nostrdb: move everything to src

Signed-off-by: William Casarin <jb55@jb55.com>

nostrdb/src/memchr.h

@@ -0,0 +1,72 @@
+
+
+#ifndef FAST_MEMCHR_H
+#define FAST_MEMCHR_H
+
+#include <string.h>
+
+#ifdef __ARM_NEON
+#define vector_strchr neon_strchr
+#else
+#define vector_strchr native_memchr
+#endif
+
+#ifdef __ARM_NEON
+#include <arm_neon.h>
+static const char *neon_strchr(const char *str, char c, size_t length) {
+	const char* end = str + length;
+
+	// Alignment handling
+	while (str < end && ((size_t)str & 0xF)) {
+		if (*str == c) 
+			return str;
+		++str;
+	}
+
+	uint8x16_t searchChar = vdupq_n_u8(c);
+
+	while (str + 16 <= end) {
+		uint8x16_t chunk = vld1q_u8((const uint8_t*)str);
+		uint8x16_t comparison = vceqq_u8(chunk, searchChar);
+
+		// Check first 64 bits
+		uint64_t result0 =
+			vgetq_lane_u64(vreinterpretq_u64_u8(comparison), 0);
+
+		if (result0)
+			return str + __builtin_ctzll(result0)/8;
+	
+		// Check second 64 bits
+		uint64_t result1 = vgetq_lane_u64(vreinterpretq_u64_u8(comparison), 1);
+		if (result1)
+			return str + 8 + __builtin_ctzll(result1)/8;
+
+		str += 16;
+	}
+
+	// Handle remaining unaligned characters
+	for (; str < end; ++str) {
+		if (*str == c)
+			return str;
+	}
+
+	return NULL;
+}
+#endif
+
+static inline const char *native_memchr(const char *str, char c, size_t length) {
+    const void *result = memchr(str, c, length);
+    return (const char *) result;
+}
+
+static inline const char *fast_strchr(const char *str, char c, size_t length)
+{
+	if (length >= 16) {
+		return vector_strchr(str, c, length);
+	}
+	
+	return native_memchr(str, c, length);
+}
+
+
+#endif // FAST_MEMCHR_H