rework hashsum verification in the acquire system

Having every item having its own code to verify the file(s) it handles
is an errorprune process and easy to break, especially if items move
through various stages (download, uncompress, patching, …). With a giant
rework we centralize (most of) the verification to have a better
enforcement rate and (hopefully) less chance for bugs, but it breaks the
ABI bigtime in exchange – and as we break it anyway, it is broken even
harder.

It shouldn't effect most frontends as they don't deal with the acquire
system at all or implement their own items, but some do and will need to
be patched (might be an opportunity to use apt on-board material).

The theory is simple: Items implement methods to decide if hashes need to
be checked (in this stage) and to return the expected hashes for this
item (in this stage). The verification itself is done in worker message
passing which has the benefit that a hashsum error is now a proper error
for the acquire system rather than a Done() which is later revised to a
Failed().

1 files changed, 10 insertions, 0 deletions

diff --git a/apt-pkg/contrib/hashes.cc b/apt-pkg/contrib/hashes.cc
index 0fa443b4a..11a7e479b 100644
--- a/apt-pkg/contrib/hashes.cc
+++ b/apt-pkg/contrib/hashes.cc
@@ -23,6 +23,7 @@
 #include <stddef.h>
 #include <algorithm>
 #include <unistd.h>
+#include <stdlib.h>
 #include <string>
 #include <iostream>
 									/*}}}*/
@@ -178,6 +179,15 @@ HashString const * HashStringList::find(char const * const type) const /*{{{*/
    return NULL;
 }
 									/*}}}*/
+unsigned long long HashStringList::FileSize() const			/*{{{*/
+{
+   HashString const * const hsf = find("Checksum-FileSize");
+   if (hsf == NULL)
+      return 0;
+   std::string const hv = hsf->HashValue();
+   return strtoull(hv.c_str(), NULL, 10);
+}
+									/*}}}*/
 bool HashStringList::supported(char const * const type)			/*{{{*/
 {
    for (char const * const * t = HashString::SupportedHashes(); *t != NULL; ++t)