hexdump -C in C

hexdump.cc

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <stdbool.h>

/*
Implement "hexdump -C" utility.
*/

void hexdump(void* ptr, size_t size, size_t addr0);

#define OUTF stdout

void hexdump(void* ptr, size_t size, size_t addr0) {
  size_t ii, jj;
  bool first_repeat=false;

  size_t sz2;
  unsigned char tmp[16+2]="", curline[16+2], prevline[16+2]="empty";

  for (jj=0; jj<(size+15)/16; jj++) {
    sz2 = 16;
    if ((jj+1)*16 > size) {
      sz2 = size - jj*16;
    }
    memcpy(tmp, ((char*)ptr) + jj*16, sz2);
    memcpy(curline, ((char*)ptr) + jj*16, sz2);
    tmp[sz2]='\0';
    curline[sz2]='\0';

    if (memcmp(prevline, curline, sz2) == 0) {
      if (sz2 != 16) {
        fprintf(OUTF, "%08lx\n", addr0 + jj*16);
        first_repeat = false;
      }
      else {
        if (first_repeat) {
          fprintf(OUTF, "*\n");
          first_repeat = false;
        }
      }
      continue;
    }
    else {
      first_repeat = true;      
    }

    fprintf(OUTF, "%08lx  ", addr0 + jj*16);
    for(ii=0; ii<8 && ii<sz2; ii++) {
      fprintf(OUTF, " %02x", tmp[ii]);
    }
    fprintf(OUTF, " ");
    for(ii=8; ii<16 && ii<sz2; ii++) {
      fprintf(OUTF, " %02x", tmp[ii]);
    }
    for(ii=sz2; ii<16; ii++) {
      fprintf(OUTF, "   ");
    }
    for(ii=0; ii<sz2; ii++) {
      if(tmp[ii] == ' ' ||
        isalnum(tmp[ii]) || 
        isgraph(tmp[ii])    )
        continue;
      tmp[ii] = '.';
    }
    fprintf(OUTF, "  |%s|\n", tmp);

    memcpy(prevline, curline, sz2);
  }
  fprintf(OUTF, "%08lx\n", addr0 + size);
}