11 Apr
2016
11 Apr
'16
2:48 p.m.
This patch includes the changes for compression algorithm and the
compression is carried out using T.4 run length coding and
the code words used are based on 3GPP 44.060
---
include/osmocom/core/bitcomp.h | 7 +++
src/bitcomp.c | 129 ++++++++++++++++++++++++++++++++++++++++
2 files changed, 136 insertions(+)
diff --git a/include/osmocom/core/bitcomp.h b/include/osmocom/core/bitcomp.h
index 89eccbc..c5c223c 100644
--- a/include/osmocom/core/bitcomp.h
+++ b/include/osmocom/core/bitcomp.h
@@ -39,4 +39,11 @@
int osmo_t4_encode(struct bitvec *bv);
int osmo_t4_decode(const struct bitvec *in, bool cc, struct bitvec *out);
+#define MOD64(X) ((X + 64) & 0x3F)
+int osmo_bitmap_compress(
+ struct bitvec *rbb_vec,
+ uint16_t *ucmp_bmplen, //Uncompressed bitmap len
+ uint8_t *cmp_bmplen, //Compressed bitmap len
+ uint8_t *crbb_bitmap //Compressed bitmap
+ );
/*! @} */
diff --git a/src/bitcomp.c b/src/bitcomp.c
index bf35927..f3326b2 100644
--- a/src/bitcomp.c
+++ b/src/bitcomp.c
@@ -476,5 +476,134 @@ int osmo_t4_encode(struct bitvec *bv)
}
return -1;
}
+void compress_bitmap(
+ uint16_t *run_len_cnt, /* cnt: run length count */
+ uint16_t *codewrd_bitmap, /* code word */
+ uint8_t *codewrd_len, /* number of bits in the code word */
+ uint8_t *cbmbuf, /* bitmap buffer to put code word in */
+ uint16_t *cstrtbits, /* start bits to put codeword. start from
+ * 0, the first bit in the first octets
+ * and increment without octets
+ * consideration. i.e. can be more than 7.
+ */
+ uint8_t *cstrtocts, /* start octets to put codeword. start from 0*/
+ uint8_t clr_code)
+{
+ int i = 0;
+ uint16_t bitsleft = 0;
+ uint16_t temp = 0;
+ *codewrd_bitmap = 0;
+ *codewrd_len = 0;
+
+ if ((*run_len_cnt) >= 64) {
+ for (i = 0; i < 15; i++) {
+ if (t4_make_up_ind[i] == *run_len_cnt) {
+ *codewrd_bitmap = t4_make_up[clr_code][i];
+ *codewrd_len = t4_make_up_length[clr_code][i];
+ }
+ }
+ } else {
+ *codewrd_bitmap = t4_term[clr_code][*run_len_cnt];
+ *codewrd_len = t4_term_length[clr_code][*run_len_cnt];
+ }
+ bitsleft = *codewrd_len;
+ /* Move the codeword_bitmap to left in two bytes*/
+ (*codewrd_bitmap) = (*codewrd_bitmap)<<(16-(*codewrd_len));
+
+ while (bitsleft != 0) {
+ /* Bring left most bits to right and start shifting by cstrtbits,
+ * we get each bit to update in compressed buffer
+ */
+ temp = (((*codewrd_bitmap) & 0x8000)>>15)<<(7-(*cstrtbits));
+ cbmbuf[*cstrtocts] = cbmbuf[*cstrtocts]|temp;
+
+ (*codewrd_bitmap) = (*codewrd_bitmap)<<1;
+ (*cstrtbits)++;
+ bitsleft--;
+ if ((*cstrtbits) >= 8) {
+ (*cstrtbits) = (*cstrtbits)-8;
+ (*cstrtocts)++;
+ /* init buf */
+ cbmbuf[*cstrtocts] = 0x00;
+ }
+ }
+}
+
+int osmo_bitmap_compress(
+ struct bitvec *rbb_vec,
+ uint16_t *ucmp_bmplen, /* Uncompressed bitmap len */
+ uint8_t *cmp_bmplen, /* Compressed bitmap len */
+ uint8_t *crbb_bitmap /* Compressed bitmap */
+ )
+{
+ char run_len_bit;
+ int buflen = *ucmp_bmplen;
+ uint16_t rlen;
+ uint16_t temprl = 0;
+ uint16_t cbmap; /* Compressed code word */
+ uint8_t nbits; /* Length of code word */
+ uint16_t cstrtbits = 0;
+ uint8_t cstrtocts = 0;
+ uint16_t uclen = 0;
+ uint8_t clen = 0;
+ uint8_t clr_code = 0;
+
+ run_len_bit = (rbb_vec->data[0] & 0x80)>>7;
+ while (buflen > 0) {
+ temprl = 0;
+ /* Find Run length */
+ if (run_len_bit == 1)
+ rlen = bitvec_rl(rbb_vec, true);
+ else
+ rlen = bitvec_rl(rbb_vec, false);
+
+ buflen = buflen - rlen;
+ /* if rlen> 64 need 2 code words */
+ //Compress the bits
+ if (run_len_bit == 0) {
+ if (rlen >= 64) {
+ temprl = (rlen/64)*64;
+ compress_bitmap(&temprl, &cbmap, &nbits,
+ crbb_bitmap, &cstrtbits,
+ &cstrtocts, clr_code);
+ }
+ temprl = MOD64(rlen);
+ compress_bitmap(&temprl,
+ &cbmap, &nbits, crbb_bitmap,
+ &cstrtbits, &cstrtocts, clr_code);
+
+ /* next time the run length will be Ones */
+ run_len_bit = 1;
+ } else {
+ if (rlen >= 64) {
+ temprl = (rlen/64)*64;
+ clr_code = 1;
+ compress_bitmap(&temprl, &cbmap,
+ &nbits, crbb_bitmap,
+ &cstrtbits, &cstrtocts,
+ clr_code);
+ }
+ temprl = MOD64(rlen);
+ compress_bitmap(&temprl, &cbmap,
+ &nbits, crbb_bitmap,
+ &cstrtbits, &cstrtocts, clr_code);
+
+ /* next time the run length will be Zeros */
+ run_len_bit = 0;
+ }
+ uclen = uclen + (rlen);
+ clen = clen + nbits;
+ }
+ *cmp_bmplen = clen;
+ if (clen >= uclen) {
+ /* No Gain is observed, So no need to compress, copy original
+ * bitmap in uncompressed bitmap
+ */
+ return 0;
+ } else {
+ /* Add compressed bitmap to final buffer */
+ return 1;
+ }
+}
--
1.7.9.5