[4/6] fixdep: refactor hash table lookup

Commit Message

Masahiro Yamada Dec. 31, 2022, 6:42 a.m. UTC

Change the hash table code so it will be easier to add the second table.

Signed-off-by: Masahiro Yamada <[e-mail]>
---

 scripts/basic/fixdep.c | 47 ++++++++++++++++++++++--------------------
 1 file changed, 25 insertions(+), 22 deletions(-)

Comments

Miguel Ojeda Jan. 3, 2023, 8:45 p.m. UTC | #1

On Sat, Dec 31, 2022 at 7:42 AM Masahiro Yamada <[e-mail]> wrote:
>
> +/*
> + * Lookup a string in the hash table. If found, just return true.
> + * If not, add it to the hashtable and return false.
> + */
> +static bool in_hashtable(const char *name, int len, struct item *hashtab[])

I think readers may find a bit surprising that a function named
`in_hashtable` mutates the table. Should we use a better name? Perhaps
`ensure_in_hashtable`?

In other words, the function is really "insert if not already there
and return the previous state". Similar methods in C++ and Rust are
called `insert`, though they return the opposite, i.e. whether the
insertion took place. If we did that, then `insert_into_hashtable` may
be a good name instead.

> +       unsigned int hash = strhash(name, len);

Nit: this could be `const`, but I see we are not using it in
`fixdep.c` (for non-pointees) and it was not done in the original. But
it could be nice to start...

Reviewed-by: Miguel Ojeda <[e-mail]>
Tested-by: Miguel Ojeda <[e-mail]>

Cheers,
Miguel

Patch

diff --git a/scripts/basic/fixdep.c b/scripts/basic/fixdep.c
index 37a40520686f..b20777b888d7 100644
--- a/scripts/basic/fixdep.c
+++ b/scripts/basic/fixdep.c
@@ -113,7 +113,7 @@  struct item {
 };
 
 #define HASHSZ 256
-static struct item *hashtab[HASHSZ];
+static struct item *config_hashtab[HASHSZ];
 
 static unsigned int strhash(const char *str, unsigned int sz)
 {
@@ -125,25 +125,11 @@  static unsigned int strhash(const char *str, unsigned int sz)
 	return hash;
 }
 
-/*
- * Lookup a value in the configuration string.
- */
-static int is_defined_config(const char *name, int len, unsigned int hash)
-{
-	struct item *aux;
-
-	for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
-		if (aux->hash == hash && aux->len == len &&
-		    memcmp(aux->name, name, len) == 0)
-			return 1;
-	}
-	return 0;
-}
-
 /*
  * Add a new value to the configuration string.
  */
-static void define_config(const char *name, int len, unsigned int hash)
+static void add_to_hashtable(const char *name, int len, unsigned int hash,
+			     struct item *hashtab[])
 {
 	struct item *aux = malloc(sizeof(*aux) + len);
 
@@ -158,17 +144,34 @@  static void define_config(const char *name, int len, unsigned int hash)
 	hashtab[hash % HASHSZ] = aux;
 }
 
+/*
+ * Lookup a string in the hash table. If found, just return true.
+ * If not, add it to the hashtable and return false.
+ */
+static bool in_hashtable(const char *name, int len, struct item *hashtab[])
+{
+	struct item *aux;
+	unsigned int hash = strhash(name, len);
+
+	for (aux = hashtab[hash % HASHSZ]; aux; aux = aux->next) {
+		if (aux->hash == hash && aux->len == len &&
+		    memcmp(aux->name, name, len) == 0)
+			return true;
+	}
+
+	add_to_hashtable(name, len, hash, hashtab);
+
+	return false;
+}
+
 /*
  * Record the use of a CONFIG_* word.
  */
 static void use_config(const char *m, int slen)
 {
-	unsigned int hash = strhash(m, slen);
-
-	if (is_defined_config(m, slen, hash))
-	    return;
+	if (in_hashtable(m, slen, config_hashtab))
+		return;
 
-	define_config(m, slen, hash);
 	/* Print out a dependency path from a symbol name. */
 	printf("    $(wildcard include/config/%.*s) \\\n", slen, m);
 }