[BITS] introduce new packed/unpacked bit conversion routines

1 files changed, 65 insertions, 0 deletions

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;
+}