1	/* bHDstruct.c
   2	 *
   3	 * Header structure
   4	 *
   5	 *  ------- ------- --- ------------ -------- ------------ -------- --------
   6	 * |hdr len|cmd len|cmd|srcfname len|srcfname|trgfname len|trgfname|file len|
   7	 *  ------- ------- --- ------------ -------- ------------ -------- --------
   8	*/
     
   9	#include <stdio.h>
  10	#include <fcntl.h>
  11	#include <stdlib.h>
  12	#include <string.h>
  13	#include <unistd.h>
     
  14	/* The following function is to build the header structure for file transfer */
     
  15	bHDstruct(char *HDbuf, int *buflen)
  16	{
  17	  int i, len;
  18	  ssize_t nread;
  19	  char rbuf[BUFSIZ];                             /* buf for KB input */
  20	  char *cptr;                                    /* a char pointer */
  21	  char *pHDbuf = HDbuf;                          /* a ptr for HDbuf */
  22	  char PROMPT[] = "Please enter command >> "; 
  23	  char PROMPT1[] = "Please enter source filename >> "; 
  24	  char PROMPT2[] = "Please enter target filename >> "; 
     
  25	  write(STDOUT_FILENO, PROMPT, strlen(PROMPT));  /* write to stdout */
  26	  nread = read(STDIN_FILENO, rbuf, BUFSIZ);      /* read from stdin */
  27	  nread--;                                       /* to strip off '\n' */
  28	  len = (int)nread;                              /* cast it to an int */
  29	   
  30	  pHDbuf += sizeof(int);                         /* leave room for hdr len */
  31	  cptr = (char *)&len;                           /* cast to char */
  32	  for (i = 0; i < sizeof(int); i++)
  33	      *pHDbuf++ = *cptr++;                       /* store cmd len in HDbuf */
  34	  bcopy(rbuf, pHDbuf, len);                      /* store cmd, no NULL */
  35	  pHDbuf += len;                                 /* point to next empty slot*/
  36	 
  37	  write(STDOUT_FILENO, PROMPT1, strlen(PROMPT1));  
  38	  nread = read(STDIN_FILENO, rbuf, BUFSIZ);        
  39	  nread--;                                       /* to strip off '\n' */
  40	  len = (int)nread;                              /* cast it to an int */
  41	  
  42	  cptr = (char *)&len;                           /* cast to char */
  43	  for (i = 0; i < sizeof(int); i++)
  44	      *pHDbuf++ = *cptr++;                       /* store srcfname len in HDbuf */
  45	  bcopy(rbuf, pHDbuf, len);                      /* store srcfname, no NULL */
  46	  pHDbuf += len;                                 /* point to next empty slot*/
  47	  
  48	  write(STDOUT_FILENO, PROMPT2, strlen(PROMPT2));  
  49	  nread = read(STDIN_FILENO, rbuf, BUFSIZ);        
  50	  nread--;                                       /* to strip off '\n' */
  51	  len = (int)nread;                              /* cast it to an int */
  52	  
  53	  cptr = (char *)&len;                           /* cast to char */
  54	  for (i = 0; i < sizeof(int); i++) 
  55	      *pHDbuf++ = *cptr++;                       /* store trgfname len in HDbuf */
  56	  bcopy(rbuf, pHDbuf, len);                      /* store trgfname, no NULL */
  57	  pHDbuf += len;                                 /* point to next empty slot*/
  58	  
  59	  len = pHDbuf - HDbuf;                          /* headr len, no file len yet */
  60	  *buflen = len;                                 /* value passed out to caller */
     
  61	  pHDbuf = HDbuf;                                /* reset ptr to beginning */
  62	  cptr = (char *)&len;                           /* cast to char */
  63	  for (i = 0; i < sizeof(int); i++) 
  64	      *pHDbuf++ = *cptr++;                       /* store header len in HDbuf */
  65	  return;
  66	}  /* bHDstruct */
     
  67	/* The following shows an example of how to extract infor from the header structure.
     
  68	*/
     
  69	main()
  70	{
     
  71	  int len, buflen = BUFSIZ * 2;                  /* a bigger buffer len */
  72	  char wbuf[BUFSIZ], hdbuf[BUFSIZ * 2];
  73	  char *cptr = hdbuf, *sptr; 
     
  74	  bHDstruct(hdbuf, &buflen);                     /* assume buffer is big enough */
     
  75	  bcopy(cptr, (char *)&len, sizeof(int));
  76	  cptr += sizeof(int);
  77	  printf("header length = %d\n", len);
     
  78	  bcopy(cptr, (char *)&len, sizeof(int));
  79	  cptr += sizeof(int);
  80	  printf("cmd length = %d\n", len);
     
  81	  bcopy(cptr, wbuf, len);
  82	  cptr += len;
  83	  wbuf[len] = '\0';
  84	  printf("Command name = %s\n", wbuf);
     
  85	  bcopy(cptr, (char *)&len, sizeof(int));
  86	  cptr += sizeof(int);
  87	  printf("source filename length = %d\n", len);
     
  88	  bcopy(cptr, wbuf, len);
  89	  cptr += len;
  90	  wbuf[len] = '\0';
  91	  printf("Source filename = %s\n", wbuf);
     
  92	  bcopy(cptr, (char *)&len, sizeof(int));
  93	  cptr += sizeof(int);
  94	  printf("target filename length = %d\n", len);
     
  95	  bcopy(cptr, wbuf, len);
  96	  cptr += len;
  97	  wbuf[len] = '\0';
  98	  printf("Target filename = %s\n", wbuf);
     
  99	  /* may need to continue for file length */
 100	}  /* main */

[pluto:~] bHDstruct
Please enter command >> recv
Please enter source filename >> sourceFile
Please enter target filename >> targetFilename
header length = 44
cmd length = 4
Command name = recv
source filename length = 10
Source filename = sourceFile
target filename length = 14
Target filename = targetFilename
[pluto:~]