2014-01-09 06:20:26 -08:00
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/*
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2016-11-04 07:18:34 -07:00
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Copyright 2016 Benjamin Vedder benjamin@vedder.se
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2014-01-09 06:20:26 -08:00
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2016-11-04 07:18:34 -07:00
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This file is part of the VESC firmware.
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The VESC firmware is free software: you can redistribute it and/or modify
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2014-01-09 06:20:26 -08:00
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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2016-11-04 07:18:34 -07:00
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The VESC firmware is distributed in the hope that it will be useful,
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2014-01-09 06:20:26 -08:00
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include "buffer.h"
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2016-11-04 07:18:34 -07:00
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#include <math.h>
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#include <stdbool.h>
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2014-01-09 06:20:26 -08:00
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2015-07-31 14:26:50 -07:00
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void buffer_append_int16(uint8_t* buffer, int16_t number, int32_t *index) {
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buffer[(*index)++] = number >> 8;
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buffer[(*index)++] = number;
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}
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void buffer_append_uint16(uint8_t* buffer, uint16_t number, int32_t *index) {
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buffer[(*index)++] = number >> 8;
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buffer[(*index)++] = number;
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}
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2014-01-09 06:20:26 -08:00
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void buffer_append_int32(uint8_t* buffer, int32_t number, int32_t *index) {
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buffer[(*index)++] = number >> 24;
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buffer[(*index)++] = number >> 16;
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buffer[(*index)++] = number >> 8;
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buffer[(*index)++] = number;
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}
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void buffer_append_uint32(uint8_t* buffer, uint32_t number, int32_t *index) {
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buffer[(*index)++] = number >> 24;
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buffer[(*index)++] = number >> 16;
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buffer[(*index)++] = number >> 8;
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buffer[(*index)++] = number;
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}
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2015-07-31 14:26:50 -07:00
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void buffer_append_float16(uint8_t* buffer, float number, float scale, int32_t *index) {
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buffer_append_int16(buffer, (int16_t)(number * scale), index);
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2014-01-09 06:20:26 -08:00
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}
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2015-07-31 14:26:50 -07:00
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void buffer_append_float32(uint8_t* buffer, float number, float scale, int32_t *index) {
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buffer_append_int32(buffer, (int32_t)(number * scale), index);
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2014-01-09 06:20:26 -08:00
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}
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2016-11-04 07:18:34 -07:00
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/*
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* See my question:
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* http://stackoverflow.com/questions/40416682/portable-way-to-serialize-float-as-32-bit-integer
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*
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* Regarding the float32_auto functions:
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*
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* Noticed that frexp and ldexp fit the format of the IEEE float representation, so
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* they should be quite fast. They are (more or less) equivalent with the following:
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*
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* float frexp_slow(float f, int *e) {
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* if (f == 0.0) {
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* *e = 0;
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* return 0.0;
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* }
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*
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* *e = ceilf(log2f(fabsf(f)));
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* float res = f / powf(2.0, (float)*e);
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*
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* if (res >= 1.0) {
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* res -= 0.5;
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* *e += 1;
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* }
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*
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* if (res <= -1.0) {
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* res += 0.5;
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* *e += 1;
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* }
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*
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* return res;
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* }
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*
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* float ldexp_slow(float f, int e) {
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* return f * powf(2.0, (float)e);
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* }
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*
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* 8388608.0 is 2^23, which scales the result to fit within 23 bits if sig_abs < 1.0.
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*
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* This should be a relatively fast and efficient way to serialize
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* floating point numbers in a fully defined manner.
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*/
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void buffer_append_float32_auto(uint8_t* buffer, float number, int32_t *index) {
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int e = 0;
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float sig = frexpf(number, &e);
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float sig_abs = fabsf(sig);
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uint32_t sig_i = 0;
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if (sig_abs >= 0.5) {
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sig_i = (uint32_t)((sig_abs - 0.5f) * 2.0f * 8388608.0f);
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e += 126;
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}
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uint32_t res = ((e & 0xFF) << 23) | (sig_i & 0x7FFFFF);
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if (sig < 0) {
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2019-01-24 19:09:08 -08:00
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res |= 1U << 31;
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}
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buffer_append_uint32(buffer, res, index);
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}
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2014-01-09 06:20:26 -08:00
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int16_t buffer_get_int16(const uint8_t *buffer, int32_t *index) {
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int16_t res = ((uint16_t) buffer[*index]) << 8 |
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((uint16_t) buffer[*index + 1]);
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*index += 2;
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return res;
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}
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uint16_t buffer_get_uint16(const uint8_t *buffer, int32_t *index) {
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uint16_t res = ((uint16_t) buffer[*index]) << 8 |
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((uint16_t) buffer[*index + 1]);
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*index += 2;
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return res;
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}
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int32_t buffer_get_int32(const uint8_t *buffer, int32_t *index) {
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int32_t res = ((uint32_t) buffer[*index]) << 24 |
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((uint32_t) buffer[*index + 1]) << 16 |
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((uint32_t) buffer[*index + 2]) << 8 |
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((uint32_t) buffer[*index + 3]);
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*index += 4;
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return res;
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}
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uint32_t buffer_get_uint32(const uint8_t *buffer, int32_t *index) {
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uint32_t res = ((uint32_t) buffer[*index]) << 24 |
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((uint32_t) buffer[*index + 1]) << 16 |
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((uint32_t) buffer[*index + 2]) << 8 |
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((uint32_t) buffer[*index + 3]);
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*index += 4;
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return res;
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}
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2015-07-31 14:26:50 -07:00
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float buffer_get_float16(const uint8_t *buffer, float scale, int32_t *index) {
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return (float)buffer_get_int16(buffer, index) / scale;
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}
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float buffer_get_float32(const uint8_t *buffer, float scale, int32_t *index) {
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return (float)buffer_get_int32(buffer, index) / scale;
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}
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float buffer_get_float32_auto(const uint8_t *buffer, int32_t *index) {
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uint32_t res = buffer_get_uint32(buffer, index);
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int e = (res >> 23) & 0xFF;
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uint32_t sig_i = res & 0x7FFFFF;
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bool neg = res & (1U << 31);
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float sig = 0.0;
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if (e != 0 || sig_i != 0) {
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sig = (float)sig_i / (8388608.0 * 2.0) + 0.5;
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e -= 126;
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}
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if (neg) {
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sig = -sig;
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}
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return ldexpf(sig, e);
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}
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