1 files changed, 74 insertions, 0 deletions
diff --git a/libsyscalls_section_value.c b/libsyscalls_section_value.c
new file mode 100644
index 0000000..dc86cca
--- /dev/null
+++ b/libsyscalls_section_value.c
@@ -0,0 +1,74 @@
+/* See LICENSE file for copyright and license details. */
+#include "common.h"
+
+
+enum libsyscalls_error
+libsyscalls_section_value(unsigned long long int value_in, size_t bits,
+                          enum libsyscalls_datatype_section section, unsigned long long int *value_out)
+{
+	unsigned long long int value = value_in, mask, shift;
+
+	if (bits > sizeof(value) / sizeof(char) * CHAR_BIT ||
+	    bits & (size_t)(LIBSYSCALLS_GET_SECTION_FRACTION(section) - 1U))
+		return LIBSYSCALLS_E_INVAL;
+
+	bits /= (size_t)LIBSYSCALLS_GET_SECTION_FRACTION(section);
+	if (bits == sizeof(mask) / sizeof(char) * CHAR_BIT)
+		mask = ~0ULL;
+	else
+		mask = (1ULL << bits) - 1ULL;
+
+	switch (section) {
+	case LIBSYSCALLS_SECTION_UNDETERMINED:
+	case LIBSYSCALLS_SECTION_WHOLE: /* 0xFFFFFFFFFFFFFFFF */
+	case LIBSYSCALLS_SECTION_LOWER_HALF: /* 0x00000000FFFFFFFF */
+	case LIBSYSCALLS_SECTION_LOWER_QUARTER: /* 0x000000000000FFFF */
+		break;
+
+	case LIBSYSCALLS_SECTION_UPPER_HALF: /* 0xFFFFFFFF00000000 */
+	case LIBSYSCALLS_SECTION_LOWER_MID_QUARTER: /* 0x00000000FFFF0000 */
+		value >>= bits;
+		break;
+
+	case LIBSYSCALLS_SECTION_INNER_HALF: /* 0x0000FFFFFFFF0000 */
+		value >>= bits / 2;
+		break;
+
+	case LIBSYSCALLS_SECTION_UPPER_MID_QUARTER: /* 0x0000FFFF00000000 */
+		value >>= bits * 2;
+		break;
+
+	case LIBSYSCALLS_SECTION_UPPER_QUARTER: /* 0xFFFF000000000000 */
+		value >>= bits * 3;
+		break;
+
+	case LIBSYSCALLS_SECTION_OUTER_HALF: /* 0xFFFF00000000FFFF */
+		value = ((value & (mask << (bits + bits / 2))) >> bits) | (value & (mask >> (bits / 2)));
+		break;
+
+	case LIBSYSCALLS_SECTION_ODD_QUARTERS_AS_HALF: /* 0xFFFF0000FFFF0000 */
+		value >>= bits / 2;
+		/* fall through */
+	case LIBSYSCALLS_SECTION_EVEN_QUARTERS_AS_HALF: /* 0x0000FFFF0000FFFF */
+		value = ((value & (mask << (bits / 2)) & ~mask) >> (bits / 2)) | (value & (mask >> (bits / 2)));
+		break;
+
+	case LIBSYSCALLS_SECTION_ODD_BYTES_AS_HALF: /* 0xFF00FF00FF00FF00 */
+		value_in >>= 8;
+		/* fall through */
+	case LIBSYSCALLS_SECTION_EVEN_BYTES_AS_HALF: /* 0x00FF00FF00FF00FF */
+		value = 0;
+		for (shift = 0; value_in; value_in >>= 16, shift += 8)
+			value |= (value_in & 0x00FFU) << shift;
+		break;
+
+	default:
+		return LIBSYSCALLS_E_INVAL;
+	}
+
+	value &= mask;
+masked:
+	if (value_out)
+		*value_out = value;
+	return LIBSYSCALLS_E_OK;
+}