mirror of
https://github.com/mpv-player/mpv
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84 lines
2.0 KiB
C
84 lines
2.0 KiB
C
/*
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* shmem.c - Shared memory allocation
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*
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* based on mpg123's xfermem.c by
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* Oliver Fromme <oliver.fromme@heim3.tu-clausthal.de>
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* Sun Apr 6 02:26:26 MET DST 1997
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <unistd.h>
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#include <errno.h>
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#include <sys/types.h>
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#include <sys/time.h>
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#include <sys/uio.h>
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#include <sys/mman.h>
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#include <sys/socket.h>
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#include <fcntl.h>
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#ifdef AIX
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#include <sys/select.h>
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#endif
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#include <sys/ipc.h>
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#include <sys/shm.h>
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extern int errno;
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#if defined(MAP_ANONYMOUS) && !defined(MAP_ANON)
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#define MAP_ANON MAP_ANONYMOUS
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#endif
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static int shmem_type=0;
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void* shmem_alloc(int size){
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void* p;
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int devzero;
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while(1){
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switch(shmem_type){
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case 0: // ========= MAP_ANON|MAP_SHARED ==========
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p=mmap(0,size,PROT_READ|PROT_WRITE,MAP_ANON|MAP_SHARED,-1,0);
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if(p==MAP_FAILED) break; // failed
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printf("shmem: %d bytes allocated using mmap anon (%X)\n",size,p);
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return p;
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case 1: // ========= MAP_SHARED + /dev/zero ==========
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if ((devzero = open("/dev/zero", O_RDWR, 0)) == -1) break;
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p=mmap(0,size,PROT_READ|PROT_WRITE,MAP_SHARED,devzero,0);
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if(p==MAP_FAILED) break; // failed
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printf("shmem: %d bytes allocated using mmap /dev/zero (%X)\n",size,p);
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return p;
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case 2: { // ========= shmget() ==========
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struct shmid_ds shmemds;
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int shmemid;
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if ((shmemid = shmget(IPC_PRIVATE, size, IPC_CREAT | 0600)) == -1) break;
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if ((int)(p = shmat(shmemid, 0, 0)) == -1){
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perror ("shmat()");
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shmctl (shmemid, IPC_RMID, &shmemds);
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break;
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}
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if (shmctl(shmemid, IPC_RMID, &shmemds) == -1) {
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perror ("shmctl()");
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if (shmdt(p) == -1) perror ("shmdt()");
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break;
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}
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printf("shmem: %d bytes allocated using shmget() & shmat() (%X)\n",size,p);
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return p;
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}
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default:
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printf("FATAL: Cannot alloate %d bytes shared memory :(\n",size);
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return NULL;
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}
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++shmem_type;
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}
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}
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void shmem_free(void* p){
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switch(shmem_type){
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case 2:
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if (shmdt(p) == -1) perror ("shmdt()");
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break;
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}
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}
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