Bytes

The following document shows functions and methods used to manipulate and process Chapel bytes variables. bytes is similar to a string but allows arbitrary data to be stored in it. Methods on bytes that interpret the data as characters assume that the bytes are ASCII characters.

Creating bytes

  • A bytes can be created using the literals similar to strings:

var b = b"my bytes";
  • If you need to create bytes using a specific buffer (i.e. data in another bytes, a c_string or a C pointer) you can use the factory functions shown below, such as createBytesWithNewBuffer.

bytes and string

As bytes can store arbitrary data, any string can be cast to bytes. In that event, the bytes will store UTF-8 encoded character data. However, a bytes can contain non-UTF-8 bytes and needs to be decoded to be converted to string.

var s = "my string";
var b = s:bytes;  // this is legal

/*
 The reverse is not. The following is a compiler error:

 var s2 = b:string;
*/

var s2 = b.decode(); // you need to decode a bytes to convert it to a string

See the documentation for the decode method for details.

Similarly, a bytes can be initialized using a string:

var s = "my string";
var b: bytes = s;

Casts from bytes to a Numeric Type

This module supports casts from bytes to numeric types. Such casts will interpret the bytes as ASCII characters and convert it to the numeric type and throw an error if the bytes does not match the expected format of a number. For example:

var b = b"a";
var number = b:int;

throws an error when it is executed, but

var b = b"1";
var number = b:int;

stores the value 1 in number.

To learn more about handling these errors, see the Error Handling technical note.

proc createBytesWithBorrowedBuffer(x: bytes): bytes

Creates a new bytes which borrows the internal buffer of another bytes. If the buffer is freed before the bytes returned from this function, accessing it is undefined behavior.

Arguments

s – The bytes to borrow the buffer from

Returns

A new bytes

proc createBytesWithBorrowedBuffer(x: c_string, length = x.size): bytes

Creates a new bytes which borrows the internal buffer of a c_string. If the buffer is freed before the bytes returned from this function, accessing it is undefined behavior.

Arguments
  • sc_string to borrow the buffer from

  • length : int – Length of s’s buffer, excluding the terminating null byte.

Returns

A new bytes

proc createBytesWithBorrowedBuffer(x: c_ptr(?t), length: int, size: int): bytes

Creates a new bytes which borrows the memory allocated for a c_ptr. If the buffer is freed before the bytes returned from this function, accessing it is undefined behavior.

Arguments
  • s – Buffer to borrow

  • length – Length of the buffer s, excluding the terminating null byte.

  • size – Size of memory allocated for s in bytes

Returns

A new bytes

proc createBytesWithOwnedBuffer(x: c_string, length = x.size): bytes

Creates a new bytes which takes ownership of the internal buffer of a c_string.The buffer will be freed when the bytes is deinitialized.

Arguments
  • s – The c_string to take ownership of the buffer from

  • length : int – Length of s’s buffer, excluding the terminating null byte.

Returns

A new bytes

proc createBytesWithOwnedBuffer(x: c_ptr(?t), length: int, size: int): bytes

Creates a new bytes which takes ownership of the memory allocated for a c_ptr. The buffer will be freed when the bytes is deinitialized.

Arguments
  • s – The buffer to take ownership of

  • length – Length of the buffer s, excluding the terminating null byte.

  • size – Size of memory allocated for s in bytes

Returns

A new bytes

proc createBytesWithNewBuffer(x: bytes): bytes

Creates a new bytes by creating a copy of the buffer of another bytes.

Arguments

s – The bytes to copy the buffer from

Returns

A new bytes

proc createBytesWithNewBuffer(x: c_string, length = x.size): bytes

Creates a new bytes by creating a copy of the buffer of a c_string.

Arguments
  • s – The c_string to copy the buffer from

  • length : int – Length of s’s buffer, excluding the terminating null byte.

Returns

A new bytes

proc createBytesWithNewBuffer(x: c_ptr(?t), length: int, size = length + 1): bytes

Creates a new bytes by creating a copy of a buffer.

Arguments
  • s – The buffer to copy

  • length – Length of buffer s, excluding the terminating null byte.

  • size – Size of memory allocated for s in bytes

Returns

A new bytes

proc bytes.size: int
Returns

The number of bytes in the bytes.

proc bytes.indices: range
Returns

The indices that can be used to index into the bytes (i.e., the range 0..<this.size)

proc bytes.numBytes: int
Returns

The number of bytes in the bytes.

proc bytes.localize(): bytes

Gets a version of the bytes that is on the currently executing locale.

Returns

A shallow copy if the bytes is already on the current locale, otherwise a deep copy is performed.

proc bytes.c_str(): c_string

Gets a c_string from a bytes. The returned c_string shares the buffer with the bytes.

Warning

This can only be called safely on a bytes whose home is the current locale. This property can be enforced by calling bytes.localize() before c_str(). If the bytes is remote, the program will halt.

For example:

var myBytes = b"Hello!";
on different_locale {
  printf("%s", myBytes.localize().c_str());
}
Returns

A c_string that points to the underlying buffer used by this bytes. The returned c_string is only valid when used on the same locale as the bytes.

proc bytes.item(i: int): bytes

Gets an ASCII character from the bytes

Arguments

i – The index

Returns

A 1-length bytes

proc bytes.this(i: int): uint(8)

Gets a byte from the bytes

Arguments

i – The index

Returns

uint(8)

proc bytes.toByte(): uint(8)
Returns

The value of a single-byte bytes as an integer.

proc bytes.byte(i: int): uint(8)

Gets a byte from the bytes

Arguments

i – The index

Returns

The value of the i th byte as an integer.

iter bytes.items(): bytes

Iterates over the bytes, yielding ASCII characters.

Yields

1-length bytes

iter bytes.these(): uint(8)

Iterates over the bytes

Yields

uint(8)

iter bytes.bytes(): uint(8)

Iterates over the bytes byte by byte.

Yields

uint(8)

proc bytes.this(r: range(?)): bytes

Slices the bytes. Halts if r is non-empty and not completely inside the range this.indices when compiled with –checks. –fast disables this check.

Arguments

r – The range of indices the new bytes should be made from

Returns

a new bytes that is a slice within this.indices. If the length of r is zero, an empty bytes is returned.

proc bytes.isEmpty(): bool

Checks if the bytes is empty.

Returns

  • true – when empty

  • false – otherwise

proc bytes.startsWith(patterns: bytes ...): bool

Checks if the bytes starts with any of the given arguments.

Arguments

patternsbytes (s) to match against.

Returns

  • true–when the bytes begins with one or more of the patterns

  • false–otherwise

proc bytes.endsWith(patterns: bytes ...): bool

Checks if the bytes ends with any of the given arguments.

Arguments

patternsbytes (s) to match against.

Returns

  • true–when the bytes ends with one or more of the patterns

  • false–otherwise

proc bytes.find(needle: bytes, region: range(?) = this.indices): idxType

Warning

the ‘needle’ and ‘region’ arguments are deprecated, use ‘pattern’ and ‘indices’ instead

proc bytes.find(pattern: bytes, indices: range(?) = this.indices): idxType

Finds the argument in the bytes

Arguments
  • patternbytes to search for

  • indices – an optional range defining the indices to search within, default is the whole. Halts if the range is not within this.indices

Returns

the index of the first occurrence from the left of pattern within the bytes, or -1 if the pattern is not in the bytes.

proc bytes.rfind(needle: bytes, region: range(?) = this.indices): idxType

Warning

the ‘needle’ and ‘region’ arguments are deprecated, use ‘pattern’ and ‘indices’ instead

proc bytes.rfind(pattern: bytes, indices: range(?) = this.indices): idxType

Finds the argument in the bytes

Arguments
  • pattern – The bytes to search for

  • indices – an optional range defining the indices to search within, default is the whole. Halts if the range is not within this.indices

Returns

the index of the first occurrence from the right of pattern within the bytes, or -1 if the pattern is not in the bytes.

proc bytes.count(needle: bytes, region: range(?) = this.indices): int

Warning

the ‘needle’ and ‘region’ arguments are deprecated, use ‘pattern’ and ‘indices’ instead

proc bytes.count(pattern: bytes, indices: range(?) = this.indices): int

Counts the number of occurrences of the argument in the bytes

Arguments
  • pattern – The bytes to search for

  • indices – an optional range defining the substring to search within, default is the whole. Halts if the range is not within this.indices

Returns

the number of times pattern occurs in the bytes

proc bytes.replace(needle: bytes, replacement: bytes, count: int = -1): bytes

Warning

the ‘needle’ argument is deprecated, use ‘pattern’ instead

proc bytes.replace(pattern: bytes, replacement: bytes, count: int = -1): bytes

Replaces occurrences of a bytes with another.

Arguments
  • pattern – The bytes to search for

  • replacement – The bytes to replace pattern with

  • count – an optional argument specifying the number of replacements to make, values less than zero will replace all occurrences

Returns

a copy of the bytes where replacement replaces pattern up to count times

iter bytes.split(sep: bytes, maxsplit: int = -1, ignoreEmpty: bool = false): bytes

Splits the bytes on sep yielding the bytes between each occurrence, up to maxsplit times.

Arguments
  • sep – The delimiter used to break the bytes into chunks.

  • maxsplit – The number of times to split the bytes, negative values indicate no limit.

  • ignoreEmpty

    • true– Empty bytes will not be yielded,

    • false– Empty bytes will be yielded

Yields

bytes

iter bytes.split(maxsplit: int = -1): bytes

Works as above, but uses runs of whitespace as the delimiter.

Arguments

maxsplit – The maximum number of times to split the bytes, negative values indicate no limit.

Yields

bytes

proc bytes.join(const ref x: bytes ...): bytes

Returns a new bytes, which is the concatenation of all of the bytes passed in with the contents of the method receiver inserted between them.

var myBytes = b"|".join(b"a",b"10",b"d");
writeln(myBytes); // prints: "a|10|d"
Arguments

xbytes values to be joined

Returns

A bytes

proc bytes.join(const ref x): bytes

Returns a new bytes, which is the concatenation of all of the bytes passed in with the contents of the method receiver inserted between them.

var tup = (b"a",b"10",b"d");
var myJoinedTuple = b"|".join(tup);
writeln(myJoinedTuple); // prints: "a|10|d"

var myJoinedArray = b"|".join([b"a",b"10",b"d"]);
writeln(myJoinedArray); // prints: "a|10|d"
Arguments

x – An array or tuple of bytes values to be joined

Returns

A bytes

proc bytes.strip(chars = b" \t\r\n", leading = true, trailing = true): bytes

Strips given set of leading and/or trailing characters.

Arguments
  • chars – Characters to remove. Defaults to b” \t\r\n”.

  • leading – Indicates if leading occurrences should be removed. Defaults to true.

  • trailing – Indicates if trailing occurrences should be removed. Defaults to true.

Returns

A new bytes with leading and/or trailing occurrences of characters in chars removed as appropriate.

proc bytes.partition(sep: bytes): 3*(bytes)

Splits the bytes on a given separator

Arguments

sep – The separator

Returns

a 3*bytes consisting of the section before sep, sep, and the section after sep. If sep is not found, the tuple will contain the whole bytes, and then two empty bytes.

proc bytes.dedent(columns = 0, ignoreFirst = true): bytes

Remove indentation from each line of bytes.

This can be useful when applied to multi-line bytes that are indented in the source code, but should not be indented in the output.

When columns == 0, determine the level of indentation to remove from all lines by finding the common leading whitespace across all non-empty lines. Empty lines are lines containing only whitespace. Tabs and spaces are the only whitespaces that are considered, but are not treated as the same characters when determining common whitespace.

When columns > 0, remove columns leading whitespace characters from each line. Tabs are not considered whitespace when columns > 0, so only leading spaces are removed.

Arguments
  • columns – The number of columns of indentation to remove. Infer common leading whitespace if columns == 0.

  • ignoreFirst – When true, ignore first line when determining the common leading whitespace, and make no changes to the first line.

Returns

A new bytes with indentation removed.

Warning

bytes.dedent is not considered stable and is subject to change in future Chapel releases.

proc bytes.decode(policy = decodePolicy.strict): string throws

Returns a UTF-8 string from the given bytes. If the data is malformed for UTF-8, policy argument determines the action.

Arguments

policy

  • decodePolicy.strict raises an error

  • decodePolicy.replace replaces the malformed character with UTF-8 replacement character

  • decodePolicy.drop drops the data silently

  • decodePolicy.escape escapes each illegal byte with private use codepoints

Throws

DecodeError if decodePolicy.strict is passed to the policy argument and the bytes contains non-UTF-8 characters.

Returns

A UTF-8 string.

proc bytes.isUpper(): bool

Checks if all the characters in the bytes are uppercase (A-Z) in ASCII. Ignores uncased (not a letter) and extended ASCII characters (decimal value larger than 127)

Returns

  • true–there is at least one uppercase and no lowercase characters

  • false–otherwise

proc bytes.isLower(): bool

Checks if all the characters in the bytes are lowercase (a-z) in ASCII. Ignores uncased (not a letter) and extended ASCII characters (decimal value larger than 127)

Returns

  • true–there is at least one lowercase and no uppercase characters

  • false–otherwise

proc bytes.isSpace(): bool

Checks if all the characters in the bytes are whitespace (‘ ‘, ‘\t’, ‘\n’, ‘\v’, ‘\f’, ‘\r’) in ASCII.

Returns

  • true – when all the characters are whitespace.

  • false – otherwise

proc bytes.isAlpha(): bool

Checks if all the characters in the bytes are alphabetic (a-zA-Z) in ASCII.

Returns

  • true – when the characters are alphabetic.

  • false – otherwise

proc bytes.isDigit(): bool

Checks if all the characters in the bytes are digits (0-9) in ASCII.

Returns

  • true – when the characters are digits.

  • false – otherwise

proc bytes.isAlnum(): bool

Checks if all the characters in the bytes are alphanumeric (a-zA-Z0-9) in ASCII.

Returns

  • true – when the characters are alphanumeric.

  • false – otherwise

proc bytes.isPrintable(): bool

Checks if all the characters in the bytes are printable in ASCII.

Returns

  • true – when the characters are printable.

  • false – otherwise

proc bytes.isTitle(): bool

Checks if all uppercase characters are preceded by uncased characters, and if all lowercase characters are preceded by cased characters in ASCII.

Returns

  • true – when the condition described above is met.

  • false – otherwise

proc bytes.toLower(): bytes

Creates a new bytes with all applicable characters converted to lowercase.

Returns

A new bytes with all uppercase characters (A-Z) replaced with their lowercase counterpart in ASCII. Other characters remain untouched.

proc bytes.toUpper(): bytes

Creates a new bytes with all applicable characters converted to uppercase.

Returns

A new bytes with all lowercase characters (a-z) replaced with their uppercase counterpart in ASCII. Other characters remain untouched.

proc bytes.toTitle(): bytes

Creates a new bytes with all applicable characters converted to title capitalization.

Returns

A new bytes with all cased characters(a-zA-Z) following an uncased character converted to uppercase, and all cased characters following another cased character converted to lowercase.

proc type bytes.+=(ref lhs: bytes, const ref rhs: bytes): void

Appends the bytes rhs to the bytes lhs.

proc type bytes.=(ref lhs: bytes, rhs: bytes): void

Copies the bytes rhs into the bytes lhs.

proc type bytes.=(ref lhs: bytes, rhs_c: c_string): void

Copies the c_string rhs_c into the bytes lhs.

Halts if lhs is a remote bytes.

proc type bytes.+(s0: bytes, s1: bytes): bytes
Returns

A new bytes which is the result of concatenating s0 and s1

proc *(s: bytes, n: integral): bytes
Returns

A new bytes which is the result of repeating s n times. If n is less than or equal to 0, an empty bytes is returned.

The operation is commutative. For example:

writeln(b"Hello! "*3);
or
writeln(3*b"Hello! ");

Results in:

Hello! Hello! Hello!