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/* Wrapper for accessing buffer through sequential reads */
module.exports = class Stream {
constructor (buffer) {
this.array = new Uint8Array(buffer);
this.position = 0;
}
eof () {
return this.position >= this.array.length;
}
read (length) {
const result = this.array.slice(this.position, this.position + length);
this.position += length;
return result;
}
readString (length) {
const data = Array.from(this.read(length));
return data.map(c => String.fromCharCode(c)).join("");
}
// read a big-endian 32-bit integer
readInt32 () {
const result = (
(this.array[this.position] << 24) +
(this.array[this.position + 1] << 16) +
(this.array[this.position + 2] << 8) +
this.array[this.position + 3]);
this.position += 4;
return result;
}
// read a big-endian 16-bit integer
readInt16 () {
const result = (
(this.array[this.position] << 8) +
this.array[this.position + 1]);
this.position += 2;
return result;
}
// read an 8-bit integer
readInt8 (signed) {
let result = this.array[this.position];
if (signed && result > 127)
result -= 256;
this.position += 1;
return result;
}
/* read a MIDI-style variable-length integer
(big-endian value in groups of 7 bits,
with top bit set to signify that another byte follows)
*/
readVarInt () {
let result = 0;
while (true) {
const b = this.readInt8();
if (b & 0x80) {
result += (b & 0x7f);
result <<= 7;
}
else {
// b is the last byte
return result + b;
}
}
}
};
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