From: Lucas De Marchi <lucas.de.marchi@gmail.com>
Date: Thu, 14 Nov 2024 05:02:07 +0000 (-0600)
Subject: strbuf: Add strbuf_shrink_to()
X-Git-Tag: v34~85
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=14ce34d755f828feb89381777a9170d5839cca61;p=thirdparty%2Fkmod.git

strbuf: Add strbuf_shrink_to()

Useful when working with paths on a loop and resetting to a base path
component on every loop iteration.

Signed-off-by: Lucas De Marchi <lucas.de.marchi@gmail.com>
Reviewed-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/239
---

diff --git a/shared/strbuf.c b/shared/strbuf.c
index 6a4c8d93..dad5da52 100644
--- a/shared/strbuf.c
+++ b/shared/strbuf.c
@@ -121,6 +121,12 @@ void strbuf_popchars(struct strbuf *buf, size_t n)
 	buf->used -= n;
 }
 
+void strbuf_shrink_to(struct strbuf *buf, size_t sz)
+{
+	assert(buf->used >= sz);
+	buf->used = sz;
+}
+
 void strbuf_clear(struct strbuf *buf)
 {
 	buf->used = 0;
diff --git a/shared/strbuf.h b/shared/strbuf.h
index 96e6ed24..02ec8955 100644
--- a/shared/strbuf.h
+++ b/shared/strbuf.h
@@ -102,6 +102,11 @@ void strbuf_popchar(struct strbuf *buf);
  */
 void strbuf_popchars(struct strbuf *buf, size_t n);
 
+/*
+ * Shrink buffer to the final size @sz, which must be less or equal the current size.
+ */
+void strbuf_shrink_to(struct strbuf *buf, size_t sz);
+
 /*
  * Return number of used chars. This may different than calling strlen() in a C string
  * since '\0' is considered a valid char - this only keeps track of how many slots are
diff --git a/testsuite/test-strbuf.c b/testsuite/test-strbuf.c
index 859f9b26..e77fbdb9 100644
--- a/testsuite/test-strbuf.c
+++ b/testsuite/test-strbuf.c
@@ -227,4 +227,35 @@ static int test_strbuf_used(const struct test *t)
 }
 DEFINE_TEST(test_strbuf_used, .description = "test strbuf_used");
 
+static int test_strbuf_shrink_to(const struct test *t)
+{
+	_cleanup_strbuf_ struct strbuf buf;
+
+	strbuf_init(&buf);
+	strbuf_shrink_to(&buf, 0);
+	assert_return(strbuf_used(&buf) == 0, EXIT_FAILURE);
+
+	strbuf_pushchars(&buf, TEXT);
+	strbuf_shrink_to(&buf, strlen(TEXT) - 1);
+	assert_return(strbuf_used(&buf) == strlen(TEXT) - 1, EXIT_FAILURE);
+
+	return 0;
+}
+DEFINE_TEST(test_strbuf_shrink_to, .description = "test strbuf_shrink_to");
+
+static int xfail_strbuf_shrink_to(const struct test *t)
+{
+	_cleanup_strbuf_ struct strbuf buf;
+
+	strbuf_init(&buf);
+	strbuf_pushchar(&buf, '/');
+
+	/* This should crash on assert */
+	strbuf_shrink_to(&buf, 2);
+
+	return 0;
+}
+DEFINE_TEST(xfail_strbuf_shrink_to, .description = "xfail strbuf_shrink_to",
+	    .expected_fail = true);
+
 TESTSUITE_MAIN();