output: cache the mapped file names

Don't repeatedly call malloc/free for each call to map_file_name.

* bootstrap.conf: We need hash-map.
* src/files.h, src/files.c (map_file_name): The caller must not free
the result.
Adjust callers.
(mapped_dir_prefix, spec_mapped_header_file): Remove.
* src/files.c
(map_file_name): Rename as...
(map_file_name_alloc): this.
(mapped_files, map_file_name, string_equals, string_hash, string_free):
New.

5 files changed, 86 insertions, 47 deletions

diff --git a/src/files.c b/src/files.c
index 72652f42..04f71197 100644
--- a/src/files.c
+++ b/src/files.c
@@ -26,7 +26,9 @@
 #include <error.h>
 #include <get-errno.h>
 #include <gl_array_list.h>
+#include <gl_hash_map.h>
 #include <gl_xlist.h>
+#include <gl_xmap.h>
 #include <quote.h>
 #include <quotearg.h>
 #include <relocatable.h> /* relocate2 */
@@ -58,7 +60,6 @@ char *spec_graph_file = NULL;    /* for -g. */
 char *spec_html_file = NULL;     /* for --html. */
 char *spec_xml_file = NULL;      /* for -x. */
 char *spec_header_file = NULL;   /* for --header. */
-char *spec_mapped_header_file = NULL;
 char *parser_file_name;
 
 /* All computed output file names.  */
@@ -95,7 +96,6 @@ uniqstr grammar_file = NULL;
 char *all_but_ext;
 static char *all_but_tab_ext;
 char *dir_prefix;
-char *mapped_dir_prefix;
 
 /* C source file extension (the parser source).  */
 static char *src_extension = NULL;
@@ -109,6 +109,10 @@ struct prefix_map
 };
 
 static gl_list_t prefix_maps = NULL;
+
+/* Map file names to prefix-mapped file names. */
+static gl_map_t mapped_files = NULL;
+
 
 /*-----------------------------------------------------------------.
 | Return a newly allocated string composed of the concatenation of |
@@ -172,29 +176,25 @@ xfdopen (int fd, char const *mode)
   return res;
 }
 
-/*  Given an input file path, returns a dynamically allocated string that
-    contains the path with the file prefix mapping rules applied, or NULL if
-    the input was NULL. */
-char *
-map_file_name (char const *filename)
+/* The mapped name of FILENAME, allocated, if there are prefix maps.
+   Otherwise NULL.  */
+static char *
+map_file_name_alloc (char const *filename)
 {
-  if (!filename)
-    return NULL;
-
   struct prefix_map const *p = NULL;
-  if (prefix_maps)
-    {
-      void const *ptr;
-      gl_list_iterator_t iter = gl_list_iterator (prefix_maps);
-      while (gl_list_iterator_next (&iter, &ptr, NULL))
-        {
-          p = ptr;
-          if (strncmp (p->oldprefix, filename, strlen (p->oldprefix)) == 0)
-            break;
-          p = NULL;
-        }
-      gl_list_iterator_free (&iter);
-    }
+  assert (prefix_maps);
+  {
+    void const *ptr;
+    gl_list_iterator_t iter = gl_list_iterator (prefix_maps);
+    while (gl_list_iterator_next (&iter, &ptr, NULL))
+      {
+        p = ptr;
+        if (strncmp (p->oldprefix, filename, strlen (p->oldprefix)) == 0)
+          break;
+        p = NULL;
+      }
+    gl_list_iterator_free (&iter);
+  }
 
   if (!p)
     return xstrdup (filename);
@@ -209,6 +209,56 @@ map_file_name (char const *filename)
   return res;
 }
 
+static bool
+string_equals (const void *x1, const void *x2)
+{
+  const char *s1 = x1;
+  const char *s2 = x2;
+  return STREQ (s1, s2);
+}
+
+/* A hash function for NUL-terminated char* strings using
+   the method described by Bruno Haible.
+   See https://www.haible.de/bruno/hashfunc.html.  */
+static size_t
+string_hash (const void *x)
+{
+#define SIZE_BITS (sizeof (size_t) * CHAR_BIT)
+
+  const char *s = x;
+  size_t h = 0;
+
+  for (; *s; s++)
+    h = *s + ((h << 9) | (h >> (SIZE_BITS - 9)));
+
+  return h;
+}
+
+static void
+string_free (const void *p)
+{
+  free ((void*) p);
+}
+
+const char *
+map_file_name (char const *filename)
+{
+  if (!filename || !prefix_maps)
+    return filename;
+  if (!mapped_files)
+    mapped_files
+      = gl_map_nx_create_empty (GL_HASH_MAP,
+                                string_equals, string_hash,
+                                string_free, string_free);
+  const void *res = gl_map_get (mapped_files, filename);
+  if (!res)
+    {
+      res = map_file_name_alloc (filename);
+      gl_map_put (mapped_files, xstrdup (filename), res);
+    }
+  return res;
+}
+
 static void
 prefix_map_free (struct prefix_map *p)
 {
@@ -445,9 +495,6 @@ compute_output_file_names (void)
       output_file_name_check (&spec_verbose_file, false);
     }
 
-  spec_mapped_header_file = map_file_name (spec_header_file);
-  mapped_dir_prefix = map_file_name (dir_prefix);
-
   free (all_but_tab_ext);
   free (src_extension);
   free (header_extension);
@@ -535,10 +582,8 @@ output_file_names_free (void)
   free (spec_html_file);
   free (spec_xml_file);
   free (spec_header_file);
-  free (spec_mapped_header_file);
   free (parser_file_name);
   free (dir_prefix);
-  free (mapped_dir_prefix);
   for (int i = 0; i < generated_files_size; i++)
     free (generated_files[i].name);
   free (generated_files);
@@ -546,4 +591,6 @@ output_file_names_free (void)
 
   if (prefix_maps)
     gl_list_free (prefix_maps);
+  if (mapped_files)
+    gl_map_free (mapped_files);
 }
diff --git a/src/files.h b/src/files.h
index d49847ab..38584773 100644
--- a/src/files.h
+++ b/src/files.h
@@ -53,15 +53,9 @@ extern char *spec_xml_file;
 /* File name specified with --header.  */
 extern char *spec_header_file;
 
-/* File name specified with --header, adjusted for mapped prefixes. */
-extern char *spec_mapped_header_file;
-
 /* Directory prefix of output file names.  */
 extern char *dir_prefix;
 
-/* Directory prefix of output file name, adjusted for mapped prefixes. */
-extern char *mapped_dir_prefix;
-
 /* The file name as given on the command line.
    Not named "input_file" because Flex uses this name for an argument,
    and therefore GCC warns about a name clash. */
@@ -94,7 +88,10 @@ FILE *xfopen (const char *name, char const *mode);
 void xfclose (FILE *ptr);
 FILE *xfdopen (int fd, char const *mode);
 
-char *map_file_name (char const *filename);
+/* Given an input file path, return a string that contains the path
+   with the file prefix mapping rules applied, or NULL if the input
+   was NULL.  Do not free the return value.  */
+const char *map_file_name (char const *filename);
 
 /* Add a new file prefix mapping. If a file path starts with
    oldprefix, it will be replaced with newprefix.  */
diff --git a/src/muscle-tab.c b/src/muscle-tab.c
index 3e7657ca..0654a3f1 100644
--- a/src/muscle-tab.c
+++ b/src/muscle-tab.c
@@ -204,10 +204,8 @@ static void
 muscle_syncline_grow (char const *key, location loc)
 {
   obstack_printf (&muscle_obstack, "]b4_syncline(%d, ", loc.start.line);
-  char *f = map_file_name (loc.start.file);
   obstack_quote (&muscle_obstack,
-                 quotearg_style (c_quoting_style, f));
-  free (f);
+                 quotearg_style (c_quoting_style, map_file_name (loc.start.file)));
   obstack_sgrow (&muscle_obstack, ")dnl\n[");
   char const *extension = obstack_finish0 (&muscle_obstack);
   muscle_grow (key, extension, "", "");
diff --git a/src/output.c b/src/output.c
index 34dbc671..4b1bb0d8 100644
--- a/src/output.c
+++ b/src/output.c
@@ -531,9 +531,7 @@ user_actions_output (FILE *out)
           {
             fprintf (out, "b4_syncline(%d, ",
                      rules[r].action_loc.start.line);
-            char *f = map_file_name (rules[r].action_loc.start.file);
-            string_output (out, f);
-            free(f);
+            string_output (out, map_file_name (rules[r].action_loc.start.file));
             fprintf (out, ")dnl\n");
           }
         fprintf (out, "[%*s%s]],\n[[",
@@ -631,10 +629,8 @@ prepare_symbol_definitions (void)
 
           if (p->code)
             {
-              char *f = map_file_name (p->location.start.file);
               SET_KEY2 (pname, "file");
-              MUSCLE_INSERT_C_STRING (key, f);
-              free (f);
+              MUSCLE_INSERT_C_STRING (key, map_file_name (p->location.start.file));
 
               SET_KEY2 (pname, "line");
               MUSCLE_INSERT_INT (key, p->location.start.line);
@@ -852,6 +848,9 @@ prepare (void)
 
   MUSCLE_INSERT_STRING ("file_name_all_but_ext", all_but_ext);
 
+  const char *spec_mapped_header_file = map_file_name (spec_header_file);
+  const char *mapped_dir_prefix = map_file_name (dir_prefix);
+
 #define DEFINE(Name) MUSCLE_INSERT_STRING (#Name, Name ? Name : "")
   DEFINE (dir_prefix);
   DEFINE (mapped_dir_prefix);
diff --git a/src/scan-skel.l b/src/scan-skel.l
index 1ec125af..20049cfb 100644
--- a/src/scan-skel.l
+++ b/src/scan-skel.l
@@ -269,7 +269,5 @@ fail_for_invalid_at (char const *at)
 static void
 output_mapped_file (char const *name)
 {
-  char *f = map_file_name (name);
-  fputs (quotearg_style (c_quoting_style, f), yyout);
-  free (f);
+  fputs (quotearg_style (c_quoting_style, map_file_name (name)), yyout);
 }