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Commit 9159207

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ungureanuvladvictorungureanuvladvictor
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Merge pull request #186 from ungureanuvladvictor/viterbi_decoder
Viterbi decoder
2 parents 0a1ac49 + b3685f4 commit 9159207

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13 files changed

+855
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‎CMakeLists.txt‎

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@@ -71,6 +71,7 @@ endif ()
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add_subdirectory(clapack-3.2.1-CMAKE)
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add_subdirectory(CBLAS)
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add_subdirectory(plover)
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add_subdirectory(libfec)
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add_subdirectory(src)
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add_subdirectory(docs)
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add_subdirectory(tests)

‎libfec/CMakeLists.txt‎

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# Disable code coverage for this subdirectory
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set(CMAKE_C_FLAGS_COVERAGE "${CMAKE_C_FLAGS_DEBUG}")
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set(CMAKE_SHARED_LINKER_FLAGS_COVERAGE "${CMAKE_SHARED_LINKER_FLAGS_DEBUG}")
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set(CMAKE_EXE_LINKER_FLAGS_COVERAGE "${CMAKE_EXE_LINKER_FLAGS_DEBUG}")
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# Build libraries with PIC flag as they will be linked into shared objects
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if (NOT CMAKE_CROSSCOMPILING)
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set(CMAKE_POSITION_INDEPENDENT_CODE ON)
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endif ()
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include_directories(${CMAKE_CURRENT_SOURCE_DIR}/include)
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add_subdirectory(src)

‎libfec/LICENSE.txt‎

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‎libfec/include/fec.h‎

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/* User include file for libfec
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* Copyright 2004, Phil Karn, KA9Q
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* May be used under the terms of the GNU Lesser General Public License (LGPL)
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*/
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#ifndef _FEC_H_
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#define _FEC_H_
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/* r=1/2 k=7 convolutional encoder polynomials
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* The NASA-DSN convention is to use V27POLYA inverted, then V27POLYB
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* The CCSDS/NASA-GSFC convention is to use V27POLYB, then V27POLYA inverted
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*/
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#define V27POLYA 0x4f
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#define V27POLYB 0x6d
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typedef union {
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unsigned int w[64];
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} metric_t;
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typedef union {
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unsigned int w[2];
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} decision_t;
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union branchtab27 {
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unsigned char c[32];
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};
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/* State info for instance of Viterbi decoder
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*/
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struct v27 {
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metric_t metrics1; /* path metric buffer 1 */
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metric_t metrics2; /* path metric buffer 2 */
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decision_t *dp; /* Pointer to current decision */
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metric_t *old_metrics,*new_metrics; /* Pointers to path metrics, swapped on every bit */
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decision_t *decisions; /* Beginning of decisions for block */
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};
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void set_decisions_viterbi27(struct v27 *vp, decision_t *dec);
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void init_viterbi27(struct v27 *vp, int starting_state);
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void set_viterbi27_polynomial(int polys[2]);
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int update_viterbi27_blk(struct v27 *p, const unsigned char sym[], int npairs);
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int chainback_viterbi27(struct v27 *p, unsigned char *data, unsigned int nbits,
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unsigned int endstate);
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static inline int parity(int x)
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{
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x ^= x >> 16;
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x ^= x >> 8;
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x ^= x >> 4;
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x &= 0xf;
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return (0x6996 >> x) & 1;
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}
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#endif

‎libfec/src/CMakeLists.txt‎

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if (NOT DEFINED BUILD_SHARED_LIBS)
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set(BUILD_SHARED_LIBS ON)
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endif (NOT DEFINED BUILD_SHARED_LIBS)
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set(CMAKE_C_FLAGS "-Wmissing-prototypes ${CMAKE_C_FLAGS}")
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file(GLOB libfec_HEADERS "${PROJECT_SOURCE_DIR}/libfec/include/*.h")
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set(viterbi27.c)
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add_library(fec viterbi27.c)
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install(TARGETS fec DESTINATION lib${LIB_SUFFIX})
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install(FILES ${libfec_HEADERS} DESTINATION include/libswiftnav)

‎libfec/src/viterbi27.c‎

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/* K=7 r=1/2 Viterbi decoder in portable C
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* Copyright Feb 2004, Phil Karn, KA9Q
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* May be used under the terms of the GNU Lesser General Public License (LGPL)
4+
*/
5+
6+
#include <stdlib.h>
7+
#include "fec.h"
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static union branchtab27 Branchtab27[2] __attribute__ ((aligned(16)));
10+
11+
void set_viterbi27_polynomial(int polys[2])
12+
{
13+
int state;
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for(state = 0; state < 32; state++) {
16+
Branchtab27[0].c[state] = (polys[0] < 0) ^ parity((2*state) & abs(polys[0])) ? 255 : 0;
17+
Branchtab27[1].c[state] = (polys[1] < 0) ^ parity((2*state) & abs(polys[1])) ? 255 : 0;
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}
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}
20+
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/* Create a new instance of a Viterbi decoder */
22+
void init_viterbi27(struct v27 *vp, int starting_state)
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{
24+
int i;
25+
int polys[2] = { V27POLYA, V27POLYB };
26+
27+
set_viterbi27_polynomial(polys);
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for(i = 0; i < 64; i++)
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vp->metrics1.w[i] = 63;
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32+
vp->old_metrics = &vp->metrics1;
33+
vp->new_metrics = &vp->metrics2;
34+
vp->dp = vp->decisions;
35+
vp->old_metrics->w[starting_state & 63] = 0; /* Bias known start state */
36+
}
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/* Viterbi chainback */
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int chainback_viterbi27(
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struct v27 *vp,
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unsigned char *data, /* Decoded output data */
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unsigned int nbits, /* Number of data bits */
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unsigned int endstate) /* Terminal encoder state */
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{
45+
decision_t *d;
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if(vp == NULL)
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return -1;
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d = vp->decisions;
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/* Make room beyond the end of the encoder register so we can
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* accumulate a full byte of decoded data
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*/
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endstate %= 64;
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endstate <<= 2;
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/* The store into data[] only needs to be done every 8 bits.
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* But this avoids a conditional branch, and the writes will
59+
* combine in the cache anyway
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*/
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d += 6; /* Look past tail */
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while(nbits-- != 0) {
63+
int k;
64+
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k = (d[nbits].w[(endstate>>2)/32] >> ((endstate>>2)%32)) & 1;
66+
data[nbits>>3] = endstate = (endstate >> 1) | (k << 7);
67+
}
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return 0;
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}
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/* C-language butterfly */
73+
#define BFLY(i) {\
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unsigned int metric,m0,m1,decision;\
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metric = (Branchtab27[0].c[i] ^ sym0) + (Branchtab27[1].c[i] ^ sym1);\
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m0 = vp->old_metrics->w[i] + metric;\
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m1 = vp->old_metrics->w[i+32] + (510 - metric);\
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decision = (signed int)(m0-m1) > 0;\
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vp->new_metrics->w[2*i] = decision ? m1 : m0;\
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d->w[i/16] |= decision << ((2*i)&31);\
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m0 -= (metric+metric-510);\
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m1 += (metric+metric-510);\
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decision = (signed int)(m0-m1) > 0;\
84+
vp->new_metrics->w[2*i+1] = decision ? m1 : m0;\
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d->w[i/16] |= decision << ((2*i+1)&31);\
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}
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/* Update decoder with a block of demodulated symbols
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* Note that nbits is the number of decoded data bits, not the number
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* of symbols!
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*/
92+
int update_viterbi27_blk(struct v27 *vp, const unsigned char *syms, int nbits)
93+
{
94+
void *tmp;
95+
decision_t *d;
96+
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if(vp == NULL)
98+
return -1;
99+
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d = (decision_t *)vp->dp;
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while(nbits--) {
103+
unsigned char sym0,sym1;
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d->w[0] = d->w[1] = 0;
106+
sym0 = *syms++;
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sym1 = *syms++;
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BFLY(0);
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BFLY(1);
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BFLY(2);
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BFLY(3);
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BFLY(4);
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BFLY(5);
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BFLY(6);
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BFLY(7);
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BFLY(8);
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BFLY(9);
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BFLY(10);
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BFLY(11);
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BFLY(12);
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BFLY(13);
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BFLY(14);
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BFLY(15);
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BFLY(16);
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BFLY(17);
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BFLY(18);
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BFLY(19);
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BFLY(20);
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BFLY(21);
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BFLY(22);
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BFLY(23);
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BFLY(24);
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BFLY(25);
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BFLY(26);
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BFLY(27);
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BFLY(28);
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BFLY(29);
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BFLY(30);
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BFLY(31);
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d++;
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/* Swap pointers to old and new metrics */
144+
tmp = vp->old_metrics;
145+
vp->old_metrics = vp->new_metrics;
146+
vp->new_metrics = tmp;
147+
}
148+
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vp->dp = d;
150+
return 0;
151+
}
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void set_decisions_viterbi27(struct v27 *vp, decision_t *dec)
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{
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vp->decisions = dec;
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}

‎src/CMakeLists.txt‎

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@@ -48,13 +48,15 @@ add_library(swiftnav-static STATIC ${libswiftnav_SRCS})
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add_dependencies(swiftnav-static generate)
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target_link_libraries(swiftnav-static cblas)
5050
target_link_libraries(swiftnav-static lapack)
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target_link_libraries(swiftnav-static fec)
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install(TARGETS swiftnav-static DESTINATION lib${LIB_SUFFIX})
5253

5354
if(BUILD_SHARED_LIBS)
5455
add_library(swiftnav SHARED ${libswiftnav_SRCS})
5556
add_dependencies(swiftnav generate)
5657
target_link_libraries(swiftnav cblas)
5758
target_link_libraries(swiftnav lapack)
59+
target_link_libraries(swiftnav fec)
5860
install(TARGETS swiftnav DESTINATION lib${LIB_SUFFIX})
5961
else(BUILD_SHARED_LIBS)
6062
message(STATUS "Not building shared libraries")

‎tests/CMakeLists.txt‎

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@@ -11,15 +11,15 @@ else (CMAKE_CROSSCOMPILING)
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include_directories("${PROJECT_SOURCE_DIR}/clapack-3.2.1-CMAKE/INCLUDE")
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1313
include_directories(${CHECK_INCLUDE_DIRS})
14-
set(TEST_LIBS ${TEST_LIBS} ${CHECK_LIBRARIES} pthread swiftnav lapack cblas m)
15-
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set(TEST_LIBS ${TEST_LIBS} ${CHECK_LIBRARIES} pthread swiftnav lapack cblas m fec)
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# Check needs to be linked against Librt on Linux
1716
if (${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
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set(TEST_LIBS ${TEST_LIBS} rt)
1918
endif(${CMAKE_SYSTEM_NAME} STREQUAL "Linux")
2019

2120
include_directories("${PROJECT_SOURCE_DIR}/include/libswiftnav")
2221
include_directories("${PROJECT_SOURCE_DIR}/src")
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include_directories("${PROJECT_SOURCE_DIR}/libfec/include")
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2424
add_executable(test_libswiftnav
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check_main.c
@@ -41,6 +41,7 @@ else (CMAKE_CROSSCOMPILING)
4141
check_filter_utils.c
4242
check_ephemeris.c
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check_set.c
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check_viterbi.c
4445
check_gpstime.c
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)
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@@ -50,6 +51,8 @@ else (CMAKE_CROSSCOMPILING)
5051
COMMENT "Running unit tests"
5152
COMMAND test_libswiftnav
5253
)
54+
file(COPY data/waas_check.bin DESTINATION ${CMAKE_BINARY_DIR}/tests)
55+
file(COPY data/waas_data.bin DESTINATION ${CMAKE_BINARY_DIR}/tests)
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5457
endif (NOT CHECK_FOUND)
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endif (CMAKE_CROSSCOMPILING)

‎tests/check_main.c‎

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srunner_add_suite(sr, filter_utils_suite());
2727
srunner_add_suite(sr, ephemeris_suite());
2828
srunner_add_suite(sr, set_suite());
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srunner_add_suite(sr, viterbi_suite());
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srunner_add_suite(sr, gpstime_test_suite());
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srunner_set_fork_status(sr, CK_NOFORK);

‎tests/check_suites.h‎

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@@ -17,6 +17,7 @@ Suite* ambiguity_test_suite(void);
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Suite* filter_utils_suite(void);
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Suite* ephemeris_suite(void);
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Suite* set_suite(void);
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Suite* viterbi_suite(void);
2021
Suite* gpstime_test_suite(void);
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#endif /* CHECK_SUITES_H */

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