1 files changed, 68 insertions, 0 deletions
diff --git a/src/include/utils/ascii.h b/src/include/utils/ascii.h
index 630acd9bfda..7df024dad39 100644
--- a/src/include/utils/ascii.h
+++ b/src/include/utils/ascii.h
@@ -11,6 +11,74 @@
 #ifndef _ASCII_H_
 #define _ASCII_H_
 
+#include "port/simd.h"
+
 extern void ascii_safe_strlcpy(char *dest, const char *src, size_t destsiz);
 
+/*
+ * Verify a chunk of bytes for valid ASCII.
+ *
+ * Returns false if the input contains any zero bytes or bytes with the
+ * high-bit set. Input len must be a multiple of the chunk size (8 or 16).
+ */
+static inline bool
+is_valid_ascii(const unsigned char *s, int len)
+{
+	const unsigned char *const s_end = s + len;
+	Vector8		chunk;
+	Vector8		highbit_cum = vector8_broadcast(0);
+#ifdef USE_NO_SIMD
+	Vector8		zero_cum = vector8_broadcast(0x80);
+#endif
+
+	Assert(len % sizeof(chunk) == 0);
+
+	while (s < s_end)
+	{
+		vector8_load(&chunk, s);
+
+		/* Capture any zero bytes in this chunk. */
+#ifdef USE_NO_SIMD
+
+		/*
+		 * First, add 0x7f to each byte. This sets the high bit in each byte,
+		 * unless it was a zero. If any resulting high bits are zero, the
+		 * corresponding high bits in the zero accumulator will be cleared.
+		 *
+		 * If none of the bytes in the chunk had the high bit set, the max
+		 * value each byte can have after the addition is 0x7f + 0x7f = 0xfe,
+		 * and we don't need to worry about carrying over to the next byte. If
+		 * any input bytes did have the high bit set, it doesn't matter
+		 * because we check for those separately.
+		 */
+		zero_cum &= (chunk + vector8_broadcast(0x7F));
+#else
+
+		/*
+		 * Set all bits in each lane of the highbit accumulator where input
+		 * bytes are zero.
+		 */
+		highbit_cum = vector8_or(highbit_cum,
+								 vector8_eq(chunk, vector8_broadcast(0)));
+#endif
+
+		/* Capture all set bits in this chunk. */
+		highbit_cum = vector8_or(highbit_cum, chunk);
+
+		s += sizeof(chunk);
+	}
+
+	/* Check if any high bits in the high bit accumulator got set. */
+	if (vector8_is_highbit_set(highbit_cum))
+		return false;
+
+#ifdef USE_NO_SIMD
+	/* Check if any high bits in the zero accumulator got cleared. */
+	if (zero_cum != vector8_broadcast(0x80))
+		return false;
+#endif
+
+	return true;
+}
+
 #endif							/* _ASCII_H_ */