blocksActuallyRead rounded bytesRead up to the next whole block
unconditionally, intending to handle the legitimate case where the
very last block of the file is naturally shorter than BLOCK_SIZE
(cache_ is deliberately over-allocated for that). But it applied the
same rounding to any short read, including a genuine failure or a
dropped connection mid-file (this loader can sit on top of the whole
Remote ISO chain via CachingFileLoader/HTTPFileLoader when "Cache full
ISO in RAM" is enabled) - marking a block as fully cached when only a
few of its bytes were actually written. Since cache_ is malloc'd (not
zeroed), every later read of that block would serve uninitialized heap
memory as if it were real file data.
Only round up when the short read's end position exactly matches the
true end of the file.
Henrik Rydgård
67f2bf57cb