1 /* 2 * Copyright (C) 2024 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 package com.android.intentresolver.util.cursor 18 19 import android.database.Cursor 20 21 /** A [Cursor] that holds values of [E] for each row. */ 22 interface CursorView<out E> : Cursor { 23 /** 24 * Reads the current row from this [CursorView]. A result of `null` indicates that the row could 25 * not be read / value could not be produced. 26 */ readRownull27 fun readRow(): E? 28 } 29 30 /** 31 * Returns a [CursorView] from the given [Cursor], and a function [readRow] used to produce the 32 * value for a single row. 33 */ 34 fun <E> Cursor.viewBy(readRow: Cursor.() -> E): CursorView<E> = 35 object : CursorView<E>, Cursor by this@viewBy { 36 override fun readRow(): E? = immobilized().readRow() 37 } 38 39 /** Returns a [CursorView] that begins (index 0) at [newStartIndex] of the given cursor. */ startAtnull40fun <E> CursorView<E>.startAt(newStartIndex: Int): CursorView<E> = 41 object : CursorView<E>, Cursor by (this@startAt as Cursor).startAt(newStartIndex) { 42 override fun readRow(): E? = this@startAt.readRow() 43 } 44 45 /** Returns a [CursorView] that is truncated to contain only [count] elements. */ limitnull46fun <E> CursorView<E>.limit(count: Int): CursorView<E> = 47 object : CursorView<E>, Cursor by (this@limit as Cursor).limit(count) { 48 override fun readRow(): E? = this@limit.readRow() 49 } 50 51 /** Retrieves a single row at index [idx] from the [CursorView]. */ getnull52operator fun <E> CursorView<E>.get(idx: Int): E? = if (moveToPosition(idx)) readRow() else null 53 54 /** Returns a [Sequence] that iterates over the [CursorView] returning each row. */ 55 fun <E> CursorView<E>.asSequence(): Sequence<E?> = sequence { 56 for (i in 0 until count) { 57 yield(get(i)) 58 } 59 } 60