rlc: Add gprs_rlc_mcs_cps_decode
To access EGPRS data blocks, the optional padding must be taken into
account. Whether padding has been used must be dervied from the CPS
field in the header of the RLC EGPRS data message.
Add this function to decode the CPS value and extract that
information.
Sponsored-by: On-Waves ehf
diff --git a/src/rlc.cpp b/src/rlc.cpp
index ca12e91..79d8f48 100644
--- a/src/rlc.cpp
+++ b/src/rlc.cpp
@@ -356,3 +356,32 @@
return -1;
}
+
+void gprs_rlc_mcs_cps_decode(unsigned int cps,
+ GprsCodingScheme cs, int *punct, int *punct2, int *with_padding)
+{
+ *punct2 = -1;
+ *with_padding = 0;
+
+ switch (GprsCodingScheme::Scheme(cs)) {
+ case GprsCodingScheme::MCS1:
+ cps -= 0b1011; *punct = cps % 2; break;
+ case GprsCodingScheme::MCS2:
+ cps -= 0b1001; *punct = cps % 2; break;
+ case GprsCodingScheme::MCS3:
+ cps -= 0b0011; *punct = cps % 3; *with_padding = cps >= 3; break;
+ case GprsCodingScheme::MCS4:
+ cps -= 0b0000; *punct = cps % 3; break;
+ case GprsCodingScheme::MCS5:
+ cps -= 0b100; *punct = cps % 2; break;
+ case GprsCodingScheme::MCS6:
+ cps -= 0b000; *punct = cps % 2; *with_padding = cps >= 2; break;
+ case GprsCodingScheme::MCS7:
+ cps -= 0b10100; *punct = cps / 3; *punct2 = cps % 3; break;
+ case GprsCodingScheme::MCS8:
+ cps -= 0b01011; *punct = cps / 3; *punct2 = cps % 3; break;
+ case GprsCodingScheme::MCS9:
+ cps -= 0b00000; *punct = cps / 4; *punct2 = cps % 3; break;
+ default: ;
+ }
+}
diff --git a/src/rlc.h b/src/rlc.h
index f6415b7..28913bd 100644
--- a/src/rlc.h
+++ b/src/rlc.h
@@ -109,6 +109,8 @@
GprsCodingScheme cs, bool with_padding);
unsigned int gprs_rlc_mcs_cps(GprsCodingScheme cs, int punct, int punct2,
int with_padding);
+void gprs_rlc_mcs_cps_decode(unsigned int cps, GprsCodingScheme cs,
+ int *punct, int *punct2, int *with_padding);
/*
* I hold the currently transferred blocks and will provide