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