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Make MimeMap final and introduce MimeMap.Builder.

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This CL topic introduces a new @CorePlatformApi MimeMap.Builder
and uses it to make MimeMap a concrete, final, immutable type.

This has the following advantages:

 - Consistency of behavior of MimeMap implementations with regards
   to lower-casing and treatment of null is trivial to guarantee
   because there is only one implementation.
 - The @CorePlatformApi surface now makes more sense. The responsibility
   for lower-casing and treatment of null was previously split between
   MimeMap in libcore and  MimeMapImpl in frameworks/base, which is why
   MimeMap.toLowerCase() and MimeMap.isNullOrEmpty() were in the
   @CorePlatformApi.
 - Most of the logic now lives in libcore / ART module.
   frameworks/base now has minimal logic. This makes it easier to write
   (in a follow-up CL) a CTS test that asserts all the default mappings,
   because that test can now duplicate that small amount of logic in
   order to read from a copy of the same data files.

Note: The semantics of the @CorePlatformApi Builder.put(String, List<String>)
are fairly complex, which isn't great. This was done because:
 - By following the semantics of the *mime.types file format, it allows
   us to minimize the logic in frameworks/base.
 - It's simpler than having multiple overloads of put() for
   mimeType -> file extension mapping and vice versa,
   and for whether or not any existing mapping should be overwritten.
   If we had named classes for MimeType and FileExtension with
   appropriate case-insensitive equals and hashCode semantics, then
   we could instead have API such as
      builder.asMimeToExtensionMap().put(...)
   but existing API (e.g. Intent.getType(), android.webkit.MimeTypeMap)
   has set precedent for treating these as Strings.

Bug: 136256059
Test: atest CtsLibcoreTestCases
Test: atest CtsMimeMapTestCases

Change-Id: I9a185a689745726dd79b15117892001461fa4a0d
This commit is contained in:
Tobias Thierer
2019-08-20 15:23:34 +01:00
parent 878c77b704
commit fd9657d032
1 changed files with 11 additions and 127 deletions
Download Patch File Download Diff File Expand all files Collapse all files

138
mime/java/android/content/type/MimeMapImpl.java
View File

@@ -21,10 +21,8 @@ import libcore.net.MimeMap;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.regex.Pattern;
/**
@@ -36,96 +34,27 @@ import java.util.regex.Pattern;
*
* @hide
*/
public class MimeMapImpl extends MimeMap {
public class MimeMapImpl {
/**
* Creates and returns a new {@link MimeMapImpl} instance that implements.
* Android's default mapping between MIME types and extensions.
*/
public static MimeMapImpl createDefaultInstance() {
public static MimeMap createDefaultInstance() {
return parseFromResources("/mime.types", "/android.mime.types");
}
private static final Pattern SPLIT_PATTERN = Pattern.compile("\\s+");
/**
* Note: These maps only contain lowercase keys/values, regarded as the
* {@link #toLowerCase(String) canonical form}.
*
* <p>This is the case for both extensions and MIME types. The mime.types
* data file contains examples of mixed-case MIME types, but some applications
* use the lowercase version of these same types. RFC 2045 section 2 states
* that MIME types are case insensitive.
*/
private final Map<String, String> mMimeTypeToExtension;
private final Map<String, String> mExtensionToMimeType;
public MimeMapImpl(Map<String, String> mimeTypeToExtension,
Map<String, String> extensionToMimeType) {
this.mMimeTypeToExtension = new HashMap<>(mimeTypeToExtension);
for (Map.Entry<String, String> entry : mimeTypeToExtension.entrySet()) {
checkValidMimeType(entry.getKey());
checkValidExtension(entry.getValue());
}
this.mExtensionToMimeType = new HashMap<>(extensionToMimeType);
for (Map.Entry<String, String> entry : extensionToMimeType.entrySet()) {
checkValidExtension(entry.getKey());
checkValidMimeType(entry.getValue());
}
}
private static void checkValidMimeType(String s) {
if (MimeMap.isNullOrEmpty(s) || !s.equals(MimeMap.toLowerCase(s))) {
throw new IllegalArgumentException("Invalid MIME type: " + s);
}
}
private static void checkValidExtension(String s) {
if (MimeMap.isNullOrEmpty(s) || !s.equals(MimeMap.toLowerCase(s))) {
throw new IllegalArgumentException("Invalid extension: " + s);
}
}
static MimeMapImpl parseFromResources(String... resourceNames) {
Map<String, String> mimeTypeToExtension = new HashMap<>();
Map<String, String> extensionToMimeType = new HashMap<>();
static MimeMap parseFromResources(String... resourceNames) {
MimeMap.Builder builder = MimeMap.builder();
for (String resourceName : resourceNames) {
parseTypes(mimeTypeToExtension, extensionToMimeType, resourceName);
parseTypes(builder, resourceName);
}
return new MimeMapImpl(mimeTypeToExtension, extensionToMimeType);
return builder.build();
}
/**
* An element of a *mime.types file: A MIME type or an extension, with an optional
* prefix of "?" (if not overriding an earlier value).
*/
private static class Element {
public final boolean keepExisting;
public final String s;
Element(boolean keepExisting, String value) {
this.keepExisting = keepExisting;
this.s = toLowerCase(value);
if (value.isEmpty()) {
throw new IllegalArgumentException();
}
}
public String toString() {
return keepExisting ? ("?" + s) : s;
}
}
private static String maybePut(Map<String, String> map, Element keyElement, String value) {
if (keyElement.keepExisting) {
return map.putIfAbsent(keyElement.s, value);
} else {
return map.put(keyElement.s, value);
}
}
private static void parseTypes(Map<String, String> mimeTypeToExtension,
Map<String, String> extensionToMimeType, String resource) {
private static void parseTypes(MimeMap.Builder builder, String resource) {
try (BufferedReader r = new BufferedReader(
new InputStreamReader(MimeMapImpl.class.getResourceAsStream(resource)))) {
String line;
@@ -135,60 +64,15 @@ public class MimeMapImpl extends MimeMap {
line = line.substring(0, commentPos);
}
line = line.trim();
// The first time a MIME type is encountered it is mapped to the first extension
// listed in its line. The first time an extension is encountered it is mapped
// to the MIME type.
//
// When encountering a previously seen MIME type or extension, then by default
// the later ones override earlier mappings (put() semantics); however if a MIME
// type or extension is prefixed with '?' then any earlier mapping _from_ that
// MIME type / extension is kept (putIfAbsent() semantics).
final String[] split = SPLIT_PATTERN.split(line);
if (split.length <= 1) {
// Need mimeType + at least one extension to make a mapping.
// "mime.types" files may also contain lines with just a mimeType without
// an extension but we skip them as they provide no mapping info.
if (line.isEmpty()) {
continue;
}
List<Element> lineElements = new ArrayList<>(split.length);
for (String s : split) {
boolean keepExisting = s.startsWith("?");
if (keepExisting) {
s = s.substring(1);
}
if (s.isEmpty()) {
throw new IllegalArgumentException("Invalid entry in '" + line + "'");
}
lineElements.add(new Element(keepExisting, s));
}
// MIME type -> first extension (one mapping)
// This will override any earlier mapping from this MIME type to another
// extension, unless this MIME type was prefixed with '?'.
Element mimeElement = lineElements.get(0);
List<Element> extensionElements = lineElements.subList(1, lineElements.size());
String firstExtension = extensionElements.get(0).s;
maybePut(mimeTypeToExtension, mimeElement, firstExtension);
// extension -> MIME type (one or more mappings).
// This will override any earlier mapping from this extension to another
// MIME type, unless this extension was prefixed with '?'.
for (Element extensionElement : extensionElements) {
maybePut(extensionToMimeType, extensionElement, mimeElement.s);
}
List<String> specs = Arrays.asList(SPLIT_PATTERN.split(line));
builder.put(specs.get(0), specs.subList(1, specs.size()));
}
} catch (IOException | RuntimeException e) {
throw new RuntimeException("Failed to parse " + resource, e);
}
}
@Override
protected String guessExtensionFromLowerCaseMimeType(String mimeType) {
return mMimeTypeToExtension.get(mimeType);
}
@Override
protected String guessMimeTypeFromLowerCaseExtension(String extension) {
return mExtensionToMimeType.get(extension);
}
}