Hand code string to integer conversion for performance.

As benchmarks show, using libc's string-to-integer conversion is
pretty slow. At least part of the reason for that is that strtol[l]
have to be more generic than what largely is required inside pg.

This patch considerably speeds up int2/int4 input (int8 already was
already using hand-rolled code).

Most of the existing pg_atoi callers have been converted. But as one
requires pg_atoi's custom delimiter functionality, and as it seems
likely that there's external pg_atoi users, it seems sensible to just
keep pg_atoi around.

Author: Andres Freund
Reviewed-By: Robert Haas
Discussion: https://postgr.es/m/20171208214437.qgn6zdltyq5hmjpk@alap3.anarazel.de

1 files changed, 149 insertions, 0 deletions

diff --git a/src/backend/utils/adt/numutils.c b/src/backend/utils/adt/numutils.c
index fb46f692e3a..49055d519cb 100644
--- a/src/backend/utils/adt/numutils.c
+++ b/src/backend/utils/adt/numutils.c
@@ -18,6 +18,7 @@
 #include <limits.h>
 #include <ctype.h>
 
+#include "common/int.h"
 #include "utils/builtins.h"
 
 /*
@@ -109,6 +110,154 @@ pg_atoi(const char *s, int size, int c)
 }
 
 /*
+ * Convert input string to a signed 16 bit integer.
+ *
+ * Allows any number of leading or trailing whitespace characters. Will throw
+ * ereport() upon bad input format or overflow.
+ *
+ * NB: Accumulate input as a negative number, to deal with two's complement
+ * representation of the most negative number, which can't be represented as a
+ * positive number.
+ */
+int16
+pg_strtoint16(const char *s)
+{
+	const char *ptr = s;
+	int16		tmp = 0;
+	bool		neg = false;
+
+	/* skip leading spaces */
+	while (likely(*ptr) && isspace((unsigned char) *ptr))
+		ptr++;
+
+	/* handle sign */
+	if (*ptr == '-')
+	{
+		ptr++;
+		neg = true;
+	}
+	else if (*ptr == '+')
+		ptr++;
+
+	/* require at least one digit */
+	if (unlikely(!isdigit((unsigned char) *ptr)))
+		goto invalid_syntax;
+
+	/* process digits */
+	while (*ptr && isdigit((unsigned char) *ptr))
+	{
+		int8		digit = (*ptr++ - '0');
+
+		if (unlikely(pg_mul_s16_overflow(tmp, 10, &tmp)) ||
+			unlikely(pg_sub_s16_overflow(tmp, digit, &tmp)))
+			goto out_of_range;
+	}
+
+	/* allow trailing whitespace, but not other trailing chars */
+	while (*ptr != '\0' && isspace((unsigned char) *ptr))
+		ptr++;
+
+	if (unlikely(*ptr != '\0'))
+		goto invalid_syntax;
+
+	if (!neg)
+	{
+		/* could fail if input is most negative number */
+		if (unlikely(tmp == PG_INT16_MIN))
+			goto out_of_range;
+		tmp = -tmp;
+	}
+
+	return tmp;
+
+out_of_range:
+	ereport(ERROR,
+			(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+			 errmsg("value \"%s\" is out of range for type %s",
+					s, "smallint")));
+
+invalid_syntax:
+	ereport(ERROR,
+			(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+			 errmsg("invalid input syntax for type %s: \"%s\"",
+					"smallint", s)));
+}
+
+/*
+ * Convert input string to a signed 32 bit integer.
+ *
+ * Allows any number of leading or trailing whitespace characters. Will throw
+ * ereport() upon bad input format or overflow.
+ *
+ * NB: Accumulate input as a negative number, to deal with two's complement
+ * representation of the most negative number, which can't be represented as a
+ * positive number.
+ */
+int32
+pg_strtoint32(const char *s)
+{
+	const char *ptr = s;
+	int32		tmp = 0;
+	bool		neg = false;
+
+	/* skip leading spaces */
+	while (likely(*ptr) && isspace((unsigned char) *ptr))
+		ptr++;
+
+	/* handle sign */
+	if (*ptr == '-')
+	{
+		ptr++;
+		neg = true;
+	}
+	else if (*ptr == '+')
+		ptr++;
+
+	/* require at least one digit */
+	if (unlikely(!isdigit((unsigned char) *ptr)))
+		goto invalid_syntax;
+
+	/* process digits */
+	while (*ptr && isdigit((unsigned char) *ptr))
+	{
+		int8		digit = (*ptr++ - '0');
+
+		if (unlikely(pg_mul_s32_overflow(tmp, 10, &tmp)) ||
+			unlikely(pg_sub_s32_overflow(tmp, digit, &tmp)))
+			goto out_of_range;
+	}
+
+	/* allow trailing whitespace, but not other trailing chars */
+	while (*ptr != '\0' && isspace((unsigned char) *ptr))
+		ptr++;
+
+	if (unlikely(*ptr != '\0'))
+		goto invalid_syntax;
+
+	if (!neg)
+	{
+		/* could fail if input is most negative number */
+		if (unlikely(tmp == PG_INT32_MIN))
+			goto out_of_range;
+		tmp = -tmp;
+	}
+
+	return tmp;
+
+out_of_range:
+	ereport(ERROR,
+			(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
+			 errmsg("value \"%s\" is out of range for type %s",
+					s, "integer")));
+
+invalid_syntax:
+	ereport(ERROR,
+			(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+			 errmsg("invalid input syntax for type %s: \"%s\"",
+					"integer", s)));
+}
+
+/*
  * pg_itoa: converts a signed 16-bit integer to its string representation
  *
  * Caller must ensure that 'a' points to enough memory to hold the result