#include <sys/ipc.h>
#include <sys/sem.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>
#include <string.h>
#include "semarray.h"



void semarray::init_creator(const char *lockname, int size)
 {
   int fd=open(lockname,O_RDONLY);
   close(fd);
   if (fd>=0) { fprintf(stderr,"lock %s exists\n",lockname); exit(1); }

   semid=semget(IPC_PRIVATE,size,0666|IPC_CREAT);
   if (semid<0) { perror("semget"); exit(1); }

   fd=open(lockname,O_CREAT|O_TRUNC|O_WRONLY,0644);
   if (fd<0) { perror(lockname); exit(1); }
   write(fd,&semid,sizeof(semid));
   close(fd);
   lockfile=strdup(lockname);
 }

semarray::semarray(const char *lockname, int size, int value)
 : creator(true), lockfile(0), numsem(size), sembuffer(new(struct sembuf)[size])
 {
   init_creator(lockname,size);
   union semun sem_union;
   sem_union.val=value;
   for (int i=0;i<size;++i)
      semctl(semid,i,SETVAL,sem_union);
 }

semarray::semarray(const char *lockname, int size, const int *valarray)
 : creator(true), lockfile(0), numsem(size), sembuffer(new(struct sembuf)[size])
 {
   init_creator(lockname,size);
   union semun sem_union;
   for (int i=0;i<size;++i)
    {
      sem_union.val=*valarray++;
      semctl(semid,i,SETVAL,sem_union);
    }
 }

semarray::semarray(const char *lockname) : creator(false), lockfile(0)
 {
   int fd=open(lockname,O_RDONLY);
   if (fd<0) { perror(lockname); exit(1); }
   int id;
   read(fd,&id,sizeof(id));
   close(fd);

   union semun sem_union;
   if (semctl(id,0,GETPID,sem_union)<0) { perror("semctl"); exit(1); }
   semid=id;

   struct semid_ds buffer;
   sem_union.buf=&buffer;
   semctl(id,0,IPC_STAT,sem_union);
   numsem=sem_union.buf->sem_nsems;
   sembuffer=new(struct sembuf)[numsem];
 }

semarray::~semarray()
 {
   if (creator)
    {
      union semun dummy;
      semctl(semid,0,IPC_RMID,dummy);
      if (lockfile) { unlink(lockfile); free((char *)lockfile); }
    }
   delete[] sembuffer;
 }

void semarray::sem_up_down(int semnum, int value)
 {
   struct sembuf sbuf={ semnum, value, 0 };
   if (semnum>=numsem) { fprintf(stderr,"illegal semaphore\n"); exit(1); }
   if (semop(semid,&sbuf,1)) { perror("semop1"); exit(1); }
 }

void semarray::sdown_sup(va_list &ap, int size, int value)
 {
   struct sembuf *P=sembuffer;
   for (int i=0;i<size;++i,++P)
    {
      int semnum=va_arg(ap,int);
      if (semnum>=numsem) { fprintf(stderr,"illegal semaphore\n"); exit(1); }
      P->sem_num=semnum;
      P->sem_op=value;
      P->sem_flg=0;
    }
   va_end(ap);
   if (semop(semid,sembuffer,size)) { perror("semop2"); exit(1); }
 }

void semarray::sdown(int size, ...)
 {
   va_list ap;
   va_start(ap,size);
   sdown_sup(ap,size,-1);
 }

void semarray::sup(int size, ...)
 {
   va_list ap;
   va_start(ap,size);
   sdown_sup(ap,size,1);
 }