util: add a strv_from_mem() helper function

Generates a strv with the buffer as hex string.

src/util-strings.c

@@ -224,6 +224,46 @@ strreplace(const char *string, const char *separator, const char *replacement)
 }
 
 
+char **
+strv_from_mem(const uint8_t *buffer, size_t sz, size_t stride)
+{
+	assert(stride > 0);
+	assert(stride <= 16);
+
+	char **strv = xalloc(((sz / stride) + 2) * sizeof *strv);
+
+	#define hex(buffer_, sz, line_, offset_) \
+		(line_ + offset_ < sz) ? buffer_[line_ + offset_] : 0u
+	for (size_t i = 0; i < sz; i += stride) {
+		char *str = xaprintf(
+			"%02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x %02x",
+			hex(buffer, sz, i, 0),
+			hex(buffer, sz, i, 1),
+			hex(buffer, sz, i, 2),
+			hex(buffer, sz, i, 3),
+			hex(buffer, sz, i, 4),
+			hex(buffer, sz, i, 5),
+			hex(buffer, sz, i, 6),
+			hex(buffer, sz, i, 7),
+			hex(buffer, sz, i, 8),
+			hex(buffer, sz, i, 9),
+			hex(buffer, sz, i, 10),
+			hex(buffer, sz, i, 11),
+			hex(buffer, sz, i, 12),
+			hex(buffer, sz, i, 13),
+			hex(buffer, sz, i, 14),
+			hex(buffer, sz, i, 15));
+
+		/* Chop the string off at the last value or our stride, whichever applies */
+		if (i + stride >= sz)
+			str[(sz - i) * 3 - 1] = '\0';
+		else if (stride < 16)
+			str[stride * 3 - 1] = '\0';
+		strv[i / stride] = str;
+	}
+	return strv;
+}
+
 #if _enable_tests_
 #include "util-munit.h"
 
@@ -498,4 +538,64 @@ MUNIT_TEST(test_strlen0)
 
 	return MUNIT_OK;
 }
+
+MUNIT_TEST(test_strv_from_mem)
+{
+	uint8_t buf[36];
+
+	for (size_t i = 0; i < sizeof(buf); i++)
+		buf[i] = i;
+
+	{
+		_cleanup_(strv_freep) char **strv = strv_from_mem(buf, 16, 16);
+		munit_assert(strv != NULL);
+		munit_assert(strv[0] != NULL);
+		munit_assert_null(strv[1]); /* we expect one line */
+		munit_assert_string_equal(strv[0], "00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f");
+	}
+
+	{
+		_cleanup_(strv_freep) char **strv = strv_from_mem(buf, 8, 16);
+		munit_assert(strv != NULL);
+		munit_assert(strv[0] != NULL);
+		munit_assert_null(strv[1]); /* we expect one line */
+		munit_assert_string_equal(strv[0], "00 01 02 03 04 05 06 07");
+	}
+
+	{
+		_cleanup_(strv_freep) char **strv = strv_from_mem(buf, 8, 4);
+		munit_assert(strv != NULL);
+		munit_assert(strv[0] != NULL);
+		munit_assert(strv[1] != NULL);
+		munit_assert_null(strv[2]); /* we expect two lines */
+		munit_assert_string_equal(strv[0], "00 01 02 03");
+		munit_assert_string_equal(strv[1], "04 05 06 07");
+	}
+
+	{
+		_cleanup_(strv_freep) char **strv = strv_from_mem(buf, sizeof(buf), 5);
+		munit_assert(strv != NULL);
+		munit_assert_string_equal(strv[0], "00 01 02 03 04");
+		munit_assert_string_equal(strv[1], "05 06 07 08 09");
+		munit_assert_string_equal(strv[2], "0a 0b 0c 0d 0e");
+		munit_assert_string_equal(strv[3], "0f 10 11 12 13");
+		munit_assert_string_equal(strv[4], "14 15 16 17 18");
+		munit_assert_string_equal(strv[5], "19 1a 1b 1c 1d");
+		munit_assert_string_equal(strv[6], "1e 1f 20 21 22");
+		munit_assert_string_equal(strv[7], "23");
+		munit_assert_null(strv[8]);
+	}
+
+	{
+		uint8_t buffer[14];
+		memset(buffer, -1, sizeof(buffer));
+		_cleanup_(strv_freep) char **strv = strv_from_mem(buffer, sizeof(buffer), 8);
+		munit_assert(strv != NULL);
+		munit_assert_string_equal(strv[0], "ff ff ff ff ff ff ff ff");
+		munit_assert_string_equal(strv[1], "ff ff ff ff ff ff");
+		munit_assert_null(strv[2]);
+	}
+
+	return MUNIT_OK;
+}
 #endif

src/util-strings.h

@@ -34,6 +34,7 @@
 #include <limits.h>
 #include <math.h>
 #include <string.h>
+#include <stdint.h>
 #include <stdio.h>
 #include <stdbool.h>
 #include <stdlib.h>
@@ -276,6 +277,13 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(char **, strv_free);
 
 char * strreplace(const char *string, const char *separator, const char *replacement);
 
+/**
+ * Creates a list of strings representing the buffer similar to hexdump, i.e.
+ * a buffer of [0, 1, 2, 3, ...] with a stride of 4 is split into
+ * the strv of ["00 01 02 03", "04 05 06 07", ...].
+ */
+char **strv_from_mem(const uint8_t *buffer, size_t sz, size_t stride);
+
 struct key_value_str{
 	char *key;
 	char *value;