Added examples (#29)

Closes #27 

Signed-off-by: Steve Winslow <swinslow@gmail.com>

1 files changed, 117 insertions, 0 deletions

diff --git a/examples/3-build/example_build.go b/examples/3-build/example_build.go
new file mode 100644
index 0000000..5ddafdd
--- /dev/null
+++ b/examples/3-build/example_build.go
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
+
+// Example for: *builder*, *tvsaver*
+
+// This example demonstrates building an 'empty' SPDX document in memory that
+// corresponds to a given directory's contents, including all files with their
+// hashes and the package's verification code, and saving the document to disk.
+
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/swinslow/spdx-go/v0/builder"
+	"github.com/swinslow/spdx-go/v0/tvsaver"
+)
+
+func main() {
+
+	// check that we've received the right number of arguments
+	args := os.Args
+	if len(args) != 4 {
+		fmt.Printf("Usage: %v <package-name> <package-root-dir> <spdx-file-out>\n", args[0])
+		fmt.Printf("  Build a SPDX 2.1 document with one package called <package-name>;\n")
+		fmt.Printf("  create files with hashes corresponding to the files in <package-root-dir>;\n")
+		fmt.Printf("  and save it out as a tag-value file to <spdx-file-out>.\n")
+		return
+	}
+
+	// get the command-line arguments
+	packageName := args[1]
+	packageRootDir := args[2]
+	fileOut := args[3]
+
+	// to use the SPDX builder package, the first step is to define a
+	// builder.Config2_1 struct. this config data can be reused, in case you
+	// are building SPDX documents for several directories in sequence.
+	config := &builder.Config2_1{
+
+		// NamespacePrefix is a prefix that will be used to populate the
+		// mandatory DocumentNamespace field in the Creation Info section.
+		// Because it needs to be unique, the value that will be filled in
+		// for the document will have the package name and verification code
+		// appended to this prefix.
+		NamespacePrefix: "https://example.com/whatever/testdata-",
+
+		// CreatorType will be used for the first part of the Creator field
+		// in the Creation Info section. Per the SPDX spec, it can be
+		// "Person", "Organization" or "Tool".
+		CreatorType: "Person",
+
+		// Creator will be used for the second part of the Creator field in
+		// the Creation Info section.
+		Creator: "Jane Doe",
+
+		// note that builder will also add the following, in addition to the
+		// Creator defined above:
+		// Creator: Tool: github.com/swinslow/spdx-go/v0/builder
+
+		// Finally, you can define one or more paths that should be ignored
+		// when walking through the directory. This is intended to omit files
+		// that are located within the package's directory, but which should
+		// be omitted from the SPDX document.
+		PathsIgnored: []string{
+
+			// ignore all files in the .git/ directory at the package root
+			"/.git/",
+
+			// ignore all files in all __pycache__/ directories, anywhere
+			// within the package directory tree
+			"**/__pycache__/",
+
+			// ignore the file with this specific path relative to the
+			// package root
+			"/.ignorefile",
+
+			// or ignore all files with this filename, anywhere within the
+			// package directory tree
+			"**/.DS_Store",
+		},
+	}
+
+	// now, when we actually ask builder to walk through a directory and
+	// build an SPDX document, we need to give it three things:
+	//   - what to name the package; and
+	//   - where the directory is located on disk; and
+	//   - the config object we just defined.
+	doc, err := builder.Build2_1(packageName, packageRootDir, config)
+	if err != nil {
+		fmt.Printf("Error while building document: %v\n", err)
+		return
+	}
+
+	// if we got here, the document has been created.
+	// all license info is marked as NOASSERTION, but file hashes and
+	// the package verification code have been filled in appropriately.
+	fmt.Printf("Successfully created document for package %s\n", packageName)
+
+	// we can now save it to disk, using tvsaver.
+
+	// create a new file for writing
+	w, err := os.Create(fileOut)
+	if err != nil {
+		fmt.Printf("Error while opening %v for writing: %v\n", fileOut, err)
+		return
+	}
+	defer w.Close()
+
+	err = tvsaver.Save2_1(doc, w)
+	if err != nil {
+		fmt.Printf("Error while saving %v: %v", fileOut, err)
+		return
+	}
+
+	fmt.Printf("Successfully saved %v\n", fileOut)
+}