Function StrHexToBytes

MdePkg/Library/BaseLib/SafeString.c:1636–1700

Convert a Null-terminated Unicode hexadecimal string to a byte array. This function outputs a byte array by interpreting the contents of the Unicode string specified by String in hexadecimal format. The format of the input Unicode string String is: [XX]* X is a hexadecimal digit character in the range [0-9], [a-f] and [A-F]. The function decodes every two he

  @retval RETURN_BUFFER_TOO_SMALL  If MaxBufferSize is less than (Length / 2).
**/
RETURN_STATUS
EFIAPI
StrHexToBytes (
  IN  CONST CHAR16       *String,
  IN  UINTN              Length,
  OUT UINT8              *Buffer,
  IN  UINTN              MaxBufferSize
  )
{
  UINTN                  Index;

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

  //
  // 1. None of String or Buffer shall be a null pointer.
  //
  SAFE_STRING_CONSTRAINT_CHECK ((String != NULL), RETURN_INVALID_PARAMETER);
  SAFE_STRING_CONSTRAINT_CHECK ((Buffer != NULL), RETURN_INVALID_PARAMETER);

  //
  // 2. Length shall not be greater than RSIZE_MAX.
  //
  if (RSIZE_MAX != 0) {
    SAFE_STRING_CONSTRAINT_CHECK ((Length <= RSIZE_MAX), RETURN_INVALID_PARAMETER);
  }

  //
  // 3. Length shall not be odd.
  //
  SAFE_STRING_CONSTRAINT_CHECK (((Length & BIT0) == 0), RETURN_INVALID_PARAMETER);

  //
  // 4. MaxBufferSize shall equal to or greater than Length / 2.
  //
  SAFE_STRING_CONSTRAINT_CHECK ((MaxBufferSize >= Length / 2), RETURN_BUFFER_TOO_SMALL);

  //
  // 5. String shall not contains invalid hexadecimal digits.
  //
  for (Index = 0; Index < Length; Index++) {
    if (!InternalIsHexaDecimalDigitCharacter (String[Index])) {
      break;
    }
  }
  if (Index != Length) {
    return RETURN_UNSUPPORTED;
  }

  //
  // Convert the hex string to bytes.
  //
  for(Index = 0; Index < Length; Index++) {

    //
    // For even characters, write the upper nibble for each buffer byte,
    // and for even characters, the lower nibble.
    //
    if ((Index & BIT0) == 0) {