USB HID: Parse bit fields with correct bit order

Implement little endian support for tvb_get_bits family of functions.
The big/little endian refers to bit numbering within an octet. In big
endian, the most significant bit is considered bit 0, while in little
endian the least significant bit is considered bit 0.

Add encoding parameters to proto tree bits format family functions.
Specify ENC_BIG_ENDIAN in all dissectors using these functions except in
USB HID that requires ENC_LITTLE_ENDIAN to work correctly.

When formatting bits values, always display most significant bit on the
leftmost position regardless of the encoding. This results in no gaps
between octets and makes the displayed value comprehensible.

Close #4478
Fix #17014

1 files changed, 23 insertions, 15 deletions

diff --git a/epan/proto.c b/epan/proto.c
index cf2cc6b5b7..104eef55ec 100644
--- a/epan/proto.c
+++ b/epan/proto.c
@@ -12272,7 +12272,7 @@ _proto_tree_add_bits_ret_val(proto_tree *tree, const int hfindex, tvbuff_t *tvb,
 	CHECK_FOR_NULL_TREE(tree);
 	TRY_TO_FAKE_THIS_ITEM(tree, hfindex, hf_field);
 
-	bf_str = decode_bits_in_field(bit_offset, no_of_bits, value);
+	bf_str = decode_bits_in_field(bit_offset, no_of_bits, value, encoding);
 
 	switch (hf_field->type) {
 	case FT_BOOLEAN:
@@ -12323,7 +12323,7 @@ _proto_tree_add_bits_ret_val(proto_tree *tree, const int hfindex, tvbuff_t *tvb,
 		break;
 
 	case FT_BYTES:
-		bytes = tvb_get_bits_array(PNODE_POOL(tree), tvb, bit_offset, no_of_bits, &bytes_length);
+		bytes = tvb_get_bits_array(PNODE_POOL(tree), tvb, bit_offset, no_of_bits, &bytes_length, encoding);
 		pi = proto_tree_add_bytes_with_length(tree, hfindex, tvb, offset, length, bytes, (gint) bytes_length);
 		proto_item_fill_label(PITEM_FINFO(pi), lbl_str);
 		proto_item_set_text(pi, "%s", lbl_str);
@@ -12541,7 +12541,8 @@ proto_tree_add_split_bits_crumb(proto_tree *tree, const int hfindex, tvbuff_t *t
 						 tvb_get_bits(tvb,
 							      bit_offset,
 							      crumb_spec[crumb_index].crumb_bit_length,
-							      ENC_BIG_ENDIAN)),
+							      ENC_BIG_ENDIAN),
+						 ENC_BIG_ENDIAN),
 			    crumb_index,
 			    hfinfo->name);
 }
@@ -12566,7 +12567,7 @@ static proto_item *
 _proto_tree_add_bits_format_value(proto_tree *tree, const int hfindex,
 				 tvbuff_t *tvb, const guint bit_offset,
 				 const gint no_of_bits, void *value_ptr,
-				 gchar *value_str)
+				 const guint encoding, gchar *value_str)
 {
 	gint     offset;
 	guint    length;
@@ -12603,14 +12604,14 @@ _proto_tree_add_bits_format_value(proto_tree *tree, const int hfindex,
 		length++;
 
 	if (no_of_bits < 65) {
-		value = tvb_get_bits64(tvb, bit_offset, no_of_bits, ENC_BIG_ENDIAN);
+		value = tvb_get_bits64(tvb, bit_offset, no_of_bits, encoding);
 	} else {
 		REPORT_DISSECTOR_BUG("field %s passed to proto_tree_add_bits_format_value() has a bit width of %u > 65",
 				     hf_field->abbrev, no_of_bits);
 		return NULL;
 	}
 
-	str = decode_bits_in_field(bit_offset, no_of_bits, value);
+	str = decode_bits_in_field(bit_offset, no_of_bits, value, encoding);
 
 	(void) g_strlcat(str, " = ", 256+64);
 	(void) g_strlcat(str, hf_field->name, 256+64);
@@ -12680,13 +12681,13 @@ static proto_item *
 proto_tree_add_bits_format_value(proto_tree *tree, const int hfindex,
 				 tvbuff_t *tvb, const guint bit_offset,
 				 const gint no_of_bits, void *value_ptr,
-				 gchar *value_str)
+				 const guint encoding, gchar *value_str)
 {
 	proto_item *item;
 
 	if ((item = _proto_tree_add_bits_format_value(tree, hfindex,
 						      tvb, bit_offset, no_of_bits,
-						      value_ptr, value_str))) {
+						      value_ptr, encoding, value_str))) {
 		FI_SET_FLAG(PNODE_FINFO(item), FI_BITS_OFFSET(bit_offset));
 		FI_SET_FLAG(PNODE_FINFO(item), FI_BITS_SIZE(no_of_bits));
 	}
@@ -12702,6 +12703,7 @@ proto_item *
 proto_tree_add_uint_bits_format_value(proto_tree *tree, const int hfindex,
 				      tvbuff_t *tvb, const guint bit_offset,
 				      const gint no_of_bits, guint32 value,
+				      const guint encoding,
 				      const char *format, ...)
 {
 	va_list ap;
@@ -12728,13 +12730,14 @@ proto_tree_add_uint_bits_format_value(proto_tree *tree, const int hfindex,
 
 	CREATE_VALUE_STRING(tree, dst, format, ap);
 
-	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, dst);
+	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, encoding, dst);
 }
 
 proto_item *
 proto_tree_add_uint64_bits_format_value(proto_tree *tree, const int hfindex,
 				      tvbuff_t *tvb, const guint bit_offset,
 				      const gint no_of_bits, guint64 value,
+				      const guint encoding,
 				      const char *format, ...)
 {
 	va_list ap;
@@ -12761,13 +12764,14 @@ proto_tree_add_uint64_bits_format_value(proto_tree *tree, const int hfindex,
 
 	CREATE_VALUE_STRING(tree, dst, format, ap);
 
-	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, dst);
+	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, encoding, dst);
 }
 
 proto_item *
 proto_tree_add_float_bits_format_value(proto_tree *tree, const int hfindex,
 				       tvbuff_t *tvb, const guint bit_offset,
 				       const gint no_of_bits, float value,
+				       const guint encoding,
 				       const char *format, ...)
 {
 	va_list ap;
@@ -12782,13 +12786,14 @@ proto_tree_add_float_bits_format_value(proto_tree *tree, const int hfindex,
 
 	CREATE_VALUE_STRING(tree, dst, format, ap);
 
-	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, dst);
+	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, encoding, dst);
 }
 
 proto_item *
 proto_tree_add_int_bits_format_value(proto_tree *tree, const int hfindex,
 				     tvbuff_t *tvb, const guint bit_offset,
 				     const gint no_of_bits, gint32 value,
+	                             const guint encoding,
 				     const char *format, ...)
 {
 	va_list ap;
@@ -12815,13 +12820,14 @@ proto_tree_add_int_bits_format_value(proto_tree *tree, const int hfindex,
 
 	CREATE_VALUE_STRING(tree, dst, format, ap);
 
-	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, dst);
+	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, encoding, dst);
 }
 
 proto_item *
 proto_tree_add_int64_bits_format_value(proto_tree *tree, const int hfindex,
 				     tvbuff_t *tvb, const guint bit_offset,
 				     const gint no_of_bits, gint64 value,
+				     const guint encoding,
 				     const char *format, ...)
 {
 	va_list ap;
@@ -12848,13 +12854,14 @@ proto_tree_add_int64_bits_format_value(proto_tree *tree, const int hfindex,
 
 	CREATE_VALUE_STRING(tree, dst, format, ap);
 
-	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, dst);
+	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, encoding, dst);
 }
 
 proto_item *
 proto_tree_add_boolean_bits_format_value(proto_tree *tree, const int hfindex,
 					 tvbuff_t *tvb, const guint bit_offset,
 					 const gint no_of_bits, guint32 value,
+				         const guint encoding,
 					 const char *format, ...)
 {
 	va_list ap;
@@ -12869,13 +12876,14 @@ proto_tree_add_boolean_bits_format_value(proto_tree *tree, const int hfindex,
 
 	CREATE_VALUE_STRING(tree, dst, format, ap);
 
-	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, dst);
+	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, encoding, dst);
 }
 
 proto_item *
 proto_tree_add_boolean_bits_format_value64(proto_tree *tree, const int hfindex,
 					 tvbuff_t *tvb, const guint bit_offset,
 					 const gint no_of_bits, guint64 value,
+				         const guint encoding,
 					 const char *format, ...)
 {
 	va_list ap;
@@ -12890,7 +12898,7 @@ proto_tree_add_boolean_bits_format_value64(proto_tree *tree, const int hfindex,
 
 	CREATE_VALUE_STRING(tree, dst, format, ap);
 
-	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, dst);
+	return proto_tree_add_bits_format_value(tree, hfindex, tvb, bit_offset, no_of_bits, &value, encoding, dst);
 }
 
 proto_item *