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198 lines
5.3 KiB
C
198 lines
5.3 KiB
C
/* GStreamer
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* Copyright (C) <1999> Erik Walthinsen <omega@cse.ogi.edu>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library General Public
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* License as published by the Free Software Foundation; either
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* version 2 of the License, or (at your option) any later version.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Library General Public License for more details.
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*
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* You should have received a copy of the GNU Library General Public
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* License along with this library; if not, write to the
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* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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* Boston, MA 02111-1307, USA.
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*/
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#ifndef __GST_TRASH_STACK_H__
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#define __GST_TRASH_STACK_H__
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#include <glib.h>
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#include "gstmacros.h"
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G_BEGIN_DECLS
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typedef struct _GstTrashStack GstTrashStack;
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typedef struct _GstTrashStackElement GstTrashStackElement;
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struct _GstTrashStackElement {
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GstTrashStackElement *next;
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};
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typedef volatile gpointer gst_vgpointer;/* gtk-doc volatile workaround */
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typedef volatile gulong gst_vgulong; /* gtk-doc volatile workaround */
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struct _GstTrashStack {
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gst_vgpointer head;
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gst_vgulong count; /* for the ABA problem */
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GMutex *lock; /* lock for C fallback */
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};
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GST_INLINE_FUNC GstTrashStack* gst_trash_stack_new (void);
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GST_INLINE_FUNC void gst_trash_stack_init (GstTrashStack *stack);
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GST_INLINE_FUNC void gst_trash_stack_destroy (GstTrashStack *stack);
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GST_INLINE_FUNC void gst_trash_stack_free (GstTrashStack *stack);
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GST_INLINE_FUNC void gst_trash_stack_push (GstTrashStack *stack, gpointer mem);
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GST_INLINE_FUNC gpointer gst_trash_stack_pop (GstTrashStack *stack);
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#if defined (GST_CAN_INLINE) || defined (__GST_TRASH_STACK_C__)
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#if defined (USE_FAST_STACK_TRASH) && defined (__i386__) && defined (__GNUC__) && __GNUC__ >= 2
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#ifdef GST_CONFIG_NO_SMP
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#define SMP_LOCK ""
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#else
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#define SMP_LOCK "lock ; "
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#endif
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/*
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* intel ia32 optimized lockfree implementations
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*/
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GST_INLINE_FUNC void
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gst_trash_stack_init (GstTrashStack *stack)
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{
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stack->head = NULL;
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stack->count = 0;
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}
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GST_INLINE_FUNC void
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gst_trash_stack_destroy (GstTrashStack *stack)
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{
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}
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GST_INLINE_FUNC void
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gst_trash_stack_push (GstTrashStack *stack, gpointer mem)
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{
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__asm__ __volatile__ (
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"1: \n\t"
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" movl %2, (%1); \n\t" /* mem->next == stack->head */
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SMP_LOCK "cmpxchg %1, %0; \n\t" /* if head unchanged, move mem into it */
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" jnz 1b; \n" /* head changed, retry */
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:
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: "m" (*stack),
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"r" (mem),
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"a" (stack->head)
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);
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}
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GST_INLINE_FUNC gpointer
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gst_trash_stack_pop (GstTrashStack *stack)
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{
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GstTrashStackElement *head;
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/* pop is a little more complicated as we need to avoid the so called ABA
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* problem that arises when a pop and push of the same element happens
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* right between when we read head->next and try to swing the new pointer
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* into place. This is usually solved using a counter which makes it highly
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* unlikely that we manage to grab the wrong head->next value.
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*/
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__asm__ __volatile__ (
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" pushl %%ebx; \n\t"
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" testl %%eax, %%eax; \n\t" /* if (head == NULL) return */
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" jz 20f; \n\t"
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"10: \n\t"
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" movl (%%eax), %%ebx; \n\t" /* take value pointed to by head (head->next) */
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" movl %%edx, %%ecx; \n\t" /* take counter */
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" incl %%ecx; \n\t" /* and increment */
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SMP_LOCK "cmpxchg8b %1; \n\t" /* if eax:edx == *stack, move ebx:ecx to *stack,
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* else *stack is moved into eax:edx again... */
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" jz 20f; \n\t" /* success */
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" testl %%eax, %%eax; \n\t" /* if (head == NULL) return */
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" jnz 10b; \n\t" /* else we retry */
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"20: \n\t"
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" popl %%ebx \n"
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: "=a" (head)
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: "m" (*stack),
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"a" (stack->head),
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"d" (stack->count)
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: "ecx"
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);
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return head;
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}
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#else
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/*
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* generic implementation
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*/
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GST_INLINE_FUNC void
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gst_trash_stack_init (GstTrashStack *stack)
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{
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stack->head = NULL;
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stack->lock = g_mutex_new();
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}
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GST_INLINE_FUNC void
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gst_trash_stack_destroy (GstTrashStack *stack)
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{
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g_mutex_free (stack->lock);
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}
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GST_INLINE_FUNC void
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gst_trash_stack_push (GstTrashStack *stack, gpointer mem)
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{
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GstTrashStackElement *elem = (GstTrashStackElement *) mem;
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g_mutex_lock (stack->lock);
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elem->next = stack->head;
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stack->head = elem;
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g_mutex_unlock (stack->lock);
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}
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GST_INLINE_FUNC gpointer
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gst_trash_stack_pop (GstTrashStack *stack)
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{
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GstTrashStackElement *head;
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g_mutex_lock (stack->lock);
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head = (GstTrashStackElement *) stack->head;
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if (head)
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stack->head = head->next;
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g_mutex_unlock (stack->lock);
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return head;
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}
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#endif
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/*
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* common functions
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*/
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GST_INLINE_FUNC GstTrashStack*
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gst_trash_stack_new (void)
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{
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GstTrashStack *stack;
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stack = g_new (GstTrashStack, 1);
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gst_trash_stack_init (stack);
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return stack;
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}
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GST_INLINE_FUNC void
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gst_trash_stack_free (GstTrashStack *stack)
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{
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gst_trash_stack_destroy (stack);
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g_free (stack);
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}
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#endif /* defined (GST_CAN_INLINE) || defined (__GST_TRASH_STACK_C__)*/
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G_END_DECLS
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#endif /* __GST_TRASH_STACK_H__ */
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