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feat(mem): Zero Copy ArrayBuffer (#279)
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* Experiment

Zero Copy Arrays

* Update ValueRepresentation.js

* Removed View
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@Ouwen
Ouwen committed Jun 17, 2022
1 parent b5a8a99 commit a17f2d7
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Showing 2 changed files with 157 additions and 57 deletions.
98 changes: 93 additions & 5 deletions packages/adapters/src/BufferStream.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -300,13 +300,19 @@ class BufferStream {
}

more(length) {
if (this.offset + length > this.buffer.byteLength) {
if (this.offset + length > this.endOffset) {
throw new Error("Request more than currently allocated buffer");
}

var newBuf = this.buffer.slice(this.offset, this.offset + length);
const newBuf = new ReadBufferStream(
this.buffer,
null,
this.offset,
this.offset + length
);
this.increment(length);
return new ReadBufferStream(newBuf);

return newBuf;
}

reset() {
Expand All @@ -324,9 +330,91 @@ class BufferStream {
}

class ReadBufferStream extends BufferStream {
constructor(buffer, littleEndian) {
constructor(buffer, littleEndian, start, end) {
super(buffer, littleEndian);
this.size = this.buffer.byteLength;
this.offset = start || 0;
this.size = end || this.buffer.byteLength;
this.startOffset = this.offset;
this.endOffset = this.size;
}

readString(length) {
var chars = [];
var start = this.offset;
var end = this.offset + length;
if (end >= this.endOffset) {
end = this.endOffset;
}
for (let i = start; i < end; ++i) {
chars.push(String.fromCharCode(this.view.getUint8(i)));
this.increment(1);
}
return chars.join("");
}

reset() {
this.offset = this.startOffset;
return this;
}

end() {
return this.offset >= this.endOffset;
}

toEnd() {
this.offset = this.endOffset;
}

writeUint8(value) {
throw new Error(value, "writeUint8 not implemented");
}

writeInt8(value) {
throw new Error(value, "writeInt8 not implemented");
}

writeUint16(value) {
throw new Error(value, "writeUint16 not implemented");
}

writeTwoUint16s(value) {
throw new Error(value, "writeTwoUint16s not implemented");
}

writeInt16(value) {
throw new Error(value, "writeInt16 not implemented");
}

writeUint32(value) {
throw new Error(value, "writeUint32 not implemented");
}

writeInt32(value) {
throw new Error(value, "writeInt32 not implemented");
}

writeFloat(value) {
throw new Error(value, "writeFloat not implemented");
}

writeDouble(value) {
throw new Error(value, "writeDouble not implemented");
}

writeString(value) {
throw new Error(value, "writeString not implemented");
}

writeHex(value) {
throw new Error(value, "writeHex not implemented");
}

checkSize(step) {
throw new Error(step, "checkSize not implemented");
}

concat(stream) {
throw new Error(stream, "concat not implemented");
}
}

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116 changes: 64 additions & 52 deletions packages/adapters/src/ValueRepresentation.js
View file
Original file line number Diff line number Diff line change
Expand Up @@ -24,6 +24,13 @@ function readTag(stream) {
return tag;
}

function toWindows(inputArray, size) {
return Array.from(
{ length: inputArray.length - (size - 1) }, //get the appropriate length
(_, index) => inputArray.slice(index, index + size) //create the windows
);
}

var binaryVRs = ["FL", "FD", "SL", "SS", "UL", "US", "AT"],
explicitVRs = ["OB", "OW", "OF", "SQ", "UC", "UR", "UT", "UN"],
singleVRs = ["SQ", "OF", "OW", "OB", "UN"];
Expand Down Expand Up @@ -342,6 +349,7 @@ class BinaryRepresentation extends ValueRepresentation {
if (length == 0xffffffff) {
var itemTagValue = Tag.readTag(stream),
frames = [];

if (itemTagValue.is(0xfffee000)) {
var itemLength = stream.readUint32(),
numOfFrames = 1,
Expand All @@ -357,68 +365,72 @@ class BinaryRepresentation extends ValueRepresentation {
offsets = [];
}

const getFrameOrFragement = stream => {
var nextTag = Tag.readTag(stream);
if (!nextTag.is(0xfffee000)) {
return [null, true];
}
let frameOrFragmentItemLength = stream.readUint32();
const buffer = stream.getBuffer(
stream.offset,
stream.offset + frameOrFragmentItemLength
);
stream.increment(frameOrFragmentItemLength);
return [buffer, false];
};

// If there is an offset table, use that to loop through pixel data sequence
// FIX: These two loops contain the exact same code, but I couldn't think of a way
// to combine the for and while loops non-confusingly so went with the explicit but
// redundant approach.
if (offsets.length > 0) {
// make offsets relative to the stream, not tag
offsets = offsets.map(e => e + stream.offset);
offsets.push(stream.size);

for (var _i = 0; _i < offsets.length - 1; _i++) {
let fragments = [];

while (stream.offset < offsets[_i + 1]) {
var nextTag = Tag.readTag(stream);

if (!nextTag.is(0xfffee000)) {
// window offsets to an array of [start,stop] locations
frames = toWindows(offsets, 2).map(range => {
const fragments = [];
const [start, stop] = range;
// create a new readable stream based on the range
const s = new ReadBufferStream(
stream.buffer,
stream.isLittleEndian,
start,
stop
);
while (!s.end()) {
const [buf, done] = getFrameOrFragement(s);
if (done) {
break;
}

let fragmentItemLength = stream.readUint32();

fragments.push(stream.more(fragmentItemLength));
fragments.push(buf);
}
return fragments;
});

const frameSize = (() => {
let size = 0;

for (const fragment of fragments) {
size += fragment.size;
}

return size;
})();
const frame = (() => {
const frame = new Uint8Array(frameSize);
let offset = 0;

for (const fragment of fragments) {
frame.set(
new Uint8Array(fragment.buffer),
offset
);
offset += fragment.size;
}

return frame;
})();

frames.push(frame.buffer);
}
frames = frames.map(fragments => {
if (fragments.length < 1) {
return fragments[0];
} else {
const frameSize = fragments.reduce(
(size, buffer) => {
return size + buffer.byteLength;
},
0
);
const mergedFrame = new Uint8Array(frameSize);
fragments.reduce((offset, buffer) => {
mergedFrame.set(new Uint8Array(buffer), offset);
return offset + buffer.byteLength;
}, 0);
return mergedFrame;
}
});
}
// If no offset table, loop through remainder of stream looking for termination tag
else {
while (stream.offset < stream.size) {
const nextTag = Tag.readTag(stream);

if (!nextTag.is(0xfffee000)) {
break;
}

const frameItemLength = stream.readUint32();
const fragmentStream = stream.more(frameItemLength);

frames.push(fragmentStream.buffer);
const [buffer, done] = getFrameOrFragement(stream);
if (done) break;
frames.push(buffer);
}
}

Expand All @@ -433,7 +445,6 @@ class BinaryRepresentation extends ValueRepresentation {
"Item tag not found after undefined binary length"
);
}

return frames;
} else {
var bytes;
Expand All @@ -442,7 +453,8 @@ class BinaryRepresentation extends ValueRepresentation {
} else if (this.type == 'OB') {
bytes = stream.readUint8Array(length);
}*/
bytes = stream.more(length).buffer;
bytes = stream.getBuffer(stream.offset, stream.offset + length);
stream.increment(length);
return [bytes];
}
}
Expand Down

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