xref: /aosp_15_r20/external/flatbuffers/ts/flexbuffers/reference-util.ts (revision 890232f25432b36107d06881e0a25aaa6b473652) 
1import { BitWidth } from './bit-width.js'
2import { toByteWidth, fromByteWidth } from './bit-width-util.js'
3import { toUTF8Array, fromUTF8Array } from './flexbuffers-util.js'
4
5export function validateOffset(dataView: DataView, offset: number, width: number): void {
6  if (dataView.byteLength <= offset + width || (offset & (toByteWidth(width) - 1)) !== 0) {
7    throw "Bad offset: " + offset + ", width: " + width;
8  }
9}
10
11export function readInt(dataView: DataView, offset: number, width: number): number | bigint {
12  if (width < 2) {
13    if (width < 1) {
14      return dataView.getInt8(offset);
15    } else {
16      return dataView.getInt16(offset, true);
17    }
18  } else {
19    if (width < 3) {
20      return dataView.getInt32(offset, true)
21    } else {
22      if (dataView.setBigInt64 === undefined) {
23        return BigInt(dataView.getUint32(offset, true)) + (BigInt(dataView.getUint32(offset + 4, true)) << BigInt(32));
24      }
25      return dataView.getBigInt64(offset, true)
26    }
27  }
28}
29
30export function readUInt(dataView: DataView, offset: number, width: number): number | bigint {
31  if (width < 2) {
32    if (width < 1) {
33      return dataView.getUint8(offset);
34    } else {
35      return dataView.getUint16(offset, true);
36    }
37  } else {
38    if (width < 3) {
39      return dataView.getUint32(offset, true)
40    } else {
41      if (dataView.getBigUint64 === undefined) {
42        return BigInt(dataView.getUint32(offset, true)) + (BigInt(dataView.getUint32(offset + 4, true)) << BigInt(32));
43      }
44      return dataView.getBigUint64(offset, true)
45    }
46  }
47}
48
49export function readFloat(dataView: DataView, offset: number, width: number): number {
50  if (width < BitWidth.WIDTH32) {
51    throw "Bad width: " + width;
52  }
53  if (width === BitWidth.WIDTH32) {
54    return dataView.getFloat32(offset, true);
55  }
56  return dataView.getFloat64(offset, true);
57}
58
59export function indirect(dataView: DataView, offset: number, width: number): number {
60  const step = readUInt(dataView, offset, width) as number;
61  return offset - step;
62}
63
64export function keyIndex(key: string, dataView: DataView, offset: number, parentWidth: number, byteWidth: number, length: number): number | null {
65  const input = toUTF8Array(key);
66  const keysVectorOffset = indirect(dataView, offset, parentWidth) - byteWidth * 3;
67  const bitWidth = fromByteWidth(byteWidth);
68  const indirectOffset = keysVectorOffset - Number(readUInt(dataView, keysVectorOffset, bitWidth));
69  const _byteWidth = Number(readUInt(dataView, keysVectorOffset + byteWidth, bitWidth));
70  let low = 0;
71  let high = length - 1;
72  while (low <= high) {
73    const mid = (high + low) >> 1;
74    const dif = diffKeys(input, mid, dataView, indirectOffset, _byteWidth);
75    if (dif === 0) return mid;
76    if (dif < 0) {
77      high = mid - 1;
78    } else {
79      low = mid + 1;
80    }
81  }
82  return null;
83}
84
85export function diffKeys(input: Uint8Array, index: number, dataView: DataView, offset: number, width: number): number {
86  const keyOffset = offset + index * width;
87  const keyIndirectOffset = keyOffset - Number(readUInt(dataView, keyOffset, fromByteWidth(width)));
88  for (let i = 0; i < input.length; i++) {
89    const dif = input[i] - dataView.getUint8(keyIndirectOffset + i);
90    if (dif !== 0) {
91      return dif;
92    }
93  }
94  return dataView.getUint8(keyIndirectOffset + input.length) === 0 ? 0 : -1;
95}
96
97export function keyForIndex(index: number, dataView: DataView, offset: number, parentWidth: number, byteWidth: number): string {
98  const keysVectorOffset = indirect(dataView, offset, parentWidth) - byteWidth * 3;
99  const bitWidth = fromByteWidth(byteWidth);
100  const indirectOffset = keysVectorOffset - Number(readUInt(dataView, keysVectorOffset, bitWidth));
101  const _byteWidth = Number(readUInt(dataView, keysVectorOffset + byteWidth, bitWidth));
102  const keyOffset = indirectOffset + index * _byteWidth;
103  const keyIndirectOffset = keyOffset - Number(readUInt(dataView, keyOffset, fromByteWidth(_byteWidth)));
104  let length = 0;
105  while (dataView.getUint8(keyIndirectOffset + length) !== 0) {
106    length++;
107  }
108  return fromUTF8Array(new Uint8Array(dataView.buffer, keyIndirectOffset, length));
109}
110