regex: fixes and optimizations (#7431)

vlib/regex/README.md

@@ -475,6 +475,7 @@ pub fn new() RE
 #### **Custom initialization**
 For some particular need it is possible initialize a fully customized regex:
 ```v ignore
+pattern = r"ab(.*)(ac)"
 // init custom regex
 mut re := regex.RE{}
 re.prog = []Token    {len: pattern.len + 1} // max program length, can not be longer then the pattern

vlib/regex/regex.v

@@ -1825,9 +1825,9 @@ pub fn (mut re RE) match_base(in_txt byteptr, in_txt_len int ) (int,int) {
 			}
 
 			// manage here dot char
-			//println("Here we are, with stop: state buffer: [${state_list.len}]")
 
 			if state_list.len > 0 {
+				//println("Here we are, with stop: state buffer: [${state_list.len}]")
 				state = state_list.pop()
 
 				state.match_flag = true
@@ -1898,6 +1898,10 @@ pub fn (mut re RE) match_base(in_txt byteptr, in_txt_len int ) (int,int) {
 
 						re.groups[g_index+1] = state.i
 
+						if g_index > 0 && re.groups[g_index] <= re.groups[g_index-1] {
+							re.groups[g_index] = re.groups[g_index-1] 
+						}
+
 						if re.groups[g_index+1] >= in_txt_len {
 							//println("clamp group!")
 							re.groups[g_index+1] = in_txt_len-1
@@ -1946,6 +1950,7 @@ pub fn (mut re RE) match_base(in_txt byteptr, in_txt_len int ) (int,int) {
 				// if we are done with max go on dot char are dedicated case!!
 				if	re.prog[state.pc].rep >= re.prog[state.pc].rep_max 
 				{
+					state_list.pop()
 					m_state = .ist_next
 					continue
 				}

vlib/regex/regex_test.v

@@ -138,6 +138,9 @@ match_test_suite = [
     TestItem{"*1*1(", r"(?:^|[*()])(\d+)([*])(\d+)(?:$|[*()])",0,5},
     TestItem{" 1*1(", r"(?:^|[*()])(\d+)([*])(\d+)(?:$|[*()])",-1,0},
     TestItem{"1*1 ", r"(?:^|[*()])(\d+)([*])(\d+)(?:$|[*()])",-1,0},
+
+    // particular groups
+    TestItem{"ababababac", r"ab(.*)(ac)",0,10},
 ]
 )
 
@@ -229,6 +232,12 @@ cgroups_test_suite = [
 		[0, 3, 4, 5, 5, 7],
 		map[string]int{}
 	},
+	TestItemCGroup{
+		"ababababac",
+		r"ab(.*)(ac)",0,10,
+		[2, 8, 8, 10],
+		map[string]int{}
+	},
 ]
 )