2 files changed, 47 insertions, 19 deletions

diff --git a/apt-pkg/acquire-item.cc b/apt-pkg/acquire-item.cc
index 208b84c64..136393359 100644
--- a/apt-pkg/acquire-item.cc
+++ b/apt-pkg/acquire-item.cc
@@ -2616,9 +2616,10 @@ std::string pkgAcqIndexDiffs::Custom600Headers() const			/*{{{*/
    if(State != StateApplyDiff)
       return pkgAcqBaseIndex::Custom600Headers();
    std::ostringstream patchhashes;
-   HashStringList const ExpectedHashes = available_patches[0].patch_hashes;
-   for (HashStringList::const_iterator hs = ExpectedHashes.begin(); hs != ExpectedHashes.end(); ++hs)
-      patchhashes <<  "\nPatch-0-" << hs->HashType() << "-Hash: " << hs->HashValue();
+   for (auto && hs : available_patches[0].result_hashes)
+      patchhashes <<  "\nStart-" << hs.HashType() << "-Hash: " << hs.HashValue();
+   for (auto && hs : available_patches[0].patch_hashes)
+      patchhashes <<  "\nPatch-0-" << hs.HashType() << "-Hash: " << hs.HashValue();
    patchhashes << pkgAcqBaseIndex::Custom600Headers();
    return patchhashes.str();
 }
@@ -2765,6 +2766,8 @@ std::string pkgAcqIndexMergeDiffs::Custom600Headers() const		/*{{{*/
       return pkgAcqBaseIndex::Custom600Headers();
    std::ostringstream patchhashes;
    unsigned int seen_patches = 0;
+   for (auto && hs : (*allPatches)[0]->patch.result_hashes)
+      patchhashes <<  "\nStart-" << hs.HashType() << "-Hash: " << hs.HashValue();
    for (std::vector<pkgAcqIndexMergeDiffs *>::const_iterator I = allPatches->begin();
 	 I != allPatches->end(); ++I)
    {
diff --git a/methods/rred.cc b/methods/rred.cc
index 51af37557..678509844 100644
--- a/methods/rred.cc
+++ b/methods/rred.cc
@@ -335,26 +335,30 @@ class Patch {
    FileChanges filechanges;
    MemBlock add_text;
 
-   static bool retry_fwrite(char *b, size_t l, FileFd &f, Hashes *hash)
+   static bool retry_fwrite(char *b, size_t l, FileFd &f, Hashes * const start_hash, Hashes * const end_hash = nullptr)
    {
       if (f.Write(b, l) == false)
 	 return false;
-      if (hash)
-	 hash->Add((unsigned char*)b, l);
+      if (start_hash)
+	 start_hash->Add((unsigned char*)b, l);
+      if (end_hash)
+	 end_hash->Add((unsigned char*)b, l);
       return true;
    }
 
-   static void dump_rest(FileFd &o, FileFd &i, Hashes *hash)
+   static void dump_rest(FileFd &o, FileFd &i,
+	 Hashes * const start_hash, Hashes * const end_hash)
    {
       char buffer[BLOCK_SIZE];
       unsigned long long l = 0;
       while (i.Read(buffer, sizeof(buffer), &l)) {
-	 if (l ==0  || !retry_fwrite(buffer, l, o, hash))
+	 if (l ==0  || !retry_fwrite(buffer, l, o, start_hash, end_hash))
 	    break;
       }
    }
 
-   static void dump_lines(FileFd &o, FileFd &i, size_t n, Hashes *hash)
+   static void dump_lines(FileFd &o, FileFd &i, size_t n,
+	 Hashes * const start_hash, Hashes * const end_hash)
    {
       char buffer[BLOCK_SIZE];
       while (n > 0) {
@@ -363,11 +367,11 @@ class Patch {
 	 size_t const l = strlen(buffer);
 	 if (l == 0 || buffer[l-1] == '\n')
 	    n--;
-	 retry_fwrite(buffer, l, o, hash);
+	 retry_fwrite(buffer, l, o, start_hash, end_hash);
       }
    }
 
-   static void skip_lines(FileFd &i, int n)
+   static void skip_lines(FileFd &i, int n, Hashes * const start_hash)
    {
       char buffer[BLOCK_SIZE];
       while (n > 0) {
@@ -376,6 +380,8 @@ class Patch {
 	 size_t const l = strlen(buffer);
 	 if (l == 0 || buffer[l-1] == '\n')
 	    n--;
+	 if (start_hash)
+	    start_hash->Add((unsigned char*)buffer, l);
       }
    }
 
@@ -525,15 +531,16 @@ class Patch {
       }
    }
 
-   void apply_against_file(FileFd &out, FileFd &in, Hashes *hash = NULL)
+   void apply_against_file(FileFd &out, FileFd &in,
+	 Hashes * const start_hash = nullptr, Hashes * const end_hash = nullptr)
    {
       std::list<struct Change>::iterator ch;
       for (ch = filechanges.begin(); ch != filechanges.end(); ++ch) {
-	 dump_lines(out, in, ch->offset, hash);
-	 skip_lines(in, ch->del_cnt);
-	 dump_mem(out, ch->add, ch->add_len, hash);
+	 dump_lines(out, in, ch->offset, start_hash, end_hash);
+	 skip_lines(in, ch->del_cnt, start_hash);
+	 dump_mem(out, ch->add, ch->add_len, end_hash);
       }
-      dump_rest(out, in, hash);
+      dump_rest(out, in, start_hash, end_hash);
       out.Flush();
    }
 };
@@ -581,6 +588,16 @@ class RredMethod : public aptMethod {
 	 std::vector<PDiffFile> patchfiles;
 	 Patch patch;
 
+	 HashStringList StartHashes;
+	 for (char const * const * type = HashString::SupportedHashes(); *type != nullptr; ++type)
+	 {
+	    std::string tagname;
+	    strprintf(tagname, "Start-%s-Hash", *type);
+	    std::string const hashsum = LookupTag(Message, tagname.c_str());
+	    if (hashsum.empty() == false)
+	       StartHashes.push_back(HashString(*type, hashsum));
+	 }
+
 	 if (FileExists(Path + ".ed") == true)
 	 {
 	    HashStringList const ExpectedHashes = ReadExpectedHashesForPatch(0, Message);
@@ -653,8 +670,16 @@ class RredMethod : public aptMethod {
 	    return _error->Error("Failed to open out %s", Itm->DestFile.c_str());
 	 }
 
-	 Hashes hash(Itm->ExpectedHashes);
-	 patch.apply_against_file(out, inp, &hash);
+	 Hashes end_hash(Itm->ExpectedHashes);
+	 if (StartHashes.usable())
+	 {
+	    Hashes start_hash(StartHashes);
+	    patch.apply_against_file(out, inp, &start_hash, &end_hash);
+	    if (start_hash.GetHashStringList() != StartHashes)
+	       _error->Error("The input file hadn't the expected hash!");
+	 }
+	 else
+	    patch.apply_against_file(out, inp, nullptr, &end_hash);
 
 	 out.Close();
 	 inp.Close();
@@ -685,7 +710,7 @@ class RredMethod : public aptMethod {
 
 	 Res.LastModified = bufbase.st_mtime;
 	 Res.Size = bufbase.st_size;
-	 Res.TakeHashes(hash);
+	 Res.TakeHashes(end_hash);
 	 URIDone(Res);
 
 	 return true;