Charles Iliya Krempeaux 27f52c4ec8 | ||
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LICENSE | ||
README.md | ||
errors.go | ||
format.go | ||
format_test.go | ||
invalidutf8.go | ||
nilreader.go | ||
nilwriter.go | ||
readrune.go | ||
readrune_test.go | ||
runeerror.go | ||
runelength.go | ||
runelength_test.go | ||
runereader.go | ||
runereader_test.go | ||
runescanner.go | ||
runescanner_test.go | ||
runewriter.go | ||
runewriter_test.go | ||
writerune.go | ||
writerune_test.go |
README.md
go-utf8
Package utf8 implements encoding and decoding of UTF-8, for the Go programming language.
This package is meant to be a replacement for Go's built-in "unicode/utf8"
package.
Documention
Online documentation, which includes examples, can be found at: http://godoc.org/sourcecode.social/reiver/go-utf8
Reading a Single UTF-8 Character
This is the simplest way of reading a single UTF-8 character.
var reader io.Reader
// ...
r, n, err := utf8.ReadRune(reader)
Write a Single UTF-8 Character
This is the simplest way of writing a single UTF-8 character.
var writer io.Writer
// ...
var r rune
// ...
n, err := utf8.WriteRune(w, r)
io.RuneReader
This is how you can create an io.RuneReader
:
var reader io.Reader
// ...
var runeReader io.RuneReader = utf8.RuneReaderWrap(reader)
// ...
r, n, err := runeReader.ReadRune()
io.RuneScanner
This is how you can create an io.RuneScanner
:
var reader io.Reader
// ...
var runeScanner io.RuneScanner := utf8.RuneScannerWrap(reader)
// ...
r, n, err := runeScanner.ReadRune()
// ...
err = runeScanner.UnreadRune()
UTF-8
UTF-8 is a variable length encoding of Unicode. An encoding of a single Unicode code point can be from 1 to 4 bytes longs.
Some examples of UTF-8 encoding of Unicode code points are:
UTF-8 encoding | value | code point | decimal | binary | name | |||
byte 1 | byte 2 | byte 3 | byte 4 | |||||
0b0,1000001 |
A | U+0041 | 65 | 0b0000,0000,0100,0001 |
LATIN CAPITAL LETTER A | |||
0b0,1110010 |
r | U+0072 | 114 | 0b0000,0000,0111,0010 |
LATIN SMALL LETTER R | |||
0b110,00010 |
0b10,100001 |
¡ | U+00A1 | 161 | 0b0000,0000,1010,0001 |
INVERTED EXCLAMATION MARK | ||
0b110,11011 |
0b10,110101 |
۵ | U+06F5 | 1781 | 0b0000,0110,1111,0101 |
EXTENDED ARABIC-INDIC DIGIT FIVE | ||
0b1110,0010 |
0b10,000000 |
0b10,110001 |
‱ | U+2031 | 8241 | 0b0010,0000,0011,0001 |
PER TEN THOUSAND SIGN | |
0b1110,0010 |
0b10,001001 |
0b10,100001 |
≡ | U+2261 | 8801 | 0b0010,0010,0110,0001 |
IDENTICAL TO | |
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┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━┳━━━━━━━━━━━━┳━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
| UTF-8 encoding | | | | | |
┣━━━━━━━━━━━━━┳━━━━━━━━━━━━━┳━━━━━━━━━━━━━┳━━━━━━━━━━━━━┫ | | | | |
| byte 1 ┋ byte 2 ┋ byte 3 ┋ byte 4 | value | code point | decimal | binary | name |
┡━━━━━━━━━━━━━╇━━━━━━━━━━━━━╇━━━━━━━━━━━━━╇━━━━━━━━━━━━━╇━━━━━━━╇━━━━━━━━━━━━╇━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┩
│ 0b0,1000001 ┊ ┊ ┊ │ A │ U+0041 │ 65 │ 0b0000,0000,0100,0001 │ LATIN CAPITAL LETTER A │
├-------------┼-------------┼-------------┼-------------┼-------┼------------┼---------┼----------------------------┼----------------------------------┤
│ 0b0,1110010 ┊ ┊ ┊ │ r │ U+0072 │ 114 │ 0b0000,0000,0111,0010 │ LATIN SMALL LETTER R │
├-------------┼-------------┼-------------┼-------------┼-------┼------------┼---------┼----------------------------┼----------------------------------┤
│ 0b110,00010 ┊ 0b10,100001 ┊ ┊ │ ¡ │ U+00A1 │ 161 │ 0b0000,0000,1010,0001 │ INVERTED EXCLAMATION MARK │
├-------------┼-------------┼-------------┼-------------┼-------┼------------┼---------┼----------------------------┼----------------------------------┤
│ 0b110,11011 ┊ 0b10,110101 ┊ ┊ │ ۵ │ U+06F5 │ 1781 │ 0b0000,0110,1111,0101 │ EXTENDED ARABIC-INDIC DIGIT FIVE │
├-------------┼-------------┼-------------┼-------------┼-------┼------------┼---------┼----------------------------┼----------------------------------┤
│ 0b1110,0010 ┊ 0b10,000000 ┊ 0b10,110001 ┊ │ ‱ │ U+2031 │ 8241 │ 0b0010,0000,0011,0001 │ PER TEN THOUSAND SIGN │
├-------------┼-------------┼-------------┼-------------┼-------┼------------┼---------┼----------------------------┼----------------------------------┤
│ 0b1110,0010 ┊ 0b10,001001 ┊ 0b10,100001 ┊ │ ≡ │ U+2261 │ 8801 │ 0b0010,0010,0110,0001 │ IDENTICAL TO │
├-------------┼-------------┼-------------┼-------------┼-------┼------------┼---------┼----------------------------┼----------------------------------┤
│ 0b11110,000 ┊ 0b10,010000 ┊ 0b10,001111 ┊ 0b10,010101 │ 𐏕 │ U+000103D5 │ 66517 │ 0b0001,0000,0011,1101,0101 │ OLD PERSIAN NUMBER HUNDRED │
├-------------┼-------------┼-------------┼-------------┼-------┼------------┼---------┼----------------------------┼----------------------------------┤
│ 0b11110,000 ┊ 0b10,011111 ┊ 0b10,011001 ┊ 0b10,000010 │ 🙂 │ U+0001F642 │ 128578 │ 0b0001,1111,0110,0100,0010 │ SLIGHTLY SMILING FACE │
└-------------┴-------------┴-------------┴-------------┴-------┴------------┴---------┴----------------------------┴----------------------------------┘
UTF-8 Versus ASCII
UTF-8 was (partially) designed to be backwards compatible with 7-bit ASCII.
Thus, all 7-bit ASCII is valid UTF-8.
UTF-8 Encoding
Since, at least as of 2003, Unicode fits into 21 bits, and thus UTF-8 was designed to support at most 21 bits of information.
This is done as described in the following table:
# of bytes | # bits for code point | 1st code point | last code point | byte 1 | byte 2 | byte 3 | byte 4 |
---|---|---|---|---|---|---|---|
1 | 7 | U+000000 | U+00007F | 0xxxxxxx |
|||
2 | 11 | U+000080 | U+0007FF | 110xxxxx |
10xxxxxx |
||
3 | 16 | U+000800 | U+00FFFF | 1110xxxx |
10xxxxxx |
10xxxxxx |
|
4 | 21 | U+010000 | U+10FFFF | 11110xxx |
10xxxxxx |
10xxxxxx |
10xxxxxx |