diff options
Diffstat (limited to 'src/encoding.cpp')
| -rw-r--r-- | src/encoding.cpp | 120 |
1 files changed, 120 insertions, 0 deletions
diff --git a/src/encoding.cpp b/src/encoding.cpp index fdc8d0ae..0756ffcb 100644 --- a/src/encoding.cpp +++ b/src/encoding.cpp @@ -25,6 +25,9 @@ #include <tbf.h> #include <gprs_debug.h> +#include <errno.h> +#include <string.h> + // GSM 04.08 9.1.18 Immediate assignment int Encoding::write_immediate_assignment( struct gprs_rlcmac_bts *bts, @@ -631,3 +634,120 @@ unsigned Encoding::write_repeated_page_info(bitvec * dest, unsigned& wp, uint8_t return wp; } +int Encoding::rlc_write_dl_data_header(const struct gprs_rlc_data_info *rlc, + uint8_t *data) +{ + struct gprs_rlc_dl_header_egprs_3 *egprs3; + struct rlc_dl_header *gprs; + unsigned int e_fbi_header; + GprsCodingScheme cs = rlc->cs; + + switch(cs.headerTypeData()) { + case GprsCodingScheme::HEADER_GPRS_DATA: + gprs = static_cast<struct rlc_dl_header *> + ((void *)data); + + gprs->usf = rlc->usf; + gprs->s_p = rlc->es_p != 0 ? 1 : 0; + gprs->rrbp = rlc->rrbp; + gprs->pt = 0; + gprs->tfi = rlc->tfi; + gprs->pr = rlc->pr; + + gprs->fbi = rlc->block_info[0].cv == 0; + gprs->e = rlc->block_info[0].e; + gprs->bsn = rlc->block_info[0].bsn; + break; + + case GprsCodingScheme::HEADER_EGPRS_DATA_TYPE_3: + egprs3 = static_cast<struct gprs_rlc_dl_header_egprs_3 *> + ((void *)data); + + egprs3->usf = rlc->usf; + egprs3->es_p = rlc->es_p; + egprs3->rrbp = rlc->rrbp; + egprs3->tfi_a = rlc->tfi >> 0; /* 1 bit LSB */ + egprs3->tfi_b = rlc->tfi >> 1; /* 4 bits */ + egprs3->pr = rlc->pr; + egprs3->cps = rlc->cps; + + egprs3->bsn1_a = rlc->block_info[0].bsn >> 0; /* 2 bits LSB */ + egprs3->bsn1_b = rlc->block_info[0].bsn >> 2; /* 8 bits */ + egprs3->bsn1_c = rlc->block_info[0].bsn >> 10; /* 1 bit */ + + egprs3->spb = rlc->block_info[0].spb; + + e_fbi_header = rlc->block_info[0].e ? 0x01 : 0; + e_fbi_header |= rlc->block_info[0].cv == 0 ? 0x02 : 0; /* FBI */ + e_fbi_header <<= 7; + data[3] = (data[3] & 0b01111111) | (e_fbi_header >> 0); + data[4] = (data[4] & 0b11111110) | (e_fbi_header >> 8); + break; + + case GprsCodingScheme::HEADER_EGPRS_DATA_TYPE_1: + case GprsCodingScheme::HEADER_EGPRS_DATA_TYPE_2: + /* TODO: Support both header types */ + /* fall through */ + default: + LOGP(DRLCMACDL, LOGL_ERROR, + "Encoding of uplink %s data blocks not yet supported.\n", + cs.name()); + return -ENOTSUP; + }; + + return 0; +} + +/** + * \brief Copy LSB bitstream RLC data block from byte aligned buffer. + * + * Note that the bitstream is encoded in LSB first order, so the two octets + * 654321xx xxxxxx87 contain the octet 87654321 starting at bit position 3 + * (LSB has bit position 1). This is a different order than the one used by + * CSN.1. + * + * \param data_block_idx The block index, 0..1 for header type 1, 0 otherwise + * \param src A pointer to the start of the RLC block (incl. the header) + * \param buffer A data area of a least the size of the RLC block + * \returns the number of bytes copied + */ +unsigned int Encoding::rlc_copy_from_aligned_buffer( + const struct gprs_rlc_data_info *rlc, + unsigned int data_block_idx, + uint8_t *dst, const uint8_t *buffer) +{ + unsigned int hdr_bytes; + unsigned int extra_bits; + unsigned int i; + + uint8_t c, last_c; + const uint8_t *src; + const struct gprs_rlc_data_block_info *rdbi; + + OSMO_ASSERT(data_block_idx < rlc->num_data_blocks); + rdbi = &rlc->block_info[data_block_idx]; + + hdr_bytes = rlc->data_offs_bits[data_block_idx] / 8; + extra_bits = (rlc->data_offs_bits[data_block_idx] % 8); + + if (extra_bits == 0) { + /* It is aligned already */ + memmove(dst + hdr_bytes, buffer, rdbi->data_len); + return rdbi->data_len; + } + + src = buffer; + dst = dst + hdr_bytes; + last_c = *dst << (8 - extra_bits); + + for (i = 0; i < rdbi->data_len; i++) { + c = src[i]; + *(dst++) = (last_c >> (8 - extra_bits)) | (c << extra_bits); + last_c = c; + } + + /* overwrite the lower extra_bits */ + *dst = (*dst & (0xff << extra_bits)) | (last_c >> (8 - extra_bits)); + + return rdbi->data_len; +} |