All kinds of stuff

Signed-off-by: Mattias Andrée <maandree@kth.se>

1 files changed, 56 insertions, 0 deletions

diff --git a/libsyscalls_make_signed_integer.c b/libsyscalls_make_signed_integer.c
new file mode 100644
index 0000000..b4142dc
--- /dev/null
+++ b/libsyscalls_make_signed_integer.c
@@ -0,0 +1,56 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+enum libsyscalls_error
+libsyscalls_make_signed_integer(unsigned long long int value_in, int negative,
+                                enum libsyscalls_datatype_sign_representation representation,
+                                size_t bits, unsigned long long int *value_out)
+{
+	unsigned long long int value = value_in, mask, highbit;
+
+	if (!bits || bits > sizeof(value) / sizeof(char) * CHAR_BIT)
+		return LIBSYSCALLS_E_INVAL;
+
+	switch (representation) {
+	case LIBSYSCALLS_SIGN_UNDETERMINED:
+		break;
+
+	case LIBSYSCALLS_SIGN_TWOS_COMPLEMENT:
+		if (negative && value) {
+			highbit = 1ULL << (bits - 1U);
+			mask = highbit - 1ULL;
+			value = ~(value - 1) & mask;
+			value |= highbit;
+		}
+		break;
+
+	case LIBSYSCALLS_SIGN_ONES_COMPLEMENT:
+		if (negative) {
+			highbit = 1ULL << (bits - 1U);
+			mask = highbit - 1ULL;
+			value = ~value & mask;
+			value |= highbit;
+		}
+		break;
+
+	case LIBSYSCALLS_SIGN_SIGN_MAGNITUDE:
+		if (negative)
+			value ^= 1ULL << (bits - 1);
+		break;
+
+	case LIBSYSCALLS_SIGN_EXCESS_HALF:
+		if (!negative)
+			value ^= 1ULL << (bits - 1);
+		else
+			value = (1ULL << (bits - 1)) - value;
+		break;
+
+	default:
+		return LIBSYSCALLS_E_INVAL;
+	}
+
+	if (value_out)
+		*value_out = value;
+	return LIBSYSCALLS_E_OK;
+}