solver3: Use zstd-compressed, base64-encoded dumps

Store the solver dumps with zstd compression and base64-encode
them in the crash report; such that they take up significantly
less space and can fit in cassandra's schema.

Base64 is wrapped at 76 characters as the base64 tool does. Do
some magic std::string_view conversion to avoid string copies
for the substr() used to get 76 characters at a time.

Note we can rely on substr(i, 76) to handle less than 76 characters
just fine; it uses std::min(76, size() - i) characters.

2 files changed, 16 insertions, 99 deletions

diff --git a/apt-private/private-install.cc b/apt-private/private-install.cc
index e3d176ffe..cf92f91ad 100644
--- a/apt-private/private-install.cc
+++ b/apt-private/private-install.cc
@@ -89,7 +89,7 @@ bool CheckNothingBroken(CacheFile &Cache)
 // ---------------------------------------------------------------------
 static void WriteApportReport(pkgCacheFile &Cache, std::string &title, std::vector<std::string> const &errors, int mode, bool distUpgrade)
 {
-   auto dumpfile = flCombine(_config->FindDir("Dir::Log"), "edsp.log");
+   auto dumpfile = flCombine(_config->FindDir("Dir::Log"), "edsp.log.zst");
    auto crashfile = flCombine(_config->FindDir("Dir::Apport", "/var/crash"), "apt-edsp." + std::to_string(getuid()) + ".crash");
    auto apt = Cache->FindPkg("apt");
    if (access(flNotFile(dumpfile).c_str(), W_OK) != 0 || access(flNotFile(crashfile).c_str(), W_OK) != 0)
@@ -97,7 +97,8 @@ static void WriteApportReport(pkgCacheFile &Cache, std::string &title, std::vect
    OpTextProgress Progress(*_config);
    Progress.OverallProgress(0, 100, 50, _("Writing error report"));
    FileFd edspDump(dumpfile,
-		   FileFd::Exclusive | FileFd::Create | FileFd::WriteOnly | FileFd::BufferedWrite);
+		   FileFd::Exclusive | FileFd::Create | FileFd::WriteOnly | FileFd::BufferedWrite,
+		   FileFd::Extension);
    int edspFlags = 0;
    if (mode || distUpgrade)
       edspFlags |= EDSP::Request::UPGRADE_ALL;
@@ -127,10 +128,18 @@ static void WriteApportReport(pkgCacheFile &Cache, std::string &title, std::vect
    for (auto &error : errors)
       crash << " " << error << "\n";
 
-   crash << "AptSolverDump:\n";
    std::ifstream toCopy(edspDump.Name());
-   for (std::string line; std::getline(toCopy, line);)
-      crash << " " << line << "\n";
+   std::ostringstream readStream;
+   readStream << toCopy.rdbuf();
+   const auto base64 = Base64Encode(readStream.str());
+   if (not base64.empty())
+   {
+      crash << "AptSolverDump:\n";
+      // Print the base64, with line wrapping, indented by one space; substr(i, 76)
+      // returns at most 76 characters or as many as are left.
+      for (size_t i=0; i < base64.size(); i += 76)
+	 crash << " " << std::string_view{base64}.substr(i, 76) << "\n";
+   }
    crash.close();
 }
 
diff --git a/test/integration/test-solver3-evaluation b/test/integration/test-solver3-evaluation
index a873d5b21..b05e7cb9b 100755
--- a/test/integration/test-solver3-evaluation
+++ b/test/integration/test-solver3-evaluation
@@ -32,99 +32,7 @@ Title: Failure: The 3.0 solver produced a worse result
 SourcePackage: apt
 ErrorMessage:
 AptSolverDump:
- Request: EDSP 0.5
- Architecture: amd64
- Architectures: amd64
- Machine-ID: 912e43bd1c1d4ba481f9f8ccab25f9ee
- Install: x:amd64 y:amd64
- Solver: internal
- 
- Package: a
- Architecture: all
- Version: 3
- APT-ID: 2
- Source: a
- Source-Version: 3
- Priority: optional
- Section: other
- Size: 42
- APT-Release:
-  a=unstable,n=sid,c=main,b=all
- APT-Pin: 500
- APT-Candidate: yes
- Depends: c
- 
- Package: b
- Architecture: all
- Version: 3
- APT-ID: 3
- Source: b
- Source-Version: 3
- Priority: optional
- Section: other
- Size: 42
- APT-Release:
-  a=unstable,n=sid,c=main,b=all
- APT-Pin: 500
- APT-Candidate: yes
- 
- Package: c
- Architecture: all
- Version: 3
- APT-ID: 4
- Source: c
- Source-Version: 3
- Priority: optional
- Section: other
- Size: 42
- APT-Release:
-  a=unstable,n=sid,c=main,b=all
- APT-Pin: 500
- APT-Candidate: yes
- 
- Package: x
- Architecture: all
- Version: 3
- APT-ID: 0
- Source: x
- Source-Version: 3
- Priority: optional
- Section: other
- Size: 42
- APT-Release:
-  a=unstable,n=sid,c=main,b=all
- APT-Pin: 500
- APT-Candidate: yes
- Depends: a | b
- 
- Package: y
- Architecture: all
- Version: 3
- APT-ID: 1
- Source: y
- Source-Version: 3
- Priority: optional
- Section: other
- Size: 42
- APT-Release:
-  a=unstable,n=sid,c=main,b=all
- APT-Pin: 500
- APT-Candidate: yes
- Depends: b | a
- 
- Package: apport
- Architecture: all
- Version: 3
- APT-ID: 6
- Source: apport
- Source-Version: 3
- Priority: optional
- Section: other
- Installed: yes
- APT-Pin: 100
- APT-Candidate: yes
- " cat rootdir/var/crash/apt-edsp.$(id -u).crash
-
+$(cat rootdir/var/log/apt/edsp.log.zst | base64 | sed 's#^# #')" cat rootdir/var/crash/apt-edsp.$(id -u).crash
 
 testsuccessequal "Request: EDSP 0.5
 Architecture: amd64
@@ -217,7 +125,7 @@ Section: other
 Installed: yes
 APT-Pin: 100
 APT-Candidate: yes
-" cat rootdir/var/log/apt/edsp.log
+" apthelper cat-file rootdir/var/log/apt/edsp.log.zst
 
 testfailureequal "Reading package lists...
 Building dependency tree...