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Refactor String model class #119

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merged 3 commits into from
Jul 23, 2018
Merged

Refactor String model class #119

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9fad766
Add support for JEP 254: Compact Strings
gayanW Jul 23, 2018
ed880f4
Update String#contentEquals(java.lang.CharSequence)
gayanW Jul 23, 2018
0d80f08
Fix invalid assignments of java.lang.String#hash
gayanW Jul 23, 2018
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73 changes: 51 additions & 22 deletions src/classes/modules/java.base/java/lang/String.java
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Original file line number Diff line number Diff line change
Expand Up @@ -63,6 +63,10 @@ public final class String

private static final long serialVersionUID = -6849794470754667710L;

static final boolean COMPACT_STRINGS;
static {
COMPACT_STRINGS = true;
}

private static final ObjectStreamField[] serialPersistentFields =
new ObjectStreamField[0];
Expand Down Expand Up @@ -90,7 +94,6 @@ public String(char value[], int offset, int count) {
String proxy=init(value,offset,count);
this.value=proxy.value;
this.coder=proxy.coder;
this.hash=proxy.hash;
}

private native String init(char[] value, int offset, int count);
Expand All @@ -99,7 +102,6 @@ public String(int[] codePoints, int offset, int count) {
String proxy=init(codePoints,offset,count);
this.value=proxy.value;
this.coder=proxy.coder;
this.hash=proxy.hash;
}

private native String init(int[] codePoints, int offset, int count);
Expand All @@ -109,7 +111,6 @@ public String(byte ascii[], int hibyte, int offset, int count) {
String proxy=init(ascii,hibyte,offset,count);
this.value=proxy.value;
this.coder=proxy.coder;
this.hash=proxy.hash;
}

private native String init(byte ascii[], int hibyte, int offset, int count);
Expand All @@ -125,7 +126,6 @@ public String(byte bytes[], int offset, int length, String charsetName){
String proxy=init(bytes,offset,length,charsetName);
this.value=proxy.value;
this.coder=proxy.coder;
this.hash=proxy.hash;
}

private native String init(byte bytes[], int offset, int length, String charsetName);
Expand Down Expand Up @@ -189,17 +189,18 @@ public String(StringBuilder x) {
if (len == 0) {
this.value = "".value;
this.coder = "".coder;
} else {
return;
}
if (COMPACT_STRINGS) {
byte[] val = StringUTF16.compress(value, off, len);
if (val != null) {
this.value = val;
this.coder = LATIN1;
return;
}

this.coder = UTF16;
this.value = StringUTF16.toBytes(value, off, len);
}
this.coder = UTF16;
this.value = StringUTF16.toBytes(value, off, len);
}

@Deprecated
Expand Down Expand Up @@ -234,11 +235,8 @@ native public byte[] getBytes(String charsetName)
throws UnsupportedEncodingException;

public byte[] getBytes(Charset x){
// No Charset model.
if (x == null){
throw new NullPointerException();
}
return StringCoding.encode(x, this.coder, this.value);
if (x == null) throw new NullPointerException();
return StringCoding.encode(x, coder(), value);
}

native public byte[] getBytes();
Expand All @@ -251,6 +249,26 @@ public boolean contentEquals(StringBuffer stringBuffer){
}
}

private boolean nonSyncContentEquals(AbstractStringBuilder abstractStringBuilder) {
int len = length();
if (len != abstractStringBuilder.length()) {
return false;
}
byte v1[] = value;
byte v2[] = abstractStringBuilder.getValue();
if (coder() == abstractStringBuilder.getCoder()) {
int n = v1.length;
for (int i = 0; i < n; i++) {
if (v1[i] != v2[i]) {
return false;
}
}
} else {
return isLatin1() && StringUTF16.contentEquals(v1, v2, len);
}
return true;
}

native static boolean equals0 (char[] a, char[] b, int len);

/**
Expand All @@ -262,21 +280,28 @@ public boolean contentEquals (CharSequence charSequence){
return false;
}

// that should be the common case (String)
if (charSequence.equals(this)){
return true;
// cs is a String
if (charSequence instanceof String) {
return equals(charSequence);
}

// we can do that natively, too
// cs is a StringBuffer, or StringBuilder
if (charSequence instanceof AbstractStringBuilder) {
byte[] val = ((AbstractStringBuilder) charSequence).getValue();
byte coder = ((AbstractStringBuilder) charSequence).getCoder();
assert coder == UTF16 : "Currently only UTF16 is supported for String comparision with an instance of type AbstractStringBuilder";
return StringUTF16.contentEquals(this.value, val, this.length());
if (charSequence instanceof StringBuffer) {
synchronized (charSequence) {
return nonSyncContentEquals((AbstractStringBuilder) charSequence);
}
} else {
return nonSyncContentEquals((AbstractStringBuilder) charSequence);
}
}

// generic CharSequence - expensive
int n = charSequence.length();
if (n != length()) {
return false;
}

byte[] val = this.value;
if (isLatin1()) {
for (int i = 0; i < n; i++) {
Expand Down Expand Up @@ -401,8 +426,12 @@ public static String valueOf(char character) {
native public static String valueOf(double d);
public native String intern();

byte coder() {
return COMPACT_STRINGS ? coder : UTF16;
}

private boolean isLatin1() {
return this.coder == LATIN1;
return COMPACT_STRINGS && coder == LATIN1;
}

/*
Expand Down