libgo/runtime/go-append.c

   1 /* go-append.c -- the go builtin append function.
   2
   3    Copyright 2010 The Go Authors. All rights reserved.
   4    Use of this source code is governed by a BSD-style
   5    license that can be found in the LICENSE file.  */
   6
   7 #include "go-assert.h"
   8 #include "go-type.h"
   9 #include "array.h"
  10 #include "runtime.h"
  11 #include "malloc.h"
  12
  13 struct __go_open_array
  14 __go_append (const struct __go_slice_type *type,
  15              struct __go_open_array a, struct __go_open_array b)
  16 {
  17   size_t element_size;
  18   unsigned int ucount;
  19   int count;
  20
  21   if (b.__values == NULL || b.__count == 0)
  22     return a;
  23
  24   __go_assert (type->__common.__code == GO_SLICE);
  25   element_size = type->__element_type->__size;
  26
  27   ucount = (unsigned int) a.__count + (unsigned int) b.__count;
  28   count = (int) ucount;
  29   __go_assert (ucount == (unsigned int) count && count >= a.__count);
  30   if (count > a.__capacity)
  31     {
  32       int m;
  33       struct __go_open_array n;
  34
  35       m = a.__capacity;
  36       if (m == 0)
  37         m = b.__count;
  38       else
  39         {
  40           do
  41             {
  42               if (a.__count < 1024)
  43                 m += m;
  44               else
  45                 m += m / 4;
  46             }
  47           while (m < count);
  48         }
  49
  50       n.__values = __go_alloc (m * element_size);
  51       n.__count = a.__count;
  52       n.__capacity = m;
  53       __builtin_memcpy (n.__values, a.__values, n.__count * element_size);
  54
  55       a = n;
  56     }
  57
  58   __builtin_memmove ((char *) a.__values + a.__count * element_size,
  59                      b.__values, b.__count * element_size);
  60   a.__count = count;
  61   return a;
  62 }