fully implemented the complile and match methods, written some tests for this

Signed-off-by: Lachlan Roberts <lachlan@webtide.com>
This commit is contained in:
Lachlan Roberts 2018-03-07 10:10:50 +11:00
parent 1b3ad11ef9
commit f68cf85e94
2 changed files with 69 additions and 31 deletions

View File

@ -22,45 +22,28 @@ public class SearchPattern
{
static final int alphabetSize = 256;
int[] table;
private String pattern;
byte[] pattern;
public int[] getTable(){ return this.table; }
/**
* @param pattern The pattern to search for.
* @return A Pattern instance for the search pattern
*/
static SearchPattern compile(String pattern)
static SearchPattern compile(byte[] pattern)
{
//Create new SearchPattern instance
SearchPattern sp = new SearchPattern();
sp.pattern = pattern;
//Copy in the Pattern
sp.pattern = pattern.clone();
/*
Build up pre-processed table for this pattern.
function preprocess(pattern):
T new table of 256 integers
for i from 0 to 256 exclusive
T[i] length(pattern)
for i from 0 to length(pattern) - 1 exclusive
T[pattern[i]] length(pattern) - 1 - i
return T
*/
//Build up the pre-processed table for this pattern.
sp.table = new int[alphabetSize];
for(int i = 0; i<sp.table.length; ++i){
sp.table[i] = pattern.length();
}
/*
for i from 0 to length(pattern) - 1 exclusive
T[pattern[i]] length(pattern) - 1 - i
*/
for(int i = 0; i<pattern.length(); ++i){
int index = pattern;
sp.table[index] = pattern.length()-1-i;
}
for(int i = 0; i<sp.table.length; ++i)
sp.table[i] = sp.pattern.length;
for(int i = 0; i<sp.pattern.length-1; ++i)
sp.table[sp.pattern[i]] = sp.pattern.length-1-i;
return sp;
}
@ -76,6 +59,15 @@ public class SearchPattern
*/
public int match(byte[] data, int offset, int length)
{
int skip = offset;
while((skip <= data.length - pattern.length) && (skip+pattern.length <= offset+length))
{
for(int i = pattern.length-1; data[skip+i] == pattern[i]; i--)
if(i==0) return skip;
skip += table[data[skip + pattern.length - 1]];
}
return -1;
}

View File

@ -27,10 +27,56 @@ public class SearchPatternTest
{
@Test
public void test()
public void testBasicSearch()
{
Assert.assertTrue(SearchPattern.compile("lol") == null);
System.out.println("Hello World!");
String p1 = "truth";
String p2 = "evident";
String p3 = "we";
String d = "we hold these truths to be self evident";
// Testing Compiled Pattern p1 "truth"
SearchPattern sp1 = SearchPattern.compile(p1.getBytes());
Assert.assertEquals(14,sp1.match(d.getBytes(), 0, d.length()));
Assert.assertEquals(14,sp1.match(d.getBytes(),14,p1.length()));
Assert.assertEquals(14,sp1.match(d.getBytes(),14,p1.length()+1));
Assert.assertEquals(-1,sp1.match(d.getBytes(),14,p1.length()-1));
Assert.assertEquals(-1,sp1.match(d.getBytes(),15,d.length()));
// Testing Compiled Pattern p2 "evident"
SearchPattern sp2 = SearchPattern.compile(p2.getBytes());
Assert.assertEquals(32,sp2.match(d.getBytes(), 0, d.length()));
Assert.assertEquals(32,sp2.match(d.getBytes(),32,p2.length()));
Assert.assertEquals(32,sp2.match(d.getBytes(),32,p2.length()+1));
Assert.assertEquals(-1,sp2.match(d.getBytes(),32,p2.length()-1));
Assert.assertEquals(-1,sp2.match(d.getBytes(),33,d.length()));
// Testing Compiled Pattern p3 "evident"
SearchPattern sp3 = SearchPattern.compile(p3.getBytes());
Assert.assertEquals( 0,sp3.match(d.getBytes(), 0, d.length()));
Assert.assertEquals( 0,sp3.match(d.getBytes(), 0, p3.length()));
Assert.assertEquals( 0,sp3.match(d.getBytes(), 0, p3.length()+1));
Assert.assertEquals(-1,sp3.match(d.getBytes(), 0, p3.length()-1));
Assert.assertEquals(-1,sp3.match(d.getBytes(), 1, d.length()));
}
@Test
public void testDoubleMatch()
{
String p = "violent";
String d = "These violent delights have violent ends.";
// Testing Compiled Pattern p1 "truth"
SearchPattern sp = SearchPattern.compile(p.getBytes());
Assert.assertEquals( 6,sp.match(d.getBytes(), 0, d.length()));
Assert.assertEquals(-1,sp.match(d.getBytes(), 6, p.length()-1));
Assert.assertEquals(28,sp.match(d.getBytes(), 7, d.length()));
Assert.assertEquals(28,sp.match(d.getBytes(), 28, d.length()));
Assert.assertEquals(-1,sp.match(d.getBytes(), 29, d.length()));
}
}