1 files changed, 125 insertions, 0 deletions
diff --git a/subprojects/exess/src/scientific.c b/subprojects/exess/src/scientific.c
new file mode 100644
index 00000000..3e441a86
--- /dev/null
+++ b/subprojects/exess/src/scientific.c
@@ -0,0 +1,125 @@
+/*
+  Copyright 2019-2021 David Robillard <d@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.
+*/
+
+#include "scientific.h"
+#include "decimal.h"
+#include "int_math.h"
+#include "read_utils.h"
+#include "write_utils.h"
+
+#include "exess/exess.h"
+
+#include <stdlib.h>
+#include <string.h>
+
+size_t
+exess_scientific_string_length(const ExessDecimalDouble value)
+{
+  switch (value.kind) {
+  case EXESS_NEGATIVE:
+    break;
+  case EXESS_NEGATIVE_INFINITY:
+    return 4;
+  case EXESS_NEGATIVE_ZERO:
+    return 6;
+  case EXESS_POSITIVE_ZERO:
+    return 5;
+  case EXESS_POSITIVE:
+    break;
+  case EXESS_POSITIVE_INFINITY:
+  case EXESS_NAN:
+    return 3;
+  }
+
+  const unsigned n_expt_digits =
+    (unsigned)exess_num_digits((unsigned)abs(value.expt));
+
+  return ((value.kind == EXESS_NEGATIVE) + // Sign
+          value.n_digits + 1 +             // Digits and point
+          (value.n_digits <= 1) +          // Added '0' after point
+          1 +                              // 'E'
+          (value.expt < 0) +               // Exponent sign
+          n_expt_digits);                  // Exponent digits
+}
+
+ExessResult
+exess_write_scientific(const ExessDecimalDouble value,
+                       const size_t             n,
+                       char* const              buf)
+{
+  size_t i = 0;
+
+  if (n < 4) {
+    return result(EXESS_NO_SPACE, 0);
+  }
+
+  switch (value.kind) {
+  case EXESS_NEGATIVE:
+    buf[i++] = '-';
+    break;
+  case EXESS_NEGATIVE_INFINITY:
+    return write_special(4, "-INF", n, buf);
+  case EXESS_NEGATIVE_ZERO:
+    return write_special(6, "-0.0E0", n, buf);
+  case EXESS_POSITIVE_ZERO:
+    return write_special(5, "0.0E0", n, buf);
+  case EXESS_POSITIVE:
+    break;
+  case EXESS_POSITIVE_INFINITY:
+    return write_special(3, "INF", n, buf);
+  case EXESS_NAN:
+    return write_special(3, "NaN", n, buf);
+  }
+
+  if (n - i <= value.n_digits + 1) {
+    buf[0] = '\0';
+    return result(EXESS_NO_SPACE, 0);
+  }
+
+  // Write mantissa, with decimal point after the first (normal form)
+  buf[i++] = value.digits[0];
+  buf[i++] = '.';
+  if (value.n_digits > 1) {
+    memcpy(buf + i, value.digits + 1, value.n_digits - 1);
+    i += value.n_digits - 1;
+  } else {
+    buf[i++] = '0';
+  }
+
+  // Write exponent
+
+  const unsigned n_expt_digits = exess_num_digits((unsigned)abs(value.expt));
+
+  if (n - i <= 1u + (value.expt < 0) + n_expt_digits) {
+    buf[0] = '\0';
+    return result(EXESS_NO_SPACE, 0);
+  }
+
+  buf[i++] = 'E';
+  if (value.expt < 0) {
+    buf[i++] = '-';
+  }
+
+  unsigned abs_expt = (unsigned)abs(value.expt);
+  char*    s        = buf + i + n_expt_digits;
+
+  *s-- = '\0';
+  do {
+    *s-- = (char)('0' + (abs_expt % 10));
+  } while ((abs_expt /= 10) > 0);
+
+  return result(EXESS_SUCCESS, i + n_expt_digits);
+}