4.2 KiB
This is a work in progress and a long overdue attempt to bring all our not-DSP-related code together and make it reusable for our future projects.
Before using any of this you should enter the tests directory and execute "make". This will check if your compiler is able to create binaries that are able to produce correct results when executed.
What we have included so far:
crc.hh
A Cyclic redundancy check helps ensuring data integrity.
For example, if we need to integrate CRC32 checking for a few bytes, like in the following:
# echo -n 'Hello World!' | rhash -C -
(stdin) 1C291CA3
We can add it to our project as simple as that:
DSP::CRC<uint32_t> crc(0xEDB88320, 0xFFFFFFFF);
for (uint8_t c: std::string("Hello World!")) crc(c);
assert(~crc() == 0x1C291CA3);
xorshift.hh
Sometimes we need a sequence of "random enough" numbers but don't want to store them in an array to get a repeatable sequence. Here a Pseudorandom number generator can help by prodiving a deterministic and thus repeatable sequence of numbers. George Marsaglia discovered a class of simple and fast pseudorandom number generators, which he called Xorshift.
mls.hh
Maximum length sequences have useful correlation properties.
bitstream.hh
When dealing with unaligned and arbitrary-bit-sized elements in a data stream, the bitwise stream container might help avoiding some headaches.
bitman.hh
Simple bit manipulation on byte arrays.
galois_field.hh
We have to thank Évariste Galois for his contribution of the Finite field to mathematics, which laid the cornerstone for a variety of applications that we take for granted today. One of them is Reed–Solomon error correction:
reed_solomon_error_correction.hh
Implemented are the following Encoders and Decoders:
- reed_solomon_encoder.hh
- reed_solomon_decoder.hh
- bose_chaudhuri_hocquenghem_encoder.hh
- bose_chaudhuri_hocquenghem_decoder.hh
ldpc_encoder.hh
Low-density parity-check encoder
ldpc_decoder.hh
SIMD intra-frame accelerated Low-density parity-check layered decoder.
exclusive_reduce.hh
Reduce N times while excluding ith input element
It computes the following, but having only O(N) complexity and using O(1) extra storage:
output[0] = input[1];
output[1] = input[0];
for (int i = 2; i < N; ++i)
output[i] = op(input[0], input[1]);
for (int i = 0; i < N; ++i)
for (int j = 2; j < N; ++j)
if (i != j)
output[i] = op(output[i], input[j]);
simd.hh
Single instruction, multiple data (SIMD) wrappers for:
rotate.hh
SIMD element wise horizontal rotation
It computes the following, but faster:
SIMD<int8_t, SIZE> rotate(SIMD<int8_t, SIZE> input, int shift, int WIDTH)
{
SIMD<int8_t, SIZE> output;
for (int n = 0; n < WIDTH; ++n)
output.v[(n + shift + WIDTH) % WIDTH] = input.v[n];
return output;
}