geo: allow case insensitive SRID= at the start of EWKT

[otan]

PostGIS allows any combination of srid at the beginning of the string.
Follow the same allowance by having a case insensitive HasPrefix.

Release note: None

[cockroach-teamcity]

This change is 

[sumeerbhola]

Reviewed 2 of 2 files at r1.
Reviewable status: complete! 0 of 0 LGTMs obtained (waiting on @otan)

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pkg/geo/parse.go, line 194 at r1 (raw file):

	}
	for i := 0; i < len(prefix); i++ {
		if unicode.ToLower(rune(str[i])) != unicode.ToLower(rune(prefix[i])) {

It is not clear to me why this is correct in the general utf-8 case (though fine for SRID): my understanding is that the string index returns a byte, not a rune. Can you fix that or add a comment that this works only for a prefix that is ascii.

[otan]

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pkg/geo/parse.go, line 194 at r1 (raw file):

Previously, sumeerbhola wrote…

It is not clear to me why this is correct in the general utf-8 case (though fine for SRID): my understanding is that the string index returns a byte, not a rune. Can you fix that or add a comment that this works only for a prefix that is ascii.

I'll just cop it and write the builtin myself.

[sumeerbhola]

Reviewed 3 of 3 files at r2.
Reviewable status: complete! 1 of 0 LGTMs obtained (waiting on @otan)

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pkg/geo/parse.go, line 194 at r1 (raw file):

Previously, otan (Oliver Tan) wrote…

I'll just cop it and write the builtin myself.

Can you add the following to the function level comment.
// It assumes that the prefix contains only ASCII bytes.

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pkg/util/strings.go, line 34 at r2 (raw file):

}

// ToLowerSingleByte returns the the lowercase of a given single ASCII byte.

can you add
// A non ASCII byte is returned unchanged.

and add a couple of non-ascii bytes to the test.

[otan]

tftr!

bors r=sumeerbhola

[craig]

Build succeeded

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