Initialize module and dependencies

vendor/golang.org/x/vuln/internal/scan/stdlib.go

@@ -0,0 +1,71 @@
+// Copyright 2022 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package scan
+
+import (
+	"fmt"
+	"strings"
+
+	"golang.org/x/mod/semver"
+)
+
+// Support functions for standard library packages.
+// These are copied from the internal/stdlib package in the pkgsite repo.
+
+// semverToGoTag returns the Go standard library repository tag corresponding
+// to semver, a version string without the initial "v".
+// Go tags differ from standard semantic versions in a few ways,
+// such as beginning with "go" instead of "v".
+func semverToGoTag(v string) string {
+	if strings.HasPrefix(v, "v0.0.0") {
+		return "master"
+	}
+	// Special case: v1.0.0 => go1.
+	if v == "v1.0.0" {
+		return "go1"
+	}
+	if !semver.IsValid(v) {
+		return fmt.Sprintf("<!%s:invalid semver>", v)
+	}
+	goVersion := semver.Canonical(v)
+	prerelease := semver.Prerelease(goVersion)
+	versionWithoutPrerelease := strings.TrimSuffix(goVersion, prerelease)
+	patch := strings.TrimPrefix(versionWithoutPrerelease, semver.MajorMinor(goVersion)+".")
+	if patch == "0" {
+		versionWithoutPrerelease = strings.TrimSuffix(versionWithoutPrerelease, ".0")
+	}
+	goVersion = fmt.Sprintf("go%s", strings.TrimPrefix(versionWithoutPrerelease, "v"))
+	if prerelease != "" {
+		// Go prereleases look like  "beta1" instead of "beta.1".
+		// "beta1" is bad for sorting (since beta10 comes before beta9), so
+		// require the dot form.
+		i := finalDigitsIndex(prerelease)
+		if i >= 1 {
+			if prerelease[i-1] != '.' {
+				return fmt.Sprintf("<!%s:final digits in a prerelease must follow a period>", v)
+			}
+			// Remove the dot.
+			prerelease = prerelease[:i-1] + prerelease[i:]
+		}
+		goVersion += strings.TrimPrefix(prerelease, "-")
+	}
+	return goVersion
+}
+
+// finalDigitsIndex returns the index of the first digit in the sequence of digits ending s.
+// If s doesn't end in digits, it returns -1.
+func finalDigitsIndex(s string) int {
+	// Assume ASCII (since the semver package does anyway).
+	var i int
+	for i = len(s) - 1; i >= 0; i-- {
+		if s[i] < '0' || s[i] > '9' {
+			break
+		}
+	}
+	if i == len(s)-1 {
+		return -1
+	}
+	return i + 1
+}