vg_mem_queue.c

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