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 "runtime.h"
   8 #include "go-panic.h"
   9 #include "go-type.h"
  10 #include "array.h"
  11 #include "arch.h"
  12 #include "malloc.h"
  13
  14 /* We should be OK if we don't split the stack here, since the only
  15    libc functions we call are memcpy and memmove.  If we don't do
  16    this, we will always split the stack, because of memcpy and
  17    memmove.  */
  18 extern struct __go_open_array
  19 __go_append (struct __go_open_array, void *, uintptr_t, uintptr_t)
  20   __attribute__ ((no_split_stack));
  21
  22 struct __go_open_array
  23 __go_append (struct __go_open_array a, void *bvalues, uintptr_t bcount,
  24              uintptr_t element_size)
  25 {
  26   uintptr_t ucount;
  27   intgo count;
  28
  29   if (bvalues == NULL || bcount == 0)
  30     return a;
  31
  32   ucount = (uintptr_t) a.__count + bcount;
  33   count = (intgo) ucount;
  34   if ((uintptr_t) count != ucount || count <= a.__count)
  35     runtime_panicstring ("append: slice overflow");
  36
  37   if (count > a.__capacity)
  38     {
  39       intgo m;
  40       void *n;
  41
  42       m = a.__capacity;
  43       if (m + m < count)
  44         m = count;
  45       else
  46         {
  47           do
  48             {
  49               if (a.__count < 1024)
  50                 m += m;
  51               else
  52                 m += m / 4;
  53             }
  54           while (m < count);
  55         }
  56
  57       if (element_size > 0 && (uintptr) m > MaxMem / element_size)
  58         runtime_panicstring ("growslice: cap out of range");
  59
  60       n = __go_alloc (m * element_size);
  61       __builtin_memcpy (n, a.__values, a.__count * element_size);
  62
  63       a.__values = n;
  64       a.__capacity = m;
  65     }
  66
  67   __builtin_memmove ((char *) a.__values + a.__count * element_size,
  68                      bvalues, bcount * element_size);
  69   a.__count = count;
  70   return a;
  71 }