add nqp::eqat to jvm and parrot.

src/vm/jvm/QAST/Compiler.nqp

@@ -2094,6 +2094,7 @@ QAST::OperationsJAST.add_core_op('substr', -> $qastcomp, $op {
         !! QAST::Op.new( :op('substr3'), |@operands ));
 });
 
+QAST::OperationsJAST.map_classlib_core_op('eqat', $TYPE_OPS, 'string_equal_at', [$RT_STR, $RT_STR, $RT_INT], $RT_INT);
 # ord can be on a the first char in a string or at a particular char.
 QAST::OperationsJAST.map_classlib_core_op('ordfirst', $TYPE_OPS, 'ordfirst', [$RT_STR], $RT_INT);
 QAST::OperationsJAST.map_classlib_core_op('ordat',    $TYPE_OPS, 'ordat',    [$RT_STR, $RT_INT], $RT_INT);

src/vm/jvm/runtime/org/perl6/nqp/runtime/Ops.java

@@ -3095,6 +3095,23 @@ public static String substr3(String val, long offset, long length) {
         return val.substring((int)offset, end);
     }
 
+    // does a have b as a substring at offset?
+    public static long string_equal_at(String haystack, String needle, long offset) {
+        long haylen = haystack.length();
+        long needlelen = needle.length();
+
+        if (offset < 0) {
+            offset += haylen;
+            if (offset < 0) {
+                offset = 0;
+            }
+        }
+        if (haylen - offset < needlelen) {
+            return 0;
+        }
+        return haystack.regionMatches((int)offset, needle, 0, (int)needlelen) ? 1 : 0;
+    }
+
     public static long ordfirst(String str) {
         return str.codePointAt(0);
     }

src/vm/parrot/QAST/Operations.nqp

@@ -1983,6 +1983,8 @@ QAST::Operations.add_core_op('substr', :inlinable(1), -> $qastcomp, $op {
         !! QAST::Op.new( :op('substr3'), |@operands ));
 });
 
+QAST::Operations.add_core_pirop_mapping('eqat', 'nqp_string_equal_at', 'Issi', :inlinable(1));
+
 # ord can be on a the first char in a string or at a particular char.
 QAST::Operations.add_core_pirop_mapping('ordfirst', 'ord', 'Is', :inlinable(1));
 QAST::Operations.add_core_pirop_mapping('ordat', 'ord', 'Isi', :inlinable(1));

src/vm/parrot/ops/nqp.ops

@@ -3246,8 +3246,6 @@ inline op is_uprop(out INT, in STR, in STR, in INT) :base_core {
     goto ADDRESS(handler);
 #endif
 }
-
-
 /*
 
 =item nqp_serialize_sc
@@ -3941,3 +3939,49 @@ inline op nqp_decode(out STR, invar PMC, in STR) {
     if (elems > 0)
         free(cbuffer);
 }
+
+/*
+
+=item nqp_string_equal_at
+
+Check if the String in $2 has the string in $3 at its offset $4.
+
+=cut
+
+*/
+inline op nqp_string_equal_at(out INT, in STR, in STR, in INT) {
+    int32_t offset;
+    uint32_t cmp_index;
+    char done;
+
+    String_iter hay_iter;
+    String_iter needle_iter;
+
+    offset = (INTVAL)($4);
+
+    if (offset < 0) {
+        offset += ($2)->strlen;
+        if (offset < 0) {
+            offset = 0;
+        }
+    }
+
+    if (($2)->strlen - offset < ($3)->strlen || offset > ($2)->strlen) {
+        $1 = 0;
+    } else {
+        done = 0;
+        $1 = 1;
+
+        STRING_ITER_INIT(interp, &hay_iter);
+        STRING_iter_skip(interp, $2, &hay_iter, offset);
+        STRING_ITER_INIT(interp, &needle_iter);
+
+        for (cmp_index = 0; cmp_index < $3->strlen && !done; cmp_index++) {
+            if (STRING_iter_get_and_advance(interp, $2, &hay_iter)
+                    != STRING_iter_get_and_advance(interp, $3, &needle_iter)) {
+                $1 = 0;
+                done = 1;
+            }
+        }
+    }
+}