[PATCH] libosmocore[master]: Add octet-aligned/unaligned shift functions

[Max]

Review at  https://gerrit.osmocom.org/326

Add octet-aligned/unaligned shift functions

The actual code is from OsmoBTS' tch.c by Harald Welte.

Change-Id: I2b1901c4161e8035f059585901dca593b661556d
---
M include/osmocom/core/bits.h
M src/bits.c
2 files changed, 49 insertions(+), 0 deletions(-)


  git pull ssh://gerrit.osmocom.org:29418/libosmocore refs/changes/26/326/1

diff --git a/include/osmocom/core/bits.h b/include/osmocom/core/bits.h
index 3218330..5535920 100644
--- a/include/osmocom/core/bits.h
+++ b/include/osmocom/core/bits.h
@@ -41,6 +41,11 @@
 
 int osmo_pbit2ubit(ubit_t *out, const pbit_t *in, unsigned int num_bits);
 
+void osmo_nibble_shift_right(uint8_t *out, const uint8_t *in,
+			     unsigned int num_nibbles);
+void osmo_nibble_shift_left_unal(uint8_t *out, const uint8_t *in,
+				 unsigned int num_nibbles);
+
 void osmo_ubit2sbit(sbit_t *out, const ubit_t *in, unsigned int num_bits);
 void osmo_sbit2ubit(ubit_t *out, const sbit_t *in, unsigned int num_bits);
 
diff --git a/src/bits.c b/src/bits.c
index 569a10f..613e258 100644
--- a/src/bits.c
+++ b/src/bits.c
@@ -61,6 +61,50 @@
 	return outptr - out;
 }
 
+/*! \brief Shift unaligned input to octet-aligned output
+ *  \param[out] out output buffer, unaligned
+ *  \param[in] in input buffer, octet-aligned
+ *  \param[in] num_nibbles number of nibbles
+ */
+void osmo_nibble_shift_right(uint8_t *out, const uint8_t *in,
+			     unsigned int num_nibbles)
+{
+	unsigned int i, num_whole_bytes = num_nibbles / 2;
+
+	/* first byte: upper nibble empty, lower nibble from src */
+	out[0] = (in[0] >> 4);
+
+	/* bytes 1.. */
+	for (i = 1; i < num_whole_bytes; i++)
+		out[i] = ((in[i - 1] & 0xF) << 4) | (in[i] >> 4);
+
+	/* shift the last nibble, in case there's an odd count */
+	i = num_whole_bytes;
+	if (num_nibbles & 1)
+		out[i] = ((in[i - 1] & 0xF) << 4) | (in[i] >> 4);
+	else
+		out[i] = (in[i - 1] & 0xF) << 4;
+}
+
+/*! \brief Shift unaligned input to octet-aligned output
+ *  \param[out] out output buffer, octet-aligned
+ *  \param[in] in input buffer, unaligned
+ *  \param[in] num_nibbles number of nibbles
+ */
+void osmo_nibble_shift_left_unal(uint8_t *out, const uint8_t *in,
+				unsigned int num_nibbles)
+{
+	unsigned int i, num_whole_bytes = num_nibbles / 2;
+
+	for (i = 0; i < num_whole_bytes; i++)
+		out[i] = ((in[i] & 0xF) << 4) | (in[i + 1] >> 4);
+
+	/* shift the last nibble, in case there's an odd count */
+	i = num_whole_bytes;
+	if (num_nibbles & 1)
+		out[i] = (in[i] & 0xF) << 4;
+}
+
 /*! \brief convert unpacked bits to soft bits
  *  \param[out] out output buffer of soft bits
  *  \param[in] in input buffer of unpacked bits

-- 
To view, visit https://gerrit.osmocom.org/326
To unsubscribe, visit https://gerrit.osmocom.org/settings

Gerrit-MessageType: newchange
Gerrit-Change-Id: I2b1901c4161e8035f059585901dca593b661556d
Gerrit-PatchSet: 1
Gerrit-Project: libosmocore
Gerrit-Branch: master
Gerrit-Owner: Max <msuraev at sysmocom.de>