Initial

bitstream.cpp

@@ -0,0 +1,87 @@
+#include <iostream>
+#include <bitset>
+#include "bitstream.h"
+
+#define min(x,y) (((x) > (y)) ? (y) : (x))
+
+// i.e when stream is 0b12345678 0bABCDEFGH and command is 
+// to read 12 bits:
+// out = 00000000 00000000 0000EFGH 12345678
+// to read 2 bits:
+// out = 00000000 00000000 00000000 00000078
+int ibitstream::getbits(size_t n) {
+    std::cerr << "To read " << n << " count: " << this->count << " " << this->cache << std::endl;
+    int out = 0, read = 0, to_read;
+
+    if (n > 32 || n < 0) {
+        throw std::runtime_error("When reading bits from bitstream n must be <= 32");
+    }
+    
+    // read to cache
+    if (this->count == -1 || this->count >= 8) {
+        if (!(this->is >> cache)) throw std::runtime_error("Stream EOF");
+        this->count = 0;
+    }
+    
+    while (n > 0) {
+        to_read = min(n, 8 - this->count);
+        std::cerr << "Iter n: " << n << " count: " << this->count << " "
+            << this->cache << " to_read: " << to_read << " already read: " << read << std::endl;
+
+        // cache & 0b11111000 if count = 3;
+        // cache & 0b10000000 if count = 7;
+        // cache & 0b11111111 if count = 0, etc;
+        uint8_t mask = (((1 << to_read) - 1) << this->count);
+        out |= ((cache & mask) >> this->count) << read;
+
+        std::cerr << "Read result: " << std::bitset<8>((cache & mask) >> this->count) << " " << std::bitset<32>(((cache & mask) >> this->count) << read) << std::endl;
+        
+        this->count += to_read;
+        read += to_read;
+        n -= to_read;
+
+        if (this->count == 8){
+            // read another byte
+            if (!(this->is >> cache)) throw std::runtime_error("Stream EOF");
+            this->count = 0;
+        }
+    }
+    
+    return out;
+}
+
+void obitstream::writebits(short bits, size_t n) {
+    std::cerr << "Write: " << std::bitset<16>(bits) << " n: " << n << " count: " << this->count << " cache: " << std::bitset<8>(this->cache) << std::endl;
+    int written = 0, to_write;
+    while (n > 0) {
+        to_write = min(n, 8 - this->count);
+
+        uint8_t chunk = (bits & (((1 << to_write) - 1) << written)) >> written;
+        this->cache |= (chunk << this->count);
+
+        this->count += to_write;
+        written += to_write;
+        n -= to_write;
+        
+        if (this->count == 8){
+            // flush chunk
+            std::cerr << "Flush: " << std::bitset<8>(this->cache) << std::endl;
+
+            os << this->cache;
+            os.flush();
+
+            this->count = 0;
+            this->cache = 0;
+        }
+    }
+    
+}
+
+void obitstream::flush() {
+    std::cerr << "Flush: " << std::bitset<8>(this->cache) << std::endl;
+    os << this->cache;
+    os.flush();
+
+    this->cache = 0;
+    this->count = 0;
+}