fish: Use a perfect hash for faster command lookups.

Existing command lookups are approx O(n^2). Replace this with a perfect hash implementation which should be a lot faster.
2026-03-22 07:03:38 +00:00 · 2010-11-03 20:34:42 +00:00
parent f661db2c39
commit 58915725b1
6 changed files with 191 additions and 70 deletions
--- a/.gitignore
+++ b/.gitignore
@@ -67,6 +67,8 @@ emptydisk
 examples/hello
 examples/to-xml
 fish/cmds.c
+fish/cmds_gperf.c
+fish/cmds_gperf.gperf
 fish/completion.c
 fish/guestfish
 fish/guestfish.static
--- a/fish/Makefile.am
+++ b/fish/Makefile.am
@@ -21,6 +21,7 @@ bin_PROGRAMS = guestfish

 generator_built = \
 	cmds.c \
+	cmds_gperf.gperf \
 	completion.c \
 	guestfish-actions.pod \
 	guestfish-commands.pod \
@@ -29,6 +30,7 @@ generator_built = \

 BUILT_SOURCES = \
 	$(generator_built) \
+	cmds_gperf.c \
 	rc_protocol.h \
 	rc_protocol.c

@@ -52,6 +54,7 @@ guestfish_SOURCES = \
 	$(generator_built) \
 	$(SHARED_SOURCE_FILES) \
 	alloc.c \
+	cmds_gperf.h \
 	copy.c \
 	destpaths.c \
 	echo.c \
@@ -82,6 +85,16 @@ guestfish_SOURCES = \
 librc_protocol_la_SOURCES = rc_protocol.c
 librc_protocol_la_CFLAGS = -Wall -Wno-unused

+# Build the command lookup perfect hash code.  The generated code has
+# lots of warnings so we must compile it in a separate mini-library.
+libcmds_la_SOURCES = cmds_gperf.c
+libcmds_la_CFLAGS =
+
+cmds_gperf.c: cmds_gperf.gperf
+	rm -f $@
+	$(GPERF) -t $< > $@-t
+	mv $@-t $@
+
 guestfish_CFLAGS = \
 	-I$(top_srcdir)/src -I$(top_builddir)/src \
 	-I$(top_srcdir)/fish -I$(top_builddir)/fish \
@@ -95,9 +108,9 @@ guestfish_LDADD = \
 	$(LIBVIRT_LIBS) $(LIBXML2_LIBS) \
 	$(top_builddir)/src/libguestfs.la $(LIBREADLINE) -lm

-# Make libguestfs use the convenience library.
-noinst_LTLIBRARIES = librc_protocol.la
-guestfish_LDADD += librc_protocol.la ../gnulib/lib/libgnu.la
+# Make guestfish use the convenience libraries.
+noinst_LTLIBRARIES = libcmds.la librc_protocol.la
+guestfish_LDADD += libcmds.la librc_protocol.la ../gnulib/lib/libgnu.la

 if HAVE_RPCGEN
 rc_protocol.c: rc_protocol.x
--- a/fish/cmds_gperf.h
+++ b/fish/cmds_gperf.h
@@ -0,0 +1,46 @@
+/* libguestfs - guestfish shell
+ * Copyright (C) 2010 Red Hat 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 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.
+ */
+
+#ifndef FISH_CMDS_GPERF_H
+#define FISH_CMDS_GPERF_H
+
+/* There is one of these structures for each individual command that
+ * guestfish can execute.
+ */
+struct command_entry {
+  /* These fields are passed to pod2text to implement the online help. */
+  const char *name;
+  const char *shortdesc;
+  const char *podbody;
+
+  /* The run_* function. */
+  int (*run) (const char *cmd, size_t argc, char *argv[]);
+};
+
+/* Command table used by the gperf-generated lookup function.
+ * Multiple rows in this table can and do point to a single command
+ * entry.  This is used to implement aliases.
+ */
+struct command_table {
+  char *name;
+  struct command_entry *entry;
+};
+
+const struct command_table *lookup_fish_command (register const char *str, register unsigned int len);
+
+#endif /* FISH_CMDS_GPERF_H */
--- a/generator/generator_fish.ml
+++ b/generator/generator_fish.ml
@@ -58,34 +58,28 @@ let generate_fish_cmds () =
  pr "#include \"full-write.h\"\n";
  pr "#include \"xstrtol.h\"\n";
  pr "#include \"fish.h\"\n";
+  pr "#include \"cmds_gperf.h\"\n";
  pr "\n";
  pr "/* Valid suffixes allowed for numbers.  See Gnulib xstrtol function. */\n";
  pr "static const char *xstrtol_suffixes = \"0kKMGTPEZY\";\n";
  pr "\n";

-  (* list_commands function, which implements guestfish -h *)
-  pr "void list_commands (void)\n";
-  pr "{\n";
-  pr "  printf (\"    %%-16s     %%s\\n\", _(\"Command\"), _(\"Description\"));\n";
-  pr "  list_builtin_commands ();\n";
  List.iter (
-    fun (name, _, _, flags, _, shortdesc, _) ->
-      let name = replace_char name '_' '-' in
-      pr "  printf (\"%%-20s %%s\\n\", \"%s\", _(\"%s\"));\n"
-        name shortdesc
-  ) all_functions_and_fish_commands_sorted;
-  pr "  printf (\"    %%s\\n\",";
-  pr "          _(\"Use -h <cmd> / help <cmd> to show detailed help for a command.\"));\n";
-  pr "}\n";
+    fun (name, _, _, _, _, _, _) ->
+      pr "static int run_%s (const char *cmd, size_t argc, char *argv[]);\n"
+        name
+  ) all_functions;
+
  pr "\n";

-  (* display_command function, which implements guestfish -h cmd *)
-  pr "int display_command (const char *cmd)\n";
-  pr "{\n";
-
+  (* List of command_entry structs. *)
  List.iter (
    fun (name, _, _, flags, _, shortdesc, longdesc) ->
+      pr "struct command_entry %s_cmd_entry = {\n" name;
+
      let name2 = replace_char name '_' '-' in
+      pr "  .name = \"%s\",\n" name2;
+
      let aliases =
        filter_map (function FishAlias n -> Some n | _ -> None) flags in
      let describe_alias =
@@ -94,29 +88,25 @@ let generate_fish_cmds () =
            (String.concat " or " (List.map (fun s -> "'" ^ s ^ "'") aliases))
        else "" in

-      pr "  if (";
-      pr "STRCASEEQ (cmd, \"%s\")" name;
-      if name <> name2 then
-        pr " || STRCASEEQ (cmd, \"%s\")" name2;
-      List.iter (
-        fun alias ->
-          pr " || STRCASEEQ (cmd, \"%s\")" alias
-      ) aliases;
-      pr ") {\n";
-      pr "    pod2text (\"%s\", _(\"%s\"), %S);\n"
-        name2 shortdesc
-        ("=head1 DESCRIPTION\n\n" ^
-         longdesc ^ describe_alias);
-      pr "    return 0;\n";
-      pr "  }\n";
-      pr "  else\n"
+      pr "  .shortdesc = \"%s\",\n" shortdesc;
+      pr "  .podbody = %S,\n"
+        ("=head1 DESCRIPTION\n\n" ^ longdesc ^ describe_alias);
+
+      pr "  .run = run_%s\n" name;
+      pr "};\n";
+      pr "\n";
  ) fish_commands;

  List.iter (
    fun (name, (_, args, optargs), _, flags, _, shortdesc, longdesc) ->
+      pr "struct command_entry %s_cmd_entry = {\n" name;
+
      let name2 = replace_char name '_' '-' in
+      pr "  .name = \"%s\",\n" name2;
+
      let aliases =
        filter_map (function FishAlias n -> Some n | _ -> None) flags in
+
      let longdesc = replace_str longdesc "C<guestfs_" "C<" in
      let synopsis =
        match args with
@@ -164,25 +154,44 @@ Guestfish will prompt for these separately."
            (String.concat " or " (List.map (fun s -> "'" ^ s ^ "'") aliases))
        else "" in

-      pr "  if (";
-      pr "STRCASEEQ (cmd, \"%s\")" name;
-      if name <> name2 then
-        pr " || STRCASEEQ (cmd, \"%s\")" name2;
-      List.iter (
-        fun alias ->
-          pr " || STRCASEEQ (cmd, \"%s\")" alias
-      ) aliases;
-      pr ") {\n";
-      pr "    pod2text (\"%s\", _(\"%s\"), %S);\n"
-        name2 shortdesc
+      pr "  .shortdesc = \"%s\",\n" shortdesc;
+      pr "  .podbody = %S,\n"
        ("=head1 SYNOPSIS\n\n " ^ synopsis ^ "\n\n" ^
         "=head1 DESCRIPTION\n\n" ^
         longdesc ^ warnings ^ describe_alias);
-      pr "    return 0;\n";
-      pr "  }\n";
-      pr "  else\n"
+
+      pr "  .run = run_%s\n" name;
+      pr "};\n";
+      pr "\n";
  ) all_functions;

+  (* list_commands function, which implements guestfish -h *)
+  pr "void list_commands (void)\n";
+  pr "{\n";
+  pr "  printf (\"    %%-16s     %%s\\n\", _(\"Command\"), _(\"Description\"));\n";
+  pr "  list_builtin_commands ();\n";
+  List.iter (
+    fun (name, _, _, flags, _, shortdesc, _) ->
+      let name = replace_char name '_' '-' in
+      pr "  printf (\"%%-20s %%s\\n\", \"%s\", _(\"%s\"));\n"
+        name shortdesc
+  ) all_functions_and_fish_commands_sorted;
+  pr "  printf (\"    %%s\\n\",";
+  pr "          _(\"Use -h <cmd> / help <cmd> to show detailed help for a command.\"));\n";
+  pr "}\n";
+  pr "\n";
+
+  (* display_command function, which implements guestfish -h cmd *)
+  pr "int display_command (const char *cmd)\n";
+  pr "{\n";
+  pr "  const struct command_table *ct;\n";
+  pr "\n";
+  pr "  ct = lookup_fish_command (cmd, strlen (cmd));\n";
+  pr "  if (ct) {\n";
+  pr "    pod2text (ct->entry->name, ct->entry->shortdesc, ct->entry->podbody);\n";
+  pr "    return 0;\n";
+  pr "  }\n";
+  pr "  else\n";
  pr "    return display_builtin_command (cmd);\n";
  pr "}\n";
  pr "\n";
@@ -279,7 +288,8 @@ Guestfish will prompt for these separately."
  (* run_<action> actions *)
  List.iter (
    fun (name, (ret, args, optargs as style), _, flags, _, _, _) ->
-      pr "static int run_%s (const char *cmd, size_t argc, char *argv[])\n" name;
+      pr "static int\n";
+      pr "run_%s (const char *cmd, size_t argc, char *argv[])\n" name;
      pr "{\n";
      (match ret with
       | RErr
@@ -582,36 +592,84 @@ Guestfish will prompt for these separately."
  ) all_functions;

  (* run_action function *)
-  pr "int run_action (const char *cmd, size_t argc, char *argv[])\n";
+  pr "int\n";
+  pr "run_action (const char *cmd, size_t argc, char *argv[])\n";
  pr "{\n";
+  pr "  const struct command_table *ct;\n";
+  pr "\n";
+  pr "  ct = lookup_fish_command (cmd, strlen (cmd));\n";
+  pr "  if (ct)\n";
+  pr "    return ct->entry->run (cmd, argc, argv);\n";
+  pr "  else {\n";
+  pr "    fprintf (stderr, _(\"%%s: unknown command\\n\"), cmd);\n";
+  pr "    if (command_num == 1)\n";
+  pr "      extended_help_message ();\n";
+  pr "    return -1;\n";
+  pr "  }\n";
+  pr "}\n"
+
+(* gperf code to do fast lookups of commands. *)
+and generate_fish_cmds_gperf () =
+  generate_header CStyle GPLv2plus;
+
+  let all_functions_sorted =
+    List.filter (
+      fun (_, _, _, flags, _, _, _) -> not (List.mem NotInFish flags)
+    ) all_functions_sorted in
+
+  let all_functions_and_fish_commands_sorted =
+    List.sort action_compare (all_functions_sorted @ fish_commands) in
+
+  pr "\
+%%language=ANSI-C
+%%define lookup-function-name lookup_fish_command
+%%ignore-case
+%%readonly-tables
+%%null-strings
+
+%%{
+
+#include <config.h>
+
+#include <stdlib.h>
+#include <string.h>
+
+#include \"cmds_gperf.h\"
+
+";
+
+  List.iter (
+    fun (name, _, _, _, _, _, _) ->
+      pr "extern struct command_entry %s_cmd_entry;\n" name
+  ) all_functions_and_fish_commands_sorted;
+
+  pr "\
+%%}
+
+struct command_table;
+
+%%%%
+";

  List.iter (
    fun (name, _, _, flags, _, _, _) ->
      let name2 = replace_char name '_' '-' in
      let aliases =
        filter_map (function FishAlias n -> Some n | _ -> None) flags in
-      pr "  if (";
-      pr "STRCASEEQ (cmd, \"%s\")" name;
+
+      (* The basic command. *)
+      pr "%s, &%s_cmd_entry\n" name name;
+
+      (* Command with dashes instead of underscores. *)
      if name <> name2 then
-        pr " || STRCASEEQ (cmd, \"%s\")" name2;
+        pr "%s, &%s_cmd_entry\n" name2 name;
+
+      (* Aliases for the command. *)
      List.iter (
        fun alias ->
-          pr " || STRCASEEQ (cmd, \"%s\")" alias;
+          pr "%s, &%s_cmd_entry\n" alias name;
      ) aliases;
-      pr ")\n";
-      pr "    return run_%s (cmd, argc, argv);\n" name;
-      pr "  else\n";
-  ) all_functions_and_fish_commands_sorted;
-
-  pr "    {\n";
-  pr "      fprintf (stderr, _(\"%%s: unknown command\\n\"), cmd);\n";
-  pr "      if (command_num == 1)\n";
-  pr "        extended_help_message ();\n";
-  pr "      return -1;\n";
-  pr "    }\n";
-  pr "  return 0;\n";
-  pr "}\n";
-  pr "\n"
+  ) all_functions_and_fish_commands_sorted

 (* Readline completion for guestfish. *)
 and generate_fish_completion () =
--- a/generator/generator_main.ml
+++ b/generator/generator_main.ml
@@ -92,6 +92,7 @@ Run it from the top source directory using the command
  output_to "daemon/optgroups.c" generate_daemon_optgroups_c;
  output_to "daemon/optgroups.h" generate_daemon_optgroups_h;
  output_to "capitests/tests.c" generate_tests;
+  output_to "fish/cmds_gperf.gperf" generate_fish_cmds_gperf;
  output_to "fish/cmds.c" generate_fish_cmds;
  output_to "fish/completion.c" generate_fish_completion;
  output_to "fish/guestfish-commands.pod" generate_fish_commands_pod;
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -73,6 +73,7 @@ daemon/zero.c
 daemon/zerofree.c
 fish/alloc.c
 fish/cmds.c
+fish/cmds_gperf.c
 fish/completion.c
 fish/copy.c
 fish/destpaths.c