1 files changed, 121 insertions, 0 deletions
diff --git a/bpkg/host-os-release.cxx b/bpkg/host-os-release.cxx
new file mode 100644
index 0000000..1a5a980
--- /dev/null
+++ b/bpkg/host-os-release.cxx
@@ -0,0 +1,121 @@
+// file      : bpkg/host-os-release.cxx -*- C++ -*-
+// license   : MIT; see accompanying LICENSE file
+
+#include <bpkg/host-os-release.hxx>
+
+#include <libbutl/string-parser.hxx> // parse_quoted()
+
+#include <bpkg/diagnostics.hxx>
+
+using namespace butl;
+
+namespace bpkg
+{
+  // Note: not static for access from the unit test.
+  //
+  os_release
+  host_os_release_linux (path f = {})
+  {
+    os_release r;
+
+    // According to os-release(5), we should use /etc/os-release and fallback
+    // to /usr/lib/os-release if the former does not exist. It also lists the
+    // fallback values for individual variables, in case some are not present.
+    //
+    if (!f.empty ()
+        ? exists (f)
+        : (exists (f = path ("/etc/os-release")) ||
+           exists (f = path ("/usr/lib/os-release"))))
+    {
+      try
+      {
+        ifdstream ifs (f, ifdstream::badbit);
+
+        string l;
+        for (uint64_t ln (1); !eof (getline (ifs, l)); ++ln)
+        {
+          trim (l);
+
+          // Skip blanks lines and comments.
+          //
+          if (l.empty () || l[0] == '#')
+            continue;
+
+          // The variable assignments are in the "shell style" and so can be
+          // quoted/escaped. For now we only handle quoting, which is what all
+          // the instances seen in the wild seems to use.
+          //
+          size_t p (l.find ('='));
+          if (p == string::npos)
+            continue;
+
+          string n (l, 0, p);
+          l.erase (0, p + 1);
+
+          using string_parser::parse_quoted;
+          using string_parser::invalid_string;
+
+          try
+          {
+            if (n == "ID_LIKE")
+            {
+              r.like_ids.clear ();
+
+              vector<string> vs (parse_quoted (l, true /* unquote */));
+              for (const string& v: vs)
+              {
+                for (size_t b (0), e (0); next_word (v, b, e); )
+                {
+                  r.like_ids.push_back (string (v, b, e - b));
+                }
+              }
+            }
+            else if (string* p = (n == "ID"               ?  &r.name_id :
+                                  n == "VERSION_ID"       ?  &r.version_id :
+                                  n == "VARIANT_ID"       ?  &r.variant_id :
+                                  n == "NAME"             ?  &r.name :
+                                  n == "VERSION_CODENAME" ?  &r.version_codename :
+                                  n == "VARIANT"          ?  &r.variant :
+                                  nullptr))
+            {
+              vector<string> vs (parse_quoted (l, true /* unquote */));
+              switch (vs.size ())
+              {
+              case 0:  *p =  ""; break;
+              case 1:  *p = move (vs.front ()); break;
+              default: throw invalid_string (0, "multiple values");
+              }
+            }
+          }
+          catch (const invalid_string& e)
+          {
+            location loc (move (f).string (), ln);
+            fail (loc) << "invalid " << n << " value: " << e;
+          }
+        }
+
+        ifs.close ();
+      }
+      catch (const io_error& e)
+      {
+        fail << "unable to read from " << f << ": " << e;
+      }
+    }
+
+    // Assign fallback values.
+    //
+    if (r.name_id.empty ()) r.name_id = "linux";
+    if (r.name.empty ())    r.name    = "Linux";
+
+    return r;
+  }
+
+  optional<os_release>
+  host_os_release (const target_triplet& host)
+  {
+    if (host.class_ == "linux")
+      return host_os_release_linux ();
+    else
+      return nullopt;
+  }
+}