| 75 | #endif |
| 76 | |
| 77 | void bitrv2(int n, float *a) |
| 78 | { |
| 79 | int j0, k0, j1, k1, l, m, i, j, k, nh; |
| 80 | float xr, xi, yr, yi; |
| 81 | |
| 82 | m = 4; |
| 83 | for (l = n >> 2; l > 8; l >>= 2) { |
| 84 | m <<= 1; |
| 85 | } |
| 86 | nh = n >> 1; |
| 87 | if (l == 8) { |
| 88 | j0 = 0; |
| 89 | for (k0 = 0; k0 < m; k0 += 4) { |
| 90 | k = k0; |
| 91 | for (j = j0; j < j0 + k0; j += 4) { |
| 92 | xr = a[j]; |
| 93 | xi = a[j + 1]; |
| 94 | yr = a[k]; |
| 95 | yi = a[k + 1]; |
| 96 | a[j] = yr; |
| 97 | a[j + 1] = yi; |
| 98 | a[k] = xr; |
| 99 | a[k + 1] = xi; |
| 100 | j1 = j + m; |
| 101 | k1 = k + 2 * m; |
| 102 | xr = a[j1]; |
| 103 | xi = a[j1 + 1]; |
| 104 | yr = a[k1]; |
| 105 | yi = a[k1 + 1]; |
| 106 | a[j1] = yr; |
| 107 | a[j1 + 1] = yi; |
| 108 | a[k1] = xr; |
| 109 | a[k1 + 1] = xi; |
| 110 | j1 += m; |
| 111 | k1 -= m; |
| 112 | xr = a[j1]; |
| 113 | xi = a[j1 + 1]; |
| 114 | yr = a[k1]; |
| 115 | yi = a[k1 + 1]; |
| 116 | a[j1] = yr; |
| 117 | a[j1 + 1] = yi; |
| 118 | a[k1] = xr; |
| 119 | a[k1 + 1] = xi; |
| 120 | j1 += m; |
| 121 | k1 += 2 * m; |
| 122 | xr = a[j1]; |
| 123 | xi = a[j1 + 1]; |
| 124 | yr = a[k1]; |
| 125 | yi = a[k1 + 1]; |
| 126 | a[j1] = yr; |
| 127 | a[j1 + 1] = yi; |
| 128 | a[k1] = xr; |
| 129 | a[k1 + 1] = xi; |
| 130 | j1 += nh; |
| 131 | k1 += 2; |
| 132 | xr = a[j1]; |
| 133 | xi = a[j1 + 1]; |
| 134 | yr = a[k1]; |