neovim/src/nvim/tempfile.c

#include <inttypes.h>
#include <stdbool.h>
#include <stdlib.h>
#include <stdio.h>

#include "nvim/ascii.h"
#include "nvim/memory.h"
#include "nvim/misc1.h"
#include "nvim/os/os.h"
#include "nvim/os/os_defs.h"
#include "nvim/path.h"
#include "nvim/strings.h"
#include "nvim/tempfile.h"

#ifdef INCLUDE_GENERATED_DECLARATIONS
# include "tempfile.c.generated.h"
#endif

/// Name of Vim's own temp dir. Ends in a slash.
static char_u *vim_tempdir = NULL;

/// Create a directory for private use by this instance of Neovim.
/// This is done once, and the same directory is used for all temp files.
/// This method avoids security problems because of symlink attacks et al.
/// It's also a bit faster, because we only need to check for an existing
/// file when creating the directory and not for each temp file.
static void vim_maketempdir(void)
{
  static const char *temp_dirs[] = TEMP_DIR_NAMES;
  // Try the entries in `TEMP_DIR_NAMES` to create the temp directory.
  char_u template[TEMP_FILE_PATH_MAXLEN];
  char_u path[TEMP_FILE_PATH_MAXLEN];
  for (size_t i = 0; i < ARRAY_SIZE(temp_dirs); ++i) {
    // Expand environment variables, leave room for "/nvimXXXXXX/999999999"
    expand_env((char_u *)temp_dirs[i], template, TEMP_FILE_PATH_MAXLEN - 22);
    if (!os_isdir(template)) {  // directory doesn't exist
      continue;
    }

    add_pathsep(template);
    // Concatenate with temporary directory name pattern
    STRCAT(template, "nvimXXXXXX");

    if (os_mkdtemp((const char *)template, (char *)path) != 0) {
      continue;
    }

    if (vim_settempdir(path)) {
      // Successfully created and set temporary directory so stop trying.
      break;
    } else {
      // Couldn't set `vim_tempdir` to `path` so remove created directory.
      os_rmdir((char *)path);
    }
  }
}

/// Delete the temp directory and all files it contains.
void vim_deltempdir(void)
{
  if (vim_tempdir != NULL) {
    snprintf((char *)NameBuff, MAXPATHL, "%s*", vim_tempdir);

    char_u **files;
    int file_count;

    // Note: We cannot just do `&NameBuff` because it is a statically
    //       sized array so `NameBuff == &NameBuff` according to C semantics.
    char_u *buff_list[1] = {(char_u*) NameBuff};
    if (gen_expand_wildcards(1, buff_list, &file_count, &files,
        EW_DIR|EW_FILE|EW_SILENT) == OK) {
      for (int i = 0; i < file_count; ++i) {
        os_remove((char *)files[i]);
      }
      FreeWild(file_count, files);
    }
    path_tail(NameBuff)[-1] = NUL;
    os_rmdir((char *)NameBuff);

    free(vim_tempdir);
    vim_tempdir = NULL;
  }
}

/// Get the name of temp directory. This directory would be created on the first
/// call to this function.
char_u *vim_gettempdir(void)
{
  if (vim_tempdir == NULL) {
    vim_maketempdir();
  }

  return vim_tempdir;
}

/// Set Neovim own temporary directory name to `tempdir`. This directory should
/// be already created. Expand this name to a full path and put it in
/// `vim_tempdir`. This avoids that using `:cd` would confuse us.
///
/// @param tempdir must be no longer than MAXPATHL.
///
/// @return false if we run out of memory.
static bool vim_settempdir(char_u *tempdir)
{
  char_u *buf = verbose_try_malloc((size_t)MAXPATHL + 2);
  if (!buf) {
    return false;
  }
  vim_FullName(tempdir, buf, MAXPATHL, false);
  add_pathsep(buf);
  vim_tempdir = vim_strsave(buf);
  free(buf);
  return true;
}

/// Return a unique name that can be used for a temp file.
///
/// @note The temp file is NOT created.
///
/// @return pointer to the temp file name or NULL if Neovim can't create
///         temporary directory for its own temporary files.
char_u *vim_tempname(void)
{
  // Temp filename counter.
  static uint32_t temp_count;

  char_u *tempdir = vim_gettempdir();
  if (!tempdir) {
    return NULL;
  }

  // There is no need to check if the file exists, because we own the directory
  // and nobody else creates a file in it.
  char_u template[TEMP_FILE_PATH_MAXLEN];
  snprintf((char *)template, TEMP_FILE_PATH_MAXLEN,
           "%s%" PRIu32, tempdir, temp_count++);
  return vim_strsave(template);
}