From 418f5a4e2562a54fae2aa02c0c9c4c082515b773 Mon Sep 17 00:00:00 2001 From: Harald Welte Date: Mon, 5 Jan 2009 20:12:47 +0000 Subject: [PATCH] * add function to change c-bits in TRAU frame from uplink to downlink * add function to re-encode an exploded TRAU frame into a bit-per-byte stream --- include/openbsc/trau_frame.h | 5 +- src/trau_frame.c | 122 +++++++++++++++++++++++++++++++++-- 2 files changed, 122 insertions(+), 5 deletions(-) diff --git a/include/openbsc/trau_frame.h b/include/openbsc/trau_frame.h index 1d0a943a9..7f0a2e69b 100644 --- a/include/openbsc/trau_frame.h +++ b/include/openbsc/trau_frame.h @@ -56,6 +56,9 @@ struct decoded_trau_frame { #define TRAU_FT_IDLE_DOWN 0x0e /* 0 1 1 1 0 - 3.5.5 */ -int decode_trau_frame(struct decoded_trau_frame *fr, u_int8_t *trau_bits); +int decode_trau_frame(struct decoded_trau_frame *fr, const u_int8_t *trau_bits); +int encode_trau_frame(u_int8_t *trau_bits, const struct decoded_trau_frame *fr); +int trau_frame_up2down(struct decoded_trau_frame *fr); + #endif /* _TRAU_FRAME_H */ diff --git a/src/trau_frame.c b/src/trau_frame.c index 8eb2b453c..9d7e517ff 100644 --- a/src/trau_frame.c +++ b/src/trau_frame.c @@ -27,7 +27,7 @@ #include -static u_int32_t get_bits(u_int8_t *bitbuf, int offset, int num) +static u_int32_t get_bits(const u_int8_t *bitbuf, int offset, int num) { int i; u_int32_t ret = 0; @@ -41,7 +41,7 @@ static u_int32_t get_bits(u_int8_t *bitbuf, int offset, int num) } /* Decode according to 3.1.1 */ -static void decode_fr(struct decoded_trau_frame *fr, u_int8_t *trau_bits) +static void decode_fr(struct decoded_trau_frame *fr, const u_int8_t *trau_bits) { int i; int d_idx = 0; @@ -62,7 +62,7 @@ static void decode_fr(struct decoded_trau_frame *fr, u_int8_t *trau_bits) } /* Decode according to 3.1.2 */ -static void decode_amr(struct decoded_trau_frame *fr, u_int8_t *trau_bits) +static void decode_amr(struct decoded_trau_frame *fr, const u_int8_t *trau_bits) { int i; int d_idx = 0; @@ -84,7 +84,7 @@ static void decode_amr(struct decoded_trau_frame *fr, u_int8_t *trau_bits) memcpy(fr->d_bits + d_idx, trau_bits + 305, 11); } -int decode_trau_frame(struct decoded_trau_frame *fr, u_int8_t *trau_bits) +int decode_trau_frame(struct decoded_trau_frame *fr, const u_int8_t *trau_bits) { u_int8_t cbits5 = get_bits(trau_bits, 17, 5); @@ -116,3 +116,117 @@ int decode_trau_frame(struct decoded_trau_frame *fr, u_int8_t *trau_bits) return 0; } + +const u_int8_t ft_fr_down_bits[] = { 1, 1, 1, 0, 0 }; +const u_int8_t ft_idle_down_bits[] = { 0, 1, 1, 1, 0 }; + +/* modify an uplink TRAU frame so we can send it downlink */ +int trau_frame_up2down(struct decoded_trau_frame *fr) +{ + u_int8_t cbits5 = get_bits(fr->c_bits, 0, 5); + + switch (cbits5) { + case TRAU_FT_FR_UP: + memcpy(fr->c_bits, ft_fr_down_bits, 5); + /* clear time alignment */ + memset(fr->c_bits+5, 0, 6); + /* FIXME: SP / BFI in case of DTx */ + /* C12 .. C21 are spare and coded as '1' */ + memset(fr->c_bits+11, 0, 10); + break; + case TRAU_FT_EFR: + /* clear time alignment */ + memset(fr->c_bits+5, 0, 6); + /* FIXME: set UFE appropriately */ + /* FIXME: SP / BFI in case of DTx */ + break; + case TRAU_FT_IDLE_UP: + memcpy(fr->c_bits, ft_idle_down_bits, 5); + /* clear time alignment */ + memset(fr->c_bits+5, 0, 6); + /* FIXME: SP / BFI in case of DTx */ + /* C12 .. C21 are spare and coded as '1' */ + memset(fr->c_bits+11, 0, 10); + break; + case TRAU_FT_FR_DOWN: + case TRAU_FT_IDLE_DOWN: + case TRAU_FT_OM_DOWN: + case TRAU_FT_DATA_DOWN: + /* we cannot convert a downlink to a downlink frame */ + return -EINVAL; + break; + case TRAU_FT_AMR: + case TRAU_FT_OM_UP: + case TRAU_FT_DATA_UP: + case TRAU_FT_D145_SYNC: + case TRAU_FT_EDATA: + fprintf(stderr, "unimplemented TRAU Frame Type 0x%02x\n", cbits5); + return -1; + break; + default: + fprintf(stderr, "unknown TRAU Frame Type 0x%02x\n", cbits5); + return -1; + break; + } + + return 0; + +} + +static void encode_fr(u_int8_t *trau_bits, const struct decoded_trau_frame *fr) +{ + int i; + int d_idx = 0; + + trau_bits[16] = 1; + /* C1 .. C15 */ + memcpy(trau_bits+17, fr->c_bits+0, 15); + /* D1 .. D255 */ + for (i = 32; i < 304; i+= 16) { + trau_bits[i] = 1; + memcpy(trau_bits+i+1, fr->d_bits + d_idx, 15); + d_idx += 15; + } + /* D256 .. D260 */ + trau_bits[304] = 1; + memcpy(trau_bits + 305, fr->d_bits + d_idx, 5); + /* C16 .. C21 */ + memcpy(trau_bits+310, fr->c_bits+15, 6); + /* T1 .. T4 */ + memcpy(trau_bits+316, fr->t_bits+0, 4); +} + + +int encode_trau_frame(u_int8_t *trau_bits, const struct decoded_trau_frame *fr) +{ + u_int8_t cbits5 = get_bits(fr->c_bits, 0, 5); + + /* 16 bits of sync header */ + memset(trau_bits, 0, 16); + + switch (cbits5) { + case TRAU_FT_FR_UP: + case TRAU_FT_FR_DOWN: + case TRAU_FT_IDLE_UP: + case TRAU_FT_IDLE_DOWN: + case TRAU_FT_EFR: + encode_fr(trau_bits, fr); + break; + case TRAU_FT_AMR: + case TRAU_FT_OM_UP: + case TRAU_FT_OM_DOWN: + case TRAU_FT_DATA_UP: + case TRAU_FT_DATA_DOWN: + case TRAU_FT_D145_SYNC: + case TRAU_FT_EDATA: + fprintf(stderr, "unimplemented TRAU Frame Type 0x%02x\n", cbits5); + return -1; + break; + default: + fprintf(stderr, "unknown TRAU Frame Type 0x%02x\n", cbits5); + return -1; + break; + } + + return 0; +}