/*-----------------------------------------------------------------------*/
/* Program:  show_hex                                                    */
/*                                                                       */
/* Purpose:  This program is used to display the blocks of a file in     */
/*           ascii or hexidecimal.                                       */
/*                                                                       */
/* Contains: GetBlock                                                    */
/*           DisplayBlock                                                */
/*           main                                                        */
/*                                                                       */
/* Author:   John Gauch                                                  */
/*                                                                       */
/* Date:     Sept. 12, 1984 - Original program.                          */
/*           June 2, 1994   - Added to KUIM as support program.          */
/*                                                                       */
/* Usage:    show_hex [filename]                                         */
/*                                                                       */
/*           Commands:  A)scii    - display block in ascii.              */
/*                      H)ex      - display block in hexadecimal.        */
/*                      N)ext     - display next block in file.          */
/*                      P)revious - display previous block in file.      */
/*                      S)pecific - display a given block in file.       */
/*                      Q)uit     - end program.                         */
/*-----------------------------------------------------------------------*/

/*-----------------------------------------------------------------------*/
/* Globals:  The following global constants and variables are used to    */
/*           keep track of file information and user commands.  A read   */
/*           buffer is used to improve I/O efficiency.                   */
/*-----------------------------------------------------------------------*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <ctype.h>

#define BufSize   512		/* Size of read buffer */
#define FromBegin   0		/* Offset type for lseek */
#define NameLen    50		/* Size of file name string */
#define CmdLen      10		/* Size of command line string */
#define Ascii       0		/* My code for ascii display */
#define Hex       1		/* My code for hex display */

char Buffer[BufSize];		/* Read buffer */
int BlockNum;			/* Block offset into file (512 byte blocks) */
long Offset;			/* Byte offset into file */
char FileName[NameLen];		/* File name string */
FILE *Fd;			/* File identifier */
char Command[CmdLen];		/* Command line string */
int DispMode;			/* Display mode (either ascii or hex) */

/*-----------------------------------------------------------------------*/
/* Purpose:  This routine is used to read a data from the file into a    */
/*           buffer 512 bytes long.  If only a partial block is read,    */
/*           the rest of the block is padded with nulls.                 */
/*-----------------------------------------------------------------------*/
void GetBlock()
{
   int ReadCnt;			/* Count of bytes read */
   int i;			/* Index into read buffer */

   /* Interpret command */
   switch (Command[0])
   {
   case 'N':
   case 'n':
      Offset = Offset + BufSize;
      BlockNum = Offset / BufSize;
      break;

   case 'P':
   case 'p':
      Offset = Offset - BufSize;
      if (Offset < 0)
	 Offset = 0;
      BlockNum = Offset / BufSize;
      break;

   case 'S':
   case 's':
      printf("\nEnter block number to be displayed: ");
      scanf("%d", &BlockNum);
      Offset = BlockNum * BufSize;
      break;

   case 'H':
   case 'h':
      DispMode = Hex;
      break;

   case 'A':
   case 'a':
      DispMode = Ascii;
      break;
   }

   /* Fill buffer with nulls */
   for (i = 0; i < BufSize; i++)
      Buffer[i] = '\000';

   /* Read block from file into buffer */
   if (fseek(Fd, Offset, FromBegin) == -1)
      printf("Error - could not seek\n");
   ReadCnt = fread(Buffer, BufSize, 1, Fd);

}

/*-----------------------------------------------------------------------*/
/* Purpose:  This procedure is used to display the data in the buffer in */
/*           ascii and hexadecimal.                                      */
/*-----------------------------------------------------------------------*/
void DisplayBlock()
{
   int Line;			/* Line number in display (0..15 range) */
   int Start;			/* Read buffer address of first byte in line */
   int End;			/* Read buffer address of last byte in line */
   int i;			/* Index into read buffer */
   char c;			/* Temp variable */

   /* Print first line */
   system("clear");
   printf("Filename: %-50s Block#: %-5d\n\n", FileName, BlockNum);

   /* Print data lines in hexadecimal OR ascii */
   for (Line = 0; Line <= 15; Line++)
   {
      /*  Print line header */
      Start = (Offset % BufSize) + Line * 32;
      End = Start + 31;
      printf("%3d - %-3d ", Start, End);

      /* Print data lines in ascii */
      if (DispMode == Ascii)
      {
	 for (i = Start; i <= End; i++)
	 {
	    c = (char) Buffer[i] & 0177;
	    if (iscntrl(c) || isspace(c))
	       printf("  ");
	    else
	       printf("%c ", c);
	 }
	 printf("\n");
      }

      /* Print data lines in hexadecimal */
      else if (DispMode == Hex)
      {
	 for (i = Start; i <= End; i++)
	    printf("%2x", Buffer[i] & 0377);
	 printf("\n");
      }

   }
}

/*-----------------------------------------------------------------------*/
/* Purpose:  This program is used to display the contents of a file in   */
/*           hexadecimal and ascii (where possible).                     */
/*-----------------------------------------------------------------------*/
main(int Argc, char *Argv[])
{
   /* Clear screen and print title */
   printf("\fSHOW_HEX Program - Version 2.0\n\n");

   /* Determine name of file to display */
   if (Argc > 1)
      strcpy(FileName, Argv[1]);
   else
   {
      printf("\nEnter name of file to be displayed: ");
      scanf("%s", FileName);
   }

   /* Open file */
   Offset = 0;
   DispMode = Ascii;
   Fd = fopen(FileName, "r");
   if (Fd == NULL)
      printf("Error - could not open file\n");

   /* Loop handling user commands */
   do
   {
      /* Read and display block */
      GetBlock();
      DisplayBlock();

      /* Print command prompt and read command line */
      printf("\nA)scii H)ex N)ext P)revious S)pecific Q)uit ? ");
      scanf("%s", Command);
   }
   while ((Command[0] != 'Q') && (Command[0] != 'q'));

   /* Close file */
   fclose(Fd);
   return (0);
}