snapdis.c

一个学习SNMP项目：tmoerlan.

/* snap-1.0. Copyright (C) 2000 by Jonathan T. Moore and Michael Hicks.
 *
 * snapdis.c : SNAP disassembler. Goes from wire-format back to
 *   (ascii) SNAP assembly language.
 *
 * $Id: snapdis.c,v 1.2 2003/09/17 11:26:10 tmoerlan Exp $
 */

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include "../lib/bytecode.h"
#include "../lib/packet.h"
#include "../lib/io.h"
#include "../lib/memalloc.h"
#include "../lib/d_printf.h"

int infd;			/* input file descriptor */
FILE *outfile;         		/* output file pointer */

extern char *basename(const char *);

void parse_cmdline(int argc, char **argv);

int main(int argc, char **argv) {
  buffer_t buf;
  packet_t *p;
  int packet_lenb;

  d_printf(10,"%s:%d: starting up\n",__FILE__,__LINE__);

  outfile = stdout;

  parse_cmdline(argc,argv);
  packet_lenb = file_to_str(infd,&buf);
  p = unmarshal_packet(buf.s,packet_lenb,buf.lenb);
  if (p != NULL) {
    fprintf_packet(outfile,p);
    fflush(outfile);
    return(0);
  }
  else
    return(1);
}

void usage(int argc, char **argv) {
  printf("usage: %s [-?] [-o outfile] infile\n",basename(argv[0]));
  printf("\t-? : print this help\n");
  printf("\t-o : set the output file name (default = stdout)\n");
}

void parse_cmdline(int argc, char **argv) {
  char *opts = "?o:";
  char c;
  int args_expected = 1;
  int args_processed = 0;
  int argidx;
  char *outfilename;
  char *infilename;

  while((c = getopt(argc,argv,opts)) != EOF) {
    switch(c) {
    case '?':
      usage(argc,argv);
      exit(1);
    case 'o':
      outfilename = optarg;
      if (strcmp(outfilename,"-") != 0) {
	outfile = fopen(outfilename,"w");
	if (outfile == NULL) {
	  fprintf(stderr,"%s: unable to open file \"%s\" for output\n",
		  basename(argv[0]),outfilename);
	  fflush(stderr);
	  exit(1);
	}
      }
      break;
    }
  }
  argidx = optind;
  while(args_processed < args_expected) {
    if (argidx >= argc) {
      /* missing arguments */
      printf("%s: missing argument(s)\n",basename(argv[0]));
      usage(argc,argv);
      exit(1);
    }
    switch(args_processed) {
    case 0:
      infilename = argv[argidx];
      if (strcmp(infilename,"-") != 0) {
	infd = open(infilename,O_RDONLY);
	if (infd < 0) {
	  fprintf(stderr,"%s: unable to open file \"%s\" for input\n",
		  basename(argv[0]),infilename);
	  fflush(stderr);
	  exit(1);
	}
      }
      break;
    }
    argidx++;
    args_processed++;
  }
  if (argidx < argc) {
    /* extra arguments */
    printf("%s: extra argument(s)\n",basename(argv[0]));
    usage(argc,argv);
    exit(1);
  }
  return;
}