#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>

#define DEF_BYTES_PER_LINE 16

static int bytes_per_line = DEF_BYTES_PER_LINE;

#define CHARS_PER_HEX_BYTE 3
#define BINARY_START_COL 6
#define MAX_LINE_LENGTH 257


static void dStrHex(const char* str, int len, long start)
{
    const char* p = str;
    unsigned char c;
    char buff[MAX_LINE_LENGTH];
    long a = start;
    const int bpstart = BINARY_START_COL;
    const int cpstart = BINARY_START_COL + 
			((CHARS_PER_HEX_BYTE * bytes_per_line) + 1) + 5;
    int cpos = cpstart;
    int bpos = bpstart;
    int midline_space = (bytes_per_line / 2) + 1;
    int i, k, line_length;
    
    if (len <= 0) 
	return;
    line_length = BINARY_START_COL + 
	          (bytes_per_line * (1 + CHARS_PER_HEX_BYTE)) + 7;
    if (line_length >= MAX_LINE_LENGTH)
    {
	fprintf(stderr, "bytes_per_line causes maximum line length of %d "
			"to be exceeded\n", MAX_LINE_LENGTH);
	return;
    }
    memset(buff, ' ', line_length);
    buff[line_length] = '\0';
    k = sprintf(buff + 1, "%.2lx", a);
    buff[k + 1] = ' ';
    if (bpos >= ((bpstart + (midline_space * CHARS_PER_HEX_BYTE))))
        bpos++;

    for(i = 0; i < len; i++)
    {
        c = *p++;
        bpos += CHARS_PER_HEX_BYTE;
        if (bpos == (bpstart + (midline_space * CHARS_PER_HEX_BYTE)))
            bpos++;
        sprintf(&buff[bpos], "%.2x", (int)(unsigned char)c);
        buff[bpos + 2] = ' ';
        if ((c < ' ') || (c >= 0x7f))
            c='.';
        buff[cpos++] = c;
        if (cpos >= (cpstart + bytes_per_line))
        {
            printf("%s\n", buff);
            bpos = bpstart;
            cpos = cpstart;
            a += bytes_per_line;
            memset(buff,' ', line_length);
            k = sprintf(buff + 1, "%.2lx", a);
            buff[k + 1] = ' ';
        }
    }
    if (cpos > cpstart)
        printf("%s\n", buff);
}


static void usage()
{
    fprintf(stderr, "Usage: hxascdmp [-b=<n>] [-h] [-?] [file+] \n");
    fprintf(stderr, "  Sends hex ASCII dump of stdin/file to stdout\n");
    fprintf(stderr, "  where:\n");
    fprintf(stderr, "          -b=<n>         bytes per line to display "
		    "(def: 16)\n");
    fprintf(stderr, "          -h             print this usage message\n");
    fprintf(stderr, "          -?             print this usage message\n");
    fprintf(stderr, "          file           reads file(s) and outputs it "
		    "as hex ASCII\n");
    fprintf(stderr, "                         if no files reads stdin\n");
}

int main(int argc, const char ** argv)
{
    char buff[8192];
    int num = 8192;
    long start = 0;
    int res, k, u;
    int inFile = 0;	/* stdin */
    int doHelp = 0;
    int hasFilename = 0;

    for (k = 1; k < argc; k++)
    {
	if (0 == strncmp("-b=", argv[k], 3)) 
	{
	    res = sscanf(argv[k] + 3, "%d", &u);
	    if ((1 != res) || (u < 1)) 
	    {
		printf("Bad value after '-b' switch\n");
		usage();
		return 1;
	    }
	    bytes_per_line = u;
	}
    	else if (0 == strcmp("-h", argv[k]))
    	    doHelp = 1;
    	else if (0 == strcmp("-?", argv[k]))
    	    doHelp = 1;
	else if (*argv[k] == '-')
	{
	    fprintf(stderr, "unknown switch: %s\n", argv[k]);
	    usage();
	    return 1;
	}
	else
	{
	    hasFilename = 1;
	    break;
	}
    }
    if (doHelp)
    {
	usage();
	return 0;
    }

    /* Make sure num to fetch is integral multiple of bytes_per_line */
    if (0 != (num % bytes_per_line))
	num = (num / bytes_per_line) * bytes_per_line;

    if (hasFilename)
    {
	for ( ; k < argc; k++)
	{
	    inFile = open(argv[k], O_RDONLY);
	    if (inFile < 0)
	    {
	    	fprintf(stderr, "Couldn't open file: %s\n", argv[k]);
	    }
	    else
	    {
	    	start = 0;
	    	printf("ASCII hex dump of file: %s\n", argv[k]);
		while ((res = read(inFile, buff, num)) > 0)
		{
		    dStrHex(buff, res, start);
		    start += (long)res;
		}
	    }
	    close(inFile);
	    printf("\n");
	}
    }
    else
    {
	while ((res = read(inFile, buff, num)) > 0)
	{
	    dStrHex(buff, res, start);
	    start += (long)res;
	}
    }
    return 0;
}