vg_mem_queue.h

   1 #ifndef VG_MEM_QUEUE_H
   2 #define VG_MEM_QUEUE_H
   3
   4 #include "vg_mem.h"
   5 #include "vg_stdint.h"
   6
   7 typedef struct vg_queue vg_queue;
   8 typedef struct vg_queue_frame vg_queue_frame;
   9
  10 struct vg_queue {
  11    u8 *buffer;
  12    u32 size;
  13
  14    struct vg_queue_frame {
  15       u32 alloc_size,size;
  16       u8 data[];
  17    }
  18    *head, *tail;
  19 };
  20
  21 /*
  22  * Allocate memory on the queue. Returns NULL if allocation failed for any
  23  * any reason.
  24  */
  25 static vg_queue_frame *vg_queue_alloc( vg_queue *q, u32 size ){
  26    u32 total = vg_align8(size) + sizeof(vg_queue_frame);
  27    vg_queue_frame *frame = NULL;
  28
  29    if( total > q->size )
  30       return NULL;
  31
  32    if( q->head ){
  33       u32 end   = ((u8 *)q->head - q->buffer) + q->head->alloc_size,
  34           start = ((u8 *)q->tail - q->buffer),
  35           r0    = 0,
  36           r1    = 0;
  37
  38       if( start < end ){
  39          r0 = q->size-end;
  40          r1 = start;
  41       }
  42       else
  43          r0 = start - end;
  44
  45       if( total < r0 ){
  46          frame = (vg_queue_frame *)(q->buffer + end);
  47       }
  48       else {
  49          if( total < r1 ){
  50             q->head->alloc_size += r0;
  51             frame = (vg_queue_frame *)q->buffer;
  52          }
  53       }
  54
  55       if( !frame ) return NULL;
  56    }
  57    else{
  58       frame = (vg_queue_frame *)q->buffer;
  59       q->tail = frame;
  60    }
  61
  62    memset( frame, 0, sizeof(vg_queue_frame) );
  63
  64    q->head = frame;
  65    frame->alloc_size = total;
  66    frame->size = size;
  67
  68    return frame;
  69 }
  70
  71 /*
  72  * Free last item from queue
  73  */
  74 static void vg_queue_pop( vg_queue *q ){
  75    if( q->head == q->tail ){
  76       q->head = NULL;
  77       q->tail = NULL;
  78       return;
  79    }
  80
  81    u32 start = ((u8 *)q->tail - q->buffer);
  82    start += q->tail->alloc_size;
  83
  84    if( start == q->size )
  85       start = 0;
  86
  87    q->tail = (vg_queue_frame *)(q->buffer + start);
  88 }
  89
  90 #endif /* VG_MEM_QUEUE_H */