1 files changed, 61 insertions, 0 deletions
diff --git a/libsyscalls_parse_signed_integer.c b/libsyscalls_parse_signed_integer.c
new file mode 100644
index 0000000..da6f078
--- /dev/null
+++ b/libsyscalls_parse_signed_integer.c
@@ -0,0 +1,61 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+enum libsyscalls_error
+libsyscalls_parse_signed_integer(unsigned long long int value_in, enum libsyscalls_datatype_sign_representation representation,
+                                 size_t bits, unsigned long long int *value_out, int *negative_out)
+{
+	unsigned long long int value = value_in, mask;
+	int negative = 0;
+
+	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 (value >> (bits - 1U)) {
+			mask = (1ULL << (bits - 1U)) - 1ULL;
+			value = ~value & mask;
+			value += 1ULL;
+			negative = 1;
+		}
+		break;
+
+	case LIBSYSCALLS_SIGN_ONES_COMPLEMENT:
+		if (value >> (bits - 1U)) {
+			mask = (1ULL << (bits - 1U)) - 1ULL;
+			value = ~value & mask;
+			negative = 1;
+		}
+		break;
+
+	case LIBSYSCALLS_SIGN_SIGN_MAGNITUDE:
+		if (value >> (bits - 1U)) {
+			value ^= 1ULL << (bits - 1U);
+			negative = 1;
+		}
+		break;
+
+	case LIBSYSCALLS_SIGN_EXCESS_HALF:
+		if (value >> (bits - 1U)) {
+			value ^= 1ULL << (bits - 1U);
+		} else {
+			value = (1ULL << (bits - 1U)) - value;
+			negative = 1;
+		}
+		break;
+
+	default:
+		return LIBSYSCALLS_E_INVAL;
+	}
+
+	if (value_out)
+		*value_out = value;
+	if (negative_out)
+		*negative_out = negative;
+	return LIBSYSCALLS_E_OK;
+}