diff --git a/lib/compress/zstd_compress_internal.h b/lib/compress/zstd_compress_internal.h index 9e4c1ac17..d9473c104 100644 --- a/lib/compress/zstd_compress_internal.h +++ b/lib/compress/zstd_compress_internal.h @@ -982,7 +982,9 @@ MEM_STATIC U32 ZSTD_window_canOverflowCorrect(ZSTD_window_t const window, { U32 const cycleSize = 1u << cycleLog; U32 const curr = (U32)((BYTE const*)src - window.base); - U32 const minIndexToOverflowCorrect = cycleSize + MAX(maxDist, cycleSize); + U32 const minIndexToOverflowCorrect = cycleSize + + MAX(maxDist, cycleSize) + + ZSTD_WINDOW_START_INDEX; /* Adjust the min index to backoff the overflow correction frequency, * so we don't waste too much CPU in overflow correction. If this @@ -1057,10 +1059,14 @@ MEM_STATIC U32 ZSTD_window_correctOverflow(ZSTD_window_t* window, U32 cycleLog, U32 const cycleSize = 1u << cycleLog; U32 const cycleMask = cycleSize - 1; U32 const curr = (U32)((BYTE const*)src - window->base); - U32 const currentCycle0 = curr & cycleMask; - /* Exclude zero so that newCurrent - maxDist >= 1. */ - U32 const currentCycle1 = currentCycle0 == 0 ? cycleSize : currentCycle0; - U32 const newCurrent = currentCycle1 + MAX(maxDist, cycleSize); + U32 const currentCycle = curr & cycleMask; + /* Ensure newCurrent - maxDist >= ZSTD_WINDOW_START_INDEX. */ + U32 const currentCycleCorrection = currentCycle < ZSTD_WINDOW_START_INDEX + ? MAX(cycleSize, ZSTD_WINDOW_START_INDEX) + : 0; + U32 const newCurrent = currentCycle + + currentCycleCorrection + + MAX(maxDist, cycleSize); U32 const correction = curr - newCurrent; /* maxDist must be a power of two so that: * (newCurrent & cycleMask) == (curr & cycleMask) @@ -1076,14 +1082,20 @@ MEM_STATIC U32 ZSTD_window_correctOverflow(ZSTD_window_t* window, U32 cycleLog, window->base += correction; window->dictBase += correction; - if (window->lowLimit <= correction) window->lowLimit = 1; - else window->lowLimit -= correction; - if (window->dictLimit <= correction) window->dictLimit = 1; - else window->dictLimit -= correction; + if (window->lowLimit < correction + ZSTD_WINDOW_START_INDEX) { + window->lowLimit = ZSTD_WINDOW_START_INDEX; + } else { + window->lowLimit -= correction; + } + if (window->dictLimit < correction + ZSTD_WINDOW_START_INDEX) { + window->dictLimit = ZSTD_WINDOW_START_INDEX; + } else { + window->dictLimit -= correction; + } /* Ensure we can still reference the full window. */ assert(newCurrent >= maxDist); - assert(newCurrent - maxDist >= 1); + assert(newCurrent - maxDist >= ZSTD_WINDOW_START_INDEX); /* Ensure that lowLimit and dictLimit didn't underflow. */ assert(window->lowLimit <= newCurrent); assert(window->dictLimit <= newCurrent);