From: Tobias Stoeckmann <tobias@stoeckmann.org>
Date: Mon, 24 Feb 2025 18:55:28 +0000 (+0100)
Subject: libkmod: refactor kmod_module_hex_to_str
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0766b418a8d7f010695925ede08e6ed8966e83dd;p=thirdparty%2Fkmod.git

libkmod: refactor kmod_module_hex_to_str

The hex output uses a heap-based strbuf. It can be turned into a
stack-based strbuf by refactoring kmod_module_hex_to_str. Instead of
returning a C string, a supplied strbuf can be filled with hex values
in ASCII representation. Renamed to kmod_module_strbuf_pushhex.

A size of 512 is sufficient for signatures on Arch Linux and removes
heap allocations. Additional benefit is implicit strbuf_init and
strbuf_release due to DECLARE_STRBUF_WITH_STACK.

Signed-off-by: Tobias Stoeckmann <tobias@stoeckmann.org>
Link: https://github.com/kmod-project/kmod/pull/296
Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
---

diff --git a/libkmod/libkmod-module.c b/libkmod/libkmod-module.c
index 661b3cf6..dc660f24 100644
--- a/libkmod/libkmod-module.c
+++ b/libkmod/libkmod-module.c
@@ -1799,46 +1799,46 @@ static struct kmod_list *kmod_module_info_append(struct kmod_list **list, const
 	return n;
 }
 
-static char *kmod_module_hex_to_str(const char *hex, size_t len)
+static bool kmod_module_strbuf_pushhex(struct strbuf *sbuf, const char *hex, size_t len)
 {
 	static const char digits[] = "0123456789ABCDEF";
-	_cleanup_strbuf_ struct strbuf sbuf;
 	const size_t line_limit = 20;
 
-	strbuf_init(&sbuf);
-
 	for (size_t i = 0; i < len; i++) {
-		if (!strbuf_pushchar(&sbuf, digits[(hex[i] >> 4) & 0x0F]) ||
-		    !strbuf_pushchar(&sbuf, digits[hex[i] & 0x0F]))
-			return NULL;
+		if (!strbuf_pushchar(sbuf, digits[(hex[i] >> 4) & 0x0F]) ||
+		    !strbuf_pushchar(sbuf, digits[hex[i] & 0x0F]))
+			return false;
 
 		if (i < len - 1) {
-			if (!strbuf_pushchar(&sbuf, ':'))
-				return NULL;
+			if (!strbuf_pushchar(sbuf, ':'))
+				return false;
 
-			if ((i + 1) % line_limit == 0 &&
-			    !strbuf_pushchars(&sbuf, "\n\t\t"))
-				return NULL;
+			if ((i + 1) % line_limit == 0 && !strbuf_pushchars(sbuf, "\n\t\t"))
+				return false;
 		}
 	}
 
-	return strbuf_steal(&sbuf);
+	return true;
 }
 
 static struct kmod_list *kmod_module_info_append_hex(struct kmod_list **list,
 						     const char *key, size_t keylen,
 						     const char *value, size_t valuelen)
 {
-	char *hex;
 	struct kmod_list *n;
 
 	if (valuelen > 0) {
+		DECLARE_STRBUF_WITH_STACK(sbuf, 512);
+		const char *hex;
+
 		/* Display as 01:12:DE:AD:BE:EF:... */
-		hex = kmod_module_hex_to_str(value, valuelen);
+		if (!kmod_module_strbuf_pushhex(&sbuf, value, valuelen))
+			goto list_error;
+		hex = strbuf_str(&sbuf);
 		if (hex == NULL)
 			goto list_error;
+
 		n = kmod_module_info_append(list, key, keylen, hex, strlen(hex));
-		free(hex);
 		if (n == NULL)
 			goto list_error;
 	} else {