libswfdec/swfdec_as_stack.c

   1 /* Swfdec
   2  * Copyright (C) 2007 Benjamin Otte <otte@gnome.org>
   3  *
   4  * This library is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU Lesser General Public
   6  * License as published by the Free Software Foundation; either
   7  * version 2.1 of the License, or (at your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * Lesser General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public
  15  * License along with this library; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor,
  17  * Boston, MA  02110-1301  USA
  18  */
  19
  20 #ifdef HAVE_CONFIG_H
  21 #include "config.h"
  22 #endif
  23
  24 #include <string.h>
  25 #include "swfdec_as_stack.h"
  26 #include "swfdec_as_context.h"
  27 #include "swfdec_as_frame_internal.h"
  28 #include "swfdec_debug.h"
  29
  30 /* FIXME: make this configurable? */
  31 #define SWFDEC_AS_STACK_SIZE 8192 /* random big number */
  32
  33 /* minimum number of elements that need to stay free that makes us remove a stack segment */
  34 #define SWFDEC_AS_STACK_LEFTOVER 16
  35
  36 static SwfdecAsStack *
  37 swfdec_as_stack_new (SwfdecAsContext *context, guint n_elements)
  38 {
  39   gsize size;
  40   SwfdecAsStack *stack;
  41
  42   size = sizeof (SwfdecAsStack) + n_elements * sizeof (SwfdecAsValue);
  43   if (!swfdec_as_context_use_mem (context, size))
  44     return NULL;
  45
  46   stack = g_slice_alloc (size);
  47   stack->n_elements = n_elements;
  48   stack->used_elements = 0;
  49   stack->next = NULL;
  50   return stack;
  51 }
  52
  53 static void
  54 swfdec_as_stack_set (SwfdecAsContext *context, SwfdecAsStack *stack)
  55 {
  56   context->stack = stack;
  57   context->base = &stack->elements[0];
  58   context->cur = context->base + stack->used_elements;
  59   context->end = context->base + SWFDEC_AS_STACK_SIZE;
  60 }
  61
  62 gboolean
  63 swfdec_as_stack_push_segment (SwfdecAsContext *context)
  64 {
  65   SwfdecAsStack *stack;
  66
  67   /* finish current stack */
  68   if (context->stack) {
  69     context->stack->used_elements = context->cur - context->base;
  70     g_assert (context->stack->used_elements <= context->stack->n_elements);
  71   }
  72
  73   stack = swfdec_as_stack_new (context, SWFDEC_AS_STACK_SIZE);
  74   if (stack == NULL)
  75     return FALSE;
  76   SWFDEC_DEBUG ("pushing new stack segment %p", stack);
  77   stack->next = context->stack;
  78   swfdec_as_stack_set (context, stack);
  79   return TRUE;
  80 }
  81
  82 static void
  83 swfdec_as_stack_free (SwfdecAsContext *context, SwfdecAsStack *stack)
  84 {
  85   gsize size;
  86
  87   size = sizeof (SwfdecAsStack) + stack->n_elements * sizeof (SwfdecAsValue);
  88   swfdec_as_context_unuse_mem (context, size);
  89   g_slice_free1 (size, stack);
  90 }
  91
  92 void
  93 swfdec_as_stack_pop_segment (SwfdecAsContext *context)
  94 {
  95   SwfdecAsStack *stack = context->stack;
  96   if (stack->next) {
  97     swfdec_as_stack_set (context, stack->next);
  98   } else {
  99     context->base = context->cur = context->end = NULL;
 100     context->stack = NULL;
 101   }
 102   SWFDEC_DEBUG ("popping stack segment %p, next is %p", stack, context->stack);
 103   swfdec_as_stack_free (context, stack);
 104 }
 105
 106 void
 107 swfdec_as_stack_mark (SwfdecAsStack *stack)
 108 {
 109   guint i;
 110
 111   for (i = 0; i < stack->used_elements; i++) {
 112     swfdec_as_value_mark (&stack->elements[i]);
 113   }
 114   if (stack->next)
 115     swfdec_as_stack_mark (stack->next);
 116 }
 117
 118 void
 119 swfdec_as_stack_ensure_size (SwfdecAsContext *context, guint n_elements)
 120 {
 121   guint current;
 122   SwfdecAsStack *next;
 123
 124   g_return_if_fail (SWFDEC_IS_AS_CONTEXT (context));
 125   g_return_if_fail (n_elements < SWFDEC_AS_STACK_SIZE / 2);
 126
 127   current = (guint) (context->cur - context->base);
 128   if (G_LIKELY (current >= n_elements))
 129     return;
 130   next = context->stack->next;
 131   /* check if we can move this to the last stack */
 132   if (next && context->base != context->frame->stack_begin &&
 133       (next->n_elements - next->used_elements > SWFDEC_AS_STACK_LEFTOVER + current)) {
 134     memmove (&next->elements[next->used_elements], context->base, current * sizeof (SwfdecAsValue));
 135     next->used_elements += current;
 136     swfdec_as_stack_pop_segment (context);
 137     return;
 138   }
 139   if (current) {
 140     n_elements -= current;
 141     memmove (context->base + n_elements, context->base, current * sizeof (SwfdecAsValue));
 142   }
 143   context->cur += n_elements;
 144   if (n_elements) {
 145     if (next && context->base != context->frame->stack_begin) {
 146       /* this should be true by a huge amount */
 147       g_assert (next->used_elements >= n_elements);
 148       if (context->frame->stack_begin <= &next->elements[next->used_elements] &&
 149           context->frame->stack_begin >= &next->elements[0]) {
 150         current = &next->elements[next->used_elements] - context->frame->stack_begin;
 151         current = MIN (n_elements, current);
 152       } else {
 153         current = n_elements;
 154       }
 155       next->used_elements -= current;
 156       n_elements -= current;
 157       memmove (context->base + n_elements, &next->elements[next->used_elements], current * sizeof (SwfdecAsValue));
 158     }
 159     if (n_elements) {
 160       memset (context->base, 0, n_elements * sizeof (SwfdecAsValue));
 161     }
 162   }
 163 }
 164
 165 void
 166 swfdec_as_stack_ensure_free (SwfdecAsContext *context, guint n_elements)
 167 {
 168   g_return_if_fail (SWFDEC_IS_AS_CONTEXT (context));
 169   g_return_if_fail (n_elements < SWFDEC_AS_STACK_SIZE / 2);
 170
 171   if (G_LIKELY ((guint) (context->end - context->cur) >= n_elements))
 172     return;
 173
 174   if (!swfdec_as_stack_push_segment (context))
 175     context->cur = context->end - n_elements;
 176 }
 177
 178 guint
 179 swfdec_as_stack_get_size (SwfdecAsContext *context)
 180 {
 181   SwfdecAsStack *stack;
 182   SwfdecAsValue *target;
 183   guint ret;
 184
 185   g_return_val_if_fail (SWFDEC_IS_AS_CONTEXT (context), 0);
 186
 187   if (context->frame == NULL)
 188     return 0;
 189   target = context->frame->stack_begin;
 190   if (target == context->base)
 191     return context->cur - context->base;
 192   stack = context->stack->next;
 193   ret = context->cur - context->base;
 194   while (target < &stack->elements[0] && target > &stack->elements[stack->used_elements]) {
 195     ret += stack->n_elements;
 196     stack = stack->next;
 197   }
 198   ret += &stack->elements[stack->used_elements] - target;
 199   return ret;
 200 }