Fix case of various components (#164)

* Fix case of various components

There were places in the code where code was duplicated or could return
different results based on the locale. Duplicate code was moved to new
methods. The locale-specic lowercase method were replaced by
an ASCII-specific lowecase method.

* fix: resolve merge conflict

* fix: code readability

---------

Co-authored-by: Jeremy Long <jeremy.long@gmail.com>

Author: dwalluck

src/main/java/com/github/packageurl/PackageURL.java

@@ -94,7 +94,7 @@ public PackageURL(final String type, final String name) throws MalformedPackageU
     public PackageURL(final String type, final String namespace, final String name, final String version,
                       final TreeMap<String, String> qualifiers, final String subpath)
             throws MalformedPackageURLException {
-        this.type = validateType(type);
+        this.type = toLowerCase(validateType(type));
         this.namespace = validateNamespace(namespace);
         this.name = validateName(name);
         this.version = validateVersion(version);
@@ -246,16 +246,19 @@ private String validateType(final String value) throws MalformedPackageURLExcept
         if (value == null || value.isEmpty()) {
             throw new MalformedPackageURLException("The PackageURL type cannot be null or empty");
         }
-        if (value.charAt(0) >= '0' && value.charAt(0) <= '9') {
+
+        if (isDigit(value.charAt(0))) {
             throw new MalformedPackageURLException("The PackageURL type cannot start with a number");
         }
-        final String retVal = value.toLowerCase();
-        if (retVal.chars().anyMatch(c -> !(c == '.' || c == '+' || c == '-'
-                || (c >= 'a' && c <= 'z')
-                || (c >= '0' && c <= '9')))) {
+
+        if (!value.chars().allMatch(c -> (c == '.' || c == '+' || c == '-'
+                || isUpperCase(c)
+                || isLowerCase(c)
+                || isDigit(c)))) {
             throw new MalformedPackageURLException("The PackageURL type contains invalid characters");
         }
-        return retVal;
+
+        return value;
     }
 
     private String validateNamespace(final String value) throws MalformedPackageURLException {
@@ -270,15 +273,14 @@ private String validateNamespace(final String[] values) throws MalformedPackageU
             return null;
         }
         final String tempNamespace = validatePath(values, false);
-
         String retVal;
         switch (type) {
             case StandardTypes.BITBUCKET:
             case StandardTypes.DEBIAN:
             case StandardTypes.GITHUB:
             case StandardTypes.GOLANG:
             case StandardTypes.RPM:
-                retVal = tempNamespace.toLowerCase();
+                retVal = tempNamespace != null ? toLowerCase(tempNamespace) : null;
                 break;
             default:
                 retVal = tempNamespace;
@@ -297,10 +299,10 @@ private String validateName(final String value) throws MalformedPackageURLExcept
             case StandardTypes.DEBIAN:
             case StandardTypes.GITHUB:
             case StandardTypes.GOLANG:
-                temp = value.toLowerCase();
+                temp = toLowerCase(value);
                 break;
             case StandardTypes.PYPI:
-                temp = value.replaceAll("_", "-").toLowerCase();
+                temp = toLowerCase(value).replace('_', '-');
                 break;
             default:
                 temp = value;
@@ -330,16 +332,15 @@ private Map<String, String> validateQualifiers(final Map<String, String> values)
         return values;
     }
 
-    private String validateKey(final String value) throws MalformedPackageURLException {
+    private void validateKey(final String value) throws MalformedPackageURLException {
         if (value == null || value.isEmpty()) {
             throw new MalformedPackageURLException("Qualifier key is invalid: " + value);
         }
-        final String retValue = value.toLowerCase();
-        if ((value.charAt(0) >= '0' && value.charAt(0) <= '9')
-                || !value.chars().allMatch(c -> (c >= 'a' && c <= 'z') || (c >= '0' && c <= '9') || c == '.' || c == '-' || c == '_')) {
+
+        if (isDigit(value.charAt(0))
+                || !value.chars().allMatch(c -> isLowerCase(c) || (isDigit(c)) || c == '.' || c == '-' || c == '_')) {
             throw new MalformedPackageURLException("Qualifier key is invalid: " + value);
         }
-        return retValue;
     }
 
     private String validatePath(final String value, final boolean isSubpath) throws MalformedPackageURLException {
@@ -418,7 +419,7 @@ private String canonicalize(boolean coordinatesOnly) {
             if (qualifiers != null && qualifiers.size() > 0) {
                 purl.append("?");
                 qualifiers.entrySet().stream().forEachOrdered((entry) -> {
-                    purl.append(entry.getKey().toLowerCase());
+                    purl.append(toLowerCase(entry.getKey()));
                     purl.append("=");
                     purl.append(percentEncode(entry.getValue()));
                     purl.append("&");
@@ -466,13 +467,56 @@ private static boolean isUnreserved(int c) {
     }
 
     private static boolean isAlpha(int c) {
-        return ((c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z'));
+        return (isLowerCase(c) || isUpperCase(c));
     }
 
     private static boolean isDigit(int c) {
         return (c >= '0' && c <= '9');
     }
 
+    private static boolean isUpperCase(int c) {
+        return (c >= 'A' && c <= 'Z');
+    }
+
+    private static int indexOfFirstUpperCaseChar(String s) {
+        int length = s.length();
+
+        for (int i = 0; i < length; i++) {
+            if (isUpperCase(s.charAt(i))) {
+                return i;
+            }
+        }
+
+        return -1;
+    }
+
+    private static boolean isLowerCase(int c) {
+        return (c >= 'a' && c <= 'z');
+    }
+
+    private static int toLowerCase(int c) {
+        return (c ^ 0x20);
+    }
+
+    private static String toLowerCase(String s) {
+        int pos = indexOfFirstUpperCaseChar(s);
+
+        if (pos == -1) {
+            return s;
+        }
+
+        char[] chars = s.toCharArray();
+        int length = chars.length;
+
+        for (int i = pos; i < length; i++) {
+            if (isUpperCase(chars[i])) {
+                chars[i] = (char) toLowerCase(chars[i]);
+            }
+        }
+
+        return new String(chars);
+    }
+
     /**
      * Optionally decodes a String, if it's encoded. If String is not encoded,
      * method will return the original input value.
@@ -571,7 +615,8 @@ private void parse(final String purl) throws MalformedPackageURLException {
             if (index <= start) {
                 throw new MalformedPackageURLException("Invalid purl: does not contain both a type and name");
             }
-            this.type = validateType(remainder.substring(start, index).toLowerCase());
+            this.type = toLowerCase(validateType(remainder.substring(start, index)));
+
             start = index + 1;
 
             // version is optional - check for existence
@@ -619,8 +664,9 @@ private Map<String, String> parseQualifiers(final String encodedString) throws M
                             (map, value) -> {
                                 final String[] entry = value.split("=", 2);
                                 if (entry.length == 2 && !entry[1].isEmpty()) {
-                                    if (map.put(entry[0].toLowerCase(), percentDecode(entry[1])) != null) {
-                                        throw new ValidationException("Duplicate package qualifier encountere - more then one value was specified for " + entry[0].toLowerCase());
+                                    String key = toLowerCase(entry[0]);
+                                    if (map.put(key, percentDecode(entry[1])) != null) {
+                                        throw new ValidationException("Duplicate package qualifier encountered. More then one value was specified for " + key);
                                     }
                                 }
                             },