Dev/decode my302 (#254)

This PR adds support for decoding digital data from the my320 test chip.
- Added BitOffset (strong type)
- Expand 24 to 32 bit 
- Python bindings for decoding my302
- Improved docs

src/decode.cpp

@@ -1,5 +1,6 @@
 // SPDX-License-Identifier: MPL-2.0
 #include "aare/decode.hpp"
+#include <fmt/format.h>
 #include <cmath>
 namespace aare {
 
@@ -105,4 +106,49 @@ void apply_custom_weights(NDView<uint16_t, 1> input, NDView<double, 1> output,
     }
 }
 
+uint32_t mask32to24bits(uint32_t input, BitOffset offset){
+    constexpr uint32_t mask24bits{0xFFFFFF};
+    return (input >> offset.value()) & mask24bits;
+}
+
+void expand24to32bit(NDView<uint8_t,1> input, NDView<uint32_t,1> output, BitOffset bit_offset){
+
+    ssize_t bytes_per_channel = 3; //24bit 
+    ssize_t min_input_size = output.size()*bytes_per_channel;
+
+    //if we have an offset we need one more byte in the input data
+    if (bit_offset.value())
+        min_input_size += 1; 
+
+    if (input.size() < min_input_size)
+        throw std::runtime_error(fmt::format(
+            "{} Mismatch between input and output size. Output "
+            "size of {} with bit offset {} requires an input of at least {} "
+            "bytes. Called with input size: {} output size: {}",
+            LOCATION, output.size(), bit_offset.value(), min_input_size, input.size(), output.size()));
+
+    auto* in = input.data();
+
+    if(bit_offset.value()){
+        //If there is a bit_offset we copy 4 bytes and then
+        //mask out the correct ones. 
+        for (auto& v : output){
+            uint32_t val{};
+            std::memcpy(&val, in, sizeof(val));
+            v = mask32to24bits(val, bit_offset);
+            in += bytes_per_channel;
+         }
+    }else{
+        //If there is no offset we can directly copy the bits
+        //without masking
+        for (auto& v : output){
+            uint32_t val{};
+            std::memcpy(&val, in, 3);
+            v = val;
+            in += bytes_per_channel;
+         }
+    }
+
+}
+
 } // namespace aare