source: trip-planner-front/node_modules/@webassemblyjs/leb128/lib/bufs.js@ fa375fe

Last change on this file since fa375fe was 6a3a178, checked in by Ema <ema_spirova@…>, 3 years ago

initial commit

  • Property mode set to 100644
File size: 4.8 KB
Line 
1"use strict";
2
3Object.defineProperty(exports, "__esModule", {
4 value: true
5});
6exports.alloc = alloc;
7exports.free = free;
8exports.resize = resize;
9exports.readInt = readInt;
10exports.readUInt = readUInt;
11exports.writeInt64 = writeInt64;
12exports.writeUInt64 = writeUInt64;
13// Copyright 2012 The Obvious Corporation.
14
15/*
16 * bufs: Buffer utilities.
17 */
18
19/*
20 * Module variables
21 */
22
23/** Pool of buffers, where `bufPool[x].length === x`. */
24var bufPool = [];
25/** Maximum length of kept temporary buffers. */
26
27var TEMP_BUF_MAXIMUM_LENGTH = 20;
28/** Minimum exactly-representable 64-bit int. */
29
30var MIN_EXACT_INT64 = -0x8000000000000000;
31/** Maximum exactly-representable 64-bit int. */
32
33var MAX_EXACT_INT64 = 0x7ffffffffffffc00;
34/** Maximum exactly-representable 64-bit uint. */
35
36var MAX_EXACT_UINT64 = 0xfffffffffffff800;
37/**
38 * The int value consisting just of a 1 in bit #32 (that is, one more
39 * than the maximum 32-bit unsigned value).
40 */
41
42var BIT_32 = 0x100000000;
43/**
44 * The int value consisting just of a 1 in bit #64 (that is, one more
45 * than the maximum 64-bit unsigned value).
46 */
47
48var BIT_64 = 0x10000000000000000;
49/*
50 * Helper functions
51 */
52
53/**
54 * Masks off all but the lowest bit set of the given number.
55 */
56
57function lowestBit(num) {
58 return num & -num;
59}
60/**
61 * Gets whether trying to add the second number to the first is lossy
62 * (inexact). The first number is meant to be an accumulated result.
63 */
64
65
66function isLossyToAdd(accum, num) {
67 if (num === 0) {
68 return false;
69 }
70
71 var lowBit = lowestBit(num);
72 var added = accum + lowBit;
73
74 if (added === accum) {
75 return true;
76 }
77
78 if (added - lowBit !== accum) {
79 return true;
80 }
81
82 return false;
83}
84/*
85 * Exported functions
86 */
87
88/**
89 * Allocates a buffer of the given length, which is initialized
90 * with all zeroes. This returns a buffer from the pool if it is
91 * available, or a freshly-allocated buffer if not.
92 */
93
94
95function alloc(length) {
96 var result = bufPool[length];
97
98 if (result) {
99 bufPool[length] = undefined;
100 } else {
101 result = new Buffer(length);
102 }
103
104 result.fill(0);
105 return result;
106}
107/**
108 * Releases a buffer back to the pool.
109 */
110
111
112function free(buffer) {
113 var length = buffer.length;
114
115 if (length < TEMP_BUF_MAXIMUM_LENGTH) {
116 bufPool[length] = buffer;
117 }
118}
119/**
120 * Resizes a buffer, returning a new buffer. Returns the argument if
121 * the length wouldn't actually change. This function is only safe to
122 * use if the given buffer was allocated within this module (since
123 * otherwise the buffer might possibly be shared externally).
124 */
125
126
127function resize(buffer, length) {
128 if (length === buffer.length) {
129 return buffer;
130 }
131
132 var newBuf = alloc(length);
133 buffer.copy(newBuf);
134 free(buffer);
135 return newBuf;
136}
137/**
138 * Reads an arbitrary signed int from a buffer.
139 */
140
141
142function readInt(buffer) {
143 var length = buffer.length;
144 var positive = buffer[length - 1] < 0x80;
145 var result = positive ? 0 : -1;
146 var lossy = false; // Note: We can't use bit manipulation here, since that stops
147 // working if the result won't fit in a 32-bit int.
148
149 if (length < 7) {
150 // Common case which can't possibly be lossy (because the result has
151 // no more than 48 bits, and loss only happens with 54 or more).
152 for (var i = length - 1; i >= 0; i--) {
153 result = result * 0x100 + buffer[i];
154 }
155 } else {
156 for (var _i = length - 1; _i >= 0; _i--) {
157 var one = buffer[_i];
158 result *= 0x100;
159
160 if (isLossyToAdd(result, one)) {
161 lossy = true;
162 }
163
164 result += one;
165 }
166 }
167
168 return {
169 value: result,
170 lossy: lossy
171 };
172}
173/**
174 * Reads an arbitrary unsigned int from a buffer.
175 */
176
177
178function readUInt(buffer) {
179 var length = buffer.length;
180 var result = 0;
181 var lossy = false; // Note: See above in re bit manipulation.
182
183 if (length < 7) {
184 // Common case which can't possibly be lossy (see above).
185 for (var i = length - 1; i >= 0; i--) {
186 result = result * 0x100 + buffer[i];
187 }
188 } else {
189 for (var _i2 = length - 1; _i2 >= 0; _i2--) {
190 var one = buffer[_i2];
191 result *= 0x100;
192
193 if (isLossyToAdd(result, one)) {
194 lossy = true;
195 }
196
197 result += one;
198 }
199 }
200
201 return {
202 value: result,
203 lossy: lossy
204 };
205}
206/**
207 * Writes a little-endian 64-bit signed int into a buffer.
208 */
209
210
211function writeInt64(value, buffer) {
212 if (value < MIN_EXACT_INT64 || value > MAX_EXACT_INT64) {
213 throw new Error("Value out of range.");
214 }
215
216 if (value < 0) {
217 value += BIT_64;
218 }
219
220 writeUInt64(value, buffer);
221}
222/**
223 * Writes a little-endian 64-bit unsigned int into a buffer.
224 */
225
226
227function writeUInt64(value, buffer) {
228 if (value < 0 || value > MAX_EXACT_UINT64) {
229 throw new Error("Value out of range.");
230 }
231
232 var lowWord = value % BIT_32;
233 var highWord = Math.floor(value / BIT_32);
234 buffer.writeUInt32LE(lowWord, 0);
235 buffer.writeUInt32LE(highWord, 4);
236}
Note: See TracBrowser for help on using the repository browser.