KernelLand/Modules/IPStack/buffer.c

   1 /*
   2  * Acess2 Networking Stack
   3  * - By John Hodge (thePowersGang)
   4  *
   5  * buffer.c
   6  * - Scatter-gather handling
   7  */
   8 #include "ipstack.h"
   9 #include "include/buffer.h"
  10
  11 // === STRUCTURES ===
  12 struct sIPStackBuffer
  13 {
  14          int    MaxSubBufffers;
  15          int    nSubBuffers;
  16         size_t  TotalLength;
  17         struct _subbuffer
  18         {
  19                 const void      *Data;
  20                 size_t  PreLength;
  21                 size_t  PostLength;
  22                 // TODO: Callbacks?
  23         } SubBuffers[];
  24 };
  25
  26 // === CODE ===
  27 tIPStackBuffer *IPStack_Buffer_CreateBuffer(int MaxBuffers)
  28 {
  29         tIPStackBuffer *ret;
  30
  31         ret = malloc( sizeof(*ret) + MaxBuffers * sizeof(ret->SubBuffers[0]) );
  32         ret->MaxSubBufffers = MaxBuffers;
  33         ret->nSubBuffers = 0;
  34         ret->TotalLength = 0;
  35         memset(ret->SubBuffers, 0, MaxBuffers * sizeof(ret->SubBuffers[0]));
  36         return ret;
  37 }
  38
  39 void IPStack_Buffer_DestroyBuffer(tIPStackBuffer *Buffer)
  40 {
  41         // TODO: Fire callbacks?
  42         Buffer->MaxSubBufffers = 0;
  43         Buffer->nSubBuffers = 0;
  44         free(Buffer);
  45 }
  46
  47 void IPStack_Buffer_AppendSubBuffer(tIPStackBuffer *Buffer,
  48         size_t HeaderLen, size_t FooterLen, const void *Data,
  49         tIPStackBufferCb Cb, void *Arg
  50         )
  51 {
  52         if( Buffer->nSubBuffers == Buffer->MaxSubBufffers ) {
  53                 // Ah, oops?
  54                 Log_Error("IPStack", "Buffer %p only had %i sub-buffers allocated, which was not enough",
  55                         Buffer, Buffer->MaxSubBufffers);
  56                 return ;
  57         }
  58
  59         int index = Buffer->nSubBuffers++;
  60         Buffer->TotalLength += HeaderLen + FooterLen;
  61
  62         Buffer->SubBuffers[index].Data = Data;
  63         Buffer->SubBuffers[index].PreLength = HeaderLen;
  64         Buffer->SubBuffers[index].PostLength = FooterLen;
  65 }
  66
  67 size_t IPStack_Buffer_GetLength(tIPStackBuffer *Buffer)
  68 {
  69         return Buffer->TotalLength;
  70 }
  71
  72 void *IPStack_Buffer_CompactBuffer(tIPStackBuffer *Buffer, size_t *Length)
  73 {
  74         void    *ret;
  75         ret = malloc(Buffer->TotalLength);
  76         if(!ret) {
  77                 *Length = 0;
  78                 return NULL;
  79         }
  80
  81         *Length = Buffer->TotalLength;
  82
  83         Uint8   *dest = ret;
  84         for( int i = Buffer->nSubBuffers; i --; )
  85         {
  86                 memcpy(dest,
  87                         Buffer->SubBuffers[i].Data,
  88                         Buffer->SubBuffers[i].PreLength
  89                         );
  90                 dest += Buffer->SubBuffers[i].PreLength;
  91         }
  92         for( int i = 0; i < Buffer->nSubBuffers; i ++ )
  93         {
  94                 if( Buffer->SubBuffers[i].PostLength )
  95                 {
  96                         memcpy(dest,
  97                                 (Uint8*)Buffer->SubBuffers[i].Data + Buffer->SubBuffers[i].PreLength,
  98                                 Buffer->SubBuffers[i].PostLength
  99                                 );
 100                         dest += Buffer->SubBuffers[i].PreLength;
 101                 }
 102         }
 103         return ret;
 104 }
 105
 106 int IPStack_Buffer_GetBuffer(tIPStackBuffer *Buffer, int Index, size_t *Length, const void **DataPtr)
 107 {
 108         if( Index == -1 )       Index = 0;
 109
 110         if( Index >= Buffer->nSubBuffers*2 ) {
 111                 return -1;
 112         }
 113
 114         if( Index > Buffer->nSubBuffers )
 115         {
 116                 // Appended buffers
 117                 Index -= Buffer->nSubBuffers;
 118
 119                 // Bit of a hack to avoid multiple calls which return a zero length
 120                 while( !Buffer->SubBuffers[Index].PostLength )
 121                 {
 122                         if( Index++ == Buffer->nSubBuffers )
 123                                 return -1;
 124                 }
 125
 126                 *DataPtr = (Uint8*)Buffer->SubBuffers[Index].Data + Buffer->SubBuffers[Index].PreLength;
 127                 *Length = Buffer->SubBuffers[Index].PostLength;
 128
 129                 return (Index + 1) + Buffer->nSubBuffers;
 130         }
 131         else
 132         {
 133                 Index = Buffer->nSubBuffers - Index;
 134                 // Prepended buffers
 135                 *DataPtr = Buffer->SubBuffers[Index].Data;
 136                 *Length = Buffer->SubBuffers[Index].PreLength;
 137                 return Buffer->nSubBuffers - (Index - 1);
 138         }
 139 }
 140