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, 11 insertions, 11 deletions

diff --git a/epan/dissectors/packet-csn1.c b/epan/dissectors/packet-csn1.c
index 5f3ee215d8..447b6e35cf 100644
--- a/epan/dissectors/packet-csn1.c
+++ b/epan/dissectors/packet-csn1.c
@@ -279,7 +279,7 @@ csnStreamDissector(proto_tree *tree, csnStream_t* ar, const CSN_DESCR* pDescr, t
             *pui8     = ui8 + (guint8)pDescr->descr.value;
 
             proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits,
-                                                  *pui8, "%u (Raw %u + Offset %u)", *pui8, ui8,
+                                                  *pui8, ENC_BIG_ENDIAN, "%u (Raw %u + Offset %u)", *pui8, ui8,
                                                   (guint8) pDescr->descr.value);
           }
           else if (no_of_bits <= 16)
@@ -289,7 +289,7 @@ csnStreamDissector(proto_tree *tree, csnStream_t* ar, const CSN_DESCR* pDescr, t
             *pui16      = ui16 + (guint16)pDescr->descr.value;
 
             proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits,
-                                                  *pui16, "%u (Raw %u + Offset %u)", *pui16, ui16,
+                                                  *pui16, ENC_BIG_ENDIAN, "%u (Raw %u + Offset %u)", *pui16, ui16,
                                                   (guint16) pDescr->descr.value);
           }
           else if (no_of_bits <= 32)
@@ -299,7 +299,7 @@ csnStreamDissector(proto_tree *tree, csnStream_t* ar, const CSN_DESCR* pDescr, t
             *pui32      = ui32 + (guint16)pDescr->descr.value;
 
             proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits,
-                                                  *pui32, "%u (Raw %u + Offset %u)", *pui32, ui32,
+                                                  *pui32, ENC_BIG_ENDIAN, "%u (Raw %u + Offset %u)", *pui32, ui32,
                                                   (guint16) pDescr->descr.value);
           }
           else
@@ -417,7 +417,7 @@ csnStreamDissector(proto_tree *tree, csnStream_t* ar, const CSN_DESCR* pDescr, t
             do
             {
               *pui8++ = tvb_get_bits8(tvb, bit_offset, no_of_bits);
-              proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, *pui8, " (Count %d)", i++);
+              proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, *pui8, ENC_BIG_ENDIAN, " (Count %d)", i++);
               bit_offset += no_of_bits;
             } while (--nCount > 0);
           }
@@ -697,7 +697,7 @@ csnStreamDissector(proto_tree *tree, csnStream_t* ar, const CSN_DESCR* pDescr, t
 
         /* Now get the bits to extract the index */
         Bits = ixBitsTab[count];
-        proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, Bits, tvb_get_bits8(tvb, bit_offset, Bits), " (Union)");
+        proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, Bits, tvb_get_bits8(tvb, bit_offset, Bits), ENC_BIG_ENDIAN, " (Union)");
         t_index = 0;
 
         while (Bits > 0)
@@ -807,21 +807,21 @@ csnStreamDissector(proto_tree *tree, csnStream_t* ar, const CSN_DESCR* pDescr, t
                 guint8 ui8 = tvb_get_bits8(tvb, bit_offset, no_of_bits);
                 pui8      = pui8DATA(data, pDescr->offset);
                 *pui8     = ui8 + (guint8)pDescr->descr.value;
-                proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, ui8, "%d", ui8);
+                proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, ui8, ENC_BIG_ENDIAN, "%d", ui8);
               }
               else if (no_of_bits <= 16)
               {
                 guint16 ui16 = tvb_get_bits16(tvb, bit_offset, no_of_bits, ENC_BIG_ENDIAN);
                 pui16       = pui16DATA(data, pDescr->offset);
                 *pui16      = ui16 + (guint16)pDescr->descr.value;
-                proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, ui16, "%d", ui16);
+                proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, ui16, ENC_BIG_ENDIAN, "%d", ui16);
               }
                 else if (no_of_bits <= 32)
               {
                 guint32 ui32 = tvb_get_bits32(tvb, bit_offset, no_of_bits, ENC_BIG_ENDIAN);
                 pui32       = pui32DATA(data, pDescr->offset);
                 *pui32      = ui32 + (guint16)pDescr->descr.value;
-                proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, ui32, "%d", ui32);
+                proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, ui32, ENC_BIG_ENDIAN, "%d", ui32);
               }
               else
               {
@@ -889,7 +889,7 @@ csnStreamDissector(proto_tree *tree, csnStream_t* ar, const CSN_DESCR* pDescr, t
                 while (nCount > 0)
                 {
                   *pui8 = tvb_get_bits8(tvb, bit_offset, no_of_bits);
-                  proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, *pui8, " (Count %d)", i++);
+                  proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, *pui8, ENC_BIG_ENDIAN, " (Count %d)", i++);
                   pui8++;
                   bit_offset += no_of_bits;
                   nCount--;
@@ -902,7 +902,7 @@ csnStreamDissector(proto_tree *tree, csnStream_t* ar, const CSN_DESCR* pDescr, t
                 while (nCount > 0)
                 {
                   *pui16 = tvb_get_bits16(tvb, bit_offset, no_of_bits, ENC_BIG_ENDIAN);
-                  proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, *pui16, " (Count %d)", i++);
+                  proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, no_of_bits, *pui16, ENC_BIG_ENDIAN, " (Count %d)", i++);
                   bit_offset += no_of_bits;
                   nCount--;
                 }
@@ -1459,7 +1459,7 @@ csnStreamDissector(proto_tree *tree, csnStream_t* ar, const CSN_DESCR* pDescr, t
           }
 
           /* control of next element's tag */
-          proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, 1, tvb_get_bits8(tvb, bit_offset, 1), "%s[%d]",
+          proto_tree_add_uint_bits_format_value(tree, *(pDescr->hf_ptr), tvb, bit_offset, 1, tvb_get_bits8(tvb, bit_offset, 1), ENC_BIG_ENDIAN, "%s[%d]",
                                      proto_registrar_get_name(*(pDescr->hf_ptr)), ElementCount);
           EndOfList         = !(existNextElement(tvb, bit_offset, Tag));