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diff --git a/src/soft_float.h b/src/soft_float.h
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+/*
+  Copyright 2019-2020 David Robillard <http://drobilla.net>
+
+  Permission to use, copy, modify, and/or distribute this software for any
+  purpose with or without fee is hereby granted, provided that the above
+  copyright notice and this permission notice appear in all copies.
+
+  THIS SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+
+#ifndef SERD_SOFT_FLOAT_H
+#define SERD_SOFT_FLOAT_H
+
+#include <stdint.h>
+
+typedef struct
+{
+	uint64_t f; ///< Significand
+	int      e; ///< Exponent
+} SerdSoftFloat;
+
+static const int min_dec_expt  = -348;
+static const int max_dec_expt  = 340;
+static const int dec_expt_step = 8;
+
+/// Convert `d` to a soft float
+SerdSoftFloat
+soft_float_from_double(double d);
+
+/// Convert `v` to a double
+double
+soft_float_to_double(SerdSoftFloat v);
+
+/// Normalize `value` so the MSb of its significand is 1
+SerdSoftFloat
+soft_float_normalize(SerdSoftFloat value);
+
+/// Multiply `lhs` by `rhs` and return the result
+SerdSoftFloat
+soft_float_multiply(SerdSoftFloat lhs, SerdSoftFloat rhs);
+
+/// Return exactly 10^e for e in [0...dec_expt_step]
+SerdSoftFloat
+soft_float_exact_pow10(int expt);
+
+/**
+   Return a cached power of 10 with exponent not greater than `max_exponent`.
+
+   Valid only for `max_exponent` values from min_dec_expt to max_dec_expt +
+   dec_expt_step.  The returned power's exponent is a multiple of
+   dec_expt_step.
+
+   @param max_exponent Maximum decimal exponent of the result.
+   @param[out] pow10_exponent Set to the decimal exponent of the result.
+   @return A cached power of 10 as a soft float.
+*/
+SerdSoftFloat
+soft_float_pow10_under(int max_exponent, int* pow10_exponent);
+
+#endif // SERD_SOFT_FLOAT_H