src/math.c: Add mul_size()

4 files changed, 105 insertions, 0 deletions

diff --git a/deps.mk b/deps.mk
index 7849036..0b113b5 100644
--- a/deps.mk
+++ b/deps.mk
@@ -7,6 +7,7 @@ sources.c = \
 	src/i18n.c \
 	src/lib.c \
 	src/logerr.c \
+	src/math.c \
 	src/random.c \
 	src/string.c \
 	src/testing.c \
@@ -18,6 +19,7 @@ tests.c = \
 	tests/i18n.c \
 	tests/lib.c \
 	tests/logerr.c \
+	tests/math.c \
 	tests/random.c \
 	tests/string.c \
 	tests/testing.c \
@@ -28,6 +30,7 @@ src/catalog.o:	src/catalog.h
 src/i18n.o:	src/i18n.h
 src/lib.o:	src/lib.h
 src/logerr.o:	src/logerr.h
+src/math.o:	src/math.h
 src/random.o:	src/random.h
 src/string.o:	src/string.h
 src/testing.o:	src/testing.h
@@ -38,6 +41,7 @@ tests/catalog.o:	src/catalog.c	src/catalog.h
 tests/i18n.o:	src/i18n.c	src/i18n.h
 tests/lib.o:	src/lib.c	src/lib.h
 tests/logerr.o:	src/logerr.c	src/logerr.h
+tests/math.o:	src/math.c	src/math.h
 tests/random.o:	src/random.c	src/random.h
 tests/string.o:	src/string.c	src/string.h
 tests/testing.o:	src/testing.c	src/testing.h
@@ -48,6 +52,7 @@ tests/catalog.a:	tests/catalog.o
 tests/i18n.a:	tests/i18n.o
 tests/lib.a:	tests/lib.o
 tests/logerr.a:	tests/logerr.o
+tests/math.a:	tests/math.o
 tests/random.a:	tests/random.o
 tests/string.a:	tests/string.o
 tests/testing.a:	tests/testing.o
@@ -58,6 +63,7 @@ tests/catalog.bin-check:	tests/catalog.bin
 tests/i18n.bin-check:	tests/i18n.bin
 tests/lib.bin-check:	tests/lib.bin
 tests/logerr.bin-check:	tests/logerr.bin
+tests/math.bin-check:	tests/math.bin
 tests/random.bin-check:	tests/random.bin
 tests/string.bin-check:	tests/string.bin
 tests/testing.bin-check:	tests/testing.bin
@@ -69,6 +75,7 @@ src/catalog.o: src/logerr.h
 src/i18n.o: src/catalog.h
 src/lib.o: src/logerr.h
 src/logerr.o:
+src/math.o:
 src/random.o: src/logerr.h
 src/string.o:
 src/testing.o:
@@ -79,6 +86,7 @@ tests/catalog.o: src/logerr.h src/testing.h tests/slurp.h
 tests/i18n.o: src/catalog.h src/logerr.h
 tests/lib.o: src/logerr.h
 tests/logerr.o: src/testing.h tests/slurp.h
+tests/math.o: src/testing.h
 tests/random.o: src/logerr.h src/testing.h
 tests/string.o:
 tests/testing.o:
@@ -89,6 +97,7 @@ tests/catalog.a: src/logerr.o src/testing.o tests/slurp.o
 tests/i18n.a: src/catalog.o src/logerr.o
 tests/lib.a: src/logerr.o
 tests/logerr.a: src/testing.o tests/slurp.o
+tests/math.a: src/testing.o
 tests/random.a: src/logerr.o src/testing.o
 tests/string.a:
 tests/testing.a:
diff --git a/src/math.c b/src/math.c
new file mode 100644
index 0000000..366bd5e
--- /dev/null
+++ b/src/math.c
@@ -0,0 +1,27 @@
+#include "config.h"
+
+#include <assert.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdint.h>
+
+#include "math.h"
+
+
+int
+mul_size(const size_t x, const size_t y, size_t *const out) {
+	int rc = -1;
+
+	assert(x != 0U);
+	assert(y != 0U);
+
+	const bool overflows = x > (SIZE_MAX / y);
+	if (overflows) {
+		goto out;
+	}
+
+	*out = x * y;
+	rc = 0;
+out:
+	return rc;
+}
diff --git a/src/math.h b/src/math.h
new file mode 100644
index 0000000..13f1795
--- /dev/null
+++ b/src/math.h
@@ -0,0 +1,2 @@
+int
+mul_size(const size_t x, const size_t y, size_t *const out);
diff --git a/tests/math.c b/tests/math.c
new file mode 100644
index 0000000..34f54ce
--- /dev/null
+++ b/tests/math.c
@@ -0,0 +1,67 @@
+#include "../src/math.c"
+
+#include "../src/testing.h"
+
+
+static void
+test_mul_size(void) {
+	test_start("mul_size()");
+
+	size_t val;
+	{
+		testing("zero values");
+
+		assert(mul_size(1U, 1U, &val) == 0);
+		assert(val == 1U);
+
+		test_ok();
+	}
+	{
+		testing("small values");
+
+		assert(mul_size(2U, 3U, &val) == 0);
+		assert(val == 6U);
+
+		assert(mul_size(10U, 10U, &val) == 0);
+		assert(val == 100U);
+
+		assert(mul_size(15U, 15U, &val) == 0);
+		assert(val == 225U);
+
+		test_ok();
+	}
+	{
+		testing("big values");
+
+		assert(mul_size(SIZE_MAX, 1U, &val) == 0);
+		assert(val == SIZE_MAX);
+
+		assert(mul_size(1U, SIZE_MAX, &val) == 0);
+		assert(val == SIZE_MAX);
+
+		assert(mul_size(SIZE_MAX / 2U, 2U, &val) == 0);
+		assert(val == SIZE_MAX - 1U);
+
+		test_ok();
+	}
+	{
+		testing("overflowing values");
+
+		val = 123U;
+
+		assert(mul_size(SIZE_MAX, 2U, &val) != 0);
+		assert(val == 123U);
+
+		assert(mul_size(3U, SIZE_MAX / 2U, &val) != 0);
+		assert(val == 123U);
+
+		test_ok();
+	}
+}
+
+
+int
+main(void) {
+	test_mul_size();
+	return 0;
+}