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1/*
2 * Copyright (C) 2022 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 */
16type TypedArray =
17  | Int8Array
18  | Uint8Array
19  | Uint8ClampedArray
20  | Int16Array
21  | Uint16Array
22  | Int32Array
23  | Uint32Array
24  | Float32Array
25  | Float64Array;
26
27class ArrayUtils {
28  static equal<T>(a: T[] | TypedArray, b: T[] | TypedArray): boolean {
29    if (a.length !== b.length) {
30      return false;
31    }
32
33    for (let i = 0; i < a.length; i++) {
34      if (a[i] !== b[i]) {
35        return false;
36      }
37    }
38
39    return true;
40  }
41
42  static searchSubarray<T>(
43    array: T[] | TypedArray,
44    subarray: T[] | TypedArray
45  ): number | undefined {
46    for (let i = 0; i + subarray.length <= array.length; ++i) {
47      let match = true;
48
49      for (let j = 0; j < subarray.length; ++j) {
50        if (array[i + j] !== subarray[j]) {
51          match = false;
52          break;
53        }
54      }
55
56      if (match) {
57        return i;
58      }
59    }
60
61    return undefined;
62  }
63
64  static binarySearchFirstGreaterOrEqual<T>(
65    values: T[] | TypedArray,
66    target: T
67  ): number | undefined {
68    if (values.length === 0) {
69      return undefined;
70    }
71
72    let low = 0;
73    let high = values.length - 1;
74
75    let result: number | undefined = undefined;
76
77    while (low <= high) {
78      const mid = (low + high) >> 1;
79
80      if (values[mid] < target) {
81        low = mid + 1;
82      } else if (values[mid] > target) {
83        if (result === undefined || result > mid) {
84          result = mid;
85        }
86        high = mid - 1;
87      } else {
88        result = mid;
89        high = mid - 1;
90      }
91    }
92
93    return result;
94  }
95
96  static binarySearchFirstGreater<T>(values: T[] | TypedArray, target: T): number | undefined {
97    if (values.length === 0) {
98      return undefined;
99    }
100
101    let low = 0;
102    let high = values.length - 1;
103
104    let result: number | undefined = undefined;
105
106    while (low <= high) {
107      const mid = (low + high) >> 1;
108
109      if (values[mid] < target) {
110        low = mid + 1;
111      } else if (values[mid] > target) {
112        if (result === undefined || result > mid) {
113          result = mid;
114        }
115        high = mid - 1;
116      } else {
117        low = mid + 1;
118      }
119    }
120
121    return result;
122  }
123
124  static toUintLittleEndian(buffer: Uint8Array, start: number, end: number): bigint {
125    let result = 0n;
126    for (let i = end - 1; i >= start; --i) {
127      result *= 256n;
128      result += BigInt(buffer[i]);
129    }
130    return result;
131  }
132
133  static toIntLittleEndian(buffer: Uint8Array, start: number, end: number): bigint {
134    const numOfBits = BigInt(Math.max(0, 8 * (end - start)));
135    if (numOfBits <= 0n) {
136      return 0n;
137    }
138
139    let result = ArrayUtils.toUintLittleEndian(buffer, start, end);
140    const maxSignedValue = 2n ** (numOfBits - 1n) - 1n;
141    if (result > maxSignedValue) {
142      const valuesRange = 2n ** numOfBits;
143      result -= valuesRange;
144    }
145
146    return result;
147  }
148}
149
150export {ArrayUtils};
151