wchar_t filter hex

#include <stdio.h>
/* using fopen, fclose, fprintf, perror */
#include <wctype.h>
/* using iswxdigit */
#include <wchar.h>
/* using fputws, fgetws */
#include <stdlib.h>
/* using getenv */
#include <locale.h>
/* using setlocale */

static const char* LOG_FILE = "LogFile_ProxyBufferContents_FJ_small.html";
static const char* OUT_FILE = "LogFile_ProxyBufferContents_FJ_small_out.html";

#define BUF_SIZE 4096


static int is_hex_line(const wchar_t* buf)
{
  for(const wchar_t* pos = buf; ; ++pos) {
    switch(*pos) {
    case L'\r':
    case L'\n':
    case L'\0':
      /* return false on empty line, true otherwise */
      return pos != buf;
    default:
      if(! iswxdigit(*pos))
    return 0;
      break;
    }
  }
}

static void filter_file(FILE* input, FILE* output)
{
  wchar_t in_buf[BUF_SIZE];
  wchar_t* buf_alias = in_buf;
  while((buf_alias = fgetws(buf_alias, BUF_SIZE, input)) != NULL) {
    if(! is_hex_line(buf_alias))
      fputws(buf_alias, output);
  }
}

static void set_locale()
{
  const char* env = "LC_CTYPE";
  const char* val = getenv(env);
  if(! val) {
    val = "en_US.UTF8";
    fprintf(stderr, "Guessing locale as %s\n", val);
  }
  if(! setlocale(LC_CTYPE, val))
    fprintf(stderr, "Cannot set locate defined in %s. Continue anyway\n", env);
}

int main(void)
{
  set_locale();
  FILE* input = fopen(LOG_FILE, "r");
  if(! input)
    return 1;
  FILE* output = fopen(OUT_FILE, "w");
  if(! output)
    return 1;
  filter_file(input, output);
  if(ferror(input))
    perror("Input error");
  fclose(output);
  fclose(input);
}