Attempting to use an external library to handle bitstreams. Isn't going the grreatest.

include/bitstream/quantization/half_precision.h

@@ -0,0 +1,114 @@
+#pragma once
+
+/*
+ *  Copyright (c) 2018 Stanislav Denisov
+ *
+ *  Permission is hereby granted, free of charge, to any person obtaining a copy
+ *  of this software and associated documentation files (the "Software"), to deal
+ *  in the Software without restriction, including without limitation the rights
+ *  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ *  copies of the Software, and to permit persons to whom the Software is
+ *  furnished to do so, subject to the following conditions:
+ *
+ *  The above copyright notice and this permission notice shall be included in all
+ *  copies or substantial portions of the Software.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ *  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ *  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ *  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ *  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ *  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ *  SOFTWARE.
+ */
+
+#include <cstdint>
+#include <cstring>
+
+namespace bitstream
+{
+	/**
+	 * @brief Class for quantizing single-precision floats into half-precision
+	*/
+	class half_precision
+	{
+	public:
+		inline static uint16_t quantize(float value) noexcept
+		{
+			int32_t tmp;
+			std::memcpy(&tmp, &value, sizeof(float));
+
+			int32_t s = (tmp >> 16) & 0x00008000;
+			int32_t e = ((tmp >> 23) & 0X000000FF) - (127 - 15);
+			int32_t m = tmp & 0X007FFFFF;
+
+			if (e <= 0) {
+				if (e < -10)
+					return static_cast<uint16_t>(s);
+
+				m |= 0x00800000;
+
+				int32_t t = 14 - e;
+				int32_t a = (1 << (t - 1)) - 1;
+				int32_t b = (m >> t) & 1;
+
+				m = (m + a + b) >> t;
+
+				return static_cast<uint16_t>(s | m);
+			}
+
+			if (e == 0XFF - (127 - 15)) {
+				if (m == 0)
+					return static_cast<uint16_t>(s | 0X7C00);
+
+				m >>= 13;
+
+				return static_cast<uint16_t>(s | 0X7C00 | m | ((m == 0) ? 1 : 0));
+			}
+
+			m = m + 0X00000FFF + ((m >> 13) & 1);
+
+			if ((m & 0x00800000) != 0) {
+				m = 0;
+				e++;
+			}
+
+			if (e > 30)
+				return static_cast<uint16_t>(s | 0X7C00);
+
+			return static_cast<uint16_t>(s | (e << 10) | (m >> 13));
+		}
+
+		inline static float dequantize(uint16_t value) noexcept
+		{
+			uint32_t tmp;
+			uint32_t mantissa = static_cast<uint32_t>(value & 1023);
+			uint32_t exponent = 0XFFFFFFF2;
+
+			if ((value & -33792) == 0) {
+				if (mantissa != 0) {
+					while ((mantissa & 1024) == 0) {
+						exponent--;
+						mantissa <<= 1;
+					}
+
+					mantissa &= 0XFFFFFBFF;
+					tmp = ((static_cast<uint32_t>(value) & 0x8000) << 16) | ((exponent + 127) << 23) | (mantissa << 13);
+				}
+				else
+				{
+					tmp = static_cast<uint32_t>((value & 0x8000) << 16);
+				}
+			}
+			else
+			{
+				tmp = ((static_cast<uint32_t>(value) & 0x8000) << 16) | (((((static_cast<uint32_t>(value) >> 10) & 0X1F) - 15) + 127) << 23) | (mantissa << 13);
+			}
+
+			float result;
+			std::memcpy(&result, &tmp, sizeof(float));
+
+			return result;
+		}
+	};
+}