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* [RFC] MdePkg/BaseLib: Change BitField functions.
@ 2018-02-09 10:59 Pankaj Bansal
  2018-02-20  4:49 ` Pankaj Bansal
  0 siblings, 1 reply; 6+ messages in thread
From: Pankaj Bansal @ 2018-02-09 10:59 UTC (permalink / raw)
  To: edk2-devel; +Cc: Pankaj Bansal, Michael D Kinney, Liming Gao

The bit field functions in MdePkg are not working as expected.
The restrictions on Value parameter such that Value should not be
greater than the bitmask value range specified by StartBit and EndBit
doesn't seem to make sense.

Also the restriction on End bit to not be equal to start bit prohibits
single bit change.

This is an attempt to correct these limitations.

Cc: Michael D Kinney <michael.d.kinney@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Pankaj Bansal <pankaj.bansal@nxp.com>
---

Notes:
    This is a RFC patch.

 MdePkg/Library/BaseLib/BitField.c | 179 ++++++++++++++--------------
 1 file changed, 89 insertions(+), 90 deletions(-)

diff --git a/MdePkg/Library/BaseLib/BitField.c b/MdePkg/Library/BaseLib/BitField.c
index eb9e276..2b5be52 100644
--- a/MdePkg/Library/BaseLib/BitField.c
+++ b/MdePkg/Library/BaseLib/BitField.c
@@ -2,6 +2,8 @@
   Bit field functions of BaseLib.
 
   Copyright (c) 2006 - 2013, Intel Corporation. All rights reserved.<BR>
+  Copyright 2018 NXP
+
   This program and the accompanying materials
   are licensed and made available under the terms and conditions of the BSD License
   which accompanies this distribution.  The full text of the license may be found at
@@ -14,6 +16,12 @@
 
 #include "BaseLibInternals.h"
 
+#define BITMASK_UNITN(StartBit, EndBit) \
+    (((MAX_UINTN) << (StartBit)) & (MAX_UINTN >> ((sizeof (UINTN) * 8) - 1 - (EndBit))))
+
+#define BITMASK_UNIT64(StartBit, EndBit) \
+    (((MAX_UINT64) << (StartBit)) & (MAX_UINT64 >> ((sizeof (UINT64) * 8) - 1 - (EndBit))))
+
 /**
   Worker function that returns a bit field from Operand.
 
@@ -34,11 +42,9 @@ InternalBaseLibBitFieldReadUint (
   IN      UINTN                     EndBit
   )
 {
-  //
-  // ~((UINTN)-2 << EndBit) is a mask in which bit[0] thru bit[EndBit]
-  // are 1's while bit[EndBit + 1] thru the most significant bit are 0's.
-  //
-  return (Operand & ~((UINTN)-2 << EndBit)) >> StartBit;
+  UINTN  Mask = BITMASK_UNITN (StartBit, EndBit);
+
+  return ( (Operand & Mask) >> StartBit);
 }
 
 /**
@@ -68,19 +74,9 @@ InternalBaseLibBitFieldOrUint (
   IN      UINTN                     OrData
   )
 {
-  //
-  // Higher bits in OrData those are not used must be zero. 
-  //
-  // EndBit - StartBit + 1 might be 32 while the result right shifting 32 on a 32bit integer is undefined,
-  // So the logic is updated to right shift (EndBit - StartBit) bits and compare the last bit directly.
-  //
-  ASSERT ((OrData >> (EndBit - StartBit)) == ((OrData >> (EndBit - StartBit)) & 1));
-  
-  //
-  // ~((UINTN)-2 << EndBit) is a mask in which bit[0] thru bit[EndBit]
-  // are 1's while bit[EndBit + 1] thru the most significant bit are 0's.
-  //
-  return Operand | ((OrData << StartBit) & ~((UINTN) -2 << EndBit));
+  UINTN  Mask = BITMASK_UNITN (StartBit, EndBit);
+
+  return ( ( (Operand | OrData) & Mask) | (Operand & ~Mask));
 }
 
 /**
@@ -110,19 +106,38 @@ InternalBaseLibBitFieldAndUint (
   IN      UINTN                     AndData
   )
 {
-  //
-  // Higher bits in AndData those are not used must be zero. 
-  //
-  // EndBit - StartBit + 1 might be 32 while the result right shifting 32 on a 32bit integer is undefined,
-  // So the logic is updated to right shift (EndBit - StartBit) bits and compare the last bit directly.
-  //
-  ASSERT ((AndData >> (EndBit - StartBit)) == ((AndData >> (EndBit - StartBit)) & 1));
-
-  //
-  // ~((UINTN)-2 << EndBit) is a mask in which bit[0] thru bit[EndBit]
-  // are 1's while bit[EndBit + 1] thru the most significant bit are 0's.
-  //
-  return Operand & ~((~AndData << StartBit) & ~((UINTN)-2 << EndBit));
+  UINTN  Mask = BITMASK_UNITN (StartBit, EndBit);
+
+  return  ( ( (Operand & AndData) & Mask) | (Operand & ~Mask));
+}
+
+/**
+  Worker function that writes a bit field to an value, and returns the result.
+
+  Writes Value to the bit field specified by the StartBit and the EndBit in
+  Operand. All other bits in Operand are preserved. The new 8-bit value is
+  returned.
+
+  @param  Operand   Operand on which to perform the bitfield operation.
+  @param  StartBit  The ordinal of the least significant bit in the bit field.
+  @param  EndBit    The ordinal of the most significant bit in the bit field.
+  @param  Value     The new value of the bit field.
+
+  @return The new value.
+
+**/
+UINTN
+EFIAPI
+InternalBaseLibBitFieldWriteUint (
+  IN      UINTN                     Operand,
+  IN      UINTN                     StartBit,
+  IN      UINTN                     EndBit,
+  IN      UINTN                     Value
+  )
+{
+  UINTN  Mask = BITMASK_UNITN (StartBit, EndBit);
+
+  return  ( (Value & Mask) | (Operand & ~Mask));
 }
 
 /**
@@ -153,7 +168,7 @@ BitFieldRead8 (
   )
 {
   ASSERT (EndBit < 8);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return (UINT8)InternalBaseLibBitFieldReadUint (Operand, StartBit, EndBit);
 }
 
@@ -190,8 +205,8 @@ BitFieldWrite8 (
   )
 {
   ASSERT (EndBit < 8);
-  ASSERT (StartBit <= EndBit);
-  return BitFieldAndThenOr8 (Operand, StartBit, EndBit, 0, Value);
+  ASSERT (StartBit < EndBit);
+  return (UINT8)InternalBaseLibBitFieldWriteUint (Operand, StartBit, EndBit, Value);
 }
 
 /**
@@ -228,7 +243,7 @@ BitFieldOr8 (
   )
 {
   ASSERT (EndBit < 8);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return (UINT8)InternalBaseLibBitFieldOrUint (Operand, StartBit, EndBit, OrData);
 }
 
@@ -266,7 +281,7 @@ BitFieldAnd8 (
   )
 {
   ASSERT (EndBit < 8);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return (UINT8)InternalBaseLibBitFieldAndUint (Operand, StartBit, EndBit, AndData);
 }
 
@@ -275,7 +290,7 @@ BitFieldAnd8 (
   bitwise OR, and returns the result.
 
   Performs a bitwise AND between the bit field specified by StartBit and EndBit
-  in Operand and the value specified by AndData, followed by a bitwise 
+  in Operand and the value specified by AndData, followed by a bitwise
   OR with value specified by OrData. All other bits in Operand are
   preserved. The new 8-bit value is returned.
 
@@ -308,7 +323,7 @@ BitFieldAndThenOr8 (
   )
 {
   ASSERT (EndBit < 8);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return BitFieldOr8 (
            BitFieldAnd8 (Operand, StartBit, EndBit, AndData),
            StartBit,
@@ -345,7 +360,7 @@ BitFieldRead16 (
   )
 {
   ASSERT (EndBit < 16);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return (UINT16)InternalBaseLibBitFieldReadUint (Operand, StartBit, EndBit);
 }
 
@@ -382,8 +397,8 @@ BitFieldWrite16 (
   )
 {
   ASSERT (EndBit < 16);
-  ASSERT (StartBit <= EndBit);
-  return BitFieldAndThenOr16 (Operand, StartBit, EndBit, 0, Value);
+  ASSERT (StartBit < EndBit);
+  return (UINT16)InternalBaseLibBitFieldWriteUint (Operand, StartBit, EndBit, Value);
 }
 
 /**
@@ -420,7 +435,7 @@ BitFieldOr16 (
   )
 {
   ASSERT (EndBit < 16);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return (UINT16)InternalBaseLibBitFieldOrUint (Operand, StartBit, EndBit, OrData);
 }
 
@@ -458,7 +473,7 @@ BitFieldAnd16 (
   )
 {
   ASSERT (EndBit < 16);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return (UINT16)InternalBaseLibBitFieldAndUint (Operand, StartBit, EndBit, AndData);
 }
 
@@ -467,7 +482,7 @@ BitFieldAnd16 (
   bitwise OR, and returns the result.
 
   Performs a bitwise AND between the bit field specified by StartBit and EndBit
-  in Operand and the value specified by AndData, followed by a bitwise 
+  in Operand and the value specified by AndData, followed by a bitwise
   OR with value specified by OrData. All other bits in Operand are
   preserved. The new 16-bit value is returned.
 
@@ -500,7 +515,7 @@ BitFieldAndThenOr16 (
   )
 {
   ASSERT (EndBit < 16);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return BitFieldOr16 (
            BitFieldAnd16 (Operand, StartBit, EndBit, AndData),
            StartBit,
@@ -537,7 +552,7 @@ BitFieldRead32 (
   )
 {
   ASSERT (EndBit < 32);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return (UINT32)InternalBaseLibBitFieldReadUint (Operand, StartBit, EndBit);
 }
 
@@ -574,8 +589,8 @@ BitFieldWrite32 (
   )
 {
   ASSERT (EndBit < 32);
-  ASSERT (StartBit <= EndBit);
-  return BitFieldAndThenOr32 (Operand, StartBit, EndBit, 0, Value);
+  ASSERT (StartBit < EndBit);
+  return (UINT32)InternalBaseLibBitFieldWriteUint (Operand, StartBit, EndBit, Value);
 }
 
 /**
@@ -612,7 +627,7 @@ BitFieldOr32 (
   )
 {
   ASSERT (EndBit < 32);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return (UINT32)InternalBaseLibBitFieldOrUint (Operand, StartBit, EndBit, OrData);
 }
 
@@ -650,7 +665,7 @@ BitFieldAnd32 (
   )
 {
   ASSERT (EndBit < 32);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return (UINT32)InternalBaseLibBitFieldAndUint (Operand, StartBit, EndBit, AndData);
 }
 
@@ -659,7 +674,7 @@ BitFieldAnd32 (
   bitwise OR, and returns the result.
 
   Performs a bitwise AND between the bit field specified by StartBit and EndBit
-  in Operand and the value specified by AndData, followed by a bitwise 
+  in Operand and the value specified by AndData, followed by a bitwise
   OR with value specified by OrData. All other bits in Operand are
   preserved. The new 32-bit value is returned.
 
@@ -692,7 +707,7 @@ BitFieldAndThenOr32 (
   )
 {
   ASSERT (EndBit < 32);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return BitFieldOr32 (
            BitFieldAnd32 (Operand, StartBit, EndBit, AndData),
            StartBit,
@@ -729,8 +744,11 @@ BitFieldRead64 (
   )
 {
   ASSERT (EndBit < 64);
-  ASSERT (StartBit <= EndBit);
-  return RShiftU64 (Operand & ~LShiftU64 ((UINT64)-2, EndBit), StartBit);
+  ASSERT (StartBit < EndBit);
+
+  UINT64  Mask = BITMASK_UNIT64 (StartBit, EndBit);
+
+  return ( (Operand & Mask) >> StartBit);
 }
 
 /**
@@ -766,8 +784,11 @@ BitFieldWrite64 (
   )
 {
   ASSERT (EndBit < 64);
-  ASSERT (StartBit <= EndBit);
-  return BitFieldAndThenOr64 (Operand, StartBit, EndBit, 0, Value);
+  ASSERT (StartBit < EndBit);
+
+  UINT64  Mask = BITMASK_UNIT64 (StartBit, EndBit);
+
+  return  ( (Value & Mask) | (Operand & ~Mask));
 }
 
 /**
@@ -803,23 +824,12 @@ BitFieldOr64 (
   IN      UINT64                    OrData
   )
 {
-  UINT64  Value1;
-  UINT64  Value2;
-
   ASSERT (EndBit < 64);
-  ASSERT (StartBit <= EndBit);
-  //
-  // Higher bits in OrData those are not used must be zero. 
-  //
-  // EndBit - StartBit + 1 might be 64 while the result right shifting 64 on RShiftU64() API is invalid,
-  // So the logic is updated to right shift (EndBit - StartBit) bits and compare the last bit directly.
-  //
-  ASSERT (RShiftU64 (OrData, EndBit - StartBit) == (RShiftU64 (OrData, EndBit - StartBit) & 1));
-
-  Value1 = LShiftU64 (OrData, StartBit);
-  Value2 = LShiftU64 ((UINT64) - 2, EndBit);
-
-  return Operand | (Value1 & ~Value2);
+  ASSERT (StartBit < EndBit);
+
+  UINT64  Mask = BITMASK_UNIT64 (StartBit, EndBit);
+
+  return ( ( (Operand | OrData) & Mask) | (Operand & ~Mask));
 }
 
 /**
@@ -855,23 +865,12 @@ BitFieldAnd64 (
   IN      UINT64                    AndData
   )
 {
-  UINT64  Value1;
-  UINT64  Value2;
-  
   ASSERT (EndBit < 64);
-  ASSERT (StartBit <= EndBit);
-  //
-  // Higher bits in AndData those are not used must be zero. 
-  //
-  // EndBit - StartBit + 1 might be 64 while the right shifting 64 on RShiftU64() API is invalid,
-  // So the logic is updated to right shift (EndBit - StartBit) bits and compare the last bit directly.
-  //
-  ASSERT (RShiftU64 (AndData, EndBit - StartBit) == (RShiftU64 (AndData, EndBit - StartBit) & 1));
-
-  Value1 = LShiftU64 (~AndData, StartBit);
-  Value2 = LShiftU64 ((UINT64)-2, EndBit);
-
-  return Operand & ~(Value1 & ~Value2);
+  ASSERT (StartBit < EndBit);
+
+  UINT64  Mask = BITMASK_UNIT64 (StartBit, EndBit);
+
+  return  ( ( (Operand & AndData) & Mask) | (Operand & ~Mask));
 }
 
 /**
@@ -879,7 +878,7 @@ BitFieldAnd64 (
   bitwise OR, and returns the result.
 
   Performs a bitwise AND between the bit field specified by StartBit and EndBit
-  in Operand and the value specified by AndData, followed by a bitwise 
+  in Operand and the value specified by AndData, followed by a bitwise
   OR with value specified by OrData. All other bits in Operand are
   preserved. The new 64-bit value is returned.
 
@@ -912,7 +911,7 @@ BitFieldAndThenOr64 (
   )
 {
   ASSERT (EndBit < 64);
-  ASSERT (StartBit <= EndBit);
+  ASSERT (StartBit < EndBit);
   return BitFieldOr64 (
            BitFieldAnd64 (Operand, StartBit, EndBit, AndData),
            StartBit,
-- 
2.7.4



^ permalink raw reply related	[flat|nested] 6+ messages in thread
end of thread, other threads:[~2018-02-26  6:28 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2018-02-09 10:59 [RFC] MdePkg/BaseLib: Change BitField functions Pankaj Bansal
2018-02-20  4:49 ` Pankaj Bansal
2018-02-23 11:02   ` Gao, Liming
2018-02-23 11:16     ` Pankaj Bansal
2018-02-23 12:12       ` Laszlo Ersek
2018-02-26  6:33         ` Pankaj Bansal

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