Native Apple Silicon SIMD code, cleanup.

src/cha1c.h

@@ -0,0 +1,29 @@
+#include <stdint.h>
+#include <string.h>
+
+// clang-format off
+#define QUARTERSTEP(a, b, c, n) a += b; c ^= a; c = (c << n) | (c >> (32 - n))
+#define QUARTERROUND(a, b, c, d) {\
+    QUARTERSTEP(a, b, d, 16); QUARTERSTEP(c, d, b, 12); \
+    QUARTERSTEP(a, b, d, 8);  QUARTERSTEP(c, d, b, 7); }
+
+static inline uint64_t _cha_block(uint8_t* buf, size_t bufsize, uint32_t state[16], unsigned rounds) {
+    unsigned blocks = bufsize / 64;
+    uint32_t* out = (uint32_t*)buf;
+    uint32_t x[16];
+    for (unsigned b = blocks; b-->0;) {
+        for (unsigned i = 0; i < 16; ++i) x[i] = state[i];  // Faster than memcpy
+        for (unsigned i = rounds / 2; i-->0;) {
+            // Mix columns, then diagonals
+            for (unsigned j = 0; j < 4; ++j) QUARTERROUND(x[j], x[4 + j], x[8 + j], x[12 + j]);
+            for (unsigned j = 0; j < 4; ++j) QUARTERROUND(x[j], x[4 + (j+1)%4], x[8 + (j+2)%4], x[12 + (j+3)%4]);
+        }
+        for (unsigned i = 0; i < 16; ++i) *out++ = x[i] + state[i];
+        ++*(uint64_t*)(state + 12); // Increment counter
+    }
+    memset(x, 0, sizeof x);
+    return blocks * CHA_BLOCK_SIZE;
+}
+
+#undef QUARTERROUND
+#undef QUARTERSTEP