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iobpad.c 1.8KB

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  1. /*
  2. * Copyright (C) 2007 Michael Brown <mbrown@fensystems.co.uk>.
  3. *
  4. * This program is free software; you can redistribute it and/or
  5. * modify it under the terms of the GNU General Public License as
  6. * published by the Free Software Foundation; either version 2 of the
  7. * License, or any later version.
  8. *
  9. * This program is distributed in the hope that it will be useful, but
  10. * WITHOUT ANY WARRANTY; without even the implied warranty of
  11. * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  12. * General Public License for more details.
  13. *
  14. * You should have received a copy of the GNU General Public License
  15. * along with this program; if not, write to the Free Software
  16. * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  17. */
  18. /**
  19. * @file
  20. *
  21. * I/O buffer padding
  22. *
  23. */
  24. #include <string.h>
  25. #include <gpxe/iobuf.h>
  26. /**
  27. * Pad I/O buffer
  28. *
  29. * @v iobuf I/O buffer
  30. * @v min_len Minimum length
  31. *
  32. * This function pads and aligns I/O buffers, for devices that
  33. * aren't capable of padding in hardware, or that require specific
  34. * alignment in TX buffers. The packet data will end up aligned to a
  35. * multiple of @c IOB_ALIGN.
  36. *
  37. * @c min_len must not exceed @v IOB_ZLEN.
  38. */
  39. void iob_pad ( struct io_buffer *iobuf, size_t min_len ) {
  40. void *data;
  41. size_t len;
  42. size_t headroom;
  43. signed int pad_len;
  44. assert ( min_len <= IOB_ZLEN );
  45. /* Move packet data to start of I/O buffer. This will both
  46. * align the data (since I/O buffers are aligned to
  47. * IOB_ALIGN) and give us sufficient space for the
  48. * zero-padding
  49. */
  50. data = iobuf->data;
  51. len = iob_len ( iobuf );
  52. headroom = iob_headroom ( iobuf );
  53. iob_push ( iobuf, headroom );
  54. memmove ( iobuf->data, data, len );
  55. iob_unput ( iobuf, headroom );
  56. /* Pad to minimum packet length */
  57. pad_len = ( min_len - iob_len ( iobuf ) );
  58. if ( pad_len > 0 )
  59. memset ( iob_put ( iobuf, pad_len ), 0, pad_len );
  60. }