From 05d9726805969ff155e8a029579113f05529ea82 Mon Sep 17 00:00:00 2001
From: Pieter Wuille <pieter.wuille@gmail.com>
Date: Sat, 27 Oct 2012 22:01:38 +0200
Subject: [PATCH] LoadExternalBlockFile switched to CBufferedFile

---
 src/main.cpp | 65 ++++++++++++++++++++--------------------------------
 1 file changed, 25 insertions(+), 40 deletions(-)

diff --git a/src/main.cpp b/src/main.cpp
index a08e393caa..7a9a32a626 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -2493,55 +2493,40 @@ bool LoadExternalBlockFile(FILE* fileIn)
 
     int nLoaded = 0;
     {
-        try {
-            CAutoFile blkdat(fileIn, SER_DISK, CLIENT_VERSION);
-            unsigned int nPos = 0;
-            while (nPos != (unsigned int)-1 && blkdat.good() && !fRequestShutdown)
-            {
-                unsigned char pchData[65536];
-                do {
-                    fseek(blkdat, nPos, SEEK_SET);
-                    int nRead = fread(pchData, 1, sizeof(pchData), blkdat);
-                    if (nRead <= 8)
-                    {
-                        nPos = (unsigned int)-1;
-                        break;
-                    }
-                    void* nFind = memchr(pchData, pchMessageStart[0], nRead+1-sizeof(pchMessageStart));
-                    if (nFind)
-                    {
-                        if (memcmp(nFind, pchMessageStart, sizeof(pchMessageStart))==0)
-                        {
-                            nPos += ((unsigned char*)nFind - pchData) + sizeof(pchMessageStart);
-                            break;
-                        }
-                        nPos += ((unsigned char*)nFind - pchData) + 1;
-                    }
-                    else
-                        nPos += sizeof(pchData) - sizeof(pchMessageStart) + 1;
-                } while(!fRequestShutdown);
-                if (nPos == (unsigned int)-1)
-                    break;
-                fseek(blkdat, nPos, SEEK_SET);
+        CBufferedFile blkdat(fileIn, 2*MAX_BLOCK_SIZE, MAX_BLOCK_SIZE+8, SER_DISK, CLIENT_VERSION);
+        uint64 nRewind = blkdat.GetPos();
+        while (blkdat.good() && !blkdat.eof() && !fShutdown) {
+            blkdat.SetPos(nRewind);
+            nRewind++; // start one byte further next time, in case of failure
+            blkdat.SetLimit(); // remove former limit
+            try {
+                // locate a header
+                unsigned char buf[4];
+                blkdat.FindByte(pchMessageStart[0]);
+                nRewind = blkdat.GetPos()+1;
+                blkdat >> FLATDATA(buf);
+                if (memcmp(buf, pchMessageStart, 4))
+                    continue;
+                // read size
                 unsigned int nSize;
                 blkdat >> nSize;
-                if (nSize > 0 && nSize <= MAX_BLOCK_SIZE)
+                if (nSize < 80 || nSize > MAX_BLOCK_SIZE)
+                    continue;
+                // read block
+                blkdat.SetLimit(blkdat.GetPos() + nSize);
+                CBlock block;
+                blkdat >> block;
+                nRewind = blkdat.GetPos();
                 {
-                    CBlock block;
-                    blkdat >> block;
                     LOCK(cs_main);
                     if (ProcessBlock(NULL,&block))
-                    {
                         nLoaded++;
-                        nPos += 4 + nSize;
-                    }
                 }
+            } catch (std::exception &e) {
+                printf("%s() : Deserialize or I/O error caught during load\n", __PRETTY_FUNCTION__);
             }
         }
-        catch (std::exception &e) {
-            printf("%s() : Deserialize or I/O error caught during load\n",
-                   __PRETTY_FUNCTION__);
-        }
+        fclose(fileIn);
     }
     printf("Loaded %i blocks from external file in %"PRI64d"ms\n", nLoaded, GetTimeMillis() - nStart);
     return nLoaded > 0;