1)
        )
    , params.srcExtent.y, params.srcExtent.z);
if (any(id >= idBoundary)) {
    return;
}

let byteOffset = params.offset + id.x * gOutputUnitSize
    + id.y * params.bytesPerRow
    + id.z * params.bytesPerRow * params.rowsPerImage;
let dstOffset = byteOffset / gOutputUnitSize;
let srcBoundary = params.srcOrigin + params.srcExtent;

// Start coord, End coord
var coordS = vec3u(id.x * params.packTexelCount, id.y, id.z) + params.srcOrigin;
var coordE = coordS;
coordE.x += params.packTexelCount - 1;

if (params.shift > 0) {
    // Adjust coordS
    if (id.x == 0) {
        // Front of a row
        if (readPreviousRow) {
            // Needs reading from previous row
            coordS.x += params.bytesPerRow / params.texelSize - params.shift;
            if (id.y == 0) {
                // Front of a layer
                if (isCompactImage) {
                    // Needs reading from previous layer
                    coordS.y += params.srcExtent.y - 1;
                    if (id.z > 0) {
                        coordS.z -= 1;
                    }
                }
            } else {
                coordS.y -= 1;
            }
        }
    } else {
        coordS.x -= params.shift;
    }
    coordE.x -= params.shift;
}

let readDstBufAtStart: bool = params.shift > 0 && (
        all(id == vec3u(0u))    // start of buffer
        || (id.x == 0 && (!readPreviousRow      // start of non-compact row
            || (id.y == 0 && !isCompactImage)   // start of non-compact image
        )));
let readDstBufAtEnd: bool = coordE.x >= srcBoundary.x;