libcommon: soak up three static functions.

Add new kitchen sink openbsc/utils.h and libcommon/utils.c to make three so far
static functions public (so I can use them in the upcoming OAP code).

A place to put them could have been the gprs_utils.h, but all general functions
in there have a gprs_ prefix, and todo markings to move them away. All other
libcommon headers are too specific, so I opened up this kitchen sink header.

Replace the implementation of encode_big_endian() with a call to
osmo_store64be_ext(). See comments.

Apply the change in Makefiles and C files.

2 files changed, 27 insertions, 1 deletions

diff --git a/openbsc/include/openbsc/Makefile.am b/openbsc/include/openbsc/Makefile.am
index 254f43dbe..828f5bd2d 100644
--- a/openbsc/include/openbsc/Makefile.am
+++ b/openbsc/include/openbsc/Makefile.am
@@ -14,7 +14,7 @@ noinst_HEADERS = abis_nm.h abis_rsl.h db.h gsm_04_08.h gsm_data.h \
 		osmo_msc_data.h osmo_bsc_grace.h sms_queue.h abis_om2000.h \
 		bss.h gsm_data_shared.h ipaccess.h mncc_int.h \
 		arfcn_range_encode.h nat_rewrite_trie.h bsc_nat_callstats.h \
-		osmux.h mgcp_transcode.h gprs_utils.h \
+		osmux.h mgcp_transcode.h gprs_utils.h utils.h \
 		 gprs_gb_parse.h smpp.h meas_feed.h gprs_gsup_messages.h \
 		 gprs_gsup_client.h bsc_msg_filter.h
 
diff --git a/openbsc/include/openbsc/utils.h b/openbsc/include/openbsc/utils.h
new file mode 100644
index 000000000..d6054873b
--- /dev/null
+++ b/openbsc/include/openbsc/utils.h
@@ -0,0 +1,26 @@
+/* OpenBSC kitchen sink */
+
+#pragma once
+
+#include <stdint.h>
+#include <stdlib.h>
+
+/* Compare count bytes of exp to rel. Return 0 if they are identical, 1
+ * otherwise. Do not return a mismatch on the first mismatching byte,
+ * but always compare all bytes, regardless. The idea is that the amount of
+ * matching bytes cannot be inferred from the time the comparison took.*/
+int constant_time_cmp(const uint8_t *exp, const uint8_t *rel, const int count);
+
+/* This is like osmo_load64be_ext, except that if data_len is less than
+ * sizeof(uint64_t), the data is interpreted as the least significant bytes
+ * (osmo_load64be_ext loads them as the most significant bytes into the
+ * returned uint64_t). In this way, any integer size up to 64 bits can be
+ * decoded conveniently by using sizeof(), without the need to call specific
+ * numbered functions (osmo_load16, 32, ...). */
+uint64_t decode_big_endian(const uint8_t *data, size_t data_len);
+
+/* This is like osmo_store64be_ext, except that this returns a static buffer of
+ * the result (for convenience, but not threadsafe). If data_len is less than
+ * sizeof(uint64_t), only the least significant bytes of value are encoded. */
+uint8_t *encode_big_endian(uint64_t value, size_t data_len);
+