84 lines
3.3 KiB
C
84 lines
3.3 KiB
C
|
/*
|
||
|
|
* This file is part of the Circuit Python project, https://github.com/adafruit/circuitpython
|
||
|
|
*
|
||
|
|
* The MIT License (MIT)
|
||
|
|
*
|
||
|
|
* Copyright (c) 2021 Jeff Epler
|
||
|
|
*
|
||
|
|
* 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 "shared-bindings/_bit_transpose/__init__.h"
|
||
|
|
|
||
|
|
#include <stdint.h>
|
||
|
|
#include <stdlib.h>
|
||
|
|
#include <string.h>
|
||
|
|
|
||
|
|
// adapted from "Hacker's Delight" - Figure 7-2 Transposing an 8x8-bit matrix
|
||
|
|
// basic idea is:
|
||
|
|
// > First, treat the 8x8-bit matrix as 16 2x2-bit matrices, and transpose each
|
||
|
|
// > of the 16 2x2-bit matrices. Second, treat the matrix as four 2x2 submatrices
|
||
|
|
// > whose elements are 2x2-bit matrices and transpose each of the four 2x2
|
||
|
|
// > submatrices. Finally, treat the matrix as a 2x2 matrix whose elements are
|
||
|
|
// > 4x4-bit matrices, and transpose the 2x2 matrix. These transformations are
|
||
|
|
// > illustrated below.
|
||
|
|
// We want a different definition of bit/byte order, deal with strides differently, etc.
|
||
|
|
// so the code is heavily re-worked compared to the original.
|
||
|
|
static void transpose8(uint32_t *result, const uint8_t *src, int src_stride) {
|
||
|
|
uint32_t x, y, t;
|
||
|
|
|
||
|
|
y = *src; src += src_stride;
|
||
|
|
y |= (*src << 8); src += src_stride;
|
||
|
|
y |= (*src << 16); src += src_stride;
|
||
|
|
y |= (*src << 24); src += src_stride;
|
||
|
|
x = *src; src += src_stride;
|
||
|
|
x |= (*src << 8); src += src_stride;
|
||
|
|
x |= (*src << 16); src += src_stride;
|
||
|
|
x |= (*src << 24); src += src_stride;
|
||
|
|
|
||
|
|
t = (x ^ (x >> 7)) & 0x00AA00AA; x = x ^ t ^ (t << 7);
|
||
|
|
t = (y ^ (y >> 7)) & 0x00AA00AA; y = y ^ t ^ (t << 7);
|
||
|
|
|
||
|
|
t = (x ^ (x >>14)) & 0x0000CCCC; x = x ^ t ^ (t <<14);
|
||
|
|
t = (y ^ (y >>14)) & 0x0000CCCC; y = y ^ t ^ (t <<14);
|
||
|
|
|
||
|
|
t = (x & 0xF0F0F0F0) | ((y >> 4) & 0x0F0F0F0F);
|
||
|
|
y = ((x << 4) & 0xF0F0F0F0) | (y & 0x0F0F0F0F);
|
||
|
|
x = t;
|
||
|
|
|
||
|
|
#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
|
||
|
|
x = __builtin_bswap32(x);
|
||
|
|
y = __builtin_bswap32(y);
|
||
|
|
#endif
|
||
|
|
result[0] = x;
|
||
|
|
result[1] = y;
|
||
|
|
}
|
||
|
|
|
||
|
|
static void bit_transpose(uint32_t *result, const uint8_t *src, size_t src_stride, size_t n) {
|
||
|
|
for(size_t i=0; i<n; i++) {
|
||
|
|
transpose8(result, src, src_stride);
|
||
|
|
result += 2;
|
||
|
|
src += 1;
|
||
|
|
}
|
||
|
|
}
|
||
|
|
|
||
|
|
void common_hal_bit_transpose_bit_transpose(uint8_t *result, const uint8_t *src, size_t n) {
|
||
|
|
bit_transpose((uint32_t*)(void*)result, src, n/8, n/8);
|
||
|
|
}
|