mongoose.c

      to_read = (int) len;
    }

    // Read from file, exit the loop on error
    if ((num_read = fread(buf, 1, (size_t) to_read, fp)) <= 0) {
      break;
    }

    // Send read bytes to the client, exit the loop on error
    if ((num_written = mg_write(conn, buf, (size_t) num_read)) != num_read) {
      break;
    }

    // Both read and were successful, adjust counters
    conn->num_bytes_sent += num_written;
    len -= num_written;
  }
}


static int forward_body_data(struct mg_connection *conn, FILE *fp,
                             SOCKET sock, SSL *ssl) {
  const char *expect, *body;
  char buf[MG_BUF_LEN];
  int nread, buffered_len, success = 0;
  int64_t left;

  expect = mg_get_header(conn, "Expect");
  assert(fp != NULL);

  if (conn->content_len == INT64_MAX) {
    send_http_error(conn, 411, "Length Required", "%s", "");
  } else if (expect != NULL && mg_strcasecmp(expect, "100-continue")) {
    send_http_error(conn, 417, "Expectation Failed", "%s", "");
  } else {
    if (expect != NULL) {
      (void) mg_printf(conn, "%s", "HTTP/1.1 100 Continue\r\n\r\n");
    }

    buffered_len = conn->data_len - conn->request_len;
    body = conn->buf + conn->request_len;
    assert(buffered_len >= 0);

    if (buffered_len > 0) {
      if ((int64_t) buffered_len > conn->content_len) {
        buffered_len = (int) conn->content_len;
      }
      push(fp, sock, ssl, body, (int64_t) buffered_len);
      memmove((char *) body, body + buffered_len, buffered_len);
      conn->data_len -= buffered_len;
    }

    nread = 0;
    while (conn->num_bytes_read < conn->content_len + conn->request_len) {
      left = left_to_read(conn);
      if (left > (int64_t) sizeof(buf)) {
        left = sizeof(buf);
      }
      nread = pull(NULL, conn, buf, (int) left);
      if (nread <= 0 || push(fp, sock, ssl, buf, nread) != nread) {
        break;
      }
    }

    if (left_to_read(conn) == 0) {
      success = nread >= 0;
    }

    // Each error code path in this function must send an error
    if (!success) {
      send_http_error(conn, 577, http_500_error, "%s", "");
    }
  }

  return success;
}


#if !defined(NO_CGI)
// This structure helps to create an environment for the spawned CGI program.
// Environment is an array of "VARIABLE=VALUE\0" ASCIIZ strings,
// last element must be NULL.
// However, on Windows there is a requirement that all these VARIABLE=VALUE\0
// strings must reside in a contiguous buffer. The end of the buffer is
// marked by two '\0' characters.
// We satisfy both worlds: we create an envp array (which is vars), all
// entries are actually pointers inside buf.
struct cgi_env_block {
  struct mg_connection *conn;
  char buf[CGI_ENVIRONMENT_SIZE]; // Environment buffer
  int len; // Space taken
  char *vars[MAX_CGI_ENVIR_VARS]; // char **envp
  int nvars; // Number of variables
};

static char *addenv(struct cgi_env_block *block,
                    PRINTF_FORMAT_STRING(const char *fmt), ...)
  PRINTF_ARGS(2, 3);

// Append VARIABLE=VALUE\0 string to the buffer, and add a respective
// pointer into the vars array.
static char *addenv(struct cgi_env_block *block, const char *fmt, ...) {
  int n, space;
  char *added;
  va_list ap;

  // Calculate how much space is left in the buffer
  space = sizeof(block->buf) - block->len - 2;
  assert(space >= 0);

  // Make a pointer to the free space int the buffer
  added = block->buf + block->len;

  // Copy VARIABLE=VALUE\0 string into the free space
  va_start(ap, fmt);
  n = mg_vsnprintf(added, (size_t) space, fmt, ap);
  va_end(ap);

  // Make sure we do not overflow buffer and the envp array
  if (n > 0 && n + 1 < space &&
      block->nvars < (int) ARRAY_SIZE(block->vars) - 2) {
    // Append a pointer to the added string into the envp array
    block->vars[block->nvars++] = added;
    // Bump up used length counter. Include \0 terminator
    block->len += n + 1;
  } else {
    cry(block->conn, "%s: CGI env buffer truncated for [%s]", __func__, fmt);
  }

  return added;
}

static void prepare_cgi_environment(struct mg_connection *conn,
                                    const char *prog,
                                    struct cgi_env_block *blk) {
  const struct mg_request_info *ri = &conn->request_info;
  const char *s, *slash;
  struct vec var_vec;
  char *p, src_addr[IP_ADDR_STR_LEN];
  int  i;

  blk->len = blk->nvars = 0;
  blk->conn = conn;
  sockaddr_to_string(src_addr, sizeof(src_addr), &conn->client.rsa);

  addenv(blk, "SERVER_NAME=%s", conn->ctx->config[AUTHENTICATION_DOMAIN]);
  addenv(blk, "SERVER_ROOT=%s", conn->ctx->config[DOCUMENT_ROOT]);
  addenv(blk, "DOCUMENT_ROOT=%s", conn->ctx->config[DOCUMENT_ROOT]);
  addenv(blk, "SERVER_SOFTWARE=%s/%s", "Mongoose", mg_version());

  // Prepare the environment block
  addenv(blk, "%s", "GATEWAY_INTERFACE=CGI/1.1");
  addenv(blk, "%s", "SERVER_PROTOCOL=HTTP/1.1");
  addenv(blk, "%s", "REDIRECT_STATUS=200"); // For PHP

  // TODO(lsm): fix this for IPv6 case
  addenv(blk, "SERVER_PORT=%d", ntohs(conn->client.lsa.sin.sin_port));

  addenv(blk, "REQUEST_METHOD=%s", ri->request_method);
  addenv(blk, "REMOTE_ADDR=%s", src_addr);
  addenv(blk, "REMOTE_PORT=%d", ri->remote_port);
  addenv(blk, "REQUEST_URI=%s%s%s", ri->uri,
         ri->query_string == NULL ? "" : "?",
         ri->query_string == NULL ? "" : ri->query_string);

  // SCRIPT_NAME
  if (conn->path_info != NULL) {
    addenv(blk, "SCRIPT_NAME=%.*s",
           (int) (strlen(ri->uri) - strlen(conn->path_info)), ri->uri);
    addenv(blk, "PATH_INFO=%s", conn->path_info);
  } else {
    s = strrchr(prog, '/');
    slash = strrchr(ri->uri, '/');
    addenv(blk, "SCRIPT_NAME=%.*s%s",
           slash == NULL ? 0 : (int) (slash - ri->uri), ri->uri,
           s == NULL ? prog : s);
  }

  addenv(blk, "SCRIPT_FILENAME=%s", prog);
  addenv(blk, "PATH_TRANSLATED=%s", prog);
  addenv(blk, "HTTPS=%s", conn->ssl == NULL ? "off" : "on");

  if ((s = mg_get_header(conn, "Content-Type")) != NULL)
    addenv(blk, "CONTENT_TYPE=%s", s);

  if (ri->query_string != NULL) {
    addenv(blk, "QUERY_STRING=%s", ri->query_string);
  }

  if ((s = mg_get_header(conn, "Content-Length")) != NULL)
    addenv(blk, "CONTENT_LENGTH=%s", s);

  if ((s = getenv("PATH")) != NULL)
    addenv(blk, "PATH=%s", s);

#if defined(_WIN32)
  if ((s = getenv("COMSPEC")) != NULL) {
    addenv(blk, "COMSPEC=%s", s);
  }
  if ((s = getenv("SYSTEMROOT")) != NULL) {
    addenv(blk, "SYSTEMROOT=%s", s);
  }
  if ((s = getenv("SystemDrive")) != NULL) {
    addenv(blk, "SystemDrive=%s", s);
  }
  if ((s = getenv("ProgramFiles")) != NULL) {
    addenv(blk, "ProgramFiles=%s", s);
  }
  if ((s = getenv("ProgramFiles(x86)")) != NULL) {
    addenv(blk, "ProgramFiles(x86)=%s", s);
  }
  if ((s = getenv("CommonProgramFiles(x86)")) != NULL) {
    addenv(blk, "CommonProgramFiles(x86)=%s", s);
  }
#else
  if ((s = getenv("LD_LIBRARY_PATH")) != NULL)
    addenv(blk, "LD_LIBRARY_PATH=%s", s);
#endif // _WIN32

  if ((s = getenv("PERLLIB")) != NULL)
    addenv(blk, "PERLLIB=%s", s);

  if (ri->remote_user != NULL) {
    addenv(blk, "REMOTE_USER=%s", ri->remote_user);
    addenv(blk, "%s", "AUTH_TYPE=Digest");
  }

  // Add all headers as HTTP_* variables
  for (i = 0; i < ri->num_headers; i++) {
    p = addenv(blk, "HTTP_%s=%s",
        ri->http_headers[i].name, ri->http_headers[i].value);

    // Convert variable name into uppercase, and change - to _
    for (; *p != '=' && *p != '\0'; p++) {
      if (*p == '-')
        *p = '_';
      *p = (char) toupper(* (unsigned char *) p);
    }
  }

  // Add user-specified variables
  s = conn->ctx->config[CGI_ENVIRONMENT];
  while ((s = next_option(s, &var_vec, NULL)) != NULL) {
    addenv(blk, "%.*s", (int) var_vec.len, var_vec.ptr);
  }

  blk->vars[blk->nvars++] = NULL;
  blk->buf[blk->len++] = '\0';

  assert(blk->nvars < (int) ARRAY_SIZE(blk->vars));
  assert(blk->len > 0);
  assert(blk->len < (int) sizeof(blk->buf));
}

static void handle_cgi_request(struct mg_connection *conn, const char *prog) {
  int headers_len, data_len, i, fdin[2] = {-1, -1}, fdout[2] = {-1, -1};
  const char *status, *status_text;
  char buf[16384], *pbuf, dir[PATH_MAX], *p;
  struct mg_request_info ri;
  struct cgi_env_block blk;
  FILE *in = NULL, *out = NULL;
  pid_t pid = (pid_t) -1;

  memset(&ri, 0, sizeof(ri));
  prepare_cgi_environment(conn, prog, &blk);

  // CGI must be executed in its own directory. 'dir' must point to the
  // directory containing executable program, 'p' must point to the
  // executable program name relative to 'dir'.
  (void) mg_snprintf(dir, sizeof(dir), "%s", prog);
  if ((p = strrchr(dir, '/')) != NULL) {
    *p++ = '\0';
  } else {
    dir[0] = '.', dir[1] = '\0';
    p = (char *) prog;
  }

  if (pipe(fdin) != 0 || pipe(fdout) != 0) {
    send_http_error(conn, 500, http_500_error,
        "Cannot create CGI pipe: %s", strerror(ERRNO));
    goto done;
  }

  pid = spawn_process(conn, p, blk.buf, blk.vars, fdin[0], fdout[1], dir);
  if (pid == (pid_t) -1) {
    send_http_error(conn, 500, http_500_error,
        "Cannot spawn CGI process [%s]: %s", prog, strerror(ERRNO));
    goto done;
  }

  // Make sure child closes all pipe descriptors. It must dup them to 0,1
  set_close_on_exec(fdin[0]);
  set_close_on_exec(fdin[1]);
  set_close_on_exec(fdout[0]);
  set_close_on_exec(fdout[1]);

  // Parent closes only one side of the pipes.
  // If we don't mark them as closed, close() attempt before
  // return from this function throws an exception on Windows.
  // Windows does not like when closed descriptor is closed again.
  (void) close(fdin[0]);
  (void) close(fdout[1]);
  fdin[0] = fdout[1] = -1;


  if ((in = fdopen(fdin[1], "wb")) == NULL ||
      (out = fdopen(fdout[0], "rb")) == NULL) {
    send_http_error(conn, 500, http_500_error,
        "fopen: %s", strerror(ERRNO));
    goto done;
  }

  setbuf(in, NULL);
  setbuf(out, NULL);

  // Send POST data to the CGI process if needed
  if (!strcmp(conn->request_info.request_method, "POST") &&
      !forward_body_data(conn, in, INVALID_SOCKET, NULL)) {
    goto done;
  }

  // Close so child gets an EOF.
  fclose(in);
  in = NULL;
  fdin[1] = -1;

  // Now read CGI reply into a buffer. We need to set correct
  // status code, thus we need to see all HTTP headers first.
  // Do not send anything back to client, until we buffer in all
  // HTTP headers.
  data_len = 0;
  headers_len = read_request(out, conn, buf, sizeof(buf), &data_len);
  if (headers_len <= 0) {
    send_http_error(conn, 500, http_500_error,
                    "CGI program sent malformed or too big (>%u bytes) "
                    "HTTP headers: [%.*s]",
                    (unsigned) sizeof(buf), data_len, buf);
    goto done;
  }
  pbuf = buf;
  buf[headers_len - 1] = '\0';
  parse_http_headers(&pbuf, &ri);

  // Make up and send the status line
  status_text = "OK";
  if ((status = get_header(&ri, "Status")) != NULL) {
    conn->status_code = atoi(status);
    status_text = status;
    while (isdigit(* (unsigned char *) status_text) || *status_text == ' ') {
      status_text++;
    }
  } else if (get_header(&ri, "Location") != NULL) {
    conn->status_code = 302;
  } else {
    conn->status_code = 200;
  }
  if (get_header(&ri, "Connection") != NULL &&
      !mg_strcasecmp(get_header(&ri, "Connection"), "keep-alive")) {
    conn->must_close = 1;
  }
  (void) mg_printf(conn, "HTTP/1.1 %d %s\r\n", conn->status_code,
                   status_text);

  // Send headers
  for (i = 0; i < ri.num_headers; i++) {
    mg_printf(conn, "%s: %s\r\n",
              ri.http_headers[i].name, ri.http_headers[i].value);
  }
  mg_write(conn, "\r\n", 2);

  // Send chunk of data that may have been read after the headers
  conn->num_bytes_sent += mg_write(conn, buf + headers_len,
                                   (size_t)(data_len - headers_len));

  // Read the rest of CGI output and send to the client
  send_file_data(conn, out, 0, INT64_MAX);

done:
  if (pid != (pid_t) -1) {
    kill(pid, SIGKILL);
  }
  if (fdin[0] != -1) {
    close(fdin[0]);
  }
  if (fdout[1] != -1) {
    close(fdout[1]);
  }

  if (in != NULL) {
    fclose(in);
  } else if (fdin[1] != -1) {
    close(fdin[1]);
  }

  if (out != NULL) {
    fclose(out);
  } else if (fdout[0] != -1) {
    close(fdout[0]);
  }
}
#endif // !NO_CGI


FILE *mg_upload(struct mg_connection *conn, const char *destination_dir,
                char *path, int path_len) {
  const char *content_type_header, *boundary_start;
  char *buf, fname[1024], boundary[100], *s;
  int bl, n, i, j, headers_len, boundary_len, eof, buf_len, to_read, len = 0;
  FILE *fp;

  // Request looks like this:
  //
  // POST /upload HTTP/1.1
  // Host: 127.0.0.1:8080
  // Content-Length: 244894
  // Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryRVr
  //
  // ------WebKitFormBoundaryRVr
  // Content-Disposition: form-data; name="file"; filename="accum.png"
  // Content-Type: image/png
  //
  //  <89>PNG
  //  <PNG DATA>
  // ------WebKitFormBoundaryRVr

  // Extract boundary string from the Content-Type header
  if ((content_type_header = mg_get_header(conn, "Content-Type")) == NULL ||
      (boundary_start = mg_strcasestr(content_type_header,
                                      "boundary=")) == NULL ||
      (sscanf(boundary_start, "boundary=\"%99[^\"]\"", boundary) == 0 &&
       sscanf(boundary_start, "boundary=%99s", boundary) == 0) ||
      boundary[0] == '\0') {
    return NULL;
  }

  boundary_len = strlen(boundary);
  bl = boundary_len + 4;  // \r\n--<boundary>

  //                     buf
  // conn->buf            |<--------- buf_len ------>|
  //    |=================|==========|===============|
  //    |<--request_len-->|<--len--->|               |
  //    |<-----------data_len------->|      conn->buf + conn->buf_size

  buf = conn->buf + conn->request_len;
  buf_len = conn->buf_size - conn->request_len;
  len = conn->data_len - conn->request_len;

  for (;;) {
    // Pull in headers
    assert(len >= 0 && len <= buf_len);
    to_read = buf_len - len;
    if (to_read > left_to_read(conn)) {
      to_read = (int) left_to_read(conn);
    }
    while (len < buf_len &&
           (n = pull(NULL, conn, buf + len, to_read)) > 0) {
      len += n;
    }
    if ((headers_len = get_request_len(buf, len)) <= 0) {
      break;
    }

    // Fetch file name.
    fname[0] = '\0';
    for (i = j = 0; i < headers_len; i++) {
      if (buf[i] == '\r' && buf[i + 1] == '\n') {
        buf[i] = buf[i + 1] = '\0';
        // TODO(lsm): don't expect filename to be the 3rd field,
        // parse the header properly instead.
        sscanf(&buf[j], "Content-Disposition: %*s %*s filename=\"%1023[^\"]",
               fname);
        j = i + 2;
      }
    }

    // Give up if the headers are not what we expect
    if (fname[0] == '\0') {
      break;
    }

    // Move data to the beginning of the buffer
    assert(len >= headers_len);
    memmove(buf, &buf[headers_len], len - headers_len);
    len -= headers_len;
    conn->data_len = conn->request_len + len;

    // We open the file with exclusive lock held. This guarantee us
    // there is no other thread can save into the same file simultaneously.
    fp = NULL;

    // Construct destination file name. Do not allow paths to have slashes.
    if ((s = strrchr(fname, '/')) == NULL &&
        (s = strrchr(fname, '\\')) == NULL) {
      s = fname;
    }

    // Open file in binary mode. TODO: set an exclusive lock.
    snprintf(path, path_len, "%s/%s", destination_dir, s);
    if ((fp = fopen(path, "wb")) == NULL) {
      break;
    }

    // Read POST data, write into file until boundary is found.
    eof = n = 0;
    do {
      len += n;
      for (i = 0; i < len - bl; i++) {
        if (!memcmp(&buf[i], "\r\n--", 4) &&
            !memcmp(&buf[i + 4], boundary, boundary_len)) {
          // Found boundary, that's the end of file data.
          fwrite(buf, 1, i, fp);
          eof = 1;
          memmove(buf, &buf[i + bl], len - (i + bl));
          len -= i + bl;
          break;
        }
      }
      if (!eof && len > bl) {
        fwrite(buf, 1, len - bl, fp);
        memmove(buf, &buf[len - bl], bl);
        len = bl;
      }
      to_read = buf_len - len;
      if (to_read > left_to_read(conn)) {
        to_read = (int) left_to_read(conn);
      }
    } while (!eof && (n = pull(NULL, conn, buf + len, to_read)) > 0);
    conn->data_len = conn->request_len + len;

    if (eof) {
      rewind(fp);
      return fp;
    } else {
      fclose(fp);
    }
  }

  return NULL;
}



static int call_user(int type, struct mg_connection *conn, void *p) {
  if (conn != NULL && conn->ctx != NULL) {
    conn->event.user_data = conn->ctx->user_data;
    conn->event.type = type;
    conn->event.event_param = p;
    conn->event.request_info = &conn->request_info;
    conn->event.conn = conn;
  }
  return conn == NULL || conn->ctx == NULL || conn->ctx->event_handler == NULL ?
    0 : conn->ctx->event_handler(&conn->event);
}

static FILE *mg_fopen(const char *path, const char *mode) {
#ifdef _WIN32
  wchar_t wbuf[PATH_MAX], wmode[20];
  to_unicode(path, wbuf, ARRAY_SIZE(wbuf));
  MultiByteToWideChar(CP_UTF8, 0, mode, -1, wmode, ARRAY_SIZE(wmode));
  return _wfopen(wbuf, wmode);
#else
  return fopen(path, mode);
#endif
}

// Print error message to the opened error log stream.
static void cry(struct mg_connection *conn, const char *fmt, ...) {
  char buf[MG_BUF_LEN], src_addr[IP_ADDR_STR_LEN];
  va_list ap;
  FILE *fp;
  time_t timestamp;

  va_start(ap, fmt);
  (void) vsnprintf(buf, sizeof(buf), fmt, ap);
  va_end(ap);

  // Do not lock when getting the callback value, here and below.
  // I suppose this is fine, since function cannot disappear in the
  // same way string option can.
  if (call_user(MG_EVENT_LOG, conn, buf) == 0) {
    fp = conn->ctx == NULL || conn->ctx->config[ERROR_LOG_FILE] == NULL ? NULL :
      fopen(conn->ctx->config[ERROR_LOG_FILE], "a+");

    if (fp != NULL) {
      flockfile(fp);
      timestamp = time(NULL);

      sockaddr_to_string(src_addr, sizeof(src_addr), &conn->client.rsa);
      fprintf(fp, "[%010lu] [error] [client %s] ", (unsigned long) timestamp,
              src_addr);

      if (conn->request_info.request_method != NULL) {
        fprintf(fp, "%s %s: ", conn->request_info.request_method,
                conn->request_info.uri);
      }

      fprintf(fp, "%s", buf);
      fputc('\n', fp);
      funlockfile(fp);
      fclose(fp);
    }
  }
}

const char *mg_version(void) {
  return MONGOOSE_VERSION;
}

// HTTP 1.1 assumes keep alive if "Connection:" header is not set
// This function must tolerate situations when connection info is not
// set up, for example if request parsing failed.
static int should_keep_alive(const struct mg_connection *conn) {
  const char *http_version = conn->request_info.http_version;
  const char *header = mg_get_header(conn, "Connection");
  if (conn->must_close ||
      conn->status_code == 401 ||
      mg_strcasecmp(conn->ctx->config[ENABLE_KEEP_ALIVE], "yes") != 0 ||
      (header != NULL && mg_strcasecmp(header, "keep-alive") != 0) ||
      (header == NULL && http_version && strcmp(http_version, "1.1"))) {
    return 0;
  }
  return 1;
}

static const char *suggest_connection_header(const struct mg_connection *conn) {
  return should_keep_alive(conn) ? "keep-alive" : "close";
}

static void send_http_error(struct mg_connection *conn, int status,
                            const char *reason, const char *fmt, ...) {
  char buf[MG_BUF_LEN];
  va_list ap;
  int len = 0;

  conn->status_code = status;
  buf[0] = '\0';

  // Errors 1xx, 204 and 304 MUST NOT send a body
  if (status > 199 && status != 204 && status != 304) {
    len = mg_snprintf(buf, sizeof(buf), "Error %d: %s", status, reason);
    buf[len++] = '\n';

    va_start(ap, fmt);
    len += mg_vsnprintf(buf + len, sizeof(buf) - len, fmt, ap);
    va_end(ap);
  }
  DEBUG_TRACE(("[%s]", buf));

  if (call_user(MG_HTTP_ERROR, conn, (void *) (long) status) == 0) {
    mg_printf(conn, "HTTP/1.1 %d %s\r\n"
              "Content-Length: %d\r\n"
              "Connection: %s\r\n\r\n", status, reason, len,
              suggest_connection_header(conn));
    conn->num_bytes_sent += mg_printf(conn, "%s", buf);
  }
}

// Return 1 if real file has been found, 0 otherwise
static int convert_uri_to_file_name(struct mg_connection *conn, char *buf,
                                    size_t buf_len, struct file *filep) {
  struct vec a, b;
  const char *rewrite, *uri = conn->request_info.uri,
        *root = conn->ctx->config[DOCUMENT_ROOT];
  char *p;
  int match_len;
  char gz_path[PATH_MAX];
  char const* accept_encoding;

  // No filesystem access
  if (root == NULL) {
    return 0;
  }

  // Using buf_len - 1 because memmove() for PATH_INFO may shift part
  // of the path one byte on the right.
  // If document_root is NULL, leave the file empty.
  mg_snprintf(buf, buf_len - 1, "%s%s", root, uri);

  rewrite = conn->ctx->config[REWRITE];
  while ((rewrite = next_option(rewrite, &a, &b)) != NULL) {
    if ((match_len = match_prefix(a.ptr, a.len, uri)) > 0) {
      mg_snprintf(buf, buf_len - 1, "%.*s%s", (int) b.len, b.ptr,
                  uri + match_len);
      break;
    }
  }

  if (mg_stat(buf, filep)) {
    return 1;
  }

  // if we can't find the actual file, look for the file
  // with the same name but a .gz extension. If we find it,
  // use that and set the gzipped flag in the file struct
  // to indicate that the response need to have the content-
  // encoding: gzip header
  // we can only do this if the browser declares support
  if ((accept_encoding = mg_get_header(conn, "Accept-Encoding")) != NULL) {
    if (strstr(accept_encoding,"gzip") != NULL) {
      snprintf(gz_path, sizeof(gz_path), "%s.gz", buf);
      if (mg_stat(gz_path, filep)) {
        filep->gzipped = 1;
        return 1;
      }
    }
  }

  // Support PATH_INFO for CGI scripts.
  for (p = buf + strlen(root == NULL ? "" : root); *p != '\0'; p++) {
    if (*p == '/') {
      *p = '\0';
      if (match_prefix(conn->ctx->config[CGI_EXTENSIONS],
                       strlen(conn->ctx->config[CGI_EXTENSIONS]), buf) > 0 &&
          mg_stat(buf, filep)) {
        // Shift PATH_INFO block one character right, e.g.
        //  "/x.cgi/foo/bar\x00" => "/x.cgi\x00/foo/bar\x00"
        // conn->path_info is pointing to the local variable "path" declared
        // in handle_request(), so PATH_INFO is not valid after
        // handle_request returns.
        conn->path_info = p + 1;
        memmove(p + 2, p + 1, strlen(p + 1) + 1);  // +1 is for trailing \0
        p[1] = '/';
        return 1;
      } else {
        *p = '/';
      }
    }
  }

  return 0;
}

static void gmt_time_string(char *buf, size_t buf_len, time_t *t) {
  strftime(buf, buf_len, "%a, %d %b %Y %H:%M:%S GMT", gmtime(t));
}

static void construct_etag(char *buf, size_t buf_len,
                           const struct file *filep) {
  snprintf(buf, buf_len, "\"%lx.%" INT64_FMT "\"",
           (unsigned long) filep->modification_time, filep->size);
}

static void fclose_on_exec(FILE *fp) {
  if (fp != NULL) {
#ifndef _WIN32
    fcntl(fileno(fp), F_SETFD, FD_CLOEXEC);
#endif
  }
}

static void handle_file_request(struct mg_connection *conn, const char *path,
                                struct file *filep) {
  char date[64], lm[64], etag[64], range[64];
  const char *msg = "OK", *hdr;
  time_t curtime = time(NULL);
  int64_t cl, r1, r2;
  struct vec mime_vec;
  int n;
  char gz_path[PATH_MAX];
  char const* encoding = "";
  FILE *fp;

  get_mime_type(conn->ctx, path, &mime_vec);
  cl = filep->size;
  conn->status_code = 200;
  range[0] = '\0';

  // if this file is in fact a pre-gzipped file, rewrite its filename
  // it's important to rewrite the filename after resolving
  // the mime type from it, to preserve the actual file's type
  if (filep->gzipped) {
    snprintf(gz_path, sizeof(gz_path), "%s.gz", path);
    path = gz_path;
    encoding = "Content-Encoding: gzip\r\n";
  }

  if ((fp = mg_fopen(path, "rb")) == NULL) {
    send_http_error(conn, 500, http_500_error,
                    "fopen(%s): %s", path, strerror(ERRNO));
    return;
  }

  fclose_on_exec(fp);

  // If Range: header specified, act accordingly
  r1 = r2 = 0;
  hdr = mg_get_header(conn, "Range");
  if (hdr != NULL && (n = parse_range_header(hdr, &r1, &r2)) > 0 &&
      r1 >= 0 && r2 >= 0) {
    // actually, range requests don't play well with a pre-gzipped
    // file (since the range is specified in the uncmpressed space)
    if (filep->gzipped) {
      send_http_error(conn, 501, "Not Implemented",
                      "range requests in gzipped files are not supported");
      return;
    }
    conn->status_code = 206;
    cl = n == 2 ? (r2 > cl ? cl : r2) - r1 + 1: cl - r1;
    mg_snprintf(range, sizeof(range),
                "Content-Range: bytes "
                "%" INT64_FMT "-%"
                INT64_FMT "/%" INT64_FMT "\r\n",
                r1, r1 + cl - 1, filep->size);
    msg = "Partial Content";
  }

  // Prepare Etag, Date, Last-Modified headers. Must be in UTC, according to
  // http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html#sec3.3
  gmt_time_string(date, sizeof(date), &curtime);
  gmt_time_string(lm, sizeof(lm), &filep->modification_time);
  construct_etag(etag, sizeof(etag), filep);

  (void) mg_printf(conn,
      "HTTP/1.1 %d %s\r\n"
      "Date: %s\r\n"
      "Last-Modified: %s\r\n"
      "Etag: %s\r\n"
      "Content-Type: %.*s\r\n"
      "Content-Length: %" INT64_FMT "\r\n"
      "Connection: %s\r\n"
      "Accept-Ranges: bytes\r\n"
      "%s%s%s\r\n",
      conn->status_code, msg, date, lm, etag, (int) mime_vec.len,
      mime_vec.ptr, cl, suggest_connection_header(conn), range, encoding,
      EXTRA_HTTP_HEADERS);

  if (strcmp(conn->request_info.request_method, "HEAD") != 0) {
    send_file_data(conn, fp, r1, cl);
  }
  fclose(fp);
}

void mg_send_file(struct mg_connection *conn, const char *path) {
  struct file file = STRUCT_FILE_INITIALIZER;
  if (mg_stat(path, &file)) {
    handle_file_request(conn, path, &file);
  } else {
    send_http_error(conn, 404, "Not Found", "%s", "File not found");
  }
}

// For given directory path, substitute it to valid index file.
// Return 0 if index file has been found, -1 if not found.
// If the file is found, it's stats is returned in stp.
static int substitute_index_file(struct mg_connection *conn, char *path,
                                 size_t path_len, struct file *filep) {
  const char *list = conn->ctx->config[INDEX_FILES];
  struct file file = STRUCT_FILE_INITIALIZER;
  struct vec filename_vec;
  size_t n = strlen(path);
  int found = 0;

  // The 'path' given to us points to the directory. Remove all trailing
  // directory separator characters from the end of the path, and
  // then append single directory separator character.
  while (n > 0 && path[n - 1] == '/') {
    n--;
  }
  path[n] = '/';

  // Traverse index files list. For each entry, append it to the given
  // path and see if the file exists. If it exists, break the loop
  while ((list = next_option(list, &filename_vec, NULL)) != NULL) {

    // Ignore too long entries that may overflow path buffer
    if (filename_vec.len > path_len - (n + 2))
      continue;

    // Prepare full path to the index file
    mg_strlcpy(path + n + 1, filename_vec.ptr, filename_vec.len + 1);

    // Does it exist?
    if (mg_stat(path, &file)) {
      // Yes it does, break the loop
      *filep = file;
      found = 1;
      break;
    }
  }

  // If no index file exists, restore directory path
  if (!found) {
    path[n] = '\0';
  }

  return found;
}

// Return True if we should reply 304 Not Modified.
static int is_not_modified(const struct mg_connection *conn,
                           const struct file *filep) {
  char etag[64];
  const char *ims = mg_get_header(conn, "If-Modified-Since");
  const char *inm = mg_get_header(conn, "If-None-Match");
  construct_etag(etag, sizeof(etag), filep);
  return (inm != NULL && !mg_strcasecmp(etag, inm)) ||
    (ims != NULL && filep->modification_time <= parse_date_string(ims));
}

static void mkcol(struct mg_connection *conn, const char *path) {
  int rc, body_len;
  struct de de;

  memset(&de.file, 0, sizeof(de.file));
  mg_stat(path, &de.file);

  if (de.file.modification_time) {
      send_http_error(conn, 405, "Method Not Allowed",
                      "mkcol(%s): %s", path, strerror(ERRNO));
      return;
  }

  body_len = conn->data_len - conn->request_len;
  if(body_len > 0) {
      send_http_error(conn, 415, "Unsupported media type",
                      "mkcol(%s): %s", path, strerror(ERRNO));
      return;
  }

  rc = mg_mkdir(path, 0755);

  if (rc == 0) {
    conn->status_code = 201;
    mg_printf(conn, "HTTP/1.1 %d Created\r\n\r\n", conn->status_code);
  } else if (rc == -1) {
      if(errno == EEXIST)
        send_http_error(conn, 405, "Method Not Allowed",
                      "mkcol(%s): %s", path, strerror(ERRNO));
      else if(errno == EACCES)
          send_http_error(conn, 403, "Forbidden",
                        "mkcol(%s): %s", path, strerror(ERRNO));
      else if(errno == ENOENT)
          send_http_error(conn, 409, "Conflict",
                        "mkcol(%s): %s", path, strerror(ERRNO));
      else
          send_http_error(conn, 500, http_500_error,
                          "fopen(%s): %s", path, strerror(ERRNO));
  }
}

static void put_file(struct mg_connection *conn, const char *path) {
  struct file file = STRUCT_FILE_INITIALIZER;
  FILE *fp;
  const char *range;
  int64_t r1, r2;
  int rc;

  conn->status_code = mg_stat(path, &file) ? 200 : 201;

  if ((rc = put_dir(path)) == 0) {
    mg_printf(conn, "HTTP/1.1 %d OK\r\n\r\n", conn->status_code);
  } else if (rc == -1) {
    send_http_error(conn, 500, http_500_error,
                    "put_dir(%s): %s", path, strerror(ERRNO));
  } else if ((fp = mg_fopen(path, "wb+")) == NULL) {
    fclose(fp);
    send_http_error(conn, 500, http_500_error,
                    "fopen(%s): %s", path, strerror(ERRNO));
  } else {
    fclose_on_exec(fp);
    range = mg_get_header(conn, "Content-Range");
    r1 = r2 = 0;
    if (range != NULL && parse_range_header(range, &r1, &r2) > 0) {
      conn->status_code = 206;
      fseeko(fp, r1, SEEK_SET);
    }
    if (!forward_body_data(conn, fp, INVALID_SOCKET, NULL)) {
      conn->status_code = 500;
    }
    mg_printf(conn, "HTTP/1.1 %d OK\r\nContent-Length: 0\r\n\r\n",
              conn->status_code);
    fclose(fp);
  }
}

static void send_ssi_file(struct mg_connection *, const char *, FILE *, int);
static void do_ssi_include(struct mg_connection *conn, const char *ssi,
                           char *tag, int include_level) {
  char file_name[MG_BUF_LEN], path[PATH_MAX], *p;
  FILE *fp;

  // sscanf() is safe here, since send_ssi_file() also uses buffer
  // of size MG_BUF_LEN to get the tag. So strlen(tag) is always < MG_BUF_LEN.
  if (sscanf(tag, " virtual=\"%[^\"]\"", file_name) == 1) {
    // File name is relative to the webserver root
    (void) mg_snprintf(path, sizeof(path), "%s%c%s",
        conn->ctx->config[DOCUMENT_ROOT], '/', file_name);
  } else if (sscanf(tag, " abspath=\"%[^\"]\"", file_name) == 1) {
    // File name is relative to the webserver working directory
    // or it is absolute system path
    (void) mg_snprintf(path, sizeof(path), "%s", file_name);
  } else if (sscanf(tag, " file=\"%[^\"]\"", file_name) == 1 ||
             sscanf(tag, " \"%[^\"]\"", file_name) == 1) {
    // File name is relative to the currect document
    (void) mg_snprintf(path, sizeof(path), "%s", ssi);
    if ((p = strrchr(path, '/')) != NULL) {
      p[1] = '\0';
    }
    (void) mg_snprintf(path + strlen(path),