util: CBufferedFile fixes

1 files changed, 13 insertions, 11 deletions

diff --git a/src/streams.h b/src/streams.h
index 4e600f1826..517eefc932 100644
--- a/src/streams.h
+++ b/src/streams.h
@@ -735,16 +735,17 @@ protected:
         size_t nBytes = fread((void*)&vchBuf[pos], 1, readNow, src);
         if (nBytes == 0) {
             throw std::ios_base::failure(feof(src) ? "CBufferedFile::Fill: end of file" : "CBufferedFile::Fill: fread failed");
-        } else {
-            nSrcPos += nBytes;
-            return true;
         }
+        nSrcPos += nBytes;
+        return true;
     }
 
 public:
     CBufferedFile(FILE *fileIn, uint64_t nBufSize, uint64_t nRewindIn, int nTypeIn, int nVersionIn) :
         nType(nTypeIn), nVersion(nVersionIn), nSrcPos(0), nReadPos(0), nReadLimit(std::numeric_limits<uint64_t>::max()), nRewind(nRewindIn), vchBuf(nBufSize, 0)
     {
+        if (nRewindIn >= nBufSize)
+            throw std::ios_base::failure("Rewind limit must be less than buffer size");
         src = fileIn;
     }
 
@@ -777,8 +778,6 @@ public:
     void read(char *pch, size_t nSize) {
         if (nSize + nReadPos > nReadLimit)
             throw std::ios_base::failure("Read attempted past buffer limit");
-        if (nSize + nRewind > vchBuf.size())
-            throw std::ios_base::failure("Read larger than buffer size");
         while (nSize > 0) {
             if (nReadPos == nSrcPos)
                 Fill();
@@ -802,16 +801,19 @@ public:
 
     //! rewind to a given reading position
     bool SetPos(uint64_t nPos) {
-        nReadPos = nPos;
-        if (nReadPos + nRewind < nSrcPos) {
-            nReadPos = nSrcPos - nRewind;
+        size_t bufsize = vchBuf.size();
+        if (nPos + bufsize < nSrcPos) {
+            // rewinding too far, rewind as far as possible
+            nReadPos = nSrcPos - bufsize;
             return false;
-        } else if (nReadPos > nSrcPos) {
+        }
+        if (nPos > nSrcPos) {
+            // can't go this far forward, go as far as possible
             nReadPos = nSrcPos;
             return false;
-        } else {
-            return true;
         }
+        nReadPos = nPos;
+        return true;
     }
 
     bool Seek(uint64_t nPos) {