X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?a=blobdiff_plain;f=src%2Fdata%2Ffile-handle-def.c;h=075f7b07901c79150e84b1b27014ca7202270d53;hb=cb08510bbbab7646bc1031427243489024d22a3b;hp=e14475b642dd4500995569503e189a5759e6d0ca;hpb=9aac12c2130257396c9ee4ee7860f618dcb202b0;p=pspp

diff --git a/src/data/file-handle-def.c b/src/data/file-handle-def.c
index e14475b642..075f7b0790 100644
--- a/src/data/file-handle-def.c
+++ b/src/data/file-handle-def.c
@@ -1,73 +1,78 @@
-/* PSPP - computes sample statistics.
-   Copyright (C) 1997-9, 2000, 2006 Free Software Foundation, Inc.
+/* PSPP - a program for statistical analysis.
+   Copyright (C) 1997-9, 2000, 2006, 2009, 2010, 2011, 2012, 2013 Free Software Foundation, Inc.
 
-   This program is free software; you can redistribute it and/or
-   modify it under the terms of the GNU General Public License as
-   published by the Free Software Foundation; either version 2 of the
-   License, or (at your option) any later version.
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
 
-   This program is distributed in the hope that it will be useful, but
-   WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   General Public License for more details.
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
 
    You should have received a copy of the GNU General Public License
-   along with this program; if not, write to the Free Software
-   Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
-   02110-1301, USA. */
+   along with this program.  If not, see <http://www.gnu.org/licenses/>. */
 
 #include <config.h>
 
-#include "file-handle-def.h"
+#include "data/file-handle-def.h"
 
 #include <assert.h>
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 
-#include <libpspp/alloc.h>
-#include <libpspp/compiler.h>
-#include <libpspp/magic.h>
-#include <libpspp/message.h>
-#include <libpspp/str.h>
-#include <data/file-name.h>
-#include <data/variable.h>
-#include <data/scratch-handle.h>
+#include "data/dataset.h"
+#include "data/variable.h"
+#include "libpspp/cast.h"
+#include "libpspp/compiler.h"
+#include "libpspp/hash-functions.h"
+#include "libpspp/hmap.h"
+#include "libpspp/i18n.h"
+#include "libpspp/message.h"
+#include "libpspp/str.h"
+
+#include <sys/stat.h>
+
+#include "gl/dirname.h"
+#include "gl/xalloc.h"
 
 #include "gettext.h"
 #define _(msgid) gettext (msgid)
 
-/* (headers) */
+#if defined _WIN32 || defined __WIN32__
+#define WIN32_LEAN_AND_MEAN  /* avoid including junk */
+#include <windows.h>
+#endif
 
 /* File handle. */
-struct file_handle 
+struct file_handle
   {
-    struct file_handle *next;   /* Next in global list. */
-    int open_cnt;               /* 0=not open, otherwise # of openers. */
-    bool deleted;               /* Destroy handle when open_cnt goes to 0? */
-
-    char id[LONG_NAME_LEN + 1]; /* Identifier token; empty string if none. */
+    struct hmap_node name_node; /* Element in named_handles hmap. */
+    size_t ref_cnt;             /* Number of references. */
+    char *id;                   /* Identifier token, NULL if none. */
     char *name;                 /* User-friendly identifying name. */
-    const char *type;           /* If open, type of file. */
-    char open_mode[3];          /* "[rw][se]". */
-    void *aux;                  /* Aux data pointer for owner if any. */
     enum fh_referent referent;  /* What the file handle refers to. */
 
     /* FH_REF_FILE only. */
     char *file_name;		/* File name as provided by user. */
-    struct file_identity *identity; /* For checking file identity. */
+    char *file_name_encoding;	/* The character encoding of file_name,
+				   This is NOT the encoding of the file contents! */
     enum fh_mode mode;  	/* File mode. */
+    enum fh_line_ends line_ends; /* Line ends for text files. */
 
     /* FH_REF_FILE and FH_REF_INLINE only. */
     size_t record_width;        /* Length of fixed-format records. */
     size_t tab_width;           /* Tab width, 0=do not expand tabs. */
+    char *encoding;             /* Charset for contents. */
 
-    /* FH_REF_SCRATCH only. */
-    struct scratch_handle *sh;  /* Scratch file data. */
+    /* FH_REF_DATASET only. */
+    struct dataset *ds;         /* Dataset. */
   };
 
-/* List of all handles. */
-static struct file_handle *file_handles;
+/* All "struct file_handle"s with nonnull 'id' member. */
+static struct hmap named_handles = HMAP_INITIALIZER (named_handles);
 
 /* Default file handle for DATA LIST, REREAD, REPEATING DATA
    commands. */
@@ -77,92 +82,131 @@ static struct file_handle *default_handle;
 static struct file_handle *inline_file;
 
 static struct file_handle *create_handle (const char *id,
-                                          const char *name, enum fh_referent);
+                                          char *name, enum fh_referent,
+                                          const char *encoding);
+static void free_handle (struct file_handle *);
+static void unname_handle (struct file_handle *);
+
+/* Hash table of all active locks. */
+static struct hmap locks = HMAP_INITIALIZER (locks);
+
+static struct file_identity *fh_get_identity (const struct file_handle *);
+static void fh_free_identity (struct file_identity *);
+static int fh_compare_file_identities (const struct file_identity *,
+                                const struct file_identity *);
+static unsigned int fh_hash_identity (const struct file_identity *);
 
 /* File handle initialization routine. */
-void 
+void
 fh_init (void)
 {
-  inline_file = create_handle ("INLINE", "INLINE", FH_REF_INLINE);
+  inline_file = create_handle ("INLINE", xstrdup ("INLINE"), FH_REF_INLINE,
+                               "Auto");
   inline_file->record_width = 80;
   inline_file->tab_width = 8;
 }
 
+/* Removes all named file handles from the global list. */
+void
+fh_done (void)
+{
+  struct file_handle *handle, *next;
+
+  HMAP_FOR_EACH_SAFE (handle, next,
+                      struct file_handle, name_node, &named_handles)
+    unname_handle (handle);
+
+  free_handle (inline_file);
+}
+
 /* Free HANDLE and remove it from the global list. */
 static void
-free_handle (struct file_handle *handle) 
+free_handle (struct file_handle *handle)
 {
+  if (handle == NULL)
+    return;
+
   /* Remove handle from global list. */
-  if (file_handles == handle)
-    file_handles = handle->next;
-  else 
-    {
-      struct file_handle *iter = file_handles;
-      while (iter->next != handle)
-        iter = iter->next;
-      iter->next = handle->next;
-    }
+  if (handle->id != NULL)
+    hmap_delete (&named_handles, &handle->name_node);
 
   /* Free data. */
+  free (handle->id);
   free (handle->name);
   free (handle->file_name);
-  fn_free_identity (handle->identity);
-  scratch_handle_destroy (handle->sh);
+  free (handle->file_name_encoding);
+  free (handle->encoding);
   free (handle);
 }
 
-/* Frees all the file handles. */
-void 
-fh_done (void)
+/* Make HANDLE unnamed, so that it can no longer be referenced by
+   name.  The caller must hold a reference to HANDLE, which is
+   not affected by this function. */
+static void
+unname_handle (struct file_handle *handle)
 {
-  while (file_handles != NULL) 
-    free_handle (file_handles);
+  assert (handle->id != NULL);
+  free (handle->id);
+  handle->id = NULL;
+  hmap_delete (&named_handles, &handle->name_node);
+
+  /* Drop the reference held by the named_handles table. */
+  fh_unref (handle);
 }
 
-/* Returns the handle with the given ID, or a null pointer if
-   there is none. */
+/* Increments HANDLE's reference count and returns HANDLE. */
 struct file_handle *
-fh_from_id (const char *id) 
+fh_ref (struct file_handle *handle)
 {
-  struct file_handle *iter;
-
-  for (iter = file_handles; iter != NULL; iter = iter->next)
-    if (!iter->deleted && !strcasecmp (id, iter->id))
-      return iter;
-  return NULL;
+  if (handle == fh_inline_file ())
+    return handle;
+  assert (handle->ref_cnt > 0);
+  handle->ref_cnt++;
+  return handle;
 }
 
-/* Returns the handle for the file named FILE_NAME,
-   or a null pointer if none exists.
-   Different names for the same file (e.g. "x" and "./x") are
-   considered equivalent. */
-struct file_handle *
-fh_from_file_name (const char *file_name)
-{
-  struct file_identity *identity;
-  struct file_handle *iter;
-      
-  /* First check for a file with the same identity. */
-  identity = fn_get_identity (file_name);
-  if (identity != NULL) 
+/* Decrements HANDLE's reference count.
+   If the reference count drops to 0, HANDLE is destroyed. */
+void
+fh_unref (struct file_handle *handle)
+{
+  if (handle != NULL)
     {
-      for (iter = file_handles; iter != NULL; iter = iter->next)
-        if (!iter->deleted
-            && iter->referent == FH_REF_FILE
-            && iter->identity != NULL
-            && !fn_compare_file_identities (identity, iter->identity))
-          {
-            fn_free_identity (identity);
-            return iter; 
-          }
-      fn_free_identity (identity);
+      if (handle == fh_inline_file ())
+        return;
+      assert (handle->ref_cnt > 0);
+      if (--handle->ref_cnt == 0)
+        free_handle (handle);
     }
+}
+
+/* Make HANDLE unnamed, so that it can no longer be referenced by
+   name.  The caller must hold a reference to HANDLE, which is
+   not affected by this function.
+
+   This function ignores a null pointer as input.  It has no
+   effect on the inline handle, which is always named INLINE.*/
+void
+fh_unname (struct file_handle *handle)
+{
+  assert (handle->ref_cnt > 1);
+  if (handle != fh_inline_file () && handle->id != NULL)
+    unname_handle (handle);
+}
+
+/* Returns the handle with the given ID, or a null pointer if
+   there is none. */
+struct file_handle *
+fh_from_id (const char *id)
+{
+  struct file_handle *handle;
 
-  /* Then check for a file with the same name. */
-  for (iter = file_handles; iter != NULL; iter = iter->next)
-    if (!iter->deleted
-        && iter->referent == FH_REF_FILE && !strcmp (file_name, iter->file_name))
-      return iter; 
+  HMAP_FOR_EACH_WITH_HASH (handle, struct file_handle, name_node,
+                           utf8_hash_case_string (id, 0), &named_handles)
+    if (!utf8_strcasecmp (id, handle->id))
+      {
+	return fh_ref (handle);
+      }
 
   return NULL;
 }
@@ -174,20 +218,23 @@ fh_from_file_name (const char *file_name)
    The new handle is not fully initialized.  The caller is
    responsible for completing its initialization. */
 static struct file_handle *
-create_handle (const char *id, const char *handle_name,
-               enum fh_referent referent) 
+create_handle (const char *id, char *handle_name, enum fh_referent referent,
+               const char *encoding)
 {
   struct file_handle *handle = xzalloc (sizeof *handle);
-  assert (id == NULL || fh_from_id (id) == NULL);
-  handle->next = file_handles;
-  handle->open_cnt = 0;
-  handle->deleted = false;
-  str_copy_trunc (handle->id, sizeof handle->id, id != NULL ? id : "");
-  handle->name = xstrdup (handle_name);
-  handle->type = NULL;
-  handle->aux = NULL;
+
+  handle->ref_cnt = 1;
+  handle->id = xstrdup_if_nonnull (id);
+  handle->name = handle_name;
   handle->referent = referent;
-  file_handles = handle;
+  handle->encoding = xstrdup (encoding);
+
+  if (id != NULL)
+    {
+      hmap_insert (&named_handles, &handle->name_node,
+                   utf8_hash_case_string (handle->id, 0));
+    }
+
   return handle;
 }
 
@@ -195,29 +242,28 @@ create_handle (const char *id, const char *handle_name,
    which refers to the "inline file" that represents character
    data in the command file between BEGIN DATA and END DATA. */
 struct file_handle *
-fh_inline_file (void) 
+fh_inline_file (void)
 {
   return inline_file;
 }
 
-/* Creates a new file handle with the given ID, which may be
-   null.  If it is non-null, it must be unique among existing
-   file identifiers.  The new handle is associated with file
-   FILE_NAME and the given PROPERTIES. */
+/* Creates and returns a new file handle with the given ID, which may be null.
+   If it is non-null, it must be a UTF-8 encoded string that is unique among
+   existing file identifiers.  The new handle is associated with file FILE_NAME
+   and the given PROPERTIES. */
 struct file_handle *
-fh_create_file (const char *id, const char *file_name,
+fh_create_file (const char *id, const char *file_name, const char *file_name_encoding,
                 const struct fh_properties *properties)
 {
   char *handle_name;
   struct file_handle *handle;
 
-  handle_name = id != NULL ? (char *) id : xasprintf ("\"%s\"", file_name);
-  handle = create_handle (id, handle_name, FH_REF_FILE);
-  if (id == NULL)
-    free (handle_name);
+  handle_name = id != NULL ? xstrdup (id) : xasprintf ("`%s'", file_name);
+  handle = create_handle (id, handle_name, FH_REF_FILE, properties->encoding);
   handle->file_name = xstrdup (file_name);
-  handle->identity = fn_get_identity (file_name);
+  handle->file_name_encoding = xstrdup_if_nonnull (file_name_encoding);
   handle->mode = properties->mode;
+  handle->line_ends = properties->line_ends;
   handle->record_width = properties->record_width;
   handle->tab_width = properties->tab_width;
   return handle;
@@ -225,14 +271,19 @@ fh_create_file (const char *id, const char *file_name,
 
 /* Creates a new file handle with the given ID, which must be
    unique among existing file identifiers.  The new handle is
-   associated with a scratch file (initially empty). */
+   associated with a dataset file (initially empty). */
 struct file_handle *
-fh_create_scratch (const char *id) 
+fh_create_dataset (struct dataset *ds)
 {
+  const char *name;
   struct file_handle *handle;
-  assert (id != NULL);
-  handle = create_handle (id, id, FH_REF_SCRATCH);
-  handle->sh = NULL;
+
+  name = dataset_name (ds);
+  if (name[0] == '\0')
+    name = _("active dataset");
+
+  handle = create_handle (NULL, xstrdup (name), FH_REF_DATASET, C_ENCODING);
+  handle->ds = ds;
   return handle;
 }
 
@@ -240,156 +291,26 @@ fh_create_scratch (const char *id)
 const struct fh_properties *
 fh_default_properties (void)
 {
+#if defined _WIN32 || defined __WIN32__
+#define DEFAULT_LINE_ENDS FH_END_CRLF
+#else
+#define DEFAULT_LINE_ENDS FH_END_LF
+#endif
+
   static const struct fh_properties default_properties
-    = {FH_MODE_TEXT, 1024, 4};
+    = {FH_MODE_TEXT, DEFAULT_LINE_ENDS, 1024, 4, (char *) "Auto"};
   return &default_properties;
 }
 
-/* Deletes FH from the global list of file handles.  Afterward,
-   attempts to search for it will fail.  Unless the file handle
-   is currently open, it will be destroyed; otherwise, it will be
-   destroyed later when it is closed.
-   Normally needed only if a file_handle needs to be re-assigned.
-   Otherwise, just let fh_done() destroy the handle. */
-void 
-fh_free (struct file_handle *handle)
-{
-  if (handle == fh_inline_file () || handle == NULL || handle->deleted)
-    return;
-  handle->deleted = true;
-
-  if (handle == default_handle)
-    default_handle = fh_inline_file ();
-
-  if (handle->open_cnt == 0)
-    free_handle (handle);
-}
-
-/* Returns an English description of MODE,
-   which is in the format of the MODE argument to fh_open(). */
-static const char *
-mode_name (const char *mode) 
-{
-  assert (mode != NULL);
-  assert (mode[0] == 'r' || mode[0] == 'w');
-
-  return mode[0] == 'r' ? "reading" : "writing";
-}
-
-/* Tries to open handle H with the given TYPE and MODE.
-
-   H's referent type must be one of the bits in MASK.  The caller
-   must verify this ahead of time; we simply assert it here.
-
-   TYPE is the sort of file, e.g. "system file".  Only one given
-   type of access is allowed on a given file handle at once.
-   If successful, a reference to TYPE is retained, so it should
-   probably be a string literal.
-
-   MODE combines the read or write mode with the sharing mode.
-   The first character is 'r' for read, 'w' for write.  The
-   second character is 's' to permit sharing, 'e' to require
-   exclusive access.
-
-   Returns the address of a void * that the caller can use for
-   data specific to the file handle if successful, or a null
-   pointer on failure.  For exclusive access modes the void *
-   will always be a null pointer at return.  In shared access
-   modes the void * will necessarily be null only if no other
-   sharers are active. */
-void **
-fh_open (struct file_handle *h, enum fh_referent mask UNUSED,
-         const char *type, const char *mode) 
-{
-  assert (h != NULL);
-  assert ((fh_get_referent (h) & mask) != 0);
-  assert (type != NULL);
-  assert (mode != NULL);
-  assert (mode[0] == 'r' || mode[0] == 'w');
-  assert (mode[1] == 's' || mode[1] == 'e');
-  assert (mode[2] == '\0');
-
-  if (h->open_cnt != 0) 
-    {
-      if (strcmp (h->type, type)) 
-        {
-          msg (SE, _("Can't open %s as a %s because it is "
-                     "already open as a %s."),
-               fh_get_name (h), type, h->type);
-          return NULL; 
-        }
-      else if (strcmp (h->open_mode, mode)) 
-        {
-          msg (SE, _("Can't open %s as a %s for %s because it is "
-                     "already open for %s."),
-               fh_get_name (h), type, mode_name (mode),
-               mode_name (h->open_mode));
-          return NULL;
-        }
-      else if (h->open_mode[1] == 'e')
-        {
-          msg (SE, _("Can't re-open %s as a %s for %s."),
-               fh_get_name (h), type, mode_name (mode));
-          return NULL;
-        }
-    }
-  else 
-    {
-      h->type = type;
-      strcpy (h->open_mode, mode);
-      assert (h->aux == NULL);
-    }
-  h->open_cnt++;
-
-  return &h->aux;
-}
-
-/* Closes file handle H, which must have been open for the
-   specified TYPE and MODE of access provided to fh_open().
-   Returns zero if the file is now closed, nonzero if it is still
-   open due to another reference.
-
-   After fh_close() returns zero for a handle, it is unsafe to
-   reference that file handle again in any way, because its
-   storage may have been freed. */
-int
-fh_close (struct file_handle *h, const char *type, const char *mode)
-{
-  assert (h != NULL);
-  assert (h->open_cnt > 0);
-  assert (type != NULL);
-  assert (!strcmp (type, h->type));
-  assert (mode != NULL);
-  assert (!strcmp (mode, h->open_mode));
-
-  if (--h->open_cnt == 0) 
-    {
-      h->type = NULL;
-      h->aux = NULL;
-      if (h->deleted)
-        free_handle (h);
-      return 0;
-    }
-  return 1;
-}
-
-/* Is the file open?  BEGIN DATA...END DATA uses this to detect
-   whether the inline file is actually in use. */
-bool
-fh_is_open (const struct file_handle *handle) 
-{
-  return handle->open_cnt > 0;
-}
-
 /* Returns the identifier that may be used in syntax to name the
    given HANDLE, which takes the form of a PSPP identifier.  If
    HANDLE has no identifier, returns a null pointer.
 
    Return value is owned by the file handle.*/
 const char *
-fh_get_id (const struct file_handle *handle) 
+fh_get_id (const struct file_handle *handle)
 {
-  return handle->id[0] != '\0' ? handle->id : NULL;
+  return handle->id;
 }
 
 /* Returns a user-friendly string to identify the given HANDLE.
@@ -406,27 +327,46 @@ fh_get_name (const struct file_handle *handle)
 
 /* Returns the type of object that HANDLE refers to. */
 enum fh_referent
-fh_get_referent (const struct file_handle *handle) 
+fh_get_referent (const struct file_handle *handle)
 {
   return handle->referent;
 }
 
 /* Returns the name of the file associated with HANDLE. */
 const char *
-fh_get_file_name (const struct file_handle *handle) 
+fh_get_file_name (const struct file_handle *handle)
 {
   assert (handle->referent == FH_REF_FILE);
   return handle->file_name;
 }
 
+
+/* Returns the character encoding of the name of the file associated with HANDLE. */
+const char *
+fh_get_file_name_encoding (const struct file_handle *handle)
+{
+  assert (handle->referent == FH_REF_FILE);
+  return handle->file_name_encoding;
+}
+
+
 /* Returns the mode of HANDLE. */
 enum fh_mode
-fh_get_mode (const struct file_handle *handle) 
+fh_get_mode (const struct file_handle *handle)
 {
   assert (handle->referent == FH_REF_FILE);
   return handle->mode;
 }
 
+/* Returns the line ends of HANDLE, which must be a handle associated with a
+   file. */
+enum fh_line_ends
+fh_get_line_ends (const struct file_handle *handle)
+{
+  assert (handle->referent == FH_REF_FILE);
+  return handle->line_ends;
+}
+
 /* Returns the width of a logical record on HANDLE. */
 size_t
 fh_get_record_width (const struct file_handle *handle)
@@ -439,42 +379,445 @@ fh_get_record_width (const struct file_handle *handle)
    zero if tabs are not to be expanded.  Applicable only to
    FH_MODE_TEXT files. */
 size_t
-fh_get_tab_width (const struct file_handle *handle) 
+fh_get_tab_width (const struct file_handle *handle)
 {
   assert (handle->referent & (FH_REF_FILE | FH_REF_INLINE));
   return handle->tab_width;
 }
 
-/* Returns the scratch file handle associated with HANDLE.
-   Applicable to only FH_REF_SCRATCH files. */
-struct scratch_handle *
-fh_get_scratch_handle (struct file_handle *handle) 
+/* Returns the encoding of characters read from HANDLE. */
+const char *
+fh_get_encoding (const struct file_handle *handle)
 {
-  assert (handle->referent == FH_REF_SCRATCH);
-  return handle->sh;
+  return handle->encoding;
 }
 
-/* Sets SH to be the scratch file handle associated with HANDLE.
-   Applicable to only FH_REF_SCRATCH files. */
-void
-fh_set_scratch_handle (struct file_handle *handle, struct scratch_handle *sh)
+/* Returns the dataset handle associated with HANDLE.
+   Applicable to only FH_REF_DATASET files. */
+struct dataset *
+fh_get_dataset (const struct file_handle *handle)
 {
-  assert (handle->referent == FH_REF_SCRATCH);
-  handle->sh = sh;
+  assert (handle->referent == FH_REF_DATASET);
+  return handle->ds;
 }
 
 /* Returns the current default handle. */
 struct file_handle *
-fh_get_default_handle (void) 
+fh_get_default_handle (void)
 {
   return default_handle ? default_handle : fh_inline_file ();
 }
 
 /* Sets NEW_DEFAULT_HANDLE as the default handle. */
 void
-fh_set_default_handle (struct file_handle *new_default_handle) 
+fh_set_default_handle (struct file_handle *new_default_handle)
 {
   assert (new_default_handle == NULL
           || (new_default_handle->referent & (FH_REF_INLINE | FH_REF_FILE)));
+  if (default_handle != NULL && default_handle != inline_file)
+    fh_unref (default_handle);
   default_handle = new_default_handle;
+  if (default_handle != NULL)
+    default_handle = fh_ref (default_handle);
+}
+
+/* Information about a file handle's readers or writers. */
+struct fh_lock
+  {
+    struct hmap_node node;      /* hmap_node member. */
+
+    /* Hash key. */
+    enum fh_referent referent;  /* Type of underlying file. */
+    union
+      {
+        struct file_identity *file; /* FH_REF_FILE only. */
+        unsigned int unique_id;    /* FH_REF_DATASET only. */
+      }
+    u;
+    enum fh_access access;      /* Type of file access. */
+
+    /* Number of openers. */
+    size_t open_cnt;
+
+    /* Applicable only when open_cnt > 0. */
+    bool exclusive;             /* No other openers allowed? */
+    const char *type;           /* Human-readable type of file. */
+    void *aux;                  /* Owner's auxiliary data. */
+  };
+
+
+static void make_key (struct fh_lock *, const struct file_handle *,
+                      enum fh_access);
+static void free_key (struct fh_lock *);
+static int compare_fh_locks (const struct fh_lock *a, const struct fh_lock *b);
+static unsigned int hash_fh_lock (const struct fh_lock *lock);
+
+/* Tries to lock handle H for the given kind of ACCESS and TYPE
+   of file.  Returns a pointer to a struct fh_lock if successful,
+   otherwise a null pointer.
+
+   H's referent type must be one of the bits in MASK.  The caller
+   must verify this ahead of time; we simply assert it here.
+
+   TYPE is the sort of file, e.g. "system file".  Only one type
+   of access is allowed on a given file at a time for reading,
+   and similarly for writing.  If successful, a reference to TYPE
+   is retained, so it should probably be a string literal.
+
+   TYPE should be marked with N_() in the caller: that is, the
+   caller should not translate it with gettext, but fh_lock will
+   do so.
+
+   ACCESS specifies whether the lock is for reading or writing.
+   EXCLUSIVE is true to require exclusive access, false to allow
+   sharing with other accessors.  Exclusive read access precludes
+   other readers, but not writers; exclusive write access
+   precludes other writers, but not readers.  A sharable read or
+   write lock precludes reader or writers, respectively, of a
+   different TYPE.
+
+   A lock may be associated with auxiliary data.  See
+   fh_lock_get_aux and fh_lock_set_aux for more details. */
+struct fh_lock *
+fh_lock (struct file_handle *h, enum fh_referent mask UNUSED,
+         const char *type, enum fh_access access, bool exclusive)
+{
+  struct fh_lock *key = NULL;
+  size_t hash ;
+  struct fh_lock *lock = NULL;
+  bool found_lock = false;
+
+  assert ((fh_get_referent (h) & mask) != 0);
+  assert (access == FH_ACC_READ || access == FH_ACC_WRITE);
+
+  key = xmalloc (sizeof *key);
+
+  make_key (key, h, access);
+
+  key->open_cnt = 1;
+  key->exclusive = exclusive;
+  key->type = type;
+  key->aux = NULL;
+
+  hash = hash_fh_lock (key);
+
+  HMAP_FOR_EACH_WITH_HASH (lock, struct fh_lock, node, hash, &locks)
+    {
+      if (0 == compare_fh_locks (lock, key))
+	{
+	  found_lock = true;
+	  break;
+	}
+    }
+
+  if (found_lock)
+    {
+      if (strcmp (lock->type, type))
+        {
+          if (access == FH_ACC_READ)
+            msg (SE, _("Can't read from %s as a %s because it is "
+                       "already being read as a %s."),
+                 fh_get_name (h), gettext (type), gettext (lock->type));
+          else
+            msg (SE, _("Can't write to %s as a %s because it is "
+                       "already being written as a %s."),
+                 fh_get_name (h), gettext (type), gettext (lock->type));
+          return NULL;
+        }
+      else if (exclusive || lock->exclusive)
+        {
+          msg (SE, _("Can't re-open %s as a %s."),
+               fh_get_name (h), gettext (type));
+          return NULL;
+        }
+      lock->open_cnt++;
+
+      free_key (key);
+      free (key);
+
+      return lock;
+    }
+
+  hmap_insert (&locks, &key->node, hash);
+  found_lock = false;
+  HMAP_FOR_EACH_WITH_HASH (lock, struct fh_lock, node, hash, &locks)
+    {
+      if (0 == compare_fh_locks (lock, key))
+	{
+	  found_lock = true;
+	  break;
+	}
+    }
+
+  assert (found_lock);
+
+  return key;
+}
+
+/* Releases LOCK that was acquired with fh_lock.
+   Returns true if LOCK is still locked, because other clients
+   also had it locked.
+
+   Returns false if LOCK has now been destroyed.  In this case
+   the caller must ensure that any auxiliary data associated with
+   LOCK is destroyed, to avoid a memory leak.  The caller must
+   obtain a pointer to the auxiliary data, e.g. via
+   fh_lock_get_aux *before* calling fh_unlock (because it yields
+   undefined behavior to call fh_lock_get_aux on a destroyed
+   lock).  */
+bool
+fh_unlock (struct fh_lock *lock)
+{
+  if (lock != NULL)
+    {
+      assert (lock->open_cnt > 0);
+      if (--lock->open_cnt == 0)
+        {
+	  hmap_delete (&locks, &lock->node);
+          free_key (lock);
+          free (lock);
+          return false;
+        }
+    }
+  return true;
+}
+
+/* Returns auxiliary data for LOCK.
+
+   Auxiliary data is shared by every client that holds LOCK (for
+   an exclusive lock, this is a single client).  To avoid leaks,
+   auxiliary data must be released before LOCK is destroyed. */
+void *
+fh_lock_get_aux (const struct fh_lock *lock)
+{
+  return lock->aux;
+}
+
+/* Sets the auxiliary data for LOCK to AUX. */
+void
+fh_lock_set_aux (struct fh_lock *lock, void *aux)
+{
+  lock->aux = aux;
+}
+
+/* Returns true if HANDLE is locked for the given type of ACCESS,
+   false otherwise. */
+bool
+fh_is_locked (const struct file_handle *handle, enum fh_access access)
+{
+  struct fh_lock key;
+  const struct fh_lock *k = NULL;
+  bool is_locked = false;
+  size_t hash ;
+
+  make_key (&key, handle, access);
+
+  hash = hash_fh_lock (&key);
+
+
+  HMAP_FOR_EACH_WITH_HASH (k, struct fh_lock, node, hash, &locks)
+    {
+      if (0 == compare_fh_locks (k, &key))
+	{
+	  is_locked = true;
+	  break;
+	}
+    }
+
+  free_key (&key);
+
+  return is_locked;
+}
+
+/* Initializes the key fields in LOCK for looking up or inserting
+   handle H for the given kind of ACCESS. */
+static void
+make_key (struct fh_lock *lock, const struct file_handle *h,
+          enum fh_access access)
+{
+  lock->referent = fh_get_referent (h);
+  lock->access = access;
+  if (lock->referent == FH_REF_FILE)
+    lock->u.file = fh_get_identity (h);
+  else if (lock->referent == FH_REF_DATASET)
+    lock->u.unique_id = dataset_seqno (fh_get_dataset (h));
+}
+
+/* Frees the key fields in LOCK. */
+static void
+free_key (struct fh_lock *lock)
+{
+  if (lock->referent == FH_REF_FILE)
+    fh_free_identity (lock->u.file);
+}
+
+/* Compares the key fields in struct fh_lock objects A and B and
+   returns a strcmp()-type result. */
+static int
+compare_fh_locks (const struct fh_lock *a, const struct fh_lock *b)
+{
+  if (a->referent != b->referent)
+    return a->referent < b->referent ? -1 : 1;
+  else if (a->access != b->access)
+    return a->access < b->access ? -1 : 1;
+  else if (a->referent == FH_REF_FILE)
+    return fh_compare_file_identities (a->u.file, b->u.file);
+  else if (a->referent == FH_REF_DATASET)
+    return (a->u.unique_id < b->u.unique_id ? -1
+            : a->u.unique_id > b->u.unique_id);
+  else
+    return 0;
+}
+
+/* Returns a hash value for LOCK. */
+static unsigned int
+hash_fh_lock (const struct fh_lock *lock)
+{
+  unsigned int basis;
+  if (lock->referent == FH_REF_FILE)
+    basis = fh_hash_identity (lock->u.file);
+  else if (lock->referent == FH_REF_DATASET)
+    basis = lock->u.unique_id;
+  else
+    basis = 0;
+  return hash_int ((lock->referent << 3) | lock->access, basis);
+}
+
+
+
+
+
+
+/* A file's identity:
+
+   - For a file that exists, this is its device and inode.
+
+   - For a file that does not exist, but which has a directory
+     name that exists, this is the device and inode of the
+     directory, plus the file's base name.
+
+   - For a file that does not exist and has a nonexistent
+     directory, this is the file name.
+
+   Windows doesn't have inode numbers, so we just use the name
+   there. */
+struct file_identity
+{
+  unsigned long long device;               /* Device number. */
+  unsigned long long inode;                /* Inode number. */
+  char *name;                 /* File name, where needed, otherwise NULL. */
+};
+
+/* Returns a pointer to a dynamically allocated structure whose
+   value can be used to tell whether two files are actually the
+   same file.  The caller is responsible for freeing the structure with
+   fh_free_identity() when finished. */
+static struct file_identity *
+fh_get_identity (const struct file_handle *fh)
+{
+  struct file_identity *identity = xmalloc (sizeof *identity);
+
+  const char *file_name = fh_get_file_name (fh);
+
+#if !(defined _WIN32 || defined __WIN32__)
+  struct stat s;
+  if (lstat (file_name, &s) == 0)
+    {
+      identity->device = s.st_dev;
+      identity->inode = s.st_ino;
+      identity->name = NULL;
+    }
+  else
+    {
+      char *dir = dir_name (file_name);
+      if (last_component (file_name) != NULL && stat (dir, &s) == 0)
+        {
+          identity->device = s.st_dev;
+          identity->inode = s.st_ino;
+          identity->name = base_name (file_name);
+        }
+      else
+        {
+          identity->device = 0;
+          identity->inode = 0;
+          identity->name = xstrdup (file_name);
+        }
+      free (dir);
+    }
+#else /* Windows */
+  bool ok = false;
+  HANDLE h = CreateFile (file_name, GENERIC_READ, 0, NULL, OPEN_EXISTING, FILE_ATTRIBUTE_READONLY, NULL);
+  if (h != INVALID_HANDLE_VALUE)
+  {
+    BY_HANDLE_FILE_INFORMATION fi;
+    ok = GetFileInformationByHandle (h, &fi);
+    if (ok)
+      {
+	identity->device = fi.dwVolumeSerialNumber;
+	identity->inode = fi.nFileIndexHigh;
+	identity->inode <<= (sizeof fi.nFileIndexLow) * CHAR_BIT;
+	identity->inode |= fi.nFileIndexLow;
+	identity->name = 0;
+      }
+    CloseHandle (h);
+  }
+
+  if (!ok)
+    {
+      identity->device = 0;
+      identity->inode = 0;
+
+      size_t bufsize;
+      size_t pathlen = 255;
+      char *cname = NULL;
+      do
+      {
+	bufsize = pathlen;
+	cname = xrealloc (cname, bufsize);
+	pathlen = GetFullPathName (file_name, bufsize, cname, NULL);
+      }
+      while (pathlen > bufsize);
+      identity->name = xstrdup (cname);
+      free (cname);
+      str_lowercase (identity->name);
+    }
+#endif /* Windows */
+
+  return identity;
+}
+
+/* Frees IDENTITY obtained from fh_get_identity(). */
+void
+fh_free_identity (struct file_identity *identity)
+{
+  if (identity != NULL)
+    {
+      free (identity->name);
+      free (identity);
+    }
+}
+
+/* Compares A and B, returning a strcmp()-type result. */
+int
+fh_compare_file_identities (const struct file_identity *a,
+                            const struct file_identity *b)
+{
+  if (a->device != b->device)
+    return a->device < b->device ? -1 : 1;
+  else if (a->inode != b->inode)
+    return a->inode < b->inode ? -1 : 1;
+  else if (a->name != NULL)
+    return b->name != NULL ? strcmp (a->name, b->name) : 1;
+  else
+    return b->name != NULL ? -1 : 0;
+}
+
+/* Returns a hash value for IDENTITY. */
+unsigned int
+fh_hash_identity (const struct file_identity *identity)
+{
+  unsigned int hash = hash_int (identity->device, identity->inode);
+  if (identity->name != NULL)
+    hash = hash_string (identity->name, hash);
+  return hash;
 }