Length of a UTF-8 byte sequence

Clash Royale CLAN TAG#URR8PPP

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Determine the length of a UTF-8 byte sequence given its first byte. The following table shows which ranges map to each possible length:

 Range Length
--------- ------
0x00-0x7F 1
0xC2-0xDF 2
0xE0-0xEF 3
0xF0-0xF4 4

_{Notes on gaps in the table: 0x80-0xBF are continuation bytes, 0xC0-0xC1 would start an overlong, invalid sequence, 0xF5-0xFF would result in a codepoint beyond the Unicode maximum.}

Write a program or function that takes the first byte of a UTF-8 byte sequence as input and outputs or returns the length of the sequence. I/O is flexible. For example, the input can be a number, an 8-bit character or a one-character string. You can assume that the first byte is part of valid sequence and falls into one of the ranges above.

This is code golf. The shortest answer in bytes wins.

Test cases

0x00 => 1
0x41 => 1
0x7F => 1
0xC2 => 2
0xDF => 2
0xE0 => 3
0xEF => 3
0xF0 => 4
0xF4 => 4

code-golf integer

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asked 3 hours ago

nwellnhof

3,978715

add a comment | 

up vote
1
down vote

favorite

Determine the length of a UTF-8 byte sequence given its first byte. The following table shows which ranges map to each possible length:

 Range Length
--------- ------
0x00-0x7F 1
0xC2-0xDF 2
0xE0-0xEF 3
0xF0-0xF4 4

_{Notes on gaps in the table: 0x80-0xBF are continuation bytes, 0xC0-0xC1 would start an overlong, invalid sequence, 0xF5-0xFF would result in a codepoint beyond the Unicode maximum.}

Write a program or function that takes the first byte of a UTF-8 byte sequence as input and outputs or returns the length of the sequence. I/O is flexible. For example, the input can be a number, an 8-bit character or a one-character string. You can assume that the first byte is part of valid sequence and falls into one of the ranges above.

This is code golf. The shortest answer in bytes wins.

Test cases

0x00 => 1
0x41 => 1
0x7F => 1
0xC2 => 2
0xDF => 2
0xE0 => 3
0xEF => 3
0xF0 => 4
0xF4 => 4

code-golf integer

share|improve this question

asked 3 hours ago

nwellnhof

3,978715

add a comment | 

up vote
1
down vote

favorite

up vote
1
down vote

favorite

Determine the length of a UTF-8 byte sequence given its first byte. The following table shows which ranges map to each possible length:

 Range Length
--------- ------
0x00-0x7F 1
0xC2-0xDF 2
0xE0-0xEF 3
0xF0-0xF4 4

_{Notes on gaps in the table: 0x80-0xBF are continuation bytes, 0xC0-0xC1 would start an overlong, invalid sequence, 0xF5-0xFF would result in a codepoint beyond the Unicode maximum.}

Write a program or function that takes the first byte of a UTF-8 byte sequence as input and outputs or returns the length of the sequence. I/O is flexible. For example, the input can be a number, an 8-bit character or a one-character string. You can assume that the first byte is part of valid sequence and falls into one of the ranges above.

This is code golf. The shortest answer in bytes wins.

Test cases

0x00 => 1
0x41 => 1
0x7F => 1
0xC2 => 2
0xDF => 2
0xE0 => 3
0xEF => 3
0xF0 => 4
0xF4 => 4

code-golf integer

share|improve this question

asked 3 hours ago

nwellnhof

3,978715

Determine the length of a UTF-8 byte sequence given its first byte. The following table shows which ranges map to each possible length:

 Range Length
--------- ------
0x00-0x7F 1
0xC2-0xDF 2
0xE0-0xEF 3
0xF0-0xF4 4

_{Notes on gaps in the table: 0x80-0xBF are continuation bytes, 0xC0-0xC1 would start an overlong, invalid sequence, 0xF5-0xFF would result in a codepoint beyond the Unicode maximum.}

Write a program or function that takes the first byte of a UTF-8 byte sequence as input and outputs or returns the length of the sequence. I/O is flexible. For example, the input can be a number, an 8-bit character or a one-character string. You can assume that the first byte is part of valid sequence and falls into one of the ranges above.

This is code golf. The shortest answer in bytes wins.

Test cases

0x00 => 1
0x41 => 1
0x7F => 1
0xC2 => 2
0xDF => 2
0xE0 => 3
0xEF => 3
0xF0 => 4
0xF4 => 4

code-golf integer

code-golf integer

share|improve this question

asked 3 hours ago

nwellnhof

3,978715

share|improve this question

asked 3 hours ago

nwellnhof

3,978715

share|improve this question

share|improve this question

asked 3 hours ago

nwellnhof

3,978715

asked 3 hours ago

nwellnhof

3,978715

asked 3 hours ago

nwellnhof

3,978715

3,978715

add a comment | 

add a comment | 

6 Answers
6

active

oldest

votes

up vote
2
down vote

Jelly, 8 7 bytes

»Ø⁷BaS

Try it online!

share|improve this answer

edited 58 mins ago

answered 1 hour ago

Dennis♦

182k32292725

add a comment | 

up vote
1
down vote

C (gcc), 39 bytes

t(char x)x=(__builtin_clz(~x)-24)%7u;

Try it online!

share|improve this answer

answered 2 hours ago

user202729

13k12549

add a comment | 

up vote
1
down vote

JavaScript (Node.js), 24 bytes

x=>7^Math.log2(255^x)||1

Try it online!

share|improve this answer

answered 2 hours ago

user202729

13k12549

add a comment | 

up vote
1
down vote

Forth, 6 bytes

x-size

see https://forth-standard.org/standard/xchar/X-SIZE

Input and output follows a standard Forth model:

Input

Memory address + length (i.e. 1) of a single-byte UTF-8 "string".

Output

UTF-8 sequence length in bytes.

share|improve this answer

edited 27 secs ago

answered 22 mins ago

zeppelin

7,08431338

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I count 5 bytes there.
  – Erik the Outgolfer
  12 mins ago
  

  
  
  
  

add a comment | 

up vote
0
down vote

Z80Golf, 19 bytes

00000000: eeff 6f3e 1037 ed6a 3d30 fbee 07b7 2002 ..o>.7.j=0.... .
00000010: 3e01 c9 >..

Port of user202729's JavaScript answer.

Example with input 0x41-Try it online!

Example with input 0xC2-Try it online!

Example with input 0xE0-Try it online!

Example with input 0xF4-Try it online!

Assembly:

;input: register a
;output: register a
byte_count:			;calculate 7^(log2(255^a))||1
	xor 0xFF
	ld l,a
	log2:
		ld	a,16
		scf
	log2loop:
		adc	hl,hl
		dec	a
		jr	nc,log2loop
	xor 7
	or a
	jr nz, return
	ld a,1
	return:
	ret

share|improve this answer

answered 1 hour ago

Logern

30115

add a comment | 

up vote
0
down vote

Haskell, 28 bytes

f x=sum[1|y<-"Áßï",x>y]+1

Try it online!

share|improve this answer

edited 1 hour ago

answered 2 hours ago

BMO

9,97921774

add a comment | 

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6 Answers
6

active

oldest

votes

6 Answers
6

active

oldest

votes

active

oldest

votes

active

oldest

votes

up vote
2
down vote

Jelly, 8 7 bytes

»Ø⁷BaS

Try it online!

share|improve this answer

edited 58 mins ago

answered 1 hour ago

Dennis♦

182k32292725

add a comment | 

up vote
2
down vote

Jelly, 8 7 bytes

»Ø⁷BaS

Try it online!

share|improve this answer

edited 58 mins ago

answered 1 hour ago

Dennis♦

182k32292725

add a comment | 

up vote
2
down vote

up vote
2
down vote

Jelly, 8 7 bytes

»Ø⁷BaS

Try it online!

share|improve this answer

edited 58 mins ago

answered 1 hour ago

Dennis♦

182k32292725

Jelly, 8 7 bytes

»Ø⁷BaS

Try it online!

share|improve this answer

edited 58 mins ago

answered 1 hour ago

Dennis♦

182k32292725

share|improve this answer

share|improve this answer

edited 58 mins ago

edited 58 mins ago

edited 58 mins ago

answered 1 hour ago

Dennis♦

182k32292725

answered 1 hour ago

Dennis♦

182k32292725

answered 1 hour ago

Dennis♦

182k32292725

182k32292725

add a comment | 

add a comment | 

up vote
1
down vote

C (gcc), 39 bytes

t(char x)x=(__builtin_clz(~x)-24)%7u;

Try it online!

share|improve this answer

answered 2 hours ago

user202729

13k12549

add a comment | 

up vote
1
down vote

C (gcc), 39 bytes

t(char x)x=(__builtin_clz(~x)-24)%7u;

Try it online!

share|improve this answer

answered 2 hours ago

user202729

13k12549

add a comment | 

up vote
1
down vote

up vote
1
down vote

C (gcc), 39 bytes

t(char x)x=(__builtin_clz(~x)-24)%7u;

Try it online!

share|improve this answer

answered 2 hours ago

user202729

13k12549

C (gcc), 39 bytes

t(char x)x=(__builtin_clz(~x)-24)%7u;

Try it online!

share|improve this answer

answered 2 hours ago

user202729

13k12549

share|improve this answer

share|improve this answer

answered 2 hours ago

user202729

13k12549

answered 2 hours ago

user202729

13k12549

answered 2 hours ago

user202729

13k12549

13k12549

add a comment | 

add a comment | 

up vote
1
down vote

JavaScript (Node.js), 24 bytes

x=>7^Math.log2(255^x)||1

Try it online!

share|improve this answer

answered 2 hours ago

user202729

13k12549

add a comment | 

up vote
1
down vote

JavaScript (Node.js), 24 bytes

x=>7^Math.log2(255^x)||1

Try it online!

share|improve this answer

answered 2 hours ago

user202729

13k12549

add a comment | 

up vote
1
down vote

up vote
1
down vote

JavaScript (Node.js), 24 bytes

x=>7^Math.log2(255^x)||1

Try it online!

share|improve this answer

answered 2 hours ago

user202729

13k12549

JavaScript (Node.js), 24 bytes

x=>7^Math.log2(255^x)||1

Try it online!

share|improve this answer

answered 2 hours ago

user202729

13k12549

share|improve this answer

share|improve this answer

answered 2 hours ago

user202729

13k12549

answered 2 hours ago

user202729

13k12549

answered 2 hours ago

user202729

13k12549

13k12549

add a comment | 

add a comment | 

up vote
1
down vote

Forth, 6 bytes

x-size

see https://forth-standard.org/standard/xchar/X-SIZE

Input and output follows a standard Forth model:

Input

Memory address + length (i.e. 1) of a single-byte UTF-8 "string".

Output

UTF-8 sequence length in bytes.

share|improve this answer

edited 27 secs ago

answered 22 mins ago

zeppelin

7,08431338

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I count 5 bytes there.
  – Erik the Outgolfer
  12 mins ago
  

  
  
  
  

add a comment | 

up vote
1
down vote

Forth, 6 bytes

x-size

see https://forth-standard.org/standard/xchar/X-SIZE

Input and output follows a standard Forth model:

Input

Memory address + length (i.e. 1) of a single-byte UTF-8 "string".

Output

UTF-8 sequence length in bytes.

share|improve this answer

edited 27 secs ago

answered 22 mins ago

zeppelin

7,08431338

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I count 5 bytes there.
  – Erik the Outgolfer
  12 mins ago
  

  
  
  
  

add a comment | 

up vote
1
down vote

up vote
1
down vote

Forth, 6 bytes

x-size

see https://forth-standard.org/standard/xchar/X-SIZE

Input and output follows a standard Forth model:

Input

Memory address + length (i.e. 1) of a single-byte UTF-8 "string".

Output

UTF-8 sequence length in bytes.

share|improve this answer

edited 27 secs ago

answered 22 mins ago

zeppelin

7,08431338

Forth, 6 bytes

x-size

see https://forth-standard.org/standard/xchar/X-SIZE

Input and output follows a standard Forth model:

Input

Memory address + length (i.e. 1) of a single-byte UTF-8 "string".

Output

UTF-8 sequence length in bytes.

share|improve this answer

edited 27 secs ago

answered 22 mins ago

zeppelin

7,08431338

share|improve this answer

share|improve this answer

edited 27 secs ago

edited 27 secs ago

edited 27 secs ago

answered 22 mins ago

zeppelin

7,08431338

answered 22 mins ago

zeppelin

7,08431338

answered 22 mins ago

zeppelin

7,08431338

7,08431338

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I count 5 bytes there.
  – Erik the Outgolfer
  12 mins ago
  

  
  
  
  

add a comment | 

• 
  
  
  

  
  

  
  
  
  
  
  

  
  I count 5 bytes there.
  – Erik the Outgolfer
  12 mins ago
  

  
  
  
  

I count 5 bytes there.
– Erik the Outgolfer
12 mins ago

I count 5 bytes there.
– Erik the Outgolfer
12 mins ago

add a comment | 

up vote
0
down vote

Z80Golf, 19 bytes

00000000: eeff 6f3e 1037 ed6a 3d30 fbee 07b7 2002 ..o>.7.j=0.... .
00000010: 3e01 c9 >..

Port of user202729's JavaScript answer.

Example with input 0x41-Try it online!

Example with input 0xC2-Try it online!

Example with input 0xE0-Try it online!

Example with input 0xF4-Try it online!

Assembly:

;input: register a
;output: register a
byte_count:			;calculate 7^(log2(255^a))||1
	xor 0xFF
	ld l,a
	log2:
		ld	a,16
		scf
	log2loop:
		adc	hl,hl
		dec	a
		jr	nc,log2loop
	xor 7
	or a
	jr nz, return
	ld a,1
	return:
	ret

share|improve this answer

answered 1 hour ago

Logern

30115

add a comment | 

up vote
0
down vote

Z80Golf, 19 bytes

00000000: eeff 6f3e 1037 ed6a 3d30 fbee 07b7 2002 ..o>.7.j=0.... .
00000010: 3e01 c9 >..

Port of user202729's JavaScript answer.

Example with input 0x41-Try it online!

Example with input 0xC2-Try it online!

Example with input 0xE0-Try it online!

Example with input 0xF4-Try it online!

Assembly:

;input: register a
;output: register a
byte_count:			;calculate 7^(log2(255^a))||1
	xor 0xFF
	ld l,a
	log2:
		ld	a,16
		scf
	log2loop:
		adc	hl,hl
		dec	a
		jr	nc,log2loop
	xor 7
	or a
	jr nz, return
	ld a,1
	return:
	ret

share|improve this answer

answered 1 hour ago

Logern

30115

add a comment | 

up vote
0
down vote

up vote
0
down vote

Z80Golf, 19 bytes

00000000: eeff 6f3e 1037 ed6a 3d30 fbee 07b7 2002 ..o>.7.j=0.... .
00000010: 3e01 c9 >..

Port of user202729's JavaScript answer.

Example with input 0x41-Try it online!

Example with input 0xC2-Try it online!

Example with input 0xE0-Try it online!

Example with input 0xF4-Try it online!

Assembly:

;input: register a
;output: register a
byte_count:			;calculate 7^(log2(255^a))||1
	xor 0xFF
	ld l,a
	log2:
		ld	a,16
		scf
	log2loop:
		adc	hl,hl
		dec	a
		jr	nc,log2loop
	xor 7
	or a
	jr nz, return
	ld a,1
	return:
	ret

share|improve this answer

answered 1 hour ago

Logern

30115

Z80Golf, 19 bytes

00000000: eeff 6f3e 1037 ed6a 3d30 fbee 07b7 2002 ..o>.7.j=0.... .
00000010: 3e01 c9 >..

Port of user202729's JavaScript answer.

Example with input 0x41-Try it online!

Example with input 0xC2-Try it online!

Example with input 0xE0-Try it online!

Example with input 0xF4-Try it online!

Assembly:

;input: register a
;output: register a
byte_count:			;calculate 7^(log2(255^a))||1
	xor 0xFF
	ld l,a
	log2:
		ld	a,16
		scf
	log2loop:
		adc	hl,hl
		dec	a
		jr	nc,log2loop
	xor 7
	or a
	jr nz, return
	ld a,1
	return:
	ret

share|improve this answer

answered 1 hour ago

Logern

30115

share|improve this answer

share|improve this answer

answered 1 hour ago

Logern

30115

answered 1 hour ago

Logern

30115

answered 1 hour ago

Logern

30115

30115

add a comment | 

add a comment | 

up vote
0
down vote

Haskell, 28 bytes

f x=sum[1|y<-"Áßï",x>y]+1

Try it online!

share|improve this answer

edited 1 hour ago

answered 2 hours ago

BMO

9,97921774

add a comment | 

up vote
0
down vote

Haskell, 28 bytes

f x=sum[1|y<-"Áßï",x>y]+1

Try it online!

share|improve this answer

edited 1 hour ago

answered 2 hours ago

BMO

9,97921774

add a comment | 

up vote
0
down vote

up vote
0
down vote

Haskell, 28 bytes

f x=sum[1|y<-"Áßï",x>y]+1

Try it online!

share|improve this answer

edited 1 hour ago

answered 2 hours ago

BMO

9,97921774

Haskell, 28 bytes

f x=sum[1|y<-"Áßï",x>y]+1

Try it online!

share|improve this answer

edited 1 hour ago

answered 2 hours ago

BMO

9,97921774

share|improve this answer

share|improve this answer

edited 1 hour ago

edited 1 hour ago

edited 1 hour ago

answered 2 hours ago

BMO

9,97921774

answered 2 hours ago

BMO

9,97921774

answered 2 hours ago

BMO

9,97921774

9,97921774

add a comment | 

add a comment | 

 

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