From 4bb4f4c97bd1b5fc97152bc2c3b2dc3c1d9cfe32 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Wed, 8 Jan 2025 17:43:22 +0100
Subject: [PATCH] LIBERTIFF: use GDALExpandPackedBitsToByteAt0Or255() and
 GDALExpandPackedBitsToByteAt0Or1()

---
 frmts/libertiff/libertiffdataset.cpp | 64 +++-------------------------
 1 file changed, 6 insertions(+), 58 deletions(-)

diff --git a/frmts/libertiff/libertiffdataset.cpp b/frmts/libertiff/libertiffdataset.cpp
index 6e88b572423b..9bfb72ec90e4 100644
--- a/frmts/libertiff/libertiffdataset.cpp
+++ b/frmts/libertiff/libertiffdataset.cpp
@@ -1166,28 +1166,6 @@ FloatingPointHorizPredictorDecode(std::vector<uint8_t> &tmpBuffer,
     return true;
 }
 
-/************************************************************************/
-/*                     ExtractBitAndConvertTo255()                      */
-/************************************************************************/
-
-#if defined(__GNUC__) || defined(_MSC_VER)
-// Signedness of char implementation dependent, so be explicit.
-// Assumes 2-complement integer types and sign extension of right shifting
-// GCC guarantees such:
-// https://gcc.gnu.org/onlinedocs/gcc/Integers-implementation.html#Integers-implementation
-static inline GByte ExtractBitAndConvertTo255(GByte byVal, int nBit)
-{
-    return static_cast<GByte>(static_cast<signed char>(byVal << (7 - nBit)) >>
-                              7);
-}
-#else
-// Portable way
-static inline GByte ExtractBitAndConvertTo255(GByte byVal, int nBit)
-{
-    return (byVal & (1 << nBit)) ? 255 : 0;
-}
-#endif
-
 /************************************************************************/
 /*                           ReadBlock()                                */
 /************************************************************************/
@@ -1582,51 +1560,21 @@ bool LIBERTIFFDataset::ReadBlock(GByte *pabyBlockData, int nBlockXOff,
         if (m_image->bitsPerSample() == 1)
         {
             const GByte *CPL_RESTRICT pabySrc = abyDecompressedStrile.data();
-            const GByte val = m_bExpand1To255 ? 255 : 1;
             GByte *CPL_RESTRICT pabyDst = bufferForOneBitExpansion.data();
             for (int iY = 0; iY < nBlockActualYSize; ++iY)
             {
-                int iX = 0;
                 if (m_bExpand1To255)
                 {
-                    for (; iX + 7 < nBlockXSize;
-                         iX += 8, ++pabySrc, pabyDst += 8)
-                    {
-                        const GByte srcByte = *pabySrc;
-                        pabyDst[0] = ExtractBitAndConvertTo255(srcByte, 7);
-                        pabyDst[1] = ExtractBitAndConvertTo255(srcByte, 6);
-                        pabyDst[2] = ExtractBitAndConvertTo255(srcByte, 5);
-                        pabyDst[3] = ExtractBitAndConvertTo255(srcByte, 4);
-                        pabyDst[4] = ExtractBitAndConvertTo255(srcByte, 3);
-                        pabyDst[5] = ExtractBitAndConvertTo255(srcByte, 2);
-                        pabyDst[6] = ExtractBitAndConvertTo255(srcByte, 1);
-                        pabyDst[7] = ExtractBitAndConvertTo255(srcByte, 0);
-                    }
+                    GDALExpandPackedBitsToByteAt0Or255(pabySrc, pabyDst,
+                                                       nBlockXSize);
                 }
                 else
                 {
-                    for (; iX + 7 < nBlockXSize;
-                         iX += 8, ++pabySrc, pabyDst += 8)
-                    {
-                        const int srcByte = *pabySrc;
-                        pabyDst[0] = (srcByte >> 7) & 1;
-                        pabyDst[1] = (srcByte >> 6) & 1;
-                        pabyDst[2] = (srcByte >> 5) & 1;
-                        pabyDst[3] = (srcByte >> 4) & 1;
-                        pabyDst[4] = (srcByte >> 3) & 1;
-                        pabyDst[5] = (srcByte >> 2) & 1;
-                        pabyDst[6] = (srcByte >> 1) & 1;
-                        pabyDst[7] = (srcByte >> 0) & 1;
-                    }
-                }
-                if (iX < nBlockXSize)
-                {
-                    for (; iX < nBlockXSize; ++iX, ++pabyDst)
-                    {
-                        *pabyDst = (*pabySrc & (0x80 >> (iX % 8))) ? val : 0;
-                    }
-                    ++pabySrc;
+                    GDALExpandPackedBitsToByteAt0Or1(pabySrc, pabyDst,
+                                                     nBlockXSize);
                 }
+                pabySrc += (nBlockXSize + 7) / 8;
+                pabyDst += nBlockXSize;
             }
 
             std::swap(abyDecompressedStrile, bufferForOneBitExpansion);