[teamai] Push 87 resource(s) from XingfenD

2026-09-10 16:10:45 +08:00
parent 425c9c078a
commit 65c04def51
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+# Slice Internals
+
+## Memory Layout
+
+A slice is a 24-byte header (3 machine words):
+
+- **Pointer** — points to backing array (heap-allocated)
+- **Length** — number of elements in use
+- **Capacity** — allocated size of backing array
+
+Assigning or passing a slice copies the 24-byte header, not the backing array. Both the original and copy point to the same underlying data—mutations are visible to both.
+
+## Capacity Growth
+
+When `append` exceeds capacity:
+
+- `oldCap < 256`: double capacity
+- `oldCap ≥ 256`: grow ~25% (`oldCap + (oldCap + 3*256) / 4`)
+
+### Growth Cost
+
+Each growth is O(n) — the entire array is copied to a new location. For a slice growing from 0 to N elements one at a time, the amortized cost per append is O(1), but the total copies are roughly 2N. **Preallocation eliminates all intermediate copies:**
+
+```go
+// Known size — direct indexing
+out := make([]Result, len(input))
+for i, v := range input {
+    out[i] = transform(v)
+}
+
+// Approximate size
+out := make([]Result, 0, len(input)*2)
+for _, v := range input {
+    out = append(out, transform(v))
+}
+```
+
+## `slices` Package (Go 1.21+)
+
+| Category | Key Functions |
+| --- | --- |
+| **Sort** | `Sort`, `SortFunc`, `SortStableFunc`, `IsSorted` |
+| **Search** | `BinarySearch`, `BinarySearchFunc`, `Contains`, `Index`, `IndexFunc` |
+| **Mutate** | `Insert`, `Delete`, `Replace`, `Compact`, `Reverse`, `Grow`, `Clip` |
+| **Create** | `Concat` (1.22+), `Repeat` (1.23+), `Chunk` (1.23+) |
+| **Compare** | `Clone`, `Equal`, `EqualFunc`, `Compare`, `DeleteFunc` |
+
+## `copy()` vs `append()` vs `slices.Clone()`
+
+| Operation             | Use When                         |
+| --------------------- | -------------------------------- |
+| `copy(dst, src)`      | Copying into pre-allocated slice |
+| `append(dst, src...)` | Appending to a slice             |
+| `slices.Clone(s)`     | Creating independent copy        |
+| `s[:len(s):len(s)]`   | Preventing append aliasing       |