diff options
Diffstat (limited to 'libgo/go/compress/lzw/reader.go')
| -rw-r--r-- | libgo/go/compress/lzw/reader.go | 10 |
1 files changed, 6 insertions, 4 deletions
diff --git a/libgo/go/compress/lzw/reader.go b/libgo/go/compress/lzw/reader.go index 1be52d55e4f..f08021190c2 100644 --- a/libgo/go/compress/lzw/reader.go +++ b/libgo/go/compress/lzw/reader.go @@ -63,8 +63,7 @@ type decoder struct { // // last is the most recently seen code, or decoderInvalidCode. // - // An invariant is that - // (hi < overflow) || (hi == overflow && last == decoderInvalidCode) + // An invariant is that hi < overflow. clear, eof, hi, overflow, last uint16 // Each code c in [lo, hi] expands to two or more bytes. For c != hi: @@ -200,15 +199,18 @@ loop: } d.last, d.hi = code, d.hi+1 if d.hi >= d.overflow { + if d.hi > d.overflow { + panic("unreachable") + } if d.width == maxWidth { d.last = decoderInvalidCode // Undo the d.hi++ a few lines above, so that (1) we maintain - // the invariant that d.hi <= d.overflow, and (2) d.hi does not + // the invariant that d.hi < d.overflow, and (2) d.hi does not // eventually overflow a uint16. d.hi-- } else { d.width++ - d.overflow <<= 1 + d.overflow = 1 << d.width } } if d.o >= flushBuffer { |