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read and write strings from arraybuffers
function strlen(buffer, byteOffset, byteLength) {
let array = new Uint8Array(buffer, byteOffset, byteLength);
for (let i = 0; i < array.length; i++) {
if (array[i] == 0)
return i;
}
throw new Error("invalid string: not ending with null byte");
}
class StringView {
constructor(buffer, byteOffset = 0, byteLength = null) {
this.buffer = buffer;
this.byteOffset = byteOffset;
this.byteLength = byteLength === null ? buffer.byteLength : byteLength;
}
getString(byteOffset = 0, encoding = "utf-8") {
let length = strlen(this.buffer, this.byteOffset+byteOffset, this.byteLength-byteOffset);
let bytes = new DataView(this.buffer, this.byteOffset+byteOffset, length);
return new TextDecoder(encoding).decode(bytes);
}
setString(value, byteOffset = 0, encoding = "utf-8") {
if (encoding != "utf-8") throw new Error("only utf-8 is supported at the moment");
let array = new Uint8Array(this.buffer, this.byteOffset, this.byteLength);
let bytes = new TextEncoder().encode(value);
let nullpos = byteOffset+bytes.byteLength;
if (nullpos >= array.length)
throw new RangeError("String too long");
array.set(bytes, byteOffset);
array[nullpos] = 0;
return bytes.byteLength+1;
}
}
let buffer = new ArrayBuffer(20);
let array = new Uint8Array(buffer);
let view = new StringView(buffer);
let bytesWritten = view.setString("Hello World");
view.setString("Foo Bar", bytesWritten);
console.log(array);
console.log(view.getString());
console.log(view.getString(bytesWritten));
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