Add a locator for libraries

This change adds a Locator that can be used to locate libraries.
If library names are specified, the ldcache is searched otherwise
symlinks are resolved.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

internal/lookup/library.go

@@ -0,0 +1,68 @@
+/*
+# Copyright (c) 2021, NVIDIA CORPORATION.  All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+*/
+
+package lookup
+
+import (
+	"fmt"
+	"strings"
+
+	"github.com/NVIDIA/nvidia-container-toolkit/internal/ldcache"
+	log "github.com/sirupsen/logrus"
+)
+
+type library struct {
+	logger  *log.Logger
+	symlink Locator
+	cache   ldcache.LDCache
+}
+
+var _ Locator = (*library)(nil)
+
+// NewLibraryLocator creates a library locator using the specified logger.
+func NewLibraryLocator(logger *log.Logger, root string) (Locator, error) {
+	cache, err := ldcache.New(logger, root)
+	if err != nil {
+		return nil, fmt.Errorf("error loading ldcache: %v", err)
+	}
+
+	l := library{
+		symlink: NewSymlinkLocator(logger, root),
+		cache:   cache,
+	}
+
+	return &l, nil
+}
+
+// Locate finds the specified libraryname.
+// If the input is a library name, the ldcache is searched otherwise the
+// provided path is resolved as a symlink.
+func (l library) Locate(libname string) ([]string, error) {
+	if strings.Contains(libname, "/") {
+		return l.symlink.Locate(libname)
+	}
+
+	paths32, paths64 := l.cache.Lookup(libname)
+	if len(paths32) > 0 {
+		l.logger.Warnf("Ignoring 32-bit libraries for %v: %v", libname, paths32)
+	}
+
+	if len(paths64) == 0 {
+		return nil, fmt.Errorf("64-bit library %v not found", libname)
+	}
+
+	return paths64, nil
+}