ECS 简略版说明七：Collection、Mathmatic

目录

Unity.Collections cheat sheet

Allocators

Array-like types

Map and set types

Bit arrays and bit fields

String types

Other types

Enumerators

Parallel readers and writers

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Unity.Collections

Collections分为三类:

• Unity.Collections 中以Native- 开头的都有一个 safety checks 以确保它们被正确地处理并以线程安全的方式使用。
• Unity.Collections.LowLevel.Unsafe 下面的，以 Unsafe- 开头的不包含safety checks.
• 其余的类型没有被 allocated and 不包含 pointers, so effectively their disposal and thread safety are never a concern. 这些类型只保存少量的数据。

Allocators

• Allocator.Temp: The fastest allocator. For very short-lived allocations. Temp allocations cannot be passed into jobs.
• Allocator.TempJob: The next fastest allocator. For short-lived allocations (4-frame lifetime). TempJob allocations can be passed into jobs.
• Allocator.Persistent: The slowest allocator. For indefinite lifetime allocations. Persistent allocations can be passed into jobs.

Array-like types

类似于数组的类型有： Unity.Collections.NativeArray and Unity.Collections.NativeSlice.

NativeList	A resizable list.
UnsafeList	A resizable list.
UnsafePtrList	A resizable list of pointers.
NativeStream	A set of append-only, untyped buffers.
UnsafeStream	A set of append-only, untyped buffers.
UnsafeAppendBuffer	An append-only untyped buffer.
NativeQueue	A resizable queue.
UnsafeRingQueue	A fixed-size circular buffer.
FixedList32Bytes	A 32-byte list, including 2 bytes of overhead, so 30 bytes are available for storage. Max capacity depends upon the type parameter.
FixedList64Bytes	A 64-byte list, including 2 bytes of overhead, so 62 bytes are available for storage. Max capacity depends upon the type parameter.
FixedList128Bytes	A 128-byte list, including 2 bytes of overhead, so 126 bytes are available for storage. Max capacity depends upon the type parameter.
FixedList512Bytes	A 512-byte list, including 2 bytes of overhead, so 510 bytes are available for storage. Max capacity depends upon the type parameter.
FixedList4096Bytes	A 4096-byte list, including 2 bytes of overhead, so 4094 bytes are available for storage. Max capacity depends upon the type parameter.

没有多维数组类型,但是可以把多维转成一维，比如：for an int[4][5] array, use an int[20] array instead (because 4 * 5 is 20).

When using the Entities package, a DynamicBuffer component is often the best choice for an array- or list-like collection.

See also NativeArrayExtensions, ListExtensions, NativeSortExtension.

Map and set types

NativeParallelHashMap	An unordered associative array of key-value pairs.
UnsafeParallelHashMap	An unordered associative array of key-value pairs.
NativeParallelHashSet	A set of unique values.
UnsafeParallelHashSet	A set of unique values.
NativeMultiHashMap	An unordered associative array of key-value pairs. The keys do not have to be unique, i.e. two pairs can have equal keys.
UnsafeMultiHashMap	An unordered associative array of key-value pairs. The keys do not have to be unique, i.e. two pairs can have equal keys.

See also HashSetExtensions, Unity.Collections.NotBurstCompatible.Extensions, and Unity.Collections.LowLevel.Unsafe.NotBurstCompatible.Extensions

Bit arrays and bit fields

BitField32	A fixed-size array of 32 bits.
BitField64	A fixed-size array of 64 bits.
NativeBitArray	An arbitrary-sized array of bits.
UnsafeBitArray	An arbitrary-sized array of bits.

String types

NativeText	A UTF-8 encoded string. Mutable and resizable.
FixedString32Bytes	A 32-byte UTF-8 encoded string, including 3 bytes of overhead, so 29 bytes available for storage.
FixedString64Bytes	A 64-byte UTF-8 encoded string, including 3 bytes of overhead, so 61 bytes available for storage.
FixedString128Bytes	A 128-byte UTF-8 encoded string, including 3 bytes of overhead, so 125 bytes available for storage.
FixedString512Bytes	A 512-byte UTF-8 encoded string, including 3 bytes of overhead, so 509 bytes available for storage.
FixedString4096Bytes	A 4096-byte UTF-8 encoded string, including 3 bytes of overhead, so 4093 bytes available for storage.

See also FixedString and FixedStringMethods.

Other types

NativeReference	A reference to a single value. Functionally equivalent to an array of length 1.
UnsafeAtomicCounter32	A 32-bit atomic counter.
UnsafeAtomicCounter64	A 64-bit atomic counter.

Enumerators

Most of the collections have a GetEnumerator method, which returns an implementation of IEnumerator. The enumerator's MoveNext method advances its Current property to the next element.

Parallel readers and writers

Several of the collection types have nested types for reading and writing from parallel jobs. For example, to write safely to a NativeList from a parallel job, you need a NativeList.ParallelWriter.