perf util: Add a function for replacing characters in a string

It finds all occurrences of a single character and replaces them with
a multi character string. This will be used in a test in a following
commit.

Reviewed-by: Ian Rogers <[e-mail]>
Signed-off-by: James Clark <[e-mail]>
Cc: Adrian Hunter <[e-mail]>
Cc: Alexander Shishkin <[e-mail]>
Cc: Chen Zhongjin <[e-mail]>
Cc: Eduard Zingerman <[e-mail]>
Cc: Haixin Yu <[e-mail]>
Cc: Ingo Molnar <[e-mail]>
Cc: Jing Zhang <[e-mail]>
Cc: Jiri Olsa <[e-mail]>
Cc: John Garry <[e-mail]>
Cc: Kajol Jain <[e-mail]>
Cc: Kan Liang <[e-mail]>
Cc: Leo Yan <[e-mail]>
Cc: Liam Howlett <[e-mail]>
Cc: Madhavan Srinivasan <[e-mail]>
Cc: Mark Rutland <[e-mail]>
Cc: Mike Leach <[e-mail]>
Cc: Namhyung Kim <[e-mail]>
Cc: Peter Zijlstra <[e-mail]>
Cc: Ravi Bangoria <[e-mail]>
Cc: Will Deacon <[e-mail]>
Cc: Yang Jihong <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>

tools/perf/tests/Build

···
 perf-y += sigtrap.o
 perf-y += event_groups.o
 perf-y += symbols.o
+perf-y += util.o
 
 ifeq ($(SRCARCH),$(filter $(SRCARCH),x86 arm arm64 powerpc))
 perf-$(CONFIG_DWARF_UNWIND) += dwarf-unwind.o

tools/perf/tests/builtin-test.c

···
 	&suite__sigtrap,
 	&suite__event_groups,
 	&suite__symbols,
+	&suite__util,
 	NULL,
 };
 

tools/perf/tests/tests.h

···
 DECLARE_SUITE(sigtrap);
 DECLARE_SUITE(event_groups);
 DECLARE_SUITE(symbols);
+DECLARE_SUITE(util);
 
 /*
  * PowerPC and S390 do not support creation of instruction breakpoints using the

tools/perf/tests/util.c

···
+// SPDX-License-Identifier: GPL-2.0
+#include "tests.h"
+#include "util/debug.h"
+
+#include <linux/compiler.h>
+#include <stdlib.h>
+#include <string2.h>
+
+static int test_strreplace(char needle, const char *haystack,
+			   const char *replace, const char *expected)
+{
+	char *new = strreplace_chars(needle, haystack, replace);
+	int ret = strcmp(new, expected);
+
+	free(new);
+	return ret == 0;
+}
+
+static int test__util(struct test_suite *t __maybe_unused, int subtest __maybe_unused)
+{
+	TEST_ASSERT_VAL("empty string", test_strreplace(' ', "", "123", ""));
+	TEST_ASSERT_VAL("no match", test_strreplace('5', "123", "4", "123"));
+	TEST_ASSERT_VAL("replace 1", test_strreplace('3', "123", "4", "124"));
+	TEST_ASSERT_VAL("replace 2", test_strreplace('a', "abcabc", "ef", "efbcefbc"));
+	TEST_ASSERT_VAL("replace long", test_strreplace('a', "abcabc", "longlong",
+							"longlongbclonglongbc"));
+
+	return 0;
+}
+
+DEFINE_SUITE("util", util);

tools/perf/util/string.c

···
 		return c - 'a' + 10;
 	return c - 'A' + 10;
 }
+
+/*
+ * Replace all occurrences of character 'needle' in string 'haystack' with
+ * string 'replace'
+ *
+ * The new string could be longer so a new string is returned which must be
+ * freed.
+ */
+char *strreplace_chars(char needle, const char *haystack, const char *replace)
+{
+	int replace_len = strlen(replace);
+	char *new_s, *to;
+	const char *loc = strchr(haystack, needle);
+	const char *from = haystack;
+	int num = 0;
+
+	/* Count occurrences */
+	while (loc) {
+		loc = strchr(loc + 1, needle);
+		num++;
+	}
+
+	/* Allocate enough space for replacements and reset first location */
+	new_s = malloc(strlen(haystack) + (num * (replace_len - 1) + 1));
+	if (!new_s)
+		return NULL;
+	loc = strchr(haystack, needle);
+	to = new_s;
+
+	while (loc) {
+		/* Copy original string up to found char and update positions */
+		memcpy(to, from, 1 + loc - from);
+		to += loc - from;
+		from = loc + 1;
+
+		/* Copy replacement string and update positions */
+		memcpy(to, replace, replace_len);
+		to += replace_len;
+
+		/* needle next occurrence or end of string */
+		loc = strchr(from, needle);
+	}
+
+	/* Copy any remaining chars + null */
+	strcpy(to, from);
+
+	return new_s;
+}

tools/perf/util/string2.h

···
 char *strdup_esc(const char *str);
 
 unsigned int hex(char c);
+char *strreplace_chars(char needle, const char *haystack, const char *replace);
 
 #endif /* PERF_STRING_H */