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// Copyright Vespa.ai. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.slime;
/**
* A mapping from an arbitrary set of unique strings to a range of
* integers. Slime users normally won't need to use this class
* directly.
*/
final class SymbolTable {
public static final int INVALID = Integer.MAX_VALUE;
private static final int[] emptyHash = new int[1];
private int capacity = 0;
private int hashSize() { return (capacity + (capacity >> 1) - 1); }
private int used = 0;
private String[] names;
private int[] hash = emptyHash;
private final void rehash() {
if (capacity == 0) {
capacity = 32;
names = new String[capacity];
hash = new int[hashSize() + (capacity << 1)];
return;
}
capacity = (capacity << 1);
String[] n = names;
names = new String[capacity];
System.arraycopy(n, 0, names, 0, used);
hash = new int[hashSize() + (capacity << 1)];
for (int i = 0; i < used; i++) {
int prev = Math.abs(names[i].hashCode() % hashSize());
int entry = hash[prev];
while (entry != 0) {
prev = entry + 1;
entry = hash[prev];
}
final int insertIdx = (hashSize() + (i << 1));
hash[prev] = insertIdx;
hash[insertIdx] = i;
}
}
/** Return count of contained symbol names. */
final int symbols() { return used; }
/**
* Return the symbol name associated with an id.
* @param symbol the id, must be in range [0, symbols()-1]
**/
final String inspect(int symbol) { return names[symbol]; }
/**
* Add a name to the symbol table; if the name is already
* in the symbol table just returns the id it already had.
* @param name the name to insert
* @return the id now associated with the name
**/
final int insert(String name) {
if (used == capacity) {
rehash();
}
int prev = Math.abs(name.hashCode() % hashSize());
int entry = hash[prev];
while (entry != 0) {
final int sym = hash[entry];
if (names[sym].equals(name)) { // found entry
return sym;
}
prev = entry + 1;
entry = hash[prev];
}
final int insertIdx = (hashSize() + (used << 1));
hash[prev] = insertIdx;
hash[insertIdx] = used;
names[used++] = name;
return (used - 1);
}
/**
* Find the id associated with a symbol name; if the
* name was not in the symbol table returns the
* INVALID constant instead.
**/
final int lookup(String name) {
int entry = hash[Math.abs(name.hashCode() % hashSize())];
while (entry != 0) {
final int sym = hash[entry];
if (names[sym].equals(name)) { // found entry
return sym;
}
entry = hash[entry + 1];
}
return INVALID;
}
}
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