[BITS] introduce new packed/unpacked bit conversion routines

4 files changed, 94 insertions, 2 deletions

diff --git a/include/osmocore/Makefile.am b/include/osmocore/Makefile.am
index 2efaa96b..a3b12ef4 100644
--- a/include/osmocore/Makefile.am
+++ b/include/osmocore/Makefile.am
@@ -1,4 +1,4 @@
-osmocore_HEADERS = signal.h linuxlist.h timer.h select.h msgb.h \
+osmocore_HEADERS = signal.h linuxlist.h timer.h select.h msgb.h bits.h \
 		   tlv.h bitvec.h comp128.h statistics.h gsm_utils.h utils.h \
 		   gsmtap.h write_queue.h rsl.h gsm48.h rxlev_stat.h mncc.h \
 		   gsm48_ie.h logging.h gsm0808.h rate_ctr.h gsmtap_util.h \
diff --git a/include/osmocore/bits.h b/include/osmocore/bits.h
new file mode 100644
index 00000000..662c4a9d
--- /dev/null
+++ b/include/osmocore/bits.h
@@ -0,0 +1,27 @@
+#ifndef _OSMO_BITS_H
+#define _OSMO_BITS_H
+
+#include <stdint.h>
+
+typedef uint8_t sbit_t;		/* soft bit (-127...127) */
+typedef uint8_t ubit_t;		/* unpacked bit (0 or 1) */
+typedef uint8_t pbit_t;		/* packed bis (8 bits in a byte) */
+
+/* determine how many bytes we would need for 'num_bits' packed bits */
+static inline unsigned int osmo_pbit_bytesize(unsigned int num_bits)
+{
+	unsigned int pbit_bytesize = num_bits / 8;
+
+	if (num_bits % 8)
+		pbit_bytesize++;
+
+	return pbit_bytesize;
+}
+
+/* convert unpacked bits to packed bits, return length in bytes */
+int osmo_ubit2pbit(pbit_t *out, const ubit_t *in, unsigned int num_bits);
+
+/* convert packed bits to unpacked bits, return length in bytes */
+int osmo_pbit2ubit(ubit_t *out, const pbit_t *in, unsigned int num_bits);
+
+#endif
diff --git a/src/Makefile.am b/src/Makefile.am
index 64310e0f..d4c6e127 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -9,7 +9,7 @@ AM_CFLAGS = -fPIC -Wall
 
 lib_LTLIBRARIES = libosmocore.la
 
-libosmocore_la_SOURCES = timer.c select.c signal.c msgb.c rxlev_stat.c \
+libosmocore_la_SOURCES = timer.c select.c signal.c msgb.c rxlev_stat.c bits.c \
 			 tlv_parser.c bitvec.c comp128.c gsm_utils.c statistics.c \
 			 write_queue.c utils.c rsl.c gsm48.c gsm48_ie.c \
 			 logging.c gsm0808.c rate_ctr.c gsmtap_util.c \
diff --git a/src/bits.c b/src/bits.c
new file mode 100644
index 00000000..fb3c7224
--- /dev/null
+++ b/src/bits.c
@@ -0,0 +1,65 @@
+
+#include <stdint.h>
+
+#include <osmocore/bits.h>
+
+/* convert unpacked bits to packed bits, return length in bytes */
+int osmo_ubit2pbit(pbit_t *out, const ubit_t *in, unsigned int num_bits)
+{
+	unsigned int i;
+	uint8_t curbyte = 0;
+	pbit_t *outptr = out;
+
+	for (i = 0; i < num_bits; i++) {
+		uint8_t bitnum = 7 - (i % 8);
+
+		curbyte |= (in[i] << bitnum);
+
+		if (i > 0 && i % 8 == 0) {
+			*outptr++ = curbyte;
+			curbyte = 0;
+		}
+	}
+	/* we have a non-modulo-8 bitcount */
+	if (i % 8)
+		*outptr++ = curbyte;
+
+	return outptr - out;
+}
+
+/* convert packed bits to unpacked bits, return length in bytes */
+int osmo_pbit2ubit(ubit_t *out, const pbit_t *in, unsigned int num_bits)
+{
+	unsigned int i;
+	ubit_t *cur = out;
+	ubit_t *limit = out + num_bits;
+
+	for (i = 0; i < (num_bits/8)+1; i++) {
+		pbit_t byte = in[i];
+		*cur++ = (byte >> 7) & 1;
+		if (cur >= limit)
+			break;
+		*cur++ = (byte >> 6) & 1;
+		if (cur >= limit)
+			break;
+		*cur++ = (byte >> 5) & 1;
+		if (cur >= limit)
+			break;
+		*cur++ = (byte >> 4) & 1;
+		if (cur >= limit)
+			break;
+		*cur++ = (byte >> 3) & 1;
+		if (cur >= limit)
+			break;
+		*cur++ = (byte >> 2) & 1;
+		if (cur >= limit)
+			break;
+		*cur++ = (byte >> 1) & 1;
+		if (cur >= limit)
+			break;
+		*cur++ = (byte >> 0) & 1;
+		if (cur >= limit)
+			break;
+	}
+	return cur - out;
+}