From f54c168031a2a9b63c0cbf61fb06fc8d4e40841b Mon Sep 17 00:00:00 2001
From: Yorick van Pelt <yorick@yorickvanpelt.nl>
Date: Sat, 7 Dec 2019 23:10:27 +0700
Subject: [PATCH] add wrapper function around libarchive to c++ errors

---
 src/libutil/tarfile.cc | 48 ++++++++++++++++++++----------------------
 1 file changed, 23 insertions(+), 25 deletions(-)

diff --git a/src/libutil/tarfile.cc b/src/libutil/tarfile.cc
index 6c3fb4634..8e2f7c8cb 100644
--- a/src/libutil/tarfile.cc
+++ b/src/libutil/tarfile.cc
@@ -18,6 +18,14 @@ std::shared_ptr<struct archive> archive_read_ptr() {
             archive_read_free(p);
         });
 }
+static void ac(std::shared_ptr<struct archive> a, int r, const char* str = "archive is corrupt (%s)") {
+    if (r == ARCHIVE_EOF) {
+        throw EndOfFile("tar ended");
+    }
+    if (r != ARCHIVE_OK) {
+        throw Error(str, archive_error_string(a.get()));
+    }
+}
 void archive_read_open_source(std::shared_ptr<struct archive> a, Source& s, unsigned int bufsize = 1024) {
     std::shared_ptr<unsigned char> buffer((unsigned char*)malloc(bufsize), [](auto p) { free(p); });
     typedef struct {
@@ -26,7 +34,7 @@ void archive_read_open_source(std::shared_ptr<struct archive> a, Source& s, unsi
         unsigned int bs;
     } St;
     St* state = new St({buffer, s, bufsize});
-    if (archive_read_open(a.get(), state,
+    ac(a, archive_read_open(a.get(), state,
             NULL /* open */,
             ([] (struct archive*, void* sptr, const void** buf) -> long int {
                  St& s = *(static_cast<St*>(sptr));
@@ -40,9 +48,7 @@ void archive_read_open_source(std::shared_ptr<struct archive> a, Source& s, unsi
              }), [] (struct archive*, void* sptr) {
                      delete static_cast<St*>(sptr);
                      return ARCHIVE_OK;
-                 })) {
-        throw Error("archive is corrupt (%s)", archive_error_string(a.get()));
-    }
+                 }));
 }
 std::shared_ptr<struct archive> archive_write_ptr() {
     return std::shared_ptr<struct archive>(archive_write_disk_new(),
@@ -53,28 +59,27 @@ std::shared_ptr<struct archive> archive_write_ptr() {
 }
 static void copy_data(std::shared_ptr<struct archive> ar, std::shared_ptr<struct archive> aw)
 {
-  int r;
   const void *buff;
   size_t size;
   la_int64_t offset;
 
   for (;;) {
-      r = archive_read_data_block(ar.get(), &buff, &size, &offset);
-      if (r == ARCHIVE_EOF) return;
-      if (r != ARCHIVE_OK) {
-          throw Error("archive is corrupt (%s)", archive_error_string(ar.get()));
-      }
-      r = archive_write_data_block(aw.get(), buff, size, offset);
-      if (r != ARCHIVE_OK) {
-          throw Error("could not write archive output (%s)", archive_error_string(aw.get()));
+      try {
+          ac(ar, archive_read_data_block(ar.get(), &buff, &size, &offset));
+      } catch (EndOfFile &) {
+          return;
       }
+      ac(aw, archive_write_data_block(aw.get(), buff, size, offset), "could not write archive output (%s)");
   }
 }
-
 static void extract_archive(std::shared_ptr<struct archive> a, const Path & destDir) {
     char * cwd = getcwd(0, 0);
     if (!cwd) throw SysError("getting current directory");
-    Finally freeCwd([&]() { chdir(cwd); free(cwd); });
+    Finally backCwd([&]() {
+                        int r = chdir(cwd);
+                        free(cwd);
+                        if (r != 0) throw SysError("resetting directory after archive extraction");
+                    });
     int r = chdir(destDir.c_str());
     if (r != 0) throw SysError("setting directory to tar output path");
     struct archive_entry *entry;
@@ -90,16 +95,12 @@ static void extract_archive(std::shared_ptr<struct archive> a, const Path & dest
         if (r == ARCHIVE_WARN) {
             std::cerr << "warning: " << archive_error_string(a.get());
         } else if (r < ARCHIVE_WARN) {
-            throw Error("archive is corrupt (%s)", archive_error_string(a.get()));
-        }
-        r = archive_write_header(ext.get(), entry);
-        if (r != ARCHIVE_OK) {
-            throw Error("could not write archive output (%s)", archive_error_string(ext.get()));
+            ac(a, r);
         }
+        ac(ext, archive_write_header(ext.get(), entry), "could not write archive output (%s)");
         copy_data(a, ext);
         archive_write_finish_entry(ext.get());
     }
-    //if (r != 0) throw SysError("resetting directory after archive extraction");
 }
 void unpackTarfile(Source & source, const Path & destDir)
 {
@@ -115,10 +116,7 @@ void unpackTarfile(const Path & tarFile, const Path & destDir)
     auto a = archive_read_ptr();
     archive_read_support_filter_all(a.get());
     archive_read_support_format_all(a.get());
-    int r = archive_read_open_filename(a.get(), tarFile.c_str(), 16384);
-    if (r != ARCHIVE_OK) {
-        throw Error("archive is corrupt (%s)", archive_error_string(a.get()));
-    }
+    ac(a, archive_read_open_filename(a.get(), tarFile.c_str(), 16384));
     createDirs(destDir);
     extract_archive(a, destDir);
 }