From ac7c48b4dee99d4c772f133d70d8d1b38262fcd2 Mon Sep 17 00:00:00 2001
From: Author Name <david@rowetel.com>
Date: Fri, 7 Jul 2023 12:20:59 +0930
Subject: shallow zip-file copy from codec2 e9d726bf20

---
 src/ldpc_dec.c | 236 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 236 insertions(+)
 create mode 100644 src/ldpc_dec.c

(limited to 'src/ldpc_dec.c')

diff --git a/src/ldpc_dec.c b/src/ldpc_dec.c
new file mode 100644
index 0000000..94d5c33
--- /dev/null
+++ b/src/ldpc_dec.c
@@ -0,0 +1,236 @@
+/* 
+  FILE...: ldpc_dec.c
+  AUTHOR.: Matthew C. Valenti, Rohit Iyer Seshadri, David Rowe
+  CREATED: Sep 2016
+
+  Command line C LDPC decoder derived from MpDecode.c in the CML
+  library.  Allows us to run the same decoder in Octave and C.
+*/
+
+#include <assert.h>
+#include <errno.h>
+#include <math.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdio.h>
+
+#include "mpdecode_core.h"
+#include "ldpc_codes.h"
+#include "ofdm_internal.h"
+
+int opt_exists(char *argv[], int argc, char opt[]) {
+    int i;
+    for (i=0; i<argc; i++) {
+        if (strcmp(argv[i], opt) == 0) {
+            return i;
+        }
+    }
+    return 0;
+}
+
+
+int main(int argc, char *argv[])
+{    
+    int         CodeLength, NumberParityBits;
+    int         i, codename, parityCheckCount, mute, testframes;
+    int         data_bits_per_frame;
+    struct LDPC ldpc;
+    int         iter, total_iters;
+    int         Tbits, Terrs, Tbits_raw, Terrs_raw, Tpackets, Tpacketerrs;
+
+    int unused_data_bits = 84;
+
+    if (argc < 2) {
+        fprintf(stderr, "\n");
+        fprintf(stderr, "usage: %s --listcodes\n\n", argv[0]);
+        fprintf(stderr, "  List supported codes (more can be added via using Octave ldpc scripts)\n");
+        fprintf(stderr, "\n");
+        fprintf(stderr, "usage: %s InOneSymbolPerFloat OutOneBitPerByte [--sd] [--half] [--code CodeName] [--testframes]", argv[0]);
+        fprintf(stderr, " [--unused numUnusedDataBits]\n\n");
+        fprintf(stderr, "   InOneSymbolPerFloat     Input file of float LLRs, use - for the \n");        
+        fprintf(stderr, "                           file names to use stdin/stdout\n");
+        fprintf(stderr, "   --code                  Use LDPC code CodeName\n");
+        fprintf(stderr, "   --listcodes             List available LDPC codes\n");
+        fprintf(stderr, "   --sd                    Treat input file samples as BPSK Soft Decision\n");
+        fprintf(stderr, "                           demod outputs rather than LLRs\n");
+        fprintf(stderr, "   --mute                  Only output frames with < 10%% parity check fails\n");
+        fprintf(stderr, "   --testframes            built in test frame modem, requires --testframes at encoder\n");
+        fprintf(stderr, "    --unused               number of unused data bits, which are set to 1's at enc and dec\n");
+        fprintf(stderr, "\n");
+
+        fprintf(stderr, "Example in testframe mode:\n\n");
+        fprintf(stderr, " $ ./ldpc_enc /dev/zero - --sd --code HRA_112_112 --testframes 10 |\n");
+        fprintf(stderr, "   ./ldpc_dec - /dev/null --code HRA_112_112 --sd --testframes\n");
+        exit(0);
+    }
+
+    if ((codename = opt_exists(argv, argc, "--listcodes")) != 0) {
+        ldpc_codes_list();
+        exit(0);
+    }
+
+    /* set up LDPC code */
+
+    int code_index = 0;
+    if ((codename = opt_exists(argv, argc, "--code")) != 0)
+        code_index = ldpc_codes_find(argv[codename+1]);
+    memcpy(&ldpc,&ldpc_codes[code_index],sizeof(struct LDPC));
+    fprintf(stderr, "Using: %s\n", ldpc.name);
+
+    CodeLength = ldpc.CodeLength;                    /* length of entire codeword */
+    NumberParityBits = ldpc.NumberParityBits;
+    data_bits_per_frame = ldpc.NumberRowsHcols;
+    unsigned char ibits[data_bits_per_frame];
+    unsigned char pbits[NumberParityBits];
+    uint8_t out_char[CodeLength];
+
+    testframes = 0;
+    total_iters = 0;
+    Tbits = Terrs = Tbits_raw = Terrs_raw = Tpackets = Tpacketerrs = 0;
+    
+    FILE *fin, *fout;
+    int   sdinput, nread, offset=0;
+
+    /* File I/O mode ------------------------------------------------*/
+
+    if (strcmp(argv[1], "-")  == 0) fin = stdin;
+    else if ( (fin = fopen(argv[1],"rb")) == NULL ) {
+        fprintf(stderr, "Error opening input SD file: %s: %s.\n",
+                argv[1], strerror(errno));
+        exit(1);
+    }
+        
+    if (strcmp(argv[2], "-") == 0) fout = stdout;
+    else if ( (fout = fopen(argv[2],"wb")) == NULL ) {
+        fprintf(stderr, "Error opening output bit file: %s: %s.\n",
+                argv[2], strerror(errno));
+        exit(1);
+    }
+
+    sdinput = 0; mute = 0; testframes = 0;
+    if (opt_exists(argv, argc, "--sd")) {
+        sdinput = 1;
+    }
+    if (opt_exists(argv, argc, "--mute")) {
+        mute = 1;
+    }
+    unused_data_bits = 0; int arg;
+    if ((arg = opt_exists(argv, argc, "--unused"))) {
+        unused_data_bits = atoi(argv[arg+1]);
+    }
+    if (opt_exists(argv, argc, "--testframes")) {
+        testframes = 1;
+        uint16_t r[data_bits_per_frame];
+        ofdm_rand(r, data_bits_per_frame);
+
+        for(i=0; i<data_bits_per_frame-unused_data_bits; i++) {
+            ibits[i] = r[i] > 16384;
+        }
+        for(i=data_bits_per_frame-unused_data_bits; i<data_bits_per_frame; i++) {
+            ibits[i] = 1;
+        }
+        encode(&ldpc, ibits, pbits);  
+    }
+
+    float  *input_float  = calloc(CodeLength, sizeof(float));
+
+    nread = CodeLength - unused_data_bits;
+    fprintf(stderr, "CodeLength: %d offset: %d\n", CodeLength, offset);
+
+    while(fread(input_float, sizeof(float), nread, fin) == nread) {
+        if (testframes) {
+            /* BPSK SD and bit LLRs get mapped roughly the same way so this just happens to work for both */
+            char in_char;
+            for (i=0; i<data_bits_per_frame-unused_data_bits; i++) {
+                in_char = input_float[i] < 0;
+                if (in_char != ibits[i]) {
+                    Terrs_raw++;
+                }
+                Tbits_raw++;
+            }
+            for (i=0; i<NumberParityBits; i++) {
+                in_char = input_float[i+data_bits_per_frame-unused_data_bits] < 0;
+                if (in_char != pbits[i]) {
+                    Terrs_raw++;
+                }
+                Tbits_raw++;
+            }
+        }
+
+        if (sdinput) {
+            /* map BPSK SDs to bit LLRs */
+            float llr[CodeLength-unused_data_bits];
+            sd_to_llr(llr, input_float, CodeLength-unused_data_bits);
+
+            /* insert unused data LLRs */
+
+            float llr_tmp[CodeLength];
+            for(i=0; i<data_bits_per_frame-unused_data_bits; i++)
+                llr_tmp[i] = llr[i];  // rx data bits
+            for(i=data_bits_per_frame-unused_data_bits; i<data_bits_per_frame; i++)
+                llr_tmp[i] = -10.0;           // known data bits high likelhood
+            for(i=data_bits_per_frame; i<CodeLength; i++)
+                llr_tmp[i] = llr[i-unused_data_bits];  // rx parity bits
+            memcpy(input_float, llr_tmp, sizeof(float)*CodeLength);                
+        }
+
+        iter = run_ldpc_decoder(&ldpc, out_char, input_float, &parityCheckCount);
+        //fprintf(stderr, "iter: %d\n", iter);
+        total_iters += iter;
+            
+        if (mute) {
+
+            // Output data bits only if decoder converged, or was
+            // within 10% of all parity checks converging (10% est
+            // BER).  Useful for real world operation as it can
+            // resync and won't send crappy packets to the decoder
+                
+            float ber_est = (float)(ldpc.NumberParityBits - parityCheckCount)/ldpc.NumberParityBits;
+            //fprintf(stderr, "iter: %4d parityCheckErrors: %4d ber: %3.2f\n", iter, ldpc.NumberParityBits - parityCheckCount, ber_est);
+            if (ber_est < 0.1) {
+                fwrite(out_char, sizeof(char), ldpc.NumberRowsHcols, fout);
+            }
+
+        }
+
+        fwrite(out_char, sizeof(char), data_bits_per_frame, fout);
+
+        if (testframes) {
+            int perr = 0;
+            for (i=0; i<data_bits_per_frame; i++) {
+                if (out_char[i] != ibits[i]) {
+                    Terrs++;
+                    perr = 1;
+                }
+                Tbits++;
+            }
+            Tpackets++; if (perr) { Tpacketerrs++; fprintf(stderr,"x"); } else fprintf(stderr,".");
+        }
+        //fprintf(stderr, "Terrs_raw: %d  Tbits_raw: %d Terr: %d Tbits: %d\n", Terrs_raw, Tbits_raw, Terrs, Tbits);
+    }
+
+    free(input_float);
+    if (fin  != NULL) fclose(fin);
+    if (fout != NULL) fclose(fout);
+
+    fprintf(stderr, "total iters %d\n", total_iters);
+
+    if (testframes) {
+        fprintf(stderr, "Raw   Tbits: %6d Terr: %6d BER: %4.3f\n", Tbits_raw, Terrs_raw,
+                (float)Terrs_raw/(Tbits_raw+1E-12));
+        float coded_ber = (float)Terrs/(Tbits+1E-12);
+        fprintf(stderr, "Coded Tbits: %6d Terr: %6d BER: %4.3f\n", Tbits, Terrs, coded_ber);
+        fprintf(stderr, "      Tpkts: %6d Tper: %6d PER: %4.3f\n", Tpackets, Tpacketerrs, Tpacketerrs/(Tpackets+1E-12));
+
+        /* set return code for Ctest */
+        if (Tpackets && (coded_ber < 0.01))
+            return 0;
+        else
+            return 1;
+    }
+    
+    return 0;
+}
+
+
-- 
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