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}
View as plain text