git-svn-id: https://crawl-ref.svn.sourceforge.net/svnroot/crawl-ref/trunk@5832 c06c8d41-db1a-0410-9941-cceddc491573
LACHYT7LBK3WRVGVDHU4BCRIYJ2Y6DLKOAXMX6NYUKZKKVG5XCIAC
OQXMUX5JEITCP2QXJKKOQRLRVTD3LTSDWGI6HTK5GVDIAJ7VKO6AC
EGV2HM7SD7UQSWJGLR65NQJTUBAJ7WHLM67FMH4UFP7JRSFKREPAC
K2CS6TCX2NDVL2ASEHGP4J4K4IJ6FP3ANNKTSIWVG43HPYSBX6ZQC
// negative idx means read from the end
// Negative idx means read from the end.