add functions for bit-reversal

Sometimes we need stuff like reversing every bit in each byte (but not
the byte-order).

3 files changed, 43 insertions, 1 deletions

diff --git a/tests/Makefile.am b/tests/Makefile.am
index 2b4ac6e6..6c3cb337 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -1,5 +1,5 @@
 if ENABLE_TESTS
-SUBDIRS = timer sms ussd smscb
+SUBDIRS = timer sms ussd smscb bits
 if ENABLE_MSGFILE
 SUBDIRS += msgfile
 endif
diff --git a/tests/bits/Makefile.am b/tests/bits/Makefile.am
new file mode 100644
index 00000000..dd03e83e
--- /dev/null
+++ b/tests/bits/Makefile.am
@@ -0,0 +1,6 @@
+INCLUDES = $(all_includes) -I$(top_srcdir)/include
+noinst_PROGRAMS = bitrev_test
+
+bitrev_test_SOURCES = bitrev_test.c
+bitrev_test_LDADD = $(top_builddir)/src/libosmocore.la
+
diff --git a/tests/bits/bitrev_test.c b/tests/bits/bitrev_test.c
new file mode 100644
index 00000000..5eca990a
--- /dev/null
+++ b/tests/bits/bitrev_test.c
@@ -0,0 +1,36 @@
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+
+#include <osmocom/core/utils.h>
+#include <osmocom/core/bits.h>
+
+static const uint8_t input[] = { 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80 };
+static const uint8_t exp_out[] = { 0x80, 0x40, 0x20, 0x10, 0x08, 0x04, 0x02, 0x01 };
+
+int main(int argc, char **argv)
+{
+	uint8_t out[ARRAY_SIZE(input)];
+	unsigned int offs;
+
+	for (offs = 0; offs < sizeof(out); offs++) {
+		uint8_t *start = out + offs;
+		uint8_t len = sizeof(out) - offs;
+
+		memcpy(out, input, sizeof(out));
+
+		printf("INORDER:  %s\n", osmo_hexdump(start, len));
+		osmo_revbytebits_buf(start, len);
+		printf("REVERSED: %s\n", osmo_hexdump(start, len));
+		if (memcmp(start, exp_out + offs, len)) {
+			printf("EXPECTED: %s\n", osmo_hexdump(exp_out+offs, len));
+			fprintf(stderr, "REVERSED != EXPECTED!\n");
+			exit(1);
+		}
+		printf("\n");
+	}
+
+	return 0;
+}