class Array[A] is Seq[A]
"""
Contiguous, resizable memory to store elements of type A.
## Usage
Creating an Array of String:
```pony
let array: Array[String] = ["dog"; "cat"; "wombat"]
// array.size() == 3
// array.space() >= 3
```
Creating an empty Array of String, which may hold at least 10 elements before
requesting more space:
```pony
let array = Array[String](10)
// array.size() == 0
// array.space() >= 10
```
Accessing elements can be done via the `apply(i: USize): this->A ?` method.
The provided index might be out of bounds so `apply` is partial and has to be
called within a try-catch block or inside another partial method:
```pony
let array: Array[String] = ["dog"; "cat"; "wombat"]
let is_second_element_wobat = try
// indexes start from 0, so 1 is the second element
array(1)? == "wombat"
else
false
end
```
Adding and removing elements to and from the end of the Array can be done via
`push` and `pop` methods. You could treat the array as a LIFO stack using
those methods:
```pony
while (array.size() > 0) do
let elem = array.pop()?
// do something with element
end
```
Modifying the Array can be done via `update`, `insert` and `delete` methods
which alter the Array at an arbitrary index, moving elements left (when
deleting) or right (when inserting) as necessary.
Iterating over the elements of an Array can be done using the `values` method:
```pony
for element in array.values() do
// do something with element
end
```
## Memory allocation
Array allocates contiguous memory. It always allocates at least enough memory
space to hold all of its elements. Space is the number of elements the Array
can hold without allocating more memory. The `space()` method returns the
number of elements an Array can hold. The `size()` method returns the number
of elements the Array holds.
Different data types require different amounts of memory. Array[U64] with size
of 6 will take more memory than an Array[U8] of the same size.
When creating an Array or adding more elements, the space allocated is the
next power of 2 of the requested number of elements, with a lower bound: the
larger of 8 elements and the number of elements that fill the runtime
allocator's minimum block (32 bytes). For small element types the block bound
dominates — an `Array[U8]` always has space for at least 32 elements and an
`Array[U16]` at least 16 — while for elements of 4 bytes or more the 8-element
bound applies.
Here's a few examples of the space allocated for an `Array[U8]` with various
numbers of elements:
| size | space |
|------|-------|
| 0 | 0 |
| 1 | 32 |
| 32 | 32 |
| 33 | 64 |
| 64 | 64 |
| 65 | 128 |
Call the `compact()` method to ask the GC to reclaim unused space. There are
no guarantees that the GC will actually reclaim any space.
"""
var _size: USize
var _alloc: USize
var _ptr: Pointer[A]
new create(len: USize = 0) =>
"""
Create an array with zero elements, but space for len elements.
"""
_size = 0
if len > 0 then
_alloc = len.next_pow2().max(len).max(8).max(Pointer[A]._min_alloc())
_ptr = Pointer[A]._alloc(_alloc)
else
_alloc = 0
_ptr = Pointer[A]
end
new init(from: A^, len: USize) =>
"""
Create an array of len elements, all initialised to the given value.
"""
_size = len
if len > 0 then
_alloc = len.next_pow2().max(len).max(8).max(Pointer[A]._min_alloc())
_ptr = Pointer[A]._alloc(_alloc)
var i: USize = 0
while i < len do
_ptr._update(i, from)
i = i + 1
end
else
_alloc = 0
_ptr = Pointer[A]
end
new from_cpointer(ptr: Pointer[A], len: USize, alloc: USize = 0) =>
"""
Create an array from a C-style pointer and length. The contents are not
copied. This must be done only with C-FFI functions that return
pony_alloc'd memory. If a null pointer is given then an empty array
is returned.
"""
if ptr.is_null() then
_size = 0
_alloc = 0
else
_size = len
if alloc > len then
_alloc = alloc
else
_alloc = len
end
end
_ptr = ptr
fun _copy_to(
ptr: Pointer[this->A!],
copy_len: USize,
from_offset: USize = 0,
to_offset: USize = 0)
=>
"""
Copy copy_len elements from this to that at specified offsets.
"""
_ptr._offset(from_offset)._copy_to(ptr._offset(to_offset), copy_len)
fun cpointer(offset: USize = 0): Pointer[A] tag =>
"""
Return the underlying C-style pointer.
"""
_ptr._offset(offset)
fun size(): USize =>
"""
The number of elements in the array.
"""
_size
fun space(): USize =>
"""
The available space in the array.
"""
_alloc
fun ref reserve(len: USize) =>
"""
Reserve space for len elements, including whatever elements are already in
the array. Array space grows geometrically. The space reserved is never
smaller than the runtime allocator's minimum block, so for small element
types it may exceed len.
"""
if _alloc < len then
_alloc = len.next_pow2().max(len).max(8).max(_ptr._min_alloc())
_ptr = _ptr._realloc(_alloc, _size)
end
fun _element_size(): USize =>
"""
Element size in bytes for an element.
"""
_ptr._element_size()
fun ref compact() =>
"""
Try to remove unused space, making it available for garbage collection. The
request may be ignored.
"""
if _size <= (512 / _ptr._element_size()) then
let target = _size.next_pow2().max(_ptr._min_alloc())
if target < _alloc then
_alloc = target
let old_ptr = _ptr = Pointer[A]._alloc(_alloc)
old_ptr._copy_to(_ptr._convert[A!](), _size)
end
elseif _size < _alloc then
_alloc = _size
let old_ptr = _ptr = Pointer[A]._alloc(_alloc)
old_ptr._copy_to(_ptr._convert[A!](), _size)
end
fun ref undefined[B: (A & Real[B] val & Number) = A](len: USize) =>
"""
Resize to len elements, populating previously empty elements with random
memory. This is only allowed for an array of numbers.
"""
reserve(len)
_size = len
fun read_u8[B: (A & Real[B] val & U8) = A](offset: USize): U8 ? =>
"""
Reads a U8 from offset. This is only allowed for an array of U8s.
"""
if offset < _size then
_ptr._offset(offset)._convert[U8]()._apply(0)
else
error
end
fun read_u16[B: (A & Real[B] val & U8) = A](offset: USize): U16 ? =>
"""
Reads a U16 from offset. This is only allowed for an array of U8s.
"""
let u16_bytes = U16(0).bytewidth()
if (offset + u16_bytes) <= _size then
_ptr._offset(offset)._convert[U16]()._apply(0)
else
error
end
fun read_u32[B: (A & Real[B] val & U8) = A](offset: USize): U32 ? =>
"""
Reads a U32 from offset. This is only allowed for an array of U8s.
"""
let u32_bytes = U32(0).bytewidth()
if (offset + u32_bytes) <= _size then
_ptr._offset(offset)._convert[U32]()._apply(0)
else
error
end
fun read_u64[B: (A & Real[B] val & U8) = A](offset: USize): U64 ? =>
"""
Reads a U64 from offset. This is only allowed for an array of U8s.
"""
let u64_bytes = U64(0).bytewidth()
if (offset + u64_bytes) <= _size then
_ptr._offset(offset)._convert[U64]()._apply(0)
else
error
end
fun read_u128[B: (A & Real[B] val & U8) = A](offset: USize): U128 ? =>
"""
Reads a U128 from offset. This is only allowed for an array of U8s.
"""
let u128_bytes = U128(0).bytewidth()
if (offset + u128_bytes) <= _size then
_ptr._offset(offset)._convert[U128]()._apply(0)
else
error
end
fun apply(i: USize): this->A ? =>
"""
Get the i-th element, raising an error if the index is out of bounds.
"""
if i < _size then
_ptr._apply(i)
else
error
end
fun ref update_u8[B: (A & Real[B] val & U8) = A](offset: USize, value: U8): U8 ? =>
"""
Write a U8 at offset. This is only allowed for an array of U8s.
"""
if offset < _size then
_ptr._offset(offset)._convert[U8]()._update(0, value)
else
error
end
fun ref update_u16[B: (A & Real[B] val & U8) = A](offset: USize, value: U16): U16 ? =>
"""
Write a U16 at offset. This is only allowed for an array of U8s.
"""
let u16_bytes = U16(0).bytewidth()
if (offset + u16_bytes) <= _size then
_ptr._offset(offset)._convert[U16]()._update(0, value)
else
error
end
fun ref update_u32[B: (A & Real[B] val & U8) = A](offset: USize, value: U32): U32 ? =>
"""
Write a U32 at offset. This is only allowed for an array of U8s.
"""
let u32_bytes = U32(0).bytewidth()
if (offset + u32_bytes) <= _size then
_ptr._offset(offset)._convert[U32]()._update(0, value)
else
error
end
fun ref update_u64[B: (A & Real[B] val & U8) = A](offset: USize, value: U64): U64 ? =>
"""
Write a U64 at offset. This is only allowed for an array of U8s.
"""
let u64_bytes = U64(0).bytewidth()
if (offset + u64_bytes) <= _size then
_ptr._offset(offset)._convert[U64]()._update(0, value)
else
error
end
fun ref update_u128[B: (A & Real[B] val & U8) = A](offset: USize, value: U128): U128 ? =>
"""
Write a U128 at offset. This is only allowed for an array of U8s.
"""
let u128_bytes = U128(0).bytewidth()
if (offset + u128_bytes) <= _size then
_ptr._offset(offset)._convert[U128]()._update(0, value)
else
error
end
fun ref update(i: USize, value: A): A^ ? =>
"""
Change the i-th element, raising an error if the index is out of bounds.
"""
if i < _size then
_ptr._update(i, consume value)
else
error
end
fun ref insert(i: USize, value: A) ? =>
"""
Insert an element into the array. Elements after this are moved up by one
index, extending the array.
When inserting right beyond the last element, at index `this.size()`,
the element will be appended, similar to `push()`,
an insert at index `0` prepends the value to the array.
An insert into an index beyond `this.size()` raises an error.
```pony
let array = Array[U8](4) // []
array.insert(0, 0xDE)? // prepend: [0xDE]
array.insert(array.size(), 0xBE)? // append: [0xDE; 0xBE]
array.insert(1, 0xAD)? // insert: [0xDE; 0xAD; 0xBE]
array.insert(array.size() + 1, 0xEF)? // error
```
"""
if i <= _size then
reserve(_size + 1)
_ptr._offset(i)._insert(1, _size - i)
_ptr._update(i, consume value)
_size = _size + 1
else
error
end
fun ref delete(i: USize): A^ ? =>
"""
Delete an element from the array. Elements after this are moved down by one
index, compacting the array.
An out of bounds index raises an error.
The deleted element is returned.
"""
if i < _size then
_size = _size - 1
_ptr._offset(i)._delete(1, _size - i)
else
error
end
fun ref truncate(len: USize) =>
"""
Truncate an array to the given length, discarding excess elements. If the
array is already smaller than len, do nothing.
"""
_size = _size.min(len)
fun ref trim_in_place(from: USize = 0, to: USize = -1) =>
"""
Trim the array to a portion of itself, covering `from` until `to`.
Unlike slice, the operation does not allocate a new array nor copy elements.
"""
let last = _size.min(to)
let offset = last.min(from)
let size' = last - offset
// use the new size' for alloc if we're not including the last used byte
// from the original data and only include the extra allocated bytes if
// we're including the last byte.
_alloc = if last == _size then _alloc - offset else size' end
_size = size'
// if _alloc == 0 then we've trimmed all the memory originally allocated.
// if we do _ptr._offset, we will spill into memory not allocated/owned
// by this array and could potentially cause a segfault if we cross
// a pagemap boundary into a pagemap address that hasn't been allocated
// yet when `reserve` is called next.
if _alloc == 0 then
_ptr = Pointer[A]
else
_ptr = _ptr._offset(offset)
end
fun val trim(from: USize = 0, to: USize = -1): Array[A] val =>
"""
Return a shared portion of this array, covering `from` until `to`.
Both the original and the new array are immutable, as they share memory.
The operation does not allocate a new array pointer nor copy elements.
"""
let last = _size.min(to)
let offset = last.min(from)
recover
let size' = last - offset
// use the new size' for alloc if we're not including the last used byte
// from the original data and only include the extra allocated bytes if
// we're including the last byte.
let alloc = if last == _size then _alloc - offset else size' end
if size' > 0 then
from_cpointer(_ptr._offset(offset)._unsafe(), size', alloc)
else
create()
end
end
fun iso chop[B: (A & Any #send) = A](split_point: USize): (Array[A] iso^, Array[A] iso^) =>
"""
Chops the array in half at the split point requested and returns both
the left and right portions. The original array is trimmed in place and
returned as the left portion. If the split point is larger than the
array, the left portion is the original array and the right portion
is a new empty array.
The operation does not allocate a new array pointer nor copy elements.
The entry type must be sendable so that the two halves can be isolated.
Otherwise, two entries may have shared references to mutable data,
or even to each other, such as in the code below:
```pony
class Example
var other: (Example | None) = None
let arr: Array[Example] iso = recover
let obj1 = Example
let obj2 = Example
obj1.other = obj2
obj2.other = obj1
[obj1; obj2]
end
```
"""
let start_ptr = cpointer(split_point)
let size' = _size - _size.min(split_point)
let alloc = _alloc - _size.min(split_point)
trim_in_place(0, split_point)
let right = recover
if size' > 0 then
from_cpointer(start_ptr._unsafe(), size', alloc)
else
create()
end
end
(consume this, consume right)
fun iso unchop(b: Array[A] iso):
((Array[A] iso^, Array[A] iso^) | Array[A] iso^)
=>
"""
Unchops two iso arrays to return the original array they were chopped from.
Both input arrays are isolated and mutable and were originally chopped from
a single array. This function checks that they are indeed two arrays chopped
from the same original array and can be unchopped before doing the
unchopping and returning the unchopped array. If the two arrays cannot be
unchopped it returns both arrays without modifying them.
The operation does not allocate a new array pointer nor copy elements.
"""
if _size == 0 then
return consume b
end
if b.size() == 0 then
return consume this
end
(let unchoppable, let a_left) =
if (_size == _alloc) and (cpointer(_size) == b.cpointer()) then
(true, true)
elseif (b.size() == b.space()) and (b.cpointer(b.size()) == cpointer())
then
(true, false)
else
(false, false)
end
if not unchoppable then
return (consume this, consume b)
end
if a_left then
_alloc = _alloc + b._alloc
_size = _size + b._size
consume this
else
b._alloc = b._alloc + _alloc
b._size = b._size + _size
consume b
end
fun ref copy_from[B: (A & Real[B] val & U8) = A](
src: Array[U8] box,
src_idx: USize,
dst_idx: USize,
len: USize)
=>
"""
Copy len elements from src(src_idx) to this(dst_idx).
Only works for Array[U8].
"""
reserve(dst_idx + len)
src._ptr._offset(src_idx)._copy_to(_ptr._convert[U8]()._offset(dst_idx), len)
if _size < (dst_idx + len) then
_size = dst_idx + len
end
fun copy_to(
dst: Array[this->A!],
src_idx: USize,
dst_idx: USize,
len: USize)
=>
"""
Copy len elements from this(src_idx) to dst(dst_idx).
"""
if (src_idx < _size) and (dst_idx <= dst._size) then
let count = len.min(_size - src_idx)
if count > 0 then
dst.reserve(dst_idx + count)
_ptr._offset(src_idx)._copy_to(dst._ptr._offset(dst_idx), count)
if dst._size < (dst_idx + count) then
dst._size = dst_idx + count
end
end
end
fun ref remove(i: USize, n: USize) =>
"""
Remove n elements from the array, beginning at index i.
"""
if i < _size then
let count = n.min(_size - i)
_size = _size - count
_ptr._offset(i)._delete(count, _size - i)
end
fun ref clear() =>
"""
Remove all elements from the array.
"""
_size = 0
fun ref push_u8[B: (A & Real[B] val & U8) = A](value: U8) =>
"""
Add a U8 to the end of the array. This is only allowed for an array of U8s.
"""
let u8_bytes = U8(0).bytewidth()
reserve(_size + u8_bytes)
_ptr._offset(_size)._convert[U8]()._update(0, value)
_size = _size + u8_bytes
fun ref push_u16[B: (A & Real[B] val & U8) = A](value: U16) =>
"""
Add a U16 to the end of the array. This is only allowed for an array of U8s.
"""
let u16_bytes = U16(0).bytewidth()
reserve(_size + u16_bytes)
_ptr._offset(_size)._convert[U16]()._update(0, value)
_size = _size + u16_bytes
fun ref push_u32[B: (A & Real[B] val & U8) = A](value: U32) =>
"""
Add a U32 to the end of the array. This is only allowed for an array of U8s.
"""
let u32_bytes = U32(0).bytewidth()
reserve(_size + u32_bytes)
_ptr._offset(_size)._convert[U32]()._update(0, value)
_size = _size + u32_bytes
fun ref push_u64[B: (A & Real[B] val & U8) = A](value: U64) =>
"""
Add a U64 to the end of the array. This is only allowed for an array of U8s.
"""
let u64_bytes = U64(0).bytewidth()
reserve(_size + u64_bytes)
_ptr._offset(_size)._convert[U64]()._update(0, value)
_size = _size + u64_bytes
fun ref push_u128[B: (A & Real[B] val & U8) = A](value: U128) =>
"""
Add a U128 to the end of the array. This is only allowed for an array of U8s.
"""
let u128_bytes = U128(0).bytewidth()
reserve(_size + u128_bytes)
_ptr._offset(_size)._convert[U128]()._update(0, value)
_size = _size + u128_bytes
fun ref push(value: A) =>
"""
Add an element to the end of the array.
"""
reserve(_size + 1)
_ptr._update(_size, consume value)
_size = _size + 1
fun ref pop(): A^ ? =>
"""
Remove an element from the end of the array.
The removed element is returned.
"""
delete(_size - 1)?
fun ref unshift(value: A) =>
"""
Add an element to the beginning of the array.
"""
try
insert(0, consume value)?
end
fun ref shift(): A^ ? =>
"""
Remove an element from the beginning of the array.
The removed element is returned.
"""
delete(0)?
fun ref append(
seq: (ReadSeq[A] & ReadElement[A^]),
offset: USize = 0,
len: USize = -1)
=>
"""
Append the elements from a sequence, starting from the given offset.
"""
if offset >= seq.size() then
return
end
let copy_len = len.min(seq.size() - offset)
reserve(_size + copy_len)
var n = USize(0)
try
while n < copy_len do
_ptr._update(_size + n, seq(offset + n)?)
n = n + 1
end
end
_size = _size + n
fun ref concat(iter: Iterator[A^], offset: USize = 0, len: USize = -1) =>
"""
Add len iterated elements to the end of the array, starting from the given
offset.
"""
var n = USize(0)
try
while n < offset do
if iter.has_next() then
iter.next()?
else
return
end
n = n + 1
end
end
n = 0
// If a concrete len is specified, we take the caller at their word
// and reserve that much space, even though we can't verify that the
// iterator actually has that many elements available. Reserving ahead
// of time lets us take a fast path of direct pointer access.
if len != -1 then
reserve(_size + len)
try
while n < len do
if iter.has_next() then
_ptr._update(_size + n, iter.next()?)
else
break
end
n = n + 1
end
end
_size = _size + n
else
try
while n < len do
if iter.has_next() then
push(iter.next()?)
else
break
end
n = n + 1
end
end
end
fun find(
value: A!,
offset: USize = 0,
nth: USize = 0,
predicate: {(box->A!, box->A!): Bool} val = {(l, r) => l is r })
: USize ?
=>
"""
Find the `nth` appearance of `value` from the beginning of the array,
starting at `offset` and examining higher indices, and using the supplied
`predicate` for comparisons. Returns the index of the value, or raise an
error if the value isn't present.
By default, the search starts at the first element of the array, returns
the first instance of `value` found, and uses object identity for
comparison.
"""
var i = offset
var n = USize(0)
while i < _size do
if predicate(_ptr._apply(i), value) then
if n == nth then
return i
end
n = n + 1
end
i = i + 1
end
error
fun contains(
value: A!,
predicate: {(box->A!, box->A!): Bool} val =
{(l: box->A!, r: box->A!): Bool => l is r })
: Bool
=>
"""
Returns true if the array contains `value`, false otherwise.
The default predicate checks for matches by identity. To search for matches
by structural equality, pass an object literal such as `{(l, r) => l == r}`.
"""
var i = USize(0)
while i < _size do
if predicate(_ptr._apply(i), value) then
return true
end
i = i + 1
end
false
fun rfind(
value: A!,
offset: USize = -1,
nth: USize = 0,
predicate: {(box->A!, box->A!): Bool} val =
{(l: box->A!, r: box->A!): Bool => l is r })
: USize ?
=>
"""
Find the `nth` appearance of `value` from the end of the array, starting at
`offset` and examining lower indices, and using the supplied `predicate` for
comparisons. Returns the index of the value, or raise an error if the value
isn't present.
By default, the search starts at the last element of the array, returns the
first instance of `value` found, and uses object identity for comparison.
"""
if _size > 0 then
var i = if offset >= _size then _size - 1 else offset end
var n = USize(0)
repeat
if predicate(_ptr._apply(i), value) then
if n == nth then
return i
end
n = n + 1
end
until (i = i - 1) == 0
end
end
error
fun clone(): Array[this->A!]^ =>
"""
Clone the array.
The new array contains references to the same elements that the old array
contains, the elements themselves are not cloned.
"""
let out = Array[this->A!](_size)
_ptr._copy_to(out._ptr, _size)
out._size = _size
out
fun slice(
from: USize = 0,
to: USize = -1,
step: USize = 1)
: Array[this->A!]^
=>
"""
Create a new array that is a clone of a portion of this array. The range is
exclusive and saturated.
The new array contains references to the same elements that the old array
contains, the elements themselves are not cloned.
"""
let out = Array[this->A!]
let last = _size.min(to)
let len = last - from
if (last > from) and (step > 0) then
out.reserve((len + (step - 1)) / step)
if step == 1 then
copy_to(out, from, 0, len)
else
try
var i = from
while i < last do
out.push(this(i)?)
i = i + step
end
end
end
end
out
fun permute(indices: Iterator[USize]): Array[this->A!]^ ? =>
"""
Create a new array with the elements permuted.
Permute to an arbitrary order that may include duplicates. An out of bounds
index raises an error.
The new array contains references to the same elements that the old array
contains, the elements themselves are not copied.
"""
let out = Array[this->A!]
for i in indices do
out.push(this(i)?)
end
out
fun reverse(): Array[this->A!]^ =>
"""
Create a new array with the elements in reverse order.
The new array contains references to the same elements that the old array
contains, the elements themselves are not copied.
"""
clone() .> reverse_in_place()
fun ref reverse_in_place() =>
"""
Reverse the array in place.
"""
if _size > 1 then
var i: USize = 0
var j = _size - 1
while i < j do
let x = _ptr._apply(i)
_ptr._update(i, _ptr._apply(j))
_ptr._update(j, x)
i = i + 1
j = j - 1
end
end
fun ref swap_elements(i: USize, j: USize) ? =>
"""
Swap the element at index i with the element at index j.
If either i or j are out of bounds, an error is raised.
"""
if (i >= _size) or (j >= _size) then error end
let x = _ptr._apply(i)
_ptr._update(i, _ptr._apply(j))
_ptr._update(j, consume x)
fun keys(): ArrayKeys[A, this->Array[A]]^ =>
"""
Return an iterator over the indices in the array.
"""
ArrayKeys[A, this->Array[A]](this)
fun values(): ArrayValues[A, this->Array[A]]^ =>
"""
Return an iterator over the values in the array.
"""
ArrayValues[A, this->Array[A]](this)
fun pairs(): ArrayPairs[A, this->Array[A]]^ =>
"""
Return an iterator over the (index, value) pairs in the array.
"""
ArrayPairs[A, this->Array[A]](this)
class ArrayKeys[A, B: Array[A] #read] is Iterator[USize]
let _array: B
var _i: USize
new create(array: B) =>
_array = array
_i = 0
fun has_next(): Bool =>
_i < _array.size()
fun ref next(): USize ? =>
if _i < _array.size() then
_i = _i + 1
else
error
end
fun ref rewind(): ArrayKeys[A, B] =>
_i = 0
this
class ArrayValues[A, B: Array[A] #read] is Iterator[B->A]
let _array: B
var _i: USize
new create(array: B) =>
_array = array
_i = 0
fun has_next(): Bool =>
_i < _array.size()
fun ref next(): B->A ? =>
_array(_i = _i + 1)?
fun ref rewind(): ArrayValues[A, B] =>
_i = 0
this
class ArrayPairs[A, B: Array[A] #read] is Iterator[(USize, B->A)]
let _array: B
var _i: USize
new create(array: B) =>
_array = array
_i = 0
fun has_next(): Bool =>
_i < _array.size()
fun ref next(): (USize, B->A) ? =>
(_i, _array(_i = _i + 1)?)
fun ref rewind(): ArrayPairs[A, B] =>
_i = 0
this