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Annotation of qemu/roms/ipxe/src/net/iobpad.c, revision 1.1

1.1     ! root        1: /*
        !             2:  * Copyright (C) 2007 Michael Brown <[email protected]>.
        !             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_LICENCE ( GPL2_OR_LATER );
        !            20: 
        !            21: /**
        !            22:  * @file
        !            23:  *
        !            24:  * I/O buffer padding
        !            25:  *
        !            26:  */
        !            27: 
        !            28: #include <string.h>
        !            29: #include <ipxe/iobuf.h>
        !            30: 
        !            31: /**
        !            32:  * Pad I/O buffer
        !            33:  *
        !            34:  * @v iobuf            I/O buffer
        !            35:  * @v min_len          Minimum length
        !            36:  *
        !            37:  * This function pads and aligns I/O buffers, for devices that
        !            38:  * aren't capable of padding in hardware, or that require specific
        !            39:  * alignment in TX buffers.  The packet data will end up aligned to a
        !            40:  * multiple of @c IOB_ALIGN.
        !            41:  *
        !            42:  * @c min_len must not exceed @v IOB_ZLEN.
        !            43:  */
        !            44: void iob_pad ( struct io_buffer *iobuf, size_t min_len ) {
        !            45:        void *data;
        !            46:        size_t len;
        !            47:        size_t headroom;
        !            48:        signed int pad_len;
        !            49: 
        !            50:        assert ( min_len <= IOB_ZLEN );
        !            51: 
        !            52:        /* Move packet data to start of I/O buffer.  This will both
        !            53:         * align the data (since I/O buffers are aligned to
        !            54:         * IOB_ALIGN) and give us sufficient space for the
        !            55:         * zero-padding
        !            56:         */
        !            57:        data = iobuf->data;
        !            58:        len = iob_len ( iobuf );
        !            59:        headroom = iob_headroom ( iobuf );
        !            60:        iob_push ( iobuf, headroom );
        !            61:        memmove ( iobuf->data, data, len );
        !            62:        iob_unput ( iobuf, headroom );
        !            63: 
        !            64:        /* Pad to minimum packet length */
        !            65:        pad_len = ( min_len - iob_len ( iobuf ) );
        !            66:        if ( pad_len > 0 )
        !            67:                memset ( iob_put ( iobuf, pad_len ), 0, pad_len );
        !            68: }

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