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fix #92 : 'for' loop initial declarations

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TT 2019-11-17 11:16:36 +09:00
parent dd4eaed475
commit 3114df7fe9
1 changed files with 10 additions and 5 deletions
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15
fft.h
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@ -28,7 +28,8 @@
static uint16_t reverse_bits(uint16_t x, int n) { static uint16_t reverse_bits(uint16_t x, int n) {
uint16_t result = 0; uint16_t result = 0;
for (int i = 0; i < n; i++, x >>= 1) int i;
for (i = 0; i < n; i++, x >>= 1)
result = (result << 1) | (x & 1U); result = (result << 1) | (x & 1U);
return result; return result;
} }
@ -43,8 +44,10 @@ static void fft256(float array[][2], const uint8_t dir) {
const uint8_t real = dir & 1; const uint8_t real = dir & 1;
const uint8_t imag = ~real & 1; const uint8_t imag = ~real & 1;
uint16_t i;
uint16_t size;
for (uint16_t i = 0; i < n; i++) { for (i = 0; i < n; i++) {
uint16_t j = reverse_bits(i, levels); uint16_t j = reverse_bits(i, levels);
if (j > i) { if (j > i) {
float temp = array[i][real]; float temp = array[i][real];
@ -57,11 +60,13 @@ static void fft256(float array[][2], const uint8_t dir) {
} }
// Cooley-Tukey decimation-in-time radix-2 FFT // Cooley-Tukey decimation-in-time radix-2 FFT
for (uint16_t size = 2; size <= n; size *= 2) { for (size = 2; size <= n; size *= 2) {
uint16_t halfsize = size / 2; uint16_t halfsize = size / 2;
uint16_t tablestep = n / size; uint16_t tablestep = n / size;
for (uint16_t i = 0; i < n; i += size) { uint16_t i;
for (uint16_t j = i, k = 0; j < i + halfsize; j++, k += tablestep) { for (i = 0; i < n; i += size) {
uint16_t j, k;
for (j = i, k = 0; j < i + halfsize; j++, k += tablestep) {
uint16_t l = j + halfsize; uint16_t l = j + halfsize;
float tpre = array[l][real] * cos(2 * M_PI * k / 256) + array[l][imag] * sin(2 * M_PI * k / 256); float tpre = array[l][real] * cos(2 * M_PI * k / 256) + array[l][imag] * sin(2 * M_PI * k / 256);
float tpim = -array[l][real] * sin(2 * M_PI * k / 256) + array[l][imag] * cos(2 * M_PI * k / 256); float tpim = -array[l][real] * sin(2 * M_PI * k / 256) + array[l][imag] * cos(2 * M_PI * k / 256);