mdbx: add mdbx_env_delete().

Resolves https://github.com/erthink/libmdbx/issues/119
Related to https://github.com/Kerollmops/heed/issues/58

Change-Id: Iec5bf5978e45bb6843f3ed8dd06ea4d34f2895cb

ChangeLog.md

@@ -11,6 +11,7 @@ TODO:
 
 Added features:
  - Provided package for [buildroot](https://buildroot.org/).
+ - Added `mdbx_env_delete()` for deletion an environment files in a proper and multiprocess-safe way.
 
 Fixes:
 

mdbx.h

@@ -1801,6 +1801,48 @@ LIBMDBX_API int mdbx_env_create(MDBX_env **penv);
 LIBMDBX_API int mdbx_env_open(MDBX_env *env, const char *pathname,
                               MDBX_env_flags_t flags, mdbx_mode_t mode);
 
+/** \brief Deletion modes for \ref mdbx_env_delete()
+ * \ingroup c_extra
+ * \see mdbx_env_delete() */
+enum MDBX_env_delete_mode_t {
+  /** \brief Just delete the environment's files and directory if any.
+   * \note On POSIX systems, processes already working with the database will
+   * continue to work without interference until it close the environment.
+   * \note On Windows, the behavior of `MDB_ENV_JUST_DELETE` is different
+   * because the system does not support deleting files that are currently
+   * memory mapped. */
+  MDBX_ENV_JUST_DELETE = 0,
+  /** Make sure that the environment is not being used by other processes,
+   * or return an error otherwise. */
+  MDBX_ENV_ENSURE_UNUSED = 1,
+  /** Wait until other processes closes the environment before deletion. */
+  MDBX_ENV_WAIT_FOR_UNUSED = 2,
+};
+#ifndef __cplusplus
+/** \c_extra c_statinfo */
+typedef enum MDBX_env_delete_mode_t MDBX_env_delete_mode_t;
+#endif
+
+/** \brief Delete the environment files in a proper and multiprocess-safe way.
+ * \ingroup c_extra
+ *
+ * \param [in] pathname  The pathname for the database or the directory in which
+ *                       the database files reside.
+ *
+ * \param [in] mode      Special deletion mode for the environment. This
+ *                       parameter must be set to one of the values described
+ *                       above in the \ref MDBX_env_delete_mode_t section.
+ *
+ * \note The \ref MDBX_ENV_JUST_DELETE don't supported on Windows since system
+ * unable to delete a memory-mapped files.
+ *
+ * \returns A non-zero error value on failure and 0 on success,
+ *          some possible errors are:
+ * \retval MDBX_RESULT_TRUE   No corresponding files or directories were found,
+ *                            so no deletion was performed. */
+LIBMDBX_API int mdbx_env_delete(const char *pathname,
+                                MDBX_env_delete_mode_t mode);
+
 /** \brief Copy an MDBX environment to the specified path, with options.
  * \ingroup c_extra
  *

src/core.c

@@ -10467,6 +10467,81 @@ __cold static int mdbx_handle_env_pathname(MDBX_handle_env_pathname *result,
   return MDBX_SUCCESS;
 }
 
+__cold int mdbx_env_delete(const char *pathname, MDBX_env_delete_mode_t mode) {
+  switch (mode) {
+  default:
+    return MDBX_EINVAL;
+  case MDBX_ENV_JUST_DELETE:
+  case MDBX_ENV_ENSURE_UNUSED:
+  case MDBX_ENV_WAIT_FOR_UNUSED:
+    break;
+  }
+
+  MDBX_env dummy_env;
+  memset(&dummy_env, 0, sizeof(dummy_env));
+  dummy_env.me_flags =
+      (mode == MDBX_ENV_ENSURE_UNUSED) ? MDBX_EXCLUSIVE : MDBX_ENV_DEFAULTS;
+  dummy_env.me_psize = dummy_env.me_os_psize = (unsigned)mdbx_syspagesize();
+  dummy_env.me_path = (char *)pathname;
+
+  MDBX_handle_env_pathname env_pathname;
+  STATIC_ASSERT(sizeof(dummy_env.me_flags) == sizeof(MDBX_env_flags_t));
+  int rc = MDBX_RESULT_TRUE,
+      err = mdbx_handle_env_pathname(
+          &env_pathname, pathname, (MDBX_env_flags_t *)&dummy_env.me_flags, 0);
+  if (likely(err == MDBX_SUCCESS)) {
+    mdbx_filehandle_t clk_handle = INVALID_HANDLE_VALUE,
+                      dxb_handle = INVALID_HANDLE_VALUE;
+    if (mode > MDBX_ENV_JUST_DELETE) {
+      err = mdbx_openfile(MDBX_OPEN_DELETE, &dummy_env, env_pathname.dxb,
+                          &dxb_handle, 0);
+      err = (err == MDBX_ENOFILE) ? MDBX_SUCCESS : err;
+      if (err == MDBX_SUCCESS) {
+        err = mdbx_openfile(MDBX_OPEN_DELETE, &dummy_env, env_pathname.lck,
+                            &clk_handle, 0);
+        err = (err == MDBX_ENOFILE) ? MDBX_SUCCESS : err;
+      }
+      if (err == MDBX_SUCCESS && clk_handle != INVALID_HANDLE_VALUE)
+        err = mdbx_lockfile(clk_handle, mode == MDBX_ENV_WAIT_FOR_UNUSED);
+      if (err == MDBX_SUCCESS && dxb_handle != INVALID_HANDLE_VALUE)
+        err = mdbx_lockfile(dxb_handle, mode == MDBX_ENV_WAIT_FOR_UNUSED);
+    }
+
+    if (err == MDBX_SUCCESS) {
+      err = mdbx_removefile(env_pathname.dxb);
+      if (err == MDBX_SUCCESS)
+        rc = MDBX_SUCCESS;
+      else if (err == MDBX_ENOFILE)
+        err = MDBX_SUCCESS;
+    }
+
+    if (err == MDBX_SUCCESS) {
+      err = mdbx_removefile(env_pathname.lck);
+      if (err == MDBX_SUCCESS)
+        rc = MDBX_SUCCESS;
+      else if (err == MDBX_ENOFILE)
+        err = MDBX_SUCCESS;
+    }
+
+    if (err == MDBX_SUCCESS && !(dummy_env.me_flags & MDBX_NOSUBDIR)) {
+      err = mdbx_removedirectory(pathname);
+      if (err == MDBX_SUCCESS)
+        rc = MDBX_SUCCESS;
+      else if (err == MDBX_ENOFILE)
+        err = MDBX_SUCCESS;
+    }
+
+    if (dxb_handle != INVALID_HANDLE_VALUE)
+      mdbx_closefile(dxb_handle);
+    if (clk_handle != INVALID_HANDLE_VALUE)
+      mdbx_closefile(clk_handle);
+  } else if (err == MDBX_ENOFILE)
+    err = MDBX_SUCCESS;
+
+  mdbx_free(env_pathname.buffer_for_free);
+  return (err == MDBX_SUCCESS) ? rc : err;
+}
+
 __cold int mdbx_env_open(MDBX_env *env, const char *pathname,
                          MDBX_env_flags_t flags, mdbx_mode_t mode) {
   int rc = check_env(env);

src/lck-posix.c

@@ -190,6 +190,14 @@ static int lck_op(mdbx_filehandle_t fd, int cmd, int lck, off_t offset,
   }
 }
 
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait) {
+#if MDBX_USE_OFDLOCKS
+  if (unlikely(op_setlk == 0))
+    choice_fcntl();
+#endif /* MDBX_USE_OFDLOCKS */
+  return lck_op(fd, wait ? op_setlkw : op_setlk, F_WRLCK, 0, OFF_T_MAX);
+}
+
 MDBX_INTERNAL_FUNC int mdbx_rpid_set(MDBX_env *env) {
   assert(env->me_lfd != INVALID_HANDLE_VALUE);
   assert(env->me_pid > 0);

src/lck-windows.c

@@ -204,6 +204,15 @@ MDBX_INTERNAL_FUNC void mdbx_rdt_unlock(MDBX_env *env) {
   mdbx_srwlock_ReleaseShared(&env->me_remap_guard);
 }
 
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait) {
+  return flock(fd,
+               wait ? LCK_EXCLUSIVE | LCK_WAITFOR
+                    : LCK_EXCLUSIVE | LCK_DONTWAIT,
+               0, LCK_MAXLEN)
+             ? MDBX_SUCCESS
+             : GetLastError();
+}
+
 static int suspend_and_append(mdbx_handle_array_t **array,
                               const DWORD ThreadId) {
   const unsigned limit = (*array)->limit;

src/osal.c

@@ -521,6 +521,20 @@ MDBX_INTERNAL_FUNC int mdbx_removefile(const char *pathname) {
 #endif
 }
 
+MDBX_INTERNAL_FUNC int mdbx_removedirectory(const char *pathname) {
+#if defined(_WIN32) || defined(_WIN64)
+  const size_t wlen = mbstowcs(nullptr, pathname, INT_MAX);
+  if (wlen < 1 || wlen > /* MAX_PATH */ INT16_MAX)
+    return ERROR_INVALID_NAME;
+  wchar_t *const pathnameW = _alloca((wlen + 1) * sizeof(wchar_t));
+  if (wlen != mbstowcs(pathnameW, pathname, wlen + 1))
+    return ERROR_INVALID_NAME;
+  return RemoveDirectoryW(pathnameW) ? MDBX_SUCCESS : GetLastError();
+#else
+  return rmdir(pathname) ? errno : MDBX_SUCCESS;
+#endif
+}
+
 MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
                                      const MDBX_env *env, const char *pathname,
                                      mdbx_filehandle_t *fd,
@@ -571,6 +585,12 @@ MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
     FlagsAndAttributes |=
         (env->me_psize < env->me_os_psize) ? 0 : FILE_FLAG_NO_BUFFERING;
     break;
+  case MDBX_OPEN_DELETE:
+    CreationDisposition = OPEN_EXISTING;
+    ShareMode |= FILE_SHARE_DELETE;
+    DesiredAccess =
+        FILE_READ_ATTRIBUTES | FILE_WRITE_ATTRIBUTES | DELETE | SYNCHRONIZE;
+    break;
   }
 
   *fd = CreateFileW(pathnameW, DesiredAccess, ShareMode, NULL,
@@ -619,6 +639,9 @@ MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
     flags |= O_FSYNC;
 #endif
     break;
+  case MDBX_OPEN_DELETE:
+    flags = O_RDWR;
+    break;
   }
 
   const bool direct_nocache_for_copy =

src/osal.h

@@ -626,7 +626,8 @@ enum mdbx_openfile_purpose {
   MDBX_OPEN_DXB_LAZY = 1,
   MDBX_OPEN_DXB_DSYNC = 2,
   MDBX_OPEN_LCK = 3,
-  MDBX_OPEN_COPY = 4
+  MDBX_OPEN_COPY = 4,
+  MDBX_OPEN_DELETE = 5
 };
 
 MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
@@ -635,7 +636,9 @@ MDBX_INTERNAL_FUNC int mdbx_openfile(const enum mdbx_openfile_purpose purpose,
                                      mdbx_mode_t unix_mode_bits);
 MDBX_INTERNAL_FUNC int mdbx_closefile(mdbx_filehandle_t fd);
 MDBX_INTERNAL_FUNC int mdbx_removefile(const char *pathname);
+MDBX_INTERNAL_FUNC int mdbx_removedirectory(const char *pathname);
 MDBX_INTERNAL_FUNC int mdbx_is_pipe(mdbx_filehandle_t fd);
+MDBX_INTERNAL_FUNC int mdbx_lockfile(mdbx_filehandle_t fd, bool wait);
 
 #define MMAP_OPTION_TRUNCATE 1
 #define MMAP_OPTION_SEMAPHORE 2