fix buggy unit test, bug in check for getDigestLength() and make it i…

…nto an assert

credit to github user @trollkarlen for finding this.

changed it to an assert since it should be caught in CI if it ever
happens.

while doing that, I detected that the unit test was not sufficient to
cover the assert.

the only consequence was that with SHA512 as checksum, an alarming output
was printed. there was no missed/false duplicate detection.

Fileinfo.cc

@@ -88,11 +88,9 @@ Fileinfo::fillwithbytes(enum readtobuffermode filltype,
     }
 
     // store the result of the checksum calculation in somebytes
-    int digestlength = chk.getDigestLength();
-    if (digestlength <= 0 ||
-        digestlength >= static_cast<int>(m_somebytes.size())) {
-      std::cerr << "wrong answer from getDigestLength! FIXME" << std::endl;
-    }
+    assert(chk.getDigestLength() > 0);
+    assert(static_cast<std::size_t>(chk.getDigestLength()) <=
+           m_somebytes.size());
     if (chk.printToBuffer(m_somebytes.data(), m_somebytes.size())) {
       std::cerr << "failed writing digest to buffer!!" << std::endl;
     }

Fileinfo.hh

@@ -194,7 +194,7 @@ private:
    */
   std::int64_t m_identity;
 
-  static const int SomeByteSize = 64;
+  static constexpr int SomeByteSize = 64;
 
   /// a buffer that will be filled with some bytes of the file or a hash
   std::array<char, SomeByteSize> m_somebytes;

testcases/checksum_options.sh

@@ -7,16 +7,37 @@ set -e
 
 
 
+allchecksumtypes="md5 sha1 sha256 sha512"
 
 
-for checksumtype in md5 sha1 sha256 sha512; do
+for checksumtype in $allchecksumtypes; do
    reset_teststate
-   dbgecho "trying checksum $checksumtype"
+   dbgecho "trying checksum $checksumtype with small files"
    echo checksumtest >a
    echo checksumtest >b
    $rdfind  -checksum $checksumtype -deleteduplicates true a b
    [ -e a ]
    [ ! -e b ]
 done
 
+for checksumtype in $allchecksumtypes; do
+   reset_teststate
+   dbgecho "trying checksum $checksumtype with large files"
+   head -c 1000000 /dev/zero >a
+   head -c 1000000 /dev/zero >b
+   $rdfind  -checksum $checksumtype -deleteduplicates true a b
+   [ -e a ]
+   [ ! -e b ]
+done
+
+for checksumtype in $allchecksumtypes; do
+   reset_teststate
+   dbgecho "trying checksum $checksumtype with large files that differ only in the middle"
+   ( head -c 1000000 /dev/zero; echo =====a=====; head -c 1000000 /dev/zero) >a
+   ( head -c 1000000 /dev/zero; echo =====b=====; head -c 1000000 /dev/zero) >b
+   $rdfind  -checksum $checksumtype -deleteduplicates true a b
+   [ -e a ]
+   [ -e b ]
+done
+
 dbgecho "all is good in this test!"