Re: [PATCH 3/7] perf util: Add a function for replacing characters in a string

[Ian Rogers]

On Thu, Aug 31, 2023 at 8:17 AM James Clark <james.clark@xxxxxxx> wrote:
>
> 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.
>
> Signed-off-by: James Clark <james.clark@xxxxxxx>
> ---
>  tools/perf/tests/Build          |  1 +
>  tools/perf/tests/builtin-test.c |  1 +
>  tools/perf/tests/tests.h        |  1 +
>  tools/perf/tests/util.c         | 30 +++++++++++++++++++++
>  tools/perf/util/string.c        | 48 +++++++++++++++++++++++++++++++++
>  tools/perf/util/string2.h       |  1 +
>  6 files changed, 82 insertions(+)
>  create mode 100644 tools/perf/tests/util.c
>
> diff --git a/tools/perf/tests/Build b/tools/perf/tests/Build
> index 63d5e6d5f165..2b45ffa462a6 100644
> --- a/tools/perf/tests/Build
> +++ b/tools/perf/tests/Build
> @@ -66,6 +66,7 @@ perf-y += dlfilter-test.o
>  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
> diff --git a/tools/perf/tests/builtin-test.c b/tools/perf/tests/builtin-test.c
> index 0ad18cf6dd22..cb6f1dd00dc4 100644
> --- a/tools/perf/tests/builtin-test.c
> +++ b/tools/perf/tests/builtin-test.c
> @@ -123,6 +123,7 @@ static struct test_suite *generic_tests[] = {
>         &suite__sigtrap,
>         &suite__event_groups,
>         &suite__symbols,
> +       &suite__util,
>         NULL,
>  };
>
> diff --git a/tools/perf/tests/tests.h b/tools/perf/tests/tests.h
> index f33cfc3c19a4..b394f3ac2d66 100644
> --- a/tools/perf/tests/tests.h
> +++ b/tools/perf/tests/tests.h
> @@ -145,6 +145,7 @@ DECLARE_SUITE(dlfilter);
>  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
> diff --git a/tools/perf/tests/util.c b/tools/perf/tests/util.c
> new file mode 100644
> index 000000000000..43e66a620b83
> --- /dev/null
> +++ b/tools/perf/tests/util.c
> @@ -0,0 +1,30 @@
> +// 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 find, const char *s, const char *replace, const char *expected)
> +{
> +       char *new = strreplace_chars(find, s, 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);
> diff --git a/tools/perf/util/string.c b/tools/perf/util/string.c
> index cf05b0b56c57..6410a683183e 100644
> --- a/tools/perf/util/string.c
> +++ b/tools/perf/util/string.c
> @@ -301,3 +301,51 @@ unsigned int hex(char c)
>                 return c - 'a' + 10;
>         return c - 'A' + 10;
>  }
> +
> +
> +/*
> + * Replace all occurrences of character 'find' in string s with string 'replace'
> + *
> + * The new string could be longer so a new string is returned which must
> + * be freed.
> + */

Fwiw, I quite like the "man strstr" parameter convention of calling
"find" as "needle" and "s" as haystack.

Reviewed-by: Ian Rogers <irogers@xxxxxxxxxx>

Thanks,
Ian

> +char *strreplace_chars(char find, const char *s, const char *replace)
> +{
> +       int replace_len = strlen(replace);
> +       char *new_s, *to;
> +       const char *loc = strchr(s, find);
> +       const char *from = s;
> +       int num = 0;
> +
> +       /* Count occurrences */
> +       while (loc) {
> +               loc = strchr(loc + 1, find);
> +               num++;
> +       }
> +
> +       /* Allocate enough space for replacements and reset first location */
> +       new_s = malloc(strlen(s) + (num * (replace_len - 1) + 1));
> +       if (!new_s)
> +               return NULL;
> +       loc = strchr(s, find);
> +       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;
> +
> +               /* Find next occurrence or end of string */
> +               loc = strchr(from, find);
> +       }
> +
> +       /* Copy any remaining chars + null */
> +       strcpy(to, from);
> +
> +       return new_s;
> +}
> diff --git a/tools/perf/util/string2.h b/tools/perf/util/string2.h
> index 56c30fef9682..920488099214 100644
> --- a/tools/perf/util/string2.h
> +++ b/tools/perf/util/string2.h
> @@ -39,5 +39,6 @@ char *strpbrk_esc(char *str, const char *stopset);
>  char *strdup_esc(const char *str);
>
>  unsigned int hex(char c);
> +char *strreplace_chars(char find, const char *s, const char *replace);
>
>  #endif /* PERF_STRING_H */
> --
> 2.34.1
>