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#include "chacha20.h"
#define ROTL(a, b) (((a) << (b)) | ((a) >> (32 - (b))))
#define QR(a, b, c, d) \
(a += b, d ^= a, d = ROTL(d, 16), c += d, b ^= c, b = ROTL(b, 12), a += b, \
d ^= a, d = ROTL(d, 8), c += d, b ^= c, b = ROTL(b, 7))
#define ROUNDS 20
void chacha_block(u32 out[16], u32 const in[16]) {
int i;
u32 x[16];
for (i = 0; i < 16; ++i) {
x[i] = in[i];
}
for (i = 0; i < ROUNDS; i += 2) {
QR(x[0], x[4], x[8], x[12]);
QR(x[1], x[5], x[9], x[13]);
QR(x[2], x[6], x[10], x[14]);
QR(x[3], x[7], x[11], x[15]);
QR(x[0], x[5], x[10], x[15]);
QR(x[1], x[6], x[11], x[12]);
QR(x[2], x[7], x[8], x[13]);
QR(x[3], x[4], x[9], x[14]);
}
for (i = 0; i < 16; ++i) {
out[i] = x[i] + in[i];
}
}
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