118 lines
2 KiB
C
118 lines
2 KiB
C
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/*++
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Copyright (c) 1993 Microsoft Corporation
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Module Name:
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slipframe.c
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Abstract:
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Author:
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Thomas J. Dimitri (TommyD)
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Environment:
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Revision History:
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Ray Patch (raypa) 04/13/94 Modified for new WAN wrapper.
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--*/
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#include "asyncall.h"
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VOID
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AssembleSLIPFrame(
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PNDIS_WAN_PACKET pFrame)
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{
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PUCHAR pOldFrame;
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PUCHAR pNewFrame;
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UINT dataSize;
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UCHAR c;
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//
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// Initialize locals
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//
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pOldFrame=pFrame->CurrentBuffer;
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pNewFrame =pFrame->StartBuffer;
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//
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// for quicker access, get a copy of data length field
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//
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dataSize=pFrame->CurrentLength;
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//
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// Now we run through the entire frame and pad it FORWARDS...
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//
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// <------------- new frame -----------> (could be twice as large)
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// +-----------------------------------+
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// | |x|
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// +-----------------------------------+
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// ^
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// <---- old frame --> |
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// +-----------------+ |
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// | |x| |
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// +-----------------+ |
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// | |
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// \-----------------/
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//
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//
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//
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// 192 is encoded as 219, 220
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// 219 is encoded as 219, 221
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//
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*pNewFrame++ = SLIP_END_BYTE; // 192 - mark beginning of frame
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//
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// loop to remove all 192 and 219 chars
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//
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while ( dataSize-- ) {
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c = *pOldFrame++;
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//
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// Check if we have to escape out this byte or not
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//
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switch (c) {
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case SLIP_END_BYTE:
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*pNewFrame++ = SLIP_ESC_BYTE;
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*pNewFrame++ = SLIP_ESC_END_BYTE;
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break;
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case SLIP_ESC_BYTE:
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*pNewFrame++ = SLIP_ESC_BYTE;
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*pNewFrame++ = SLIP_ESC_ESC_BYTE;
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break;
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default:
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*pNewFrame++ = c;
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}
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}
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//
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// Mark end of frame
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//
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*pNewFrame++ = SLIP_END_BYTE;
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//
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// Calc how many bytes we expanded to including CRC
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//
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pFrame->CurrentLength = (ULONG)(pNewFrame - pFrame->StartBuffer);
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//
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// Put in the adjusted length -- actual num of bytes to send
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//
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pFrame->CurrentBuffer = pFrame->StartBuffer;
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}
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