/** @file
  Unicode and ASCII string primitives.

  Copyright (c) 2006 - 2019, Intel Corporation. All rights reserved.<BR>
  SPDX-License-Identifier: BSD-2-Clause-Patent

**/

#include "BaseLibInternals.h"

/**
  Returns the length of a Null-terminated Unicode string.

  This function returns the number of Unicode characters in the Null-terminated
  Unicode string specified by String.

  If String is NULL, then ASSERT().
  If String is not aligned on a 16-bit boundary, then ASSERT().
  If PcdMaximumUnicodeStringLength is not zero, and String contains more than
  PcdMaximumUnicodeStringLength Unicode characters, not including the
  Null-terminator, then ASSERT().

  @param  String  A pointer to a Null-terminated Unicode string.

  @return The length of String.

**/
UINTN
EFIAPI
StrLen (
  IN      CONST CHAR16  *String
  )
{
  UINTN  Length;

  ASSERT (String != NULL);
  ASSERT (((UINTN)String & BIT0) == 0);

  for (Length = 0; *String != L'\0'; String++, Length++) {
    //
    // If PcdMaximumUnicodeStringLength is not zero,
    // length should not more than PcdMaximumUnicodeStringLength
    //
    if (PcdGet32 (PcdMaximumUnicodeStringLength) != 0) {
      ASSERT (Length < PcdGet32 (PcdMaximumUnicodeStringLength));
    }
  }

  return Length;
}

/**
  Returns the size of a Null-terminated Unicode string in bytes, including the
  Null terminator.

  This function returns the size, in bytes, of the Null-terminated Unicode string
  specified by String.

  If String is NULL, then ASSERT().
  If String is not aligned on a 16-bit boundary, then ASSERT().
  If PcdMaximumUnicodeStringLength is not zero, and String contains more than
  PcdMaximumUnicodeStringLength Unicode characters, not including the
  Null-terminator, then ASSERT().

  @param  String  A pointer to a Null-terminated Unicode string.

  @return The size of String.

**/
UINTN
EFIAPI
StrSize (
  IN      CONST CHAR16  *String
  )
{
  return (StrLen (String) + 1) * sizeof (*String);
}

/**
  Compares two Null-terminated Unicode strings, and returns the difference
  between the first mismatched Unicode characters.

  This function compares the Null-terminated Unicode string FirstString to the
  Null-terminated Unicode string SecondString. If FirstString is identical to
  SecondString, then 0 is returned. Otherwise, the value returned is the first
  mismatched Unicode character in SecondString subtracted from the first
  mismatched Unicode character in FirstString.

  If FirstString is NULL, then ASSERT().
  If FirstString is not aligned on a 16-bit boundary, then ASSERT().
  If SecondString is NULL, then ASSERT().
  If SecondString is not aligned on a 16-bit boundary, then ASSERT().
  If PcdMaximumUnicodeStringLength is not zero, and FirstString contains more
  than PcdMaximumUnicodeStringLength Unicode characters, not including the
  Null-terminator, then ASSERT().
  If PcdMaximumUnicodeStringLength is not zero, and SecondString contains more
  than PcdMaximumUnicodeStringLength Unicode characters, not including the
  Null-terminator, then ASSERT().

  @param  FirstString   A pointer to a Null-terminated Unicode string.
  @param  SecondString  A pointer to a Null-terminated Unicode string.

  @retval 0      FirstString is identical to SecondString.
  @return others FirstString is not identical to SecondString.

**/
INTN
EFIAPI
StrCmp (
  IN      CONST CHAR16  *FirstString,
  IN      CONST CHAR16  *SecondString
  )
{
  //
  // ASSERT both strings are less long than PcdMaximumUnicodeStringLength
  //
  ASSERT (StrSize (FirstString) != 0);
  ASSERT (StrSize (SecondString) != 0);

  while ((*FirstString != L'\0') && (*FirstString == *SecondString)) {
    FirstString++;
    SecondString++;
  }

  return *FirstString - *SecondString;
}

/**
  Compares up to a specified length the contents of two Null-terminated Unicode strings,
  and returns the difference between the first mismatched Unicode characters.

  This function compares the Null-terminated Unicode string FirstString to the
  Null-terminated Unicode string SecondString. At most, Length Unicode
  characters will be compared. If Length is 0, then 0 is returned. If
  FirstString is identical to SecondString, then 0 is returned. Otherwise, the
  value returned is the first mismatched Unicode character in SecondString
  subtracted from the first mismatched Unicode character in FirstString.

  If Length > 0 and FirstString is NULL, then ASSERT().
  If Length > 0 and FirstString is not aligned on a 16-bit boundary, then ASSERT().
  If Length > 0 and SecondString is NULL, then ASSERT().
  If Length > 0 and SecondString is not aligned on a 16-bit boundary, then ASSERT().
  If PcdMaximumUnicodeStringLength is not zero, and Length is greater than
  PcdMaximumUnicodeStringLength, then ASSERT().
  If PcdMaximumUnicodeStringLength is not zero, and FirstString contains more than
  PcdMaximumUnicodeStringLength Unicode characters, not including the Null-terminator,
  then ASSERT().
  If PcdMaximumUnicodeStringLength is not zero, and SecondString contains more than
  PcdMaximumUnicodeStringLength Unicode characters, not including the Null-terminator,
  then ASSERT().

  @param  FirstString   A pointer to a Null-terminated Unicode string.
  @param  SecondString  A pointer to a Null-terminated Unicode string.
  @param  Length        The maximum number of Unicode characters to compare.

  @retval 0      FirstString is identical to SecondString.
  @return others FirstString is not identical to SecondString.

**/
INTN
EFIAPI
StrnCmp (
  IN      CONST CHAR16  *FirstString,
  IN      CONST CHAR16  *SecondString,
  IN      UINTN         Length
  )
{
  if (Length == 0) {
    return 0;
  }

  //
  // ASSERT both strings are less long than PcdMaximumUnicodeStringLength.
  // Length tests are performed inside StrLen().
  //
  ASSERT (StrSize (FirstString) != 0);
  ASSERT (StrSize (SecondString) != 0);

  if (PcdGet32 (PcdMaximumUnicodeStringLength) != 0) {
    ASSERT (Length <= PcdGet32 (PcdMaximumUnicodeStringLength));
  }

  while ((*FirstString != L'\0') &&
         (*SecondString != L'\0') &&
         (*FirstString == *SecondString) &&
         (Length > 1))
  {
    FirstString++;
    SecondString++;
    Length--;
  }

  return *FirstString - *SecondString;
}

/**
  Returns the first occurrence of a Null-terminated Unicode sub-string
  in a Null-terminated Unicode string.

  This function scans the contents of the Null-terminated Unicode string
  specified by String and returns the first occurrence of SearchString.
  If SearchString is not found in String, then NULL is returned.  If
  the length of SearchString is zero, then String is
  returned.

  If String is NULL, then ASSERT().
  If String is not aligned on a 16-bit boundary, then ASSERT().
  If SearchString is NULL, then ASSERT().
  If SearchString is not aligned on a 16-bit boundary, then ASSERT().

  If PcdMaximumUnicodeStringLength is not zero, and SearchString
  or String contains more than PcdMaximumUnicodeStringLength Unicode
  characters, not including the Null-terminator, then ASSERT().

  @param  String          A pointer to a Null-terminated Unicode string.
  @param  SearchString    A pointer to a Null-terminated Unicode string to search for.

  @retval NULL            If the SearchString does not appear in String.
  @return others          If there is a match.

**/
CHAR16 *
EFIAPI
StrStr (
  IN      CONST CHAR16  *String,
  IN      CONST CHAR16  *SearchString
  )
{
  CONST CHAR16  *FirstMatch;
  CONST CHAR16  *SearchStringTmp;

  //
  // ASSERT both strings are less long than PcdMaximumUnicodeStringLength.
  // Length tests are performed inside StrLen().
  //
  ASSERT (StrSize (String) != 0);
  ASSERT (StrSize (SearchString) != 0);

  if (*SearchString == L'\0') {
    return (CHAR16 *)String;
  }

  while (*String != L'\0') {
    SearchStringTmp = SearchString;
    FirstMatch      = String;

    while (  (*String == *SearchStringTmp)
          && (*String != L'\0'))
    {
      String++;
      SearchStringTmp++;
    }

    if (*SearchStringTmp == L'\0') {
      return (CHAR16 *)FirstMatch;
    }

    if (*String == L'\0') {
      return NULL;
    }

    String = FirstMatch + 1;
  }

  return NULL;
}

/**
  Check if a Unicode character is a decimal character.

  This internal function checks if a Unicode character is a
  decimal character. The valid decimal character is from
  L'0' to L'9'.

  @param  Char  The character to check against.

  @retval TRUE  If the Char is a decmial character.
  @retval FALSE If the Char is not a decmial character.

**/
BOOLEAN
EFIAPI
InternalIsDecimalDigitCharacter (
  IN      CHAR16  Char
  )
{
  return (BOOLEAN)(Char >= L'0' && Char <= L'9');
}

/**
  Convert a Unicode character to upper case only if
  it maps to a valid small-case ASCII character.

  This internal function only deal with Unicode character
  which maps to a valid small-case ASCII character, i.e.
  L'a' to L'z'. For other Unicode character, the input character
  is returned directly.

  @param  Char  The character to convert.

  @retval LowerCharacter   If the Char is with range L'a' to L'z'.
  @retval Unchanged        Otherwise.

**/
CHAR16
EFIAPI
CharToUpper (
  IN      CHAR16  Char
  )
{
  if ((Char >= L'a') && (Char <= L'z')) {
    return (CHAR16)(Char - (L'a' - L'A'));
  }

  return Char;
}

/**
  Convert a Unicode character to numerical value.

  This internal function only deal with Unicode character
  which maps to a valid hexadecimal ASII character, i.e.
  L'0' to L'9', L'a' to L'f' or L'A' to L'F'. For other
  Unicode character, the value returned does not make sense.

  @param  Char  The character to convert.

  @return The numerical value converted.

**/
UINTN
EFIAPI
InternalHexCharToUintn (
  IN      CHAR16  Char
  )
{
  if (InternalIsDecimalDigitCharacter (Char)) {
    return Char - L'0';
  }

  return (10 + CharToUpper (Char) - L'A');
}

/**
  Check if a Unicode character is a hexadecimal character.

  This internal function checks if a Unicode character is a
  decimal character.  The valid hexadecimal character is
  L'0' to L'9', L'a' to L'f', or L'A' to L'F'.


  @param  Char  The character to check against.

  @retval TRUE  If the Char is a hexadecmial character.
  @retval FALSE If the Char is not a hexadecmial character.

**/
BOOLEAN
EFIAPI
InternalIsHexaDecimalDigitCharacter (
  IN      CHAR16  Char
  )
{
  return (BOOLEAN)(InternalIsDecimalDigitCharacter (Char) ||
                   (Char >= L'A' && Char <= L'F') ||
                   (Char >= L'a' && Char <= L'f'));
}

/**
  Convert a Null-terminated Unicode decimal string to a value of
  type UINTN.

  This function returns a value of type UINTN by interpreting the contents
  of the Unicode string specified by String as a decimal number. The format
  of the input Unicode string String is:

                  [spaces] [decimal digits].

  The valid decimal digit character is in the range [0-9]. The
  function will ignore the pad space, which includes spaces or
  tab characters, before [decimal digits]. The running zero in the
  beginning of [decimal digits] will be ignored. Then, the function
  stops at the first character that is a not a valid decimal character
  or a Null-terminator, whichever one comes first.

  If String is NULL, then ASSERT().
  If String is not aligned in a 16-bit boundary, then ASSERT().
  If String has only pad spaces, then 0 is returned.
  If String has no pad spaces or valid decimal digits,
  then 0 is returned.
  If the number represented by String overflows according
  to the range defined by UINTN, then MAX_UINTN is returned.

  If PcdMaximumUnicodeStringLength is not zero, and String contains
  more than PcdMaximumUnicodeStringLength Unicode characters, not including
  the Null-terminator, then ASSERT().

  @param  String      A pointer to a Null-terminated Unicode string.

  @retval Value translated from String.

**/
UINTN
EFIAPI
StrDecimalToUintn (
  IN      CONST CHAR16  *String
  )
{
  UINTN          Result;
  RETURN_STATUS  Status;

  Status = StrDecimalToUintnS (String, (CHAR16 **)NULL, &Result);
  if (Status == RETURN_INVALID_PARAMETER) {
    Result = 0;
  }

  return Result;
}

/**
  Convert a Null-terminated Unicode decimal string to a value of
  type UINT64.

  This function returns a value of type UINT64 by interpreting the contents
  of the Unicode string specified by String as a decimal number. The format
  of the input Unicode string String is:

                  [spaces] [decimal digits].

  The valid decimal digit character is in the range [0-9]. The
  function will ignore the pad space, which includes spaces or
  tab characters, before [decimal digits]. The running zero in the
  beginning of [decimal digits] will be ignored. Then, the function
  stops at the first character that is a not a valid decimal character
  or a Null-terminator, whichever one comes first.

  If String is NULL, then ASSERT().
  If String is not aligned in a 16-bit boundary, then ASSERT().
  If String has only pad spaces, then 0 is returned.
  If String has no pad spaces or valid decimal digits,
  then 0 is returned.
  If the number represented by String overflows according
  to the range defined by UINT64, then MAX_UINT64 is returned.

  If PcdMaximumUnicodeStringLength is not zero, and String contains
  more than PcdMaximumUnicodeStringLength Unicode characters, not including
  the Null-terminator, then ASSERT().

  @param  String          A pointer to a Null-terminated Unicode string.

  @retval Value translated from String.

**/
UINT64
EFIAPI
StrDecimalToUint64 (
  IN      CONST CHAR16  *String
  )
{
  UINT64         Result;
  RETURN_STATUS  Status;

  Status = StrDecimalToUint64S (String, (CHAR16 **)NULL, &Result);
  if (Status == RETURN_INVALID_PARAMETER) {
    Result = 0;
  }

  return Result;
}

/**
  Convert a Null-terminated Unicode hexadecimal string to a value of type UINTN.

  This function returns a value of type UINTN by interpreting the contents
  of the Unicode string specified by String as a hexadecimal number.
  The format of the input Unicode string String is:

                  [spaces][zeros][x][hexadecimal digits].

  The valid hexadecimal digit character is in the range [0-9], [a-f] and [A-F].
  The prefix "0x" is optional. Both "x" and "X" is allowed in "0x" prefix.
  If "x" appears in the input string, it must be prefixed with at least one 0.
  The function will ignore the pad space, which includes spaces or tab characters,
  before [zeros], [x] or [hexadecimal digit]. The running zero before [x] or
  [hexadecimal digit] will be ignored. Then, the decoding starts after [x] or the
  first valid hexadecimal digit. Then, the function stops at the first character that is
  a not a valid hexadecimal character or NULL, whichever one comes first.

  If String is NULL, then ASSERT().
  If String is not aligned in a 16-bit boundary, then ASSERT().
  If String has only pad spaces, then zero is returned.
  If String has no leading pad spaces, leading zeros or valid hexadecimal digits,
  then zero is returned.
  If the number represented by String overflows according to the range defined by
  UINTN, then MAX_UINTN is returned.

  If PcdMaximumUnicodeStringLength is not zero, and String contains more than
  PcdMaximumUnicodeStringLength Unicode characters, not including the Null-terminator,
  then ASSERT().

  @param  String          A pointer to a Null-terminated Unicode string.

  @retval Value translated from String.

**/
UINTN
EFIAPI
StrHexToUintn (
  IN      CONST CHAR16  *String
  )
{
  UINTN          Result;
  RETURN_STATUS  Status;

  Status = StrHexToUintnS (String, (CHAR16 **)NULL, &Result);
  if (Status == RETURN_INVALID_PARAMETER) {
    Result = 0;
  }

  return Result;
}

/**
  Convert a Null-terminated Unicode hexadecimal string to a value of type UINT64.

  This function returns a value of type UINT64 by interpreting the contents
  of the Unicode string specified by String as a hexadecimal number.
  The format of the input Unicode string String is

                  [spaces][zeros][x][hexadecimal digits].

  The valid hexadecimal digit character is in the range [0-9], [a-f] and [A-F].
  The prefix "0x" is optional. Both "x" and "X" is allowed in "0x" prefix.
  If "x" appears in the input string, it must be prefixed with at least one 0.
  The function will ignore the pad space, which includes spaces or tab characters,
  before [zeros], [x] or [hexadecimal digit]. The running zero before [x] or
  [hexadecimal digit] will be ignored. Then, the decoding starts after [x] or the
  first valid hexadecimal digit. Then, the function stops at the first character that is
  a not a valid hexadecimal character or NULL, whichever one comes first.

  If String is NULL, then ASSERT().
  If String is not aligned in a 16-bit boundary, then ASSERT().
  If String has only pad spaces, then zero is returned.
  If String has no leading pad spaces, leading zeros or valid hexadecimal digits,
  then zero is returned.
  If the number represented by String overflows according to the range defined by
  UINT64, then MAX_UINT64 is returned.

  If PcdMaximumUnicodeStringLength is not zero, and String contains more than
  PcdMaximumUnicodeStringLength Unicode characters, not including the Null-terminator,
  then ASSERT().

  @param  String          A pointer to a Null-terminated Unicode string.

  @retval Value translated from String.

**/
UINT64
EFIAPI
StrHexToUint64 (
  IN      CONST CHAR16  *String
  )
{
  UINT64         Result;
  RETURN_STATUS  Status;

  Status = StrHexToUint64S (String, (CHAR16 **)NULL, &Result);
  if (Status == RETURN_INVALID_PARAMETER) {
    Result = 0;
  }

  return Result;
}

/**
  Check if a ASCII character is a decimal character.

  This internal function checks if a Unicode character is a
  decimal character. The valid decimal character is from
  '0' to '9'.

  @param  Char  The character to check against.

  @retval TRUE  If the Char is a decmial character.
  @retval FALSE If the Char is not a decmial character.

**/
BOOLEAN
EFIAPI
InternalAsciiIsDecimalDigitCharacter (
  IN      CHAR8  Char
  )
{
  return (BOOLEAN)(Char >= '0' && Char <= '9');
}

/**
  Check if a ASCII character is a hexadecimal character.

  This internal function checks if a ASCII character is a
  decimal character.  The valid hexadecimal character is
  L'0' to L'9', L'a' to L'f', or L'A' to L'F'.


  @param  Char  The character to check against.

  @retval TRUE  If the Char is a hexadecmial character.
  @retval FALSE If the Char is not a hexadecmial character.

**/
BOOLEAN
EFIAPI
InternalAsciiIsHexaDecimalDigitCharacter (
  IN      CHAR8  Char
  )
{
  return (BOOLEAN)(InternalAsciiIsDecimalDigitCharacter (Char) ||
                   (Char >= 'A' && Char <= 'F') ||
                   (Char >= 'a' && Char <= 'f'));
}

/**
  Returns the length of a Null-terminated ASCII string.

  This function returns the number of ASCII characters in the Null-terminated
  ASCII string specified by String.

  If Length > 0 and Destination is NULL, then ASSERT().
  If Length > 0 and Source is NULL, then ASSERT().
  If PcdMaximumAsciiStringLength is not zero and String contains more than
  PcdMaximumAsciiStringLength ASCII characters, not including the Null-terminator,
  then ASSERT().

  @param  String  A pointer to a Null-terminated ASCII string.

  @return The length of String.

**/
UINTN
EFIAPI
AsciiStrLen (
  IN      CONST CHAR8  *String
  )
{
  UINTN  Length;

  ASSERT (String != NULL);

  for (Length = 0; *String != '\0'; String++, Length++) {
    //
    // If PcdMaximumUnicodeStringLength is not zero,
    // length should not more than PcdMaximumUnicodeStringLength
    //
    if (PcdGet32 (PcdMaximumAsciiStringLength) != 0) {
      ASSERT (Length < PcdGet32 (PcdMaximumAsciiStringLength));
    }
  }

  return Length;
}

/**
  Returns the size of a Null-terminated ASCII string in bytes, including the
  Null terminator.

  This function returns the size, in bytes, of the Null-terminated ASCII string
  specified by String.

  If String is NULL, then ASSERT().
  If PcdMaximumAsciiStringLength is not zero and String contains more than
  PcdMaximumAsciiStringLength ASCII characters, not including the Null-terminator,
  then ASSERT().

  @param  String  A pointer to a Null-terminated ASCII string.

  @return The size of String.

**/
UINTN
EFIAPI
AsciiStrSize (
  IN      CONST CHAR8  *String
  )
{
  return (AsciiStrLen (String) + 1) * sizeof (*String);
}

/**
  Compares two Null-terminated ASCII strings, and returns the difference
  between the first mismatched ASCII characters.

  This function compares the Null-terminated ASCII string FirstString to the
  Null-terminated ASCII string SecondString. If FirstString is identical to
  SecondString, then 0 is returned. Otherwise, the value returned is the first
  mismatched ASCII character in SecondString subtracted from the first
  mismatched ASCII character in FirstString.

  If FirstString is NULL, then ASSERT().
  If SecondString is NULL, then ASSERT().
  If PcdMaximumAsciiStringLength is not zero and FirstString contains more than
  PcdMaximumAsciiStringLength ASCII characters, not including the Null-terminator,
  then ASSERT().
  If PcdMaximumAsciiStringLength is not zero and SecondString contains more
  than PcdMaximumAsciiStringLength ASCII characters, not including the
  Null-terminator, then ASSERT().

  @param  FirstString   A pointer to a Null-terminated ASCII string.
  @param  SecondString  A pointer to a Null-terminated ASCII string.

  @retval ==0      FirstString is identical to SecondString.
  @retval !=0      FirstString is not identical to SecondString.

**/
INTN
EFIAPI
AsciiStrCmp (
  IN      CONST CHAR8  *FirstString,
  IN      CONST CHAR8  *SecondString
  )
{
  //
  // ASSERT both strings are less long than PcdMaximumAsciiStringLength
  //
  ASSERT (AsciiStrSize (FirstString));
  ASSERT (AsciiStrSize (SecondString));

  while ((*FirstString != '\0') && (*FirstString == *SecondString)) {
    FirstString++;
    SecondString++;
  }

  return *FirstString - *SecondString;
}

/**
  Converts a lowercase Ascii character to upper one.

  If Chr is lowercase Ascii character, then converts it to upper one.

  If Value >= 0xA0, then ASSERT().
  If (Value & 0x0F) >= 0x0A, then ASSERT().

  @param  Chr   one Ascii character

  @return The uppercase value of Ascii character

**/
CHAR8
EFIAPI
AsciiCharToUpper (
  IN      CHAR8  Chr
  )
{
  return (UINT8)((Chr >= 'a' && Chr <= 'z') ? Chr - ('a' - 'A') : Chr);
}

/**
  Convert a ASCII character to numerical value.

  This internal function only deal with Unicode character
  which maps to a valid hexadecimal ASII character, i.e.
  '0' to '9', 'a' to 'f' or 'A' to 'F'. For other
  ASCII character, the value returned does not make sense.

  @param  Char  The character to convert.

  @return The numerical value converted.

**/
UINTN
EFIAPI
InternalAsciiHexCharToUintn (
  IN      CHAR8  Char
  )
{
  if (InternalIsDecimalDigitCharacter (Char)) {
    return Char - '0';
  }

  return (10 + AsciiCharToUpper (Char) - 'A');
}

/**
  Performs a case insensitive comparison of two Null-terminated ASCII strings,
  and returns the difference between the first mismatched ASCII characters.

  This function performs a case insensitive comparison of the Null-terminated
  ASCII string FirstString to the Null-terminated ASCII string SecondString. If
  FirstString is identical to SecondString, then 0 is returned. Otherwise, the
  value returned is the first mismatched lower case ASCII character in
  SecondString subtracted from the first mismatched lower case ASCII character
  in FirstString.

  If FirstString is NULL, then ASSERT().
  If SecondString is NULL, then ASSERT().
  If PcdMaximumAsciiStringLength is not zero and FirstString contains more than
  PcdMaximumAsciiStringLength ASCII characters, not including the Null-terminator,
  then ASSERT().
  If PcdMaximumAsciiStringLength is not zero and SecondString contains more
  than PcdMaximumAsciiStringLength ASCII characters, not including the
  Null-terminator, then ASSERT().

  @param  FirstString   A pointer to a Null-terminated ASCII string.
  @param  SecondString  A pointer to a Null-terminated ASCII string.

  @retval ==0    FirstString is identical to SecondString using case insensitive
                 comparisons.
  @retval !=0    FirstString is not identical to SecondString using case
                 insensitive comparisons.

**/
INTN
EFIAPI
AsciiStriCmp (
  IN      CONST CHAR8  *FirstString,
  IN      CONST CHAR8  *SecondString
  )
{
  CHAR8  UpperFirstString;
  CHAR8  UpperSecondString;

  //
  // ASSERT both strings are less long than PcdMaximumAsciiStringLength
  //
  ASSERT (AsciiStrSize (FirstString));
  ASSERT (AsciiStrSize (SecondString));

  UpperFirstString  = AsciiCharToUpper (*FirstString);
  UpperSecondString = AsciiCharToUpper (*SecondString);
  while ((*FirstString != '\0') && (*SecondString != '\0') && (UpperFirstString == UpperSecondString)) {
    FirstString++;
    SecondString++;
    UpperFirstString  = AsciiCharToUpper (*FirstString);
    UpperSecondString = AsciiCharToUpper (*SecondString);
  }

  return UpperFirstString - UpperSecondString;
}

/**
  Compares two Null-terminated ASCII strings with maximum lengths, and returns
  the difference between the first mismatched ASCII characters.

  This function compares the Null-terminated ASCII string FirstString to the
  Null-terminated ASCII  string SecondString. At most, Length ASCII characters
  will be compared. If Length is 0, then 0 is returned. If FirstString is
  identical to SecondString, then 0 is returned. Otherwise, the value returned
  is the first mismatched ASCII character in SecondString subtracted from the
  first mismatched ASCII character in FirstString.

  If Length > 0 and FirstString is NULL, then ASSERT().
  If Length > 0 and SecondString is NULL, then ASSERT().
  If PcdMaximumAsciiStringLength is not zero, and Length is greater than
  PcdMaximumAsciiStringLength, then ASSERT().
  If PcdMaximumAsciiStringLength is not zero, and FirstString contains more than
  PcdMaximumAsciiStringLength ASCII characters, not including the Null-terminator,
  then ASSERT().
  If PcdMaximumAsciiStringLength is not zero, and SecondString contains more than
  PcdMaximumAsciiStringLength ASCII characters, not including the Null-terminator,
  then ASSERT().

  @param  FirstString   A pointer to a Null-terminated ASCII string.
  @param  SecondString  A pointer to a Null-terminated ASCII string.
  @param  Length        The maximum number of ASCII characters for compare.

  @retval ==0       FirstString is identical to SecondString.
  @retval !=0       FirstString is not identical to SecondString.

**/
INTN
EFIAPI
AsciiStrnCmp (
  IN      CONST CHAR8  *FirstString,
  IN      CONST CHAR8  *SecondString,
  IN      UINTN        Length
  )
{
  if (Length == 0) {
    return 0;
  }

  //
  // ASSERT both strings are less long than PcdMaximumAsciiStringLength
  //
  ASSERT (AsciiStrSize (FirstString));
  ASSERT (AsciiStrSize (SecondString));

  if (PcdGet32 (PcdMaximumAsciiStringLength) != 0) {
    ASSERT (Length <= PcdGet32 (PcdMaximumAsciiStringLength));
  }

  while ((*FirstString != '\0') &&
         (*SecondString != '\0') &&
         (*FirstString == *SecondString) &&
         (Length > 1))
  {
    FirstString++;
    SecondString++;
    Length--;
  }

  return *FirstString - *SecondString;
}

/**
  Returns the first occurrence of a Null-terminated ASCII sub-string
  in a Null-terminated ASCII string.

  This function scans the contents of the ASCII string specified by String
  and returns the first occurrence of SearchString. If SearchString is not
  found in String, then NULL is returned. If the length of SearchString is zero,
  then String is returned.

  If String is NULL, then ASSERT().
  If SearchString is NULL, then ASSERT().

  If PcdMaximumAsciiStringLength is not zero, and SearchString or
  String contains more than PcdMaximumAsciiStringLength Unicode characters
  not including the Null-terminator, then ASSERT().

  @param  String          A pointer to a Null-terminated ASCII string.
  @param  SearchString    A pointer to a Null-terminated ASCII string to search for.

  @retval NULL            If the SearchString does not appear in String.
  @retval others          If there is a match return the first occurrence of SearchingString.
                          If the length of SearchString is zero,return String.

**/
CHAR8 *
EFIAPI
AsciiStrStr (
  IN      CONST CHAR8  *String,
  IN      CONST CHAR8  *SearchString
  )
{
  CONST CHAR8  *FirstMatch;
  CONST CHAR8  *SearchStringTmp;

  //
  // ASSERT both strings are less long than PcdMaximumAsciiStringLength
  //
  ASSERT (AsciiStrSize (String) != 0);
  ASSERT (AsciiStrSize (SearchString) != 0);

  if (*SearchString == '\0') {
    return (CHAR8 *)String;
  }

  while (*String != '\0') {
    SearchStringTmp = SearchString;
    FirstMatch      = String;

    while (  (*String == *SearchStringTmp)
          && (*String != '\0'))
    {
      String++;
      SearchStringTmp++;
    }

    if (*SearchStringTmp == '\0') {
      return (CHAR8 *)FirstMatch;
    }

    if (*String == '\0') {
      return NULL;
    }

    String = FirstMatch + 1;
  }

  return NULL;
}

/**
  Convert a Null-terminated ASCII decimal string to a value of type
  UINTN.

  This function returns a value of type UINTN by interpreting the contents
  of the ASCII string String as a decimal number. The format of the input
  ASCII string String is:

                    [spaces] [decimal digits].

  The valid decimal digit character is in the range [0-9]. The function will
  ignore the pad space, which includes spaces or tab characters, before the digits.
  The running zero in the beginning of [decimal digits] will be ignored. Then, the
  function stops at the first character that is a not a valid decimal character or
  Null-terminator, whichever on comes first.

  If String has only pad spaces, then 0 is returned.
  If String has no pad spaces or valid decimal digits, then 0 is returned.
  If the number represented by String overflows according to the range defined by
  UINTN, then MAX_UINTN is returned.
  If String is NULL, then ASSERT().
  If PcdMaximumAsciiStringLength is not zero, and String contains more than
  PcdMaximumAsciiStringLength ASCII characters not including the Null-terminator,
  then ASSERT().

  @param  String          A pointer to a Null-terminated ASCII string.

  @retval Value translated from String.

**/
UINTN
EFIAPI
AsciiStrDecimalToUintn (
  IN      CONST CHAR8  *String
  )
{
  UINTN          Result;
  RETURN_STATUS  Status;

  Status = AsciiStrDecimalToUintnS (String, (CHAR8 **)NULL, &Result);
  if (Status == RETURN_INVALID_PARAMETER) {
    Result = 0;
  }

  return Result;
}

/**
  Convert a Null-terminated ASCII decimal string to a value of type
  UINT64.

  This function returns a value of type UINT64 by interpreting the contents
  of the ASCII string String as a decimal number. The format of the input
  ASCII string String is:

                    [spaces] [decimal digits].

  The valid decimal digit character is in the range [0-9]. The function will
  ignore the pad space, which includes spaces or tab characters, before the digits.
  The running zero in the beginning of [decimal digits] will be ignored. Then, the
  function stops at the first character that is a not a valid decimal character or
  Null-terminator, whichever on comes first.

  If String has only pad spaces, then 0 is returned.
  If String has no pad spaces or valid decimal digits, then 0 is returned.
  If the number represented by String overflows according to the range defined by
  UINT64, then MAX_UINT64 is returned.
  If String is NULL, then ASSERT().
  If PcdMaximumAsciiStringLength is not zero, and String contains more than
  PcdMaximumAsciiStringLength ASCII characters not including the Null-terminator,
  then ASSERT().

  @param  String          A pointer to a Null-terminated ASCII string.

  @retval Value translated from String.

**/
UINT64
EFIAPI
AsciiStrDecimalToUint64 (
  IN      CONST CHAR8  *String
  )
{
  UINT64         Result;
  RETURN_STATUS  Status;

  Status = AsciiStrDecimalToUint64S (String, (CHAR8 **)NULL, &Result);
  if (Status == RETURN_INVALID_PARAMETER) {
    Result = 0;
  }

  return Result;
}

/**
  Convert a Null-terminated ASCII hexadecimal string to a value of type UINTN.

  This function returns a value of type UINTN by interpreting the contents of
  the ASCII string String as a hexadecimal number. The format of the input ASCII
  string String is:

                  [spaces][zeros][x][hexadecimal digits].

  The valid hexadecimal digit character is in the range [0-9], [a-f] and [A-F].
  The prefix "0x" is optional. Both "x" and "X" is allowed in "0x" prefix. If "x"
  appears in the input string, it must be prefixed with at least one 0. The function
  will ignore the pad space, which includes spaces or tab characters, before [zeros],
  [x] or [hexadecimal digits]. The running zero before [x] or [hexadecimal digits]
  will be ignored. Then, the decoding starts after [x] or the first valid hexadecimal
  digit. Then, the function stops at the first character that is a not a valid
  hexadecimal character or Null-terminator, whichever on comes first.

  If String has only pad spaces, then 0 is returned.
  If String has no leading pad spaces, leading zeros or valid hexadecimal digits, then
  0 is returned.

  If the number represented by String overflows according to the range defined by UINTN,
  then MAX_UINTN is returned.
  If String is NULL, then ASSERT().
  If PcdMaximumAsciiStringLength is not zero,
  and String contains more than PcdMaximumAsciiStringLength ASCII characters not including
  the Null-terminator, then ASSERT().

  @param  String          A pointer to a Null-terminated ASCII string.

  @retval Value translated from String.

**/
UINTN
EFIAPI
AsciiStrHexToUintn (
  IN      CONST CHAR8  *String
  )
{
  UINTN          Result;
  RETURN_STATUS  Status;

  Status = AsciiStrHexToUintnS (String, (CHAR8 **)NULL, &Result);
  if (Status == RETURN_INVALID_PARAMETER) {
    Result = 0;
  }

  return Result;
}

/**
  Convert a Null-terminated ASCII hexadecimal string to a value of type UINT64.

  This function returns a value of type UINT64 by interpreting the contents of
  the ASCII string String as a hexadecimal number. The format of the input ASCII
  string String is:

                  [spaces][zeros][x][hexadecimal digits].

  The valid hexadecimal digit character is in the range [0-9], [a-f] and [A-F].
  The prefix "0x" is optional. Both "x" and "X" is allowed in "0x" prefix. If "x"
  appears in the input string, it must be prefixed with at least one 0. The function
  will ignore the pad space, which includes spaces or tab characters, before [zeros],
  [x] or [hexadecimal digits]. The running zero before [x] or [hexadecimal digits]
  will be ignored. Then, the decoding starts after [x] or the first valid hexadecimal
  digit. Then, the function stops at the first character that is a not a valid
  hexadecimal character or Null-terminator, whichever on comes first.

  If String has only pad spaces, then 0 is returned.
  If String has no leading pad spaces, leading zeros or valid hexadecimal digits, then
  0 is returned.

  If the number represented by String overflows according to the range defined by UINT64,
  then MAX_UINT64 is returned.
  If String is NULL, then ASSERT().
  If PcdMaximumAsciiStringLength is not zero,
  and String contains more than PcdMaximumAsciiStringLength ASCII characters not including
  the Null-terminator, then ASSERT().

  @param  String          A pointer to a Null-terminated ASCII string.

  @retval Value translated from String.

**/
UINT64
EFIAPI
AsciiStrHexToUint64 (
  IN      CONST CHAR8  *String
  )
{
  UINT64         Result;
  RETURN_STATUS  Status;

  Status = AsciiStrHexToUint64S (String, (CHAR8 **)NULL, &Result);
  if (Status == RETURN_INVALID_PARAMETER) {
    Result = 0;
  }

  return Result;
}

STATIC CHAR8  EncodingTable[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                "abcdefghijklmnopqrstuvwxyz"
                                "0123456789+/";

/**
  Convert binary data to a Base64 encoded ascii string based on RFC4648.

  Produce a Null-terminated Ascii string in the output buffer specified by Destination and DestinationSize.
  The Ascii string is produced by converting the data string specified by Source and SourceLength.

  @param Source            Input UINT8 data
  @param SourceLength      Number of UINT8 bytes of data
  @param Destination       Pointer to output string buffer
  @param DestinationSize   Size of ascii buffer. Set to 0 to get the size needed.
                           Caller is responsible for passing in buffer of DestinationSize

  @retval RETURN_SUCCESS             When ascii buffer is filled in.
  @retval RETURN_INVALID_PARAMETER   If Source is NULL or DestinationSize is NULL.
  @retval RETURN_INVALID_PARAMETER   If SourceLength or DestinationSize is bigger than (MAX_ADDRESS - (UINTN)Destination).
  @retval RETURN_BUFFER_TOO_SMALL    If SourceLength is 0 and DestinationSize is <1.
  @retval RETURN_BUFFER_TOO_SMALL    If Destination is NULL or DestinationSize is smaller than required buffersize.

**/
RETURN_STATUS
EFIAPI
Base64Encode (
  IN  CONST UINT8  *Source,
  IN        UINTN  SourceLength,
  OUT       CHAR8  *Destination   OPTIONAL,
  IN OUT    UINTN  *DestinationSize
  )
{
  UINTN  RequiredSize;
  UINTN  Left;

  //
  // Check pointers, and SourceLength is valid
  //
  if ((Source == NULL) || (DestinationSize == NULL)) {
    return RETURN_INVALID_PARAMETER;
  }

  //
  // Allow for RFC 4648 test vector 1
  //
  if (SourceLength == 0) {
    if (*DestinationSize < 1) {
      *DestinationSize = 1;
      return RETURN_BUFFER_TOO_SMALL;
    }

    *DestinationSize = 1;
    *Destination     = '\0';
    return RETURN_SUCCESS;
  }

  //
  // Check if SourceLength or  DestinationSize is valid
  //
  if ((SourceLength >= (MAX_ADDRESS - (UINTN)Source)) || (*DestinationSize >= (MAX_ADDRESS - (UINTN)Destination))) {
    return RETURN_INVALID_PARAMETER;
  }

  //
  // 4 ascii per 3 bytes + NULL
  //
  RequiredSize = ((SourceLength + 2) / 3) * 4 + 1;
  if ((Destination == NULL) || (*DestinationSize < RequiredSize)) {
    *DestinationSize = RequiredSize;
    return RETURN_BUFFER_TOO_SMALL;
  }

  Left = SourceLength;

  //
  // Encode 24 bits (three bytes) into 4 ascii characters
  //
  while (Left >= 3) {
    *Destination++ = EncodingTable[(Source[0] & 0xfc) >> 2];
    *Destination++ = EncodingTable[((Source[0] & 0x03) << 4) + ((Source[1] & 0xf0) >> 4)];
    *Destination++ = EncodingTable[((Source[1] & 0x0f) << 2) + ((Source[2] & 0xc0) >> 6)];
    *Destination++ = EncodingTable[(Source[2] & 0x3f)];
    Left          -= 3;
    Source        += 3;
  }

  //
  // Handle the remainder, and add padding '=' characters as necessary.
  //
  switch (Left) {
    case 0:

      //
      // No bytes Left, done.
      //
      break;
    case 1:

      //
      // One more data byte, two pad characters
      //
      *Destination++ = EncodingTable[(Source[0] & 0xfc) >> 2];
      *Destination++ = EncodingTable[((Source[0] & 0x03) << 4)];
      *Destination++ = '=';
      *Destination++ = '=';
      break;
    case 2:

      //
      // Two more data bytes, and one pad character
      //
      *Destination++ = EncodingTable[(Source[0] & 0xfc) >> 2];
      *Destination++ = EncodingTable[((Source[0] & 0x03) << 4) + ((Source[1] & 0xf0) >> 4)];
      *Destination++ = EncodingTable[((Source[1] & 0x0f) << 2)];
      *Destination++ = '=';
      break;
  }

  //
  // Add terminating NULL
  //
  *Destination = '\0';
  return RETURN_SUCCESS;
}

/**
  Decode Base64 ASCII encoded data to 8-bit binary representation, based on
  RFC4648.

  Decoding occurs according to "Table 1: The Base 64 Alphabet" in RFC4648.

  Whitespace is ignored at all positions:
  - 0x09 ('\t') horizontal tab
  - 0x0A ('\n') new line
  - 0x0B ('\v') vertical tab
  - 0x0C ('\f') form feed
  - 0x0D ('\r') carriage return
  - 0x20 (' ')  space

  The minimum amount of required padding (with ASCII 0x3D, '=') is tolerated
  and enforced at the end of the Base64 ASCII encoded data, and only there.

  Other characters outside of the encoding alphabet cause the function to
  reject the Base64 ASCII encoded data.

  @param[in] Source               Array of CHAR8 elements containing the Base64
                                  ASCII encoding. May be NULL if SourceSize is
                                  zero.

  @param[in] SourceSize           Number of CHAR8 elements in Source.

  @param[out] Destination         Array of UINT8 elements receiving the decoded
                                  8-bit binary representation. Allocated by the
                                  caller. May be NULL if DestinationSize is
                                  zero on input. If NULL, decoding is
                                  performed, but the 8-bit binary
                                  representation is not stored. If non-NULL and
                                  the function returns an error, the contents
                                  of Destination are indeterminate.

  @param[in,out] DestinationSize  On input, the number of UINT8 elements that
                                  the caller allocated for Destination. On
                                  output, if the function returns
                                  RETURN_SUCCESS or RETURN_BUFFER_TOO_SMALL,
                                  the number of UINT8 elements that are
                                  required for decoding the Base64 ASCII
                                  representation. If the function returns a
                                  value different from both RETURN_SUCCESS and
                                  RETURN_BUFFER_TOO_SMALL, then DestinationSize
                                  is indeterminate on output.

  @retval RETURN_SUCCESS            SourceSize CHAR8 elements at Source have
                                    been decoded to on-output DestinationSize
                                    UINT8 elements at Destination. Note that
                                    RETURN_SUCCESS covers the case when
                                    DestinationSize is zero on input, and
                                    Source decodes to zero bytes (due to
                                    containing at most ignored whitespace).

  @retval RETURN_BUFFER_TOO_SMALL   The input value of DestinationSize is not
                                    large enough for decoding SourceSize CHAR8
                                    elements at Source. The required number of
                                    UINT8 elements has been stored to
                                    DestinationSize.

  @retval RETURN_INVALID_PARAMETER  DestinationSize is NULL.

  @retval RETURN_INVALID_PARAMETER  Source is NULL, but SourceSize is not zero.

  @retval RETURN_INVALID_PARAMETER  Destination is NULL, but DestinationSize is
                                    not zero on input.

  @retval RETURN_INVALID_PARAMETER  Source is non-NULL, and (Source +
                                    SourceSize) would wrap around MAX_ADDRESS.

  @retval RETURN_INVALID_PARAMETER  Destination is non-NULL, and (Destination +
                                    DestinationSize) would wrap around
                                    MAX_ADDRESS, as specified on input.

  @retval RETURN_INVALID_PARAMETER  None of Source and Destination are NULL,
                                    and CHAR8[SourceSize] at Source overlaps
                                    UINT8[DestinationSize] at Destination, as
                                    specified on input.

  @retval RETURN_INVALID_PARAMETER  Invalid CHAR8 element encountered in
                                    Source.
**/
RETURN_STATUS
EFIAPI
Base64Decode (
  IN     CONST CHAR8  *Source          OPTIONAL,
  IN     UINTN        SourceSize,
  OUT    UINT8        *Destination     OPTIONAL,
  IN OUT UINTN        *DestinationSize
  )
{
  BOOLEAN  PaddingMode;
  UINTN    SixBitGroupsConsumed;
  UINT32   Accumulator;
  UINTN    OriginalDestinationSize;
  UINTN    SourceIndex;
  CHAR8    SourceChar;
  UINT32   Base64Value;
  UINT8    DestinationOctet;

  if (DestinationSize == NULL) {
    return RETURN_INVALID_PARAMETER;
  }

  //
  // Check Source array validity.
  //
  if (Source == NULL) {
    if (SourceSize > 0) {
      //
      // At least one CHAR8 element at NULL Source.
      //
      return RETURN_INVALID_PARAMETER;
    }
  } else if (SourceSize > MAX_ADDRESS - (UINTN)Source) {
    //
    // Non-NULL Source, but it wraps around.
    //
    return RETURN_INVALID_PARAMETER;
  }

  //
  // Check Destination array validity.
  //
  if (Destination == NULL) {
    if (*DestinationSize > 0) {
      //
      // At least one UINT8 element at NULL Destination.
      //
      return RETURN_INVALID_PARAMETER;
    }
  } else if (*DestinationSize > MAX_ADDRESS - (UINTN)Destination) {
    //
    // Non-NULL Destination, but it wraps around.
    //
    return RETURN_INVALID_PARAMETER;
  }

  //
  // Check for overlap.
  //
  if ((Source != NULL) && (Destination != NULL)) {
    //
    // Both arrays have been provided, and we know from earlier that each array
    // is valid in itself.
    //
    if ((UINTN)Source + SourceSize <= (UINTN)Destination) {
      //
      // Source array precedes Destination array, OK.
      //
    } else if ((UINTN)Destination + *DestinationSize <= (UINTN)Source) {
      //
      // Destination array precedes Source array, OK.
      //
    } else {
      //
      // Overlap.
      //
      return RETURN_INVALID_PARAMETER;
    }
  }

  //
  // Decoding loop setup.
  //
  PaddingMode             = FALSE;
  SixBitGroupsConsumed    = 0;
  Accumulator             = 0;
  OriginalDestinationSize = *DestinationSize;
  *DestinationSize        = 0;

  //
  // Decoding loop.
  //
  for (SourceIndex = 0; SourceIndex < SourceSize; SourceIndex++) {
    SourceChar = Source[SourceIndex];

    //
    // Whitespace is ignored at all positions (regardless of padding mode).
    //
    if ((SourceChar == '\t') || (SourceChar == '\n') || (SourceChar == '\v') ||
        (SourceChar == '\f') || (SourceChar == '\r') || (SourceChar == ' '))
    {
      continue;
    }

    //
    // If we're in padding mode, accept another padding character, as long as
    // that padding character completes the quantum. This completes case (2)
    // from RFC4648, Chapter 4. "Base 64 Encoding":
    //
    // (2) The final quantum of encoding input is exactly 8 bits; here, the
    //     final unit of encoded output will be two characters followed by two
    //     "=" padding characters.
    //
    if (PaddingMode) {
      if ((SourceChar == '=') && (SixBitGroupsConsumed == 3)) {
        SixBitGroupsConsumed = 0;
        continue;
      }

      return RETURN_INVALID_PARAMETER;
    }

    //
    // When not in padding mode, decode Base64Value based on RFC4648, "Table 1:
    // The Base 64 Alphabet".
    //
    if (('A' <= SourceChar) && (SourceChar <= 'Z')) {
      Base64Value = SourceChar - 'A';
    } else if (('a' <= SourceChar) && (SourceChar <= 'z')) {
      Base64Value = 26 + (SourceChar - 'a');
    } else if (('0' <= SourceChar) && (SourceChar <= '9')) {
      Base64Value = 52 + (SourceChar - '0');
    } else if (SourceChar == '+') {
      Base64Value = 62;
    } else if (SourceChar == '/') {
      Base64Value = 63;
    } else if (SourceChar == '=') {
      //
      // Enter padding mode.
      //
      PaddingMode = TRUE;

      if (SixBitGroupsConsumed == 2) {
        //
        // If we have consumed two 6-bit groups from the current quantum before
        // encountering the first padding character, then this is case (2) from
        // RFC4648, Chapter 4. "Base 64 Encoding". Bump SixBitGroupsConsumed,
        // and we'll enforce another padding character.
        //
        SixBitGroupsConsumed = 3;
      } else if (SixBitGroupsConsumed == 3) {
        //
        // If we have consumed three 6-bit groups from the current quantum
        // before encountering the first padding character, then this is case
        // (3) from RFC4648, Chapter 4. "Base 64 Encoding". The quantum is now
        // complete.
        //
        SixBitGroupsConsumed = 0;
      } else {
        //
        // Padding characters are not allowed at the first two positions of a
        // quantum.
        //
        return RETURN_INVALID_PARAMETER;
      }

      //
      // Wherever in a quantum we enter padding mode, we enforce the padding
      // bits pending in the accumulator -- from the last 6-bit group just
      // preceding the padding character -- to be zero. Refer to RFC4648,
      // Chapter 3.5. "Canonical Encoding".
      //
      if (Accumulator != 0) {
        return RETURN_INVALID_PARAMETER;
      }

      //
      // Advance to the next source character.
      //
      continue;
    } else {
      //
      // Other characters outside of the encoding alphabet are rejected.
      //
      return RETURN_INVALID_PARAMETER;
    }

    //
    // Feed the bits of the current 6-bit group of the quantum to the
    // accumulator.
    //
    Accumulator = (Accumulator << 6) | Base64Value;
    SixBitGroupsConsumed++;
    switch (SixBitGroupsConsumed) {
      case 1:
        //
        // No octet to spill after consuming the first 6-bit group of the
        // quantum; advance to the next source character.
        //
        continue;
      case 2:
        //
        // 12 bits accumulated (6 pending + 6 new); prepare for spilling an
        // octet. 4 bits remain pending.
        //
        DestinationOctet = (UINT8)(Accumulator >> 4);
        Accumulator     &= 0xF;
        break;
      case 3:
        //
        // 10 bits accumulated (4 pending + 6 new); prepare for spilling an
        // octet. 2 bits remain pending.
        //
        DestinationOctet = (UINT8)(Accumulator >> 2);
        Accumulator     &= 0x3;
        break;
      default:
        ASSERT (SixBitGroupsConsumed == 4);
        //
        // 8 bits accumulated (2 pending + 6 new); prepare for spilling an octet.
        // The quantum is complete, 0 bits remain pending.
        //
        DestinationOctet     = (UINT8)Accumulator;
        Accumulator          = 0;
        SixBitGroupsConsumed = 0;
        break;
    }

    //
    // Store the decoded octet if there's room left. Increment
    // (*DestinationSize) unconditionally.
    //
    if (*DestinationSize < OriginalDestinationSize) {
      ASSERT (Destination != NULL);
      Destination[*DestinationSize] = DestinationOctet;
    }

    (*DestinationSize)++;

    //
    // Advance to the next source character.
    //
  }

  //
  // If Source terminates mid-quantum, then Source is invalid.
  //
  if (SixBitGroupsConsumed != 0) {
    return RETURN_INVALID_PARAMETER;
  }

  //
  // Done.
  //
  if (*DestinationSize <= OriginalDestinationSize) {
    return RETURN_SUCCESS;
  }

  return RETURN_BUFFER_TOO_SMALL;
}

/**
  Converts an 8-bit value to an 8-bit BCD value.

  Converts the 8-bit value specified by Value to BCD. The BCD value is
  returned.

  If Value >= 100, then ASSERT().

  @param  Value The 8-bit value to convert to BCD. Range 0..99.

  @return The BCD value.

**/
UINT8
EFIAPI
DecimalToBcd8 (
  IN      UINT8  Value
  )
{
  ASSERT (Value < 100);
  return (UINT8)(((Value / 10) << 4) | (Value % 10));
}

/**
  Converts an 8-bit BCD value to an 8-bit value.

  Converts the 8-bit BCD value specified by Value to an 8-bit value. The 8-bit
  value is returned.

  If Value >= 0xA0, then ASSERT().
  If (Value & 0x0F) >= 0x0A, then ASSERT().

  @param  Value The 8-bit BCD value to convert to an 8-bit value.

  @return The 8-bit value is returned.

**/
UINT8
EFIAPI
BcdToDecimal8 (
  IN      UINT8  Value
  )
{
  ASSERT (Value < 0xa0);
  ASSERT ((Value & 0xf) < 0xa);
  return (UINT8)((Value >> 4) * 10 + (Value & 0xf));
}
