Refactor utf-8 conversion (irc) (#1767)

1 files changed, 87 insertions, 0 deletions

diff --git a/vendor/golang.org/x/text/internal/utf8internal/utf8internal.go b/vendor/golang.org/x/text/internal/utf8internal/utf8internal.go
new file mode 100644
index 00000000..575cea87
--- /dev/null
+++ b/vendor/golang.org/x/text/internal/utf8internal/utf8internal.go
@@ -0,0 +1,87 @@
+// Copyright 2015 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package utf8internal contains low-level utf8-related constants, tables, etc.
+// that are used internally by the text package.
+package utf8internal
+
+// The default lowest and highest continuation byte.
+const (
+	LoCB = 0x80 // 1000 0000
+	HiCB = 0xBF // 1011 1111
+)
+
+// Constants related to getting information of first bytes of UTF-8 sequences.
+const (
+	// ASCII identifies a UTF-8 byte as ASCII.
+	ASCII = as
+
+	// FirstInvalid indicates a byte is invalid as a first byte of a UTF-8
+	// sequence.
+	FirstInvalid = xx
+
+	// SizeMask is a mask for the size bits. Use use x&SizeMask to get the size.
+	SizeMask = 7
+
+	// AcceptShift is the right-shift count for the first byte info byte to get
+	// the index into the AcceptRanges table. See AcceptRanges.
+	AcceptShift = 4
+
+	// The names of these constants are chosen to give nice alignment in the
+	// table below. The first nibble is an index into acceptRanges or F for
+	// special one-byte cases. The second nibble is the Rune length or the
+	// Status for the special one-byte case.
+	xx = 0xF1 // invalid: size 1
+	as = 0xF0 // ASCII: size 1
+	s1 = 0x02 // accept 0, size 2
+	s2 = 0x13 // accept 1, size 3
+	s3 = 0x03 // accept 0, size 3
+	s4 = 0x23 // accept 2, size 3
+	s5 = 0x34 // accept 3, size 4
+	s6 = 0x04 // accept 0, size 4
+	s7 = 0x44 // accept 4, size 4
+)
+
+// First is information about the first byte in a UTF-8 sequence.
+var First = [256]uint8{
+	//   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
+	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x00-0x0F
+	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x10-0x1F
+	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x20-0x2F
+	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x30-0x3F
+	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x40-0x4F
+	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x50-0x5F
+	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x60-0x6F
+	as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, as, // 0x70-0x7F
+	//   1   2   3   4   5   6   7   8   9   A   B   C   D   E   F
+	xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x80-0x8F
+	xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0x90-0x9F
+	xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xA0-0xAF
+	xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xB0-0xBF
+	xx, xx, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xC0-0xCF
+	s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, s1, // 0xD0-0xDF
+	s2, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s3, s4, s3, s3, // 0xE0-0xEF
+	s5, s6, s6, s6, s7, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, xx, // 0xF0-0xFF
+}
+
+// AcceptRange gives the range of valid values for the second byte in a UTF-8
+// sequence for any value for First that is not ASCII or FirstInvalid.
+type AcceptRange struct {
+	Lo uint8 // lowest value for second byte.
+	Hi uint8 // highest value for second byte.
+}
+
+// AcceptRanges is a slice of AcceptRange values. For a given byte sequence b
+//
+//		AcceptRanges[First[b[0]]>>AcceptShift]
+//
+// will give the value of AcceptRange for the multi-byte UTF-8 sequence starting
+// at b[0].
+var AcceptRanges = [...]AcceptRange{
+	0: {LoCB, HiCB},
+	1: {0xA0, HiCB},
+	2: {LoCB, 0x9F},
+	3: {0x90, HiCB},
+	4: {LoCB, 0x8F},
+}