floored_exponent_notation() {
+	const size_t bufsize = 128;
+	char* msg = malloc(bufsize);
+
+	exp_notated res = int_floored_exponent_notation(9489345, 3);
+	snprintf(msg, bufsize,
+		"int_floored_exponent_notation(9489345, 3): expected 948*10^4, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == 948 &&
+		res.base == 10 &&
+		res.exponent == 4
+	, msg);
+
+	res = int_floored_exponent_notation(-88, 1);
+	snprintf(msg, bufsize,
+		"int_floored_exponent_notation(-88, 1): expected -9*10^1, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == -9 &&
+		res.base == 10 &&
+		res.exponent == 1
+	, msg);
+
+	res = int_floored_exponent_notation(-99, 1);
+	snprintf(msg, bufsize,
+		"int_floored_exponent_notation(-99, 1): expected -1*10^2, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == -1 &&
+		res.base == 10 &&
+		res.exponent == 2
+	, msg);
+
+	res = int_floored_exponent_notation_base(3145733, 1, 1024);
+	snprintf(msg, bufsize,
+		"int_floored_exponent_notation_base(3145733, 1, 1024): expected 3*1024^2, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == 3 &&
+		res.base == 1024 &&
+		res.exponent == 2
+	, msg);
+
+	res = int_floored_exponent_notation_base(-1022, 1, 1024);
+	snprintf(msg, bufsize,
+		"int_floored_exponent_notation(-1022, 1, 1024): expected -1022*1024^0, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == -1022 &&
+		res.base == 1024 &&
+		res.exponent == 0
+	, msg);
+
+	res = int_floored_exponent_notation_base(-1023, 1, 1024);
+	snprintf(msg, bufsize,
+		"int_floored_exponent_notation(-1023, 1, 1024): expected -1023*1024^0, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == -1023 &&
+		res.base == 1024 &&
+		res.exponent == 0
+	, msg);
+
+	res = int_floored_exponent_notation_base(-1024, 1, 1024);
+	snprintf(msg, bufsize,
+		"int_floored_exponent_notation(-1024, 1, 1024): expected -1*1024^1, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == -1 &&
+		res.base == 1024 &&
+		res.exponent == 1
+	, msg);
+
+	free(msg);
+	return 0;
+}
+
+char* test_ceiled_exponent_notation() {
+	const size_t bufsize = 128;
+	char* msg = malloc(bufsize);
+
+	exp_notated res = int_ceiled_exponent_notation(9489345, 3);
+	snprintf(msg, bufsize,
+		"int_ceiled_exponent_notation(9489345, 3): expected 949*10^4, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == 949 &&
+		res.base == 10 &&
+		res.exponent == 4
+	, msg);
+
+	res = int_ceiled_exponent_notation(-99, 1);
+	snprintf(msg, bufsize,
+		"int_ceiled_exponent_notation(-99, 1): expected -9*10^1, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == -9 &&
+		res.base == 10 &&
+		res.exponent == 1
+	, msg);
+
+	res = int_ceiled_exponent_notation(-100, 1);
+	snprintf(msg, bufsize,
+		"int_ceiled_exponent_notation(-100, 1): expected -1*10^2, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == -1 &&
+		res.base == 10 &&
+		res.exponent == 2
+	, msg);
+
+	res = int_ceiled_exponent_notation_base(3145733, 1, 1024);
+	snprintf(msg, bufsize,
+		"int_ceiled_exponent_notation_base(3145733, 1, 1024): expected 4*1024^2, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == 4 &&
+		res.base == 1024 &&
+		res.exponent == 2
+	, msg);
+
+	res = int_ceiled_exponent_notation_base(-1023, 1, 1024);
+	snprintf(msg, bufsize,
+		"int_ceiled_exponent_notation(-1023, 1, 1024): expected -1023*1024^0, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == -1023 &&
+		res.base == 1024 &&
+		res.exponent == 0
+	, msg);
+
+	res = int_ceiled_exponent_notation_base(-1024, 1, 1024);
+	snprintf(msg, bufsize,
+		"int_ceiled_exponent_notation(-1024, 1, 1024): expected -1*1024^1, got %d*%d^%d",
+		res.mantissa, res.base, res.exponent
+	);
+	mt_assert(
+		res.mantissa == -1 &&
+		res.base == 1024 &&
+		res.exponent == 1
+	, msg);
+
+	free(msg);
+	return 0;
+}
+
+char* test_exponent_notated_to_int() {
+	exp_notated x = {
+		.mantissa = 3,
+		.exponent = 2,
+		.base = 10
+	};
+	mt_assert_eq(300, exp_notated_to_int(x));
+	return 0;
+}
+
+char* test_floored_with_binary_prefix() {
+	const size_t bufsize = 64;
+	char* msg = malloc(bufsize);
+
+	char* res = int_floored_with_binary_prefix(1026);
+	snprintf(msg, bufsize, "1026 yielded `%s` instead of `1 Ki`", res);
+	mt_assert(strcmp(
+		res,
+		"1 Ki"
+	) == 0, msg);
+	free(res);
+
+	res = int_floored_with_binary_prefix(-1023);
+	snprintf(msg, bufsize, "-1023 yielded `%s` instead of `-1023`", res);
+	mt_assert(strcmp(
+		res,
+		"-1023"
+	) == 0, msg);
+	free(res);
+
+	res = int_floored_with_binary_prefix(-1026);
+	snprintf(msg, bufsize, "-1026 yielded `%s` instead of `-2 Ki`", res);
+	mt_assert(strcmp(
+		res,
+		"-2 Ki"
+	) == 0, msg);
+	free(res);
+
+	res = int_floored_with_binary_prefix(1049088);
+	snprintf(msg, bufsize, "1049088 yielded `%s` instead of `1 Mi`", res);
+	mt_assert(strcmp(
+		res,
+		"1 Mi"
+	) == 0, msg);
+	free(res);
+
+	res = int_floored_with_binary_prefix(5243392);
+	snprintf(msg, bufsize, "5243392 yielded `%s` instead of `5 Mi`", res);
+	mt_assert(strcmp(
+		res,
+		"5 Mi"
+	) == 0, msg);
+	free(res);
+
+	free(msg);
+	return 0;
+}
+
+void intmath_tests() {
+	mt_run_test(test_pown);
+	mt_run_test(test_pow10);
+	mt_run_test(test_floor);
+	mt_run_test(test_ceil);
+	mt_run_test(test_min);
+	mt_run_test(test_max);
+	mt_run_test(test_floored_exponent_notation);
+	mt_run_test(test_ceiled_exponent_notation);
+	mt_run_test(test_exponent_notated_to_int);
+	mt_run_test(test_floored_with_binary_prefix);
+}