MdePkg/BaseLib: Add QuickSort function on BaseLib

[mirror_edk2.git] / MdePkg / Library / BaseLib / QuickSort.c

/** @file\r
  Math worker functions.\r
\r
  Copyright (c) 2021, Intel Corporation. All rights reserved.<BR>\r
  SPDX-License-Identifier: BSD-2-Clause-Patent\r
\r
**/\r
\r
#include "BaseLibInternals.h"\r
\r
/**\r
  This function is identical to perform QuickSort,\r
  except that is uses the pre-allocated buffer so the in place sorting does not need to\r
  allocate and free buffers constantly.\r
\r
  Each element must be equal sized.\r
\r
  if BufferToSort is NULL, then ASSERT.\r
  if CompareFunction is NULL, then ASSERT.\r
  if BufferOneElement is NULL, then ASSERT.\r
  if ElementSize is < 1, then ASSERT.\r
\r
  if Count is < 2 then perform no action.\r
\r
  @param[in, out] BufferToSort   on call a Buffer of (possibly sorted) elements\r
                                 on return a buffer of sorted elements\r
  @param[in] Count               the number of elements in the buffer to sort\r
  @param[in] ElementSize         Size of an element in bytes\r
  @param[in] CompareFunction     The function to call to perform the comparison\r
                                 of any 2 elements\r
  @param[out] BufferOneElement   Caller provided buffer whose size equals to ElementSize.\r
                                 It's used by QuickSort() for swapping in sorting.\r
**/\r
VOID\r
EFIAPI\r
QuickSort (\r
  IN OUT VOID                           *BufferToSort,\r
  IN CONST UINTN                        Count,\r
  IN CONST UINTN                        ElementSize,\r
  IN       BASE_SORT_COMPARE            CompareFunction,\r
  OUT VOID                              *BufferOneElement\r
  )\r
{\r
  VOID        *Pivot;\r
  UINTN       LoopCount;\r
  UINTN       NextSwapLocation;\r
\r
  ASSERT (BufferToSort     != NULL);\r
  ASSERT (CompareFunction  != NULL);\r
  ASSERT (BufferOneElement != NULL);\r
  ASSERT (ElementSize      >= 1);\r
\r
  if (Count < 2) {\r
    return;\r
  }\r
\r
  NextSwapLocation = 0;\r
\r
  //\r
  // pick a pivot (we choose last element)\r
  //\r
  Pivot = ((UINT8*) BufferToSort + ((Count - 1) * ElementSize));\r
\r
  //\r
  // Now get the pivot such that all on "left" are below it\r
  // and everything "right" are above it\r
  //\r
  for (LoopCount = 0; LoopCount < Count -1; LoopCount++) {\r
    //\r
    // if the element is less than or equal to the pivot\r
    //\r
    if (CompareFunction ((VOID*) ((UINT8*) BufferToSort + ((LoopCount) * ElementSize)), Pivot) <= 0){\r
      //\r
      // swap\r
      //\r
      CopyMem (BufferOneElement, (UINT8*) BufferToSort + (NextSwapLocation * ElementSize), ElementSize);\r
      CopyMem ((UINT8*) BufferToSort + (NextSwapLocation * ElementSize), (UINT8*) BufferToSort + ((LoopCount) * ElementSize), ElementSize);\r
      CopyMem ((UINT8*) BufferToSort + ((LoopCount)*ElementSize), BufferOneElement, ElementSize);\r
\r
      //\r
      // increment NextSwapLocation\r
      //\r
      NextSwapLocation++;\r
    }\r
  }\r
  //\r
  // swap pivot to it's final position (NextSwapLocation)\r
  //\r
  CopyMem (BufferOneElement, Pivot, ElementSize);\r
  CopyMem (Pivot, (UINT8*) BufferToSort + (NextSwapLocation * ElementSize), ElementSize);\r
  CopyMem ((UINT8*) BufferToSort + (NextSwapLocation * ElementSize), BufferOneElement, ElementSize);\r
\r
  //\r
  // Now recurse on 2 partial lists.  neither of these will have the 'pivot' element\r
  // IE list is sorted left half, pivot element, sorted right half...\r
  //\r
  if (NextSwapLocation >= 2) {\r
    QuickSort (\r
      BufferToSort,\r
      NextSwapLocation,\r
      ElementSize,\r
      CompareFunction,\r
      BufferOneElement\r
      );\r
  }\r
\r
  if ((Count - NextSwapLocation - 1) >= 2) {\r
    QuickSort (\r
      (UINT8 *)BufferToSort + (NextSwapLocation + 1) * ElementSize,\r
      Count - NextSwapLocation - 1,\r
      ElementSize,\r
      CompareFunction,\r
      BufferOneElement\r
      );\r
  }\r
}\r