Import of the watch repository from Pebble

2025-11-21 06:50:54 -05:00 · 2024-12-12 16:43:03 -08:00
commit 3b92768480
10334 changed files with 2564465 additions and 0 deletions
--- a/src/libutil/trig.c
+++ b/src/libutil/trig.c
@@ -0,0 +1,623 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include "util/trig.h"
+
+#include "util/math.h"
+
+
+// lookup points on the first quarter sin wave
+// generated by tintin/tools/trigTable.py
+static const uint16_t SIN_LOOKUP[] = {
+0,
+401,
+801,
+1202,
+1602,
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+};
+
+// lookup points on the first quarter atan wave
+// generated by tintin/tools/trigTable.py
+static const uint16_t ATAN_LOOKUP[] = {
+0,
+328,
+648,
+976,
+1296,
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+1944,
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+};
+
+int32_t sin_lookup(int32_t angle) {
+  int32_t mult = 1;
+
+  // modify the input angle and output multiplier for use in a first quadrent sine lookup
+  if (angle < 0) {
+    angle = -angle;
+    mult = -mult;
+  }
+  if (angle >= TRIG_MAX_ANGLE) {
+    angle %= TRIG_MAX_ANGLE;
+  }
+  if (angle >= TRIG_MAX_ANGLE / 2) {
+    mult = -mult;
+    angle -= TRIG_MAX_ANGLE / 2;
+  }
+  if (angle >= TRIG_MAX_ANGLE / 4 && angle <= TRIG_MAX_ANGLE / 2) {
+    angle = TRIG_MAX_ANGLE / 2 - angle;
+  }
+
+  // if I can interpolate linearly
+  int32_t lookup_angle =  angle * 4 / 0xff;
+  if ((uint32_t)(lookup_angle + 1) < sizeof(SIN_LOOKUP) / sizeof(int32_t)) {
+    return  mult * (SIN_LOOKUP[lookup_angle] + ((angle * 4) % 0xff) * (SIN_LOOKUP[lookup_angle + 1] - SIN_LOOKUP[lookup_angle]) / 0xff);
+  }
+
+  return mult * SIN_LOOKUP[lookup_angle];
+}
+
+int32_t cos_lookup(int32_t angle) {
+  return sin_lookup(angle + TRIG_MAX_ANGLE / 4);
+}
+
+#define ATAN_LUT_STRIDE 0xff
+
+int32_t atan2_lookup(int16_t y, int16_t x) {
+  // inspired by http://www.coranac.com/documents/arctangent/
+  if (y == 0) {
+    return (x >= 0 ? 0 : TRIG_PI);
+  }
+
+  // moving x and y values into bigger containers to avoid overflows
+  int32_t x_wide = x;
+  int32_t y_wide = y;
+  int32_t angle = 0;
+  // Find octant
+  if (y_wide < 0) {
+    x_wide = -x_wide;
+    y_wide = -y_wide;
+    angle += 4;
+  }
+  if (x_wide <= 0) {
+    uint32_t t = x_wide;
+    x_wide = y_wide;
+    y_wide = -t;
+    angle += 2;
+  }
+  if (x_wide <= y_wide) {
+    uint32_t t = y_wide - x_wide;
+    x_wide = x_wide + y_wide;
+    y_wide = t;
+    angle += 1;
+  }
+
+  angle *= TRIG_PI / 4;
+  uint32_t ratio = (y_wide << TRIG_FP) / x_wide;
+
+  return (angle + ATAN_LOOKUP[ratio / ATAN_LUT_STRIDE] / 8);
+}
+
+uint32_t normalize_angle(int32_t angle) {
+  uint32_t normalized_angle = ABS(angle) % TRIG_MAX_ANGLE;
+  if (angle < 0) {
+    normalized_angle = TRIG_MAX_ANGLE - normalized_angle;
+  }
+  return normalized_angle;
+}