#include <fcntl.h>
#include <pthread.h>
#include <scsi/sg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>

#define CMD_SIZE 6

#define MIN_STRLEN 1
pthread_mutex_t out_mutex = PTHREAD_MUTEX_INITIALIZER;

void dump_buf(unsigned char *buf, int len) {
  int i, nz = 0;
  for (i = 0; i < len; i++) {
    if (buf[i]) {
      nz = 1;
      break;
    }
  }
  if (!nz)
    // The buffer is empty.
    return;

  pthread_mutex_lock(&out_mutex);
  for (i = 0; i < len; i++) {
    if (buf[i]) {
      int str_len = strlen(&buf[i]);
      // Short string pieces are too boring.
      if (str_len >= MIN_STRLEN) {
        unsigned char *c;
        for (c = &buf[i]; c < &buf[i + str_len]; c++) {
          if ((*c > 127) || ((*c < 32) && (*c != 10) && (*c != 13)))  {
            *c = ' ';
            continue;
          }
        }
        // Dump the buffer.
        fprintf(stderr, "%s\n", &buf[i]);
      }
      i += str_len;
    }
  }
  pthread_mutex_unlock(&out_mutex);
}

int main(int argc, char *argv[])
{
  int npages = 128, pages;
  if (argc > 1) {
    pages = atoi(argv[1]);
    if (pages > 0 && pages < 1024)
      npages = pages;
  }
  int buf_size = 4096 * npages;

  int fd = open("/dev/sg0", O_RDONLY);
  if (fd == -1) {
    fprintf(stderr, "open failed!\n");
    return 1;
  }

  char *out_buf = calloc(1, buf_size);
  if (!out_buf) {
    fprintf(stderr, "calloc failed!\n");
    return 1;
  }

  char cmd[CMD_SIZE] = {};
  struct sg_io_hdr hdr;
  memset(&hdr, 0, sizeof(hdr));
  hdr.interface_id = 'S';
  hdr.dxfer_direction = SG_DXFER_FROM_DEV;
  hdr.cmd_len = CMD_SIZE;
  hdr.dxfer_len = buf_size;
  hdr.dxferp = out_buf;
  hdr.cmdp = cmd;

  int ret = ioctl(fd, SG_IO, &hdr);
  if (ret == -1) {
    fprintf(stderr, "ioctl failed!\n");
  }
  dump_buf(out_buf, buf_size);
  return 0;
}