fun readRows()

in plot-api/src/commonMain/kotlin/org/jetbrains/letsPlot/util/pngj/PngReader.kt [354:388]
35 lines of code
11 McCabe index (conditional complexity)

    fun readRows(nRows: Int, rowOffset: Int, rowStep: Int): IImageLineSet<out IImageLine> {
        @Suppress("NAME_SHADOWING")
        var nRows = nRows
        if (chunkseq!!.firstChunksNotYetRead()) readFirstChunks()
        if (nRows < 0) nRows = (curImgInfo.rows - rowOffset) / rowStep
        if (rowStep < 1 || rowOffset < 0 || nRows == 0 || nRows * rowStep + rowOffset > curImgInfo.rows) throw PngjInputException(
            "bad args"
        )
        if (rowNum >= rowOffset) throw PngjInputException("readRows cannot be mixed with readRow")
        imlinesSet = createLineSet(false, nRows, rowOffset, rowStep)
        if (!isInterlaced) {
            var m = -1 // last row already read in
            while (m < nRows - 1) {
                while (!chunkseq.idatSet!!.isRowReady) {
                    if (streamFeeder!!.feed(chunkseq) < 1) throw PngjInputException("Premature ending")
                }
                rowNum++
                chunkseq.idatSet!!.updateCrcs(idatCrca, idatCrcb)
                m = (rowNum - rowOffset) / rowStep
                if (rowNum >= rowOffset && rowStep * m + rowOffset == rowNum) {
                    val line: IImageLine = imlinesSet!!.getImageLine(rowNum)
                    line.readFromPngRaw(
                        chunkseq.idatSet!!.unfilteredRow!!, curImgInfo.bytesPerRow + 1, 0,
                        1
                    )
                    line.endReadFromPngRaw()
                }
                chunkseq.idatSet!!.advanceToNextRow()
            }
        } else { // and now, for something completely different (interlaced)
            loadAllInterlaced(nRows, rowOffset, rowStep)
        }
        chunkseq.idatSet!!.markAsDone()
        return imlinesSet!!
    }