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Simplified encode174() routine

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This commit is contained in:
Karlis Goba 2018-10-29 17:58:11 +02:00
parent 609e045f07
commit a4992b068e
1 changed files with 28 additions and 42 deletions
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70
encode_91.cpp
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@ -140,34 +140,19 @@ void encode174(const uint8_t *message, uint8_t *codeword) {
// codeword(1:K)=message // codeword(1:K)=message
// codeword(K+1:N)=pchecks // codeword(K+1:N)=pchecks
printf("Encode "); // printf("Encode ");
for (int i = 0; i < K_BYTES; ++i) { // for (int i = 0; i < K_BYTES; ++i) {
printf("%02x ", message[i]); // printf("%02x ", message[i]);
} // }
printf("\n"); // printf("\n");
int colidx = 0; // track the current column in codeword // Fill the codeword with message and zeros, as we will only update binary ones later
for (int j = 0; j < (7 + N) / 8; ++j) {
// Fill the codeword with zeroes, as we will only update binary ones later codeword[j] = (j < K_BYTES) ? message[j] : 0;
for (int i = 0; i < (N + 7) / 8; i++) {
codeword[i] = 0;
} }
// Compute the second part of itmp (M+1:N) and store the result in codeword uint8_t col_mask = (0x80 >> (K % 8)); // bitmask of current byte
uint8_t mask = 0x80; // Rolling mask starting with the MSB uint8_t col_idx = K_BYTES - 1; // index into byte array
for (int j = 0; j < K; ++j) {
// Copy the j-th bit from message to codeword
if (message[j/8] & mask) {
//uint8_t col = colorder[colidx]; // Index of the bit to set
uint8_t col = colidx;
codeword[col/8] |= (1 << (7 - col%8));
}
++colidx;
// Roll the bitmask to the right
mask >>= 1;
if (mask == 0) mask = 0x80;
}
// Compute the first part of itmp (1:M) and store the result in codeword // Compute the first part of itmp (1:M) and store the result in codeword
for (int i = 0; i < M; ++i) { // do i=1,M for (int i = 0; i < M; ++i) { // do i=1,M
@ -181,18 +166,21 @@ void encode174(const uint8_t *message, uint8_t *codeword) {
} }
// Check if we need to set a bit in codeword // Check if we need to set a bit in codeword
if (nsum % 2) { // pchecks(i)=mod(nsum,2) if (nsum % 2) { // pchecks(i)=mod(nsum,2)
//uint8_t col = colorder[colidx]; // Index of the bit to set codeword[col_idx] |= col_mask;
uint8_t col = colidx; }
codeword[col/8] |= (1 << (7 - col%8));
col_mask >>= 1;
if (col_mask == 0) {
col_mask = 0x80;
++col_idx;
} }
++colidx;
} }
printf("Result "); // printf("Result ");
for (int i = 0; i < (N + 7) / 8; ++i) { // for (int i = 0; i < (N + 7) / 8; ++i) {
printf("%02x ", codeword[i]); // printf("%02x ", codeword[i]);
} // }
printf("\n"); // printf("\n");
} }
@ -204,11 +192,11 @@ uint16_t ft8_crc(uint8_t *message, int num_bits) {
constexpr int WIDTH = 14; constexpr int WIDTH = 14;
constexpr uint16_t TOPBIT = (1 << (WIDTH - 1)); constexpr uint16_t TOPBIT = (1 << (WIDTH - 1));
printf("CRC, %d bits: ", num_bits); // printf("CRC, %d bits: ", num_bits);
for (int i = 0; i < (num_bits + 7) / 8; ++i) { // for (int i = 0; i < (num_bits + 7) / 8; ++i) {
printf("%02x ", message[i]); // printf("%02x ", message[i]);
} // }
printf("\n"); // printf("\n");
uint16_t remainder = 0; uint16_t remainder = 0;
int idx_byte = 0; int idx_byte = 0;
@ -229,7 +217,7 @@ uint16_t ft8_crc(uint8_t *message, int num_bits) {
remainder = (remainder << 1); remainder = (remainder << 1);
} }
} }
printf("CRC = %04xh\n", remainder & ((1 << WIDTH) - 1)); // printf("CRC = %04xh\n", remainder & ((1 << WIDTH) - 1));
return remainder & ((1 << WIDTH) - 1); return remainder & ((1 << WIDTH) - 1);
} }
@ -289,8 +277,6 @@ void genft8(const uint8_t *payload, uint8_t *itone) {
if (codeword[i_byte] & mask) bits3 |= 1; if (codeword[i_byte] & mask) bits3 |= 1;
if (0 == (mask >>= 1)) { mask = 0x80; i_byte++; } if (0 == (mask >>= 1)) { mask = 0x80; i_byte++; }
// Before Gray: 2560413 00000000117314000020544743734 2560413 74502537003717523102453566214 2560413
// After Gray: 2560413 00000000117215000030655752725 2560413 75603627002717632103562644315 2560413
itone[k] = GRAY[bits3]; itone[k] = GRAY[bits3];
++k; ++k;
} }