/*-
 * Copyright (c) 2001
 *     Jeff Wheelhouse (jdw@wwwi.com)
 *
 * This code was originally developed by Jeff Wheelhouse (jdw@wwwi.com).
 * 
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistribution of source code must retail the above copyright 
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY JEFF WHEELHOUSE ``AS IS'' AND ANY EXPRESS OR 
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN 
 * NO EVENT SHALL JEFF WHEELHOUSE BE LIABLE FOR ANY DIRECT, INDIRECT, 
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING BUT NOT 
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, 
 * OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF 
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING 
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE,
 * EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $Id: clog.c,v 1.3 2001/10/02 18:51:26 jdw Exp $
 */


#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <sys/mman.h>
#include <sys/sched.h>
#include <sys/stat.h>
#include <sys/uio.h>


#include "clog.h"


/*
 *  The BUFFER_SIZE value is just used to allocate a buffer full of NULLs 
 *  so that a new logfile can be extended to its full size.
 *
 *  Compiling with -pedantic complains when the buffer array is declared
 *  if I declare this as a const instead of a #define.
 */
#define BUFFER_SIZE 16384

static void init_log(const char *lname, size_t size) __dead2;
static void read_log(const char *lname, int optf) __dead2;
static void usage(void) __dead2;

static const char *pname;

int
main(int argc, char **argv)
{
        int ch;
        int init = 0;
        int size = 0;
        int optf = 0;

        pname = argv[0];

        while ((ch = getopt(argc, argv, "fis:")) != -1)
                switch(ch) {
                case 'i':
                        init = 1;
                        break;
                case 's':
                        size = atol(optarg);
                        if (size==0) usage();
                        break;
                case 'f':
                        optf = 1;
                }

        if ((size>0)&&(init==0)) {
                fprintf(stderr,"%s: WARNING: -s argument ignored without -i.\n",pname);
                size = 0;
        }
        if (argv[optind]==NULL) {
                fprintf(stderr,"%s: ERROR: log_file argument must be specified.\n",pname);
                usage();
        }
        if ((init==1)&&(size==0)) {
                fprintf(stderr,"%s: ERROR: -i argument requires -s.\n",pname);
                usage();
        }
        if ((init==1)&&(optf==1)) {
                fprintf(stderr,"%s: ERROR: flags -f and -i are incompatible.\n",pname);
                usage();
        }

        if (init==1) init_log(argv[optind],size);
        /* if (optf==1) follow_log(artv[optind]); */
        read_log(argv[optind],optf);
                
        return 0;
}


static void
usage(void)
{
  fprintf(stderr,"usage: %s [-i -s log_size] [ -f ] log_file\n",pname);
  exit(1);
}


static void
read_log(const char *lname, int optf)
{
        int fd;
        struct stat sb;
        struct clog_footer *pcf;
        char *pbuffer;
        struct iovec iov[2];
        int iovcnt = 0;
        uint32_t start = 0;
        uint32_t next;
        struct pollfd pfd;

        pfd.fd = -1;

        fd = open(lname,O_RDONLY);
        if (fd==-1) {
                fprintf(stderr,"%s: ERROR: could not open %s (%s)\n",pname,lname,strerror(errno));
                exit(11);
        }

        if (fstat(fd,&sb)==-1) {
                fprintf(stderr,"%s: ERROR: could not stat %s (%s)\n",pname,lname,strerror(errno));
                exit(13);
        }
        pbuffer = mmap(NULL,sb.st_size,PROT_READ,MAP_SHARED,fd,0);
        if (pbuffer==NULL) {
                fprintf(stderr,"%s: ERROR: could not mmap %s body (%s)\n",pname,lname,strerror(errno));
                exit(14);
        }
        pcf = (struct clog_footer*)(pbuffer + sb.st_size - sizeof(struct clog_footer));

        if (pcf->cf_wrap==1) start = pcf->cf_next + 1;
        while(1) {
                while(pcf->cf_lock==1) sched_yield();
                next = pcf->cf_next;
                iovcnt = 0;
                if (start>next) {
                        iov[iovcnt].iov_base = pbuffer + start;
                        iov[iovcnt++].iov_len = pcf->cf_max - start;
                        start = 0;
                }
                iov[iovcnt].iov_base = pbuffer + start;
                iov[iovcnt++].iov_len = next - start;
                if (writev(1,iov,iovcnt)==-1) {
                        fprintf(stderr,"%s: ERROR: could not write output (%s)\n",pname,strerror(errno));
                        exit(15);
                }
                start = next;
                if (optf==0) break;
                if (poll(&pfd,1,50)==-1) {
                        fprintf(stderr,"%s: ERROR: could not poll (%s)\n",pname,strerror(errno));
                        exit(16);
                }
        }
        
        munmap(pbuffer,sb.st_size);
        close(fd);

        exit(0);
}


static void
init_log(const char *lname, size_t size)
{
        int fd;
        size_t fill = size;
        char buffer[BUFFER_SIZE];
        struct clog_footer cf;

        memcpy(&cf.cf_magic,MAGIC_CONST,4);
        cf.cf_max = size - sizeof(struct clog_footer);

        memset(buffer,0,BUFFER_SIZE);

        fd = open(lname,O_RDWR|O_CREAT,0666); 
        if (fd==-1) {
                fprintf(stderr,"%s: ERROR: could not open %s (%s)\n",pname,lname,strerror(errno));
                exit(2);
        }
        if (ftruncate(fd,(off_t)0)==-1) {
                fprintf(stderr,"%s: ERROR: could not truncate %s (%s)\n",pname,lname,strerror(errno));
                exit(3);
        }
        
        while(fill>BUFFER_SIZE) {
                if (write(fd,buffer,BUFFER_SIZE)==-1){
                        fprintf(stderr,"%s: ERROR: could not write %s (%s)\n",pname,lname,strerror(errno));
                        exit(4);
                }
                fill -= BUFFER_SIZE;
        }
        assert(fill<=BUFFER_SIZE);
        if (fill>0) {
                if (write(fd,buffer,fill)==-1) {
                        fprintf(stderr,"%s: ERROR: could not write %s (%s)\n",pname,lname,strerror(errno));
                        exit(5);
                }
        }
        if (lseek(fd,-(off_t)(sizeof(struct clog_footer)),SEEK_END)==-1) {
                fprintf(stderr,"%s: ERROR: could not seek in %s (%s)\n",pname,lname,strerror(errno));
                exit(6);
        }
        if (write(fd,&cf,sizeof(cf))==-1) {
                fprintf(stderr,"%s: ERROR: could not write magic in %s (%s)\n",pname,lname,strerror(errno));
                exit(7);
        }
        close(fd);
        exit(0);
}