mirror of
https://github.com/superseriousbusiness/gotosocial.git
synced 2024-12-13 10:46:33 +00:00
e3c2b790fd
* when appending log field only do so by minimal amount * move slice utils to separate package to fix import cycle, add GrowJust() and AppendJust() functions * fix GrowJust() not returning slice of same length * improved xslices tests * make AppendJust() test check for slice contents, fix AppendJust() final copying behaviour * add a +1 with field growth to try minimise allocation for log 'msg' field
223 lines
5.1 KiB
Go
223 lines
5.1 KiB
Go
// GoToSocial
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// Copyright (C) GoToSocial Authors admin@gotosocial.org
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// SPDX-License-Identifier: AGPL-3.0-or-later
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//
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// This program is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Affero General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// This program is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Affero General Public License for more details.
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//
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// You should have received a copy of the GNU Affero General Public License
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// along with this program. If not, see <http://www.gnu.org/licenses/>.
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package xslices
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import (
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"slices"
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)
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// GrowJust increases slice capacity to guarantee
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// extra room 'size', where in the case that it does
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// need to allocate more it ONLY allocates 'size' extra.
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// This is different to typical slices.Grow behaviour,
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// which simply guarantees extra through append() which
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// may allocate more than necessary extra size.
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func GrowJust[T any](in []T, size int) []T {
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if cap(in)-len(in) < size {
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// Reallocate enough for in + size.
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in2 := make([]T, len(in), len(in)+size)
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_ = copy(in2, in)
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in = in2
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}
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return in
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}
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// AppendJust appends extra elements to slice,
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// ONLY allocating at most len(extra) elements. This
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// is different to the typical append behaviour which
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// will append extra, in a manner to reduce the need
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// for new allocations on every call to append.
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func AppendJust[T any](in []T, extra ...T) []T {
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l := len(in)
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if cap(in)-l < len(extra) {
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// Reallocate enough for + extra.
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in2 := make([]T, l+len(extra))
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_ = copy(in2, in)
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in = in2
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} else {
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// Reslice for + extra.
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in = in[:l+len(extra)]
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}
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// Copy extra into slice.
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_ = copy(in[l:], extra)
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return in
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}
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// Deduplicate deduplicates entries in the given slice.
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func Deduplicate[T comparable](in []T) []T {
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var (
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inL = len(in)
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unique = make(map[T]struct{}, inL)
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deduped = make([]T, 0, inL)
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)
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for _, v := range in {
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if _, ok := unique[v]; ok {
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// Already have this.
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continue
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}
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unique[v] = struct{}{}
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deduped = append(deduped, v)
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}
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return deduped
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}
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// DeduplicateFunc deduplicates entries in the given
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// slice, using the result of key() to gauge uniqueness.
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func DeduplicateFunc[T any, C comparable](in []T, key func(v T) C) []T {
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var (
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inL = len(in)
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unique = make(map[C]struct{}, inL)
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deduped = make([]T, 0, inL)
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)
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if key == nil {
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panic("nil func")
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}
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for _, v := range in {
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k := key(v)
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if _, ok := unique[k]; ok {
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// Already have this.
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continue
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}
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unique[k] = struct{}{}
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deduped = append(deduped, v)
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}
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return deduped
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}
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// Gather will collect the values of type V from input type []T,
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// passing each item to 'get' and appending V to the return slice.
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func Gather[T, V any](out []V, in []T, get func(T) V) []V {
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if get == nil {
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panic("nil func")
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}
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// Starting write index
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// in the resliced / re
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// alloc'd output slice.
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start := len(out)
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// Total required slice len.
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total := start + len(in)
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if total > cap(out) {
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// Reallocate output with
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// capacity for total len.
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out2 := make([]V, len(out), total)
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copy(out2, out)
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out = out2
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}
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// Reslice with capacity
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// up to total required.
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out = out[:total]
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// Gather vs from 'in'.
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for i, v := range in {
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j := start + i
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out[j] = get(v)
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}
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return out
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}
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// GatherIf is functionally similar to Gather(), but only when return bool is true.
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// If you don't need to check the boolean, Gather() will be very slightly faster.
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func GatherIf[T, V any](out []V, in []T, get func(T) (V, bool)) []V {
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if get == nil {
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panic("nil func")
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}
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if cap(out)-len(out) < len(in) {
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// Reallocate output with capacity for 'in'.
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out2 := make([]V, len(out), cap(out)+len(in))
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copy(out2, out)
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out = out2
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}
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// Gather vs from 'in'.
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for _, v := range in {
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if v, ok := get(v); ok {
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out = append(out, v)
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}
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}
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return out
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}
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// Collate will collect the values of type K from input type []T,
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// passing each item to 'get' and deduplicating the end result.
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// This is equivalent to calling Gather() followed by Deduplicate().
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func Collate[T any, K comparable](in []T, get func(T) K) []K {
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if get == nil {
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panic("nil func")
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}
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ks := make([]K, 0, len(in))
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km := make(map[K]struct{}, len(in))
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for i := 0; i < len(in); i++ {
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// Get next k.
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k := get(in[i])
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if _, ok := km[k]; !ok {
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// New value, add
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// to map + slice.
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ks = append(ks, k)
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km[k] = struct{}{}
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}
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}
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return ks
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}
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// OrderBy orders a slice of given type by the provided alternative slice of comparable type.
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func OrderBy[T any, K comparable](in []T, keys []K, key func(T) K) {
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if key == nil {
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panic("nil func")
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}
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// Create lookup of keys->idx.
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m := make(map[K]int, len(in))
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for i, k := range keys {
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m[k] = i
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}
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// Sort according to the reverse lookup.
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slices.SortFunc(in, func(a, b T) int {
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ai := m[key(a)]
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bi := m[key(b)]
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if ai < bi {
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return -1
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} else if bi < ai {
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return +1
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}
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return 0
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})
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}
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