1 files changed, 8 insertions, 19 deletions
diff --git a/src/mongo/db/update/path_support.cpp b/src/mongo/db/update/path_support.cpp
index 73a7b5528db..4f33006444b 100644
--- a/src/mongo/db/update/path_support.cpp
+++ b/src/mongo/db/update/path_support.cpp
@@ -34,6 +34,7 @@
 #include "mongo/bson/mutable/element.h"
 #include "mongo/util/assert_util.h"
 #include "mongo/util/mongoutils/str.h"
+#include "mongo/util/stringutils.h"
 
 namespace mongo {
 namespace pathsupport {
@@ -69,19 +70,6 @@ Status maybePadTo(mutablebson::Element* elemArray, size_t sizeRequired) {
 
 }  // unnamed namespace
 
-bool isNumericPathComponent(StringData str, size_t* num) {
-    size_t res = 0;
-    for (size_t i = 0; i < str.size(); ++i) {
-        if (str[i] < '0' || str[i] > '9') {
-            return false;
-        } else {
-            res = res * 10 + (str[i] - '0');
-        }
-    }
-    *num = res;
-    return true;
-}
-
 Status findLongestPrefix(const FieldRef& prefix,
                          mutablebson::Element root,
                          size_t* idxFound,
@@ -97,7 +85,7 @@ Status findLongestPrefix(const FieldRef& prefix,
     mutablebson::Element curr = root;
     mutablebson::Element prev = root;
     size_t i = 0;
-    size_t numericPart = 0;
+    boost::optional<size_t> numericPart;
     bool viable = true;
     for (; i < prefixSize; i++) {
         // If prefix wants to reach 'curr' by applying a non-numeric index to an array
@@ -111,10 +99,11 @@ Status findLongestPrefix(const FieldRef& prefix,
                 break;
 
             case Array:
-                if (!isNumericPathComponent(prefixPart, &numericPart)) {
+                numericPart = parseUnsignedBase10Integer(prefixPart);
+                if (!numericPart) {
                     viable = false;
                 } else {
-                    curr = prev[numericPart];
+                    curr = prev[*numericPart];
                 }
                 break;
 
@@ -184,8 +173,8 @@ StatusWith<mutablebson::Element> createPathAt(const FieldRef& prefix,
     size_t i = idxFound;
     bool inArray = false;
     if (elemFound.getType() == mongo::Array) {
-        size_t newIdx = 0;
-        if (!isNumericPathComponent(prefix.getPart(idxFound), &newIdx)) {
+        boost::optional<size_t> newIdx = parseUnsignedBase10Integer(prefix.getPart(idxFound));
+        if (!newIdx) {
             return Status(ErrorCodes::PathNotViable,
                           str::stream() << "Cannot create field '" << prefix.getPart(idxFound)
                                         << "' in element {"
@@ -193,7 +182,7 @@ StatusWith<mutablebson::Element> createPathAt(const FieldRef& prefix,
                                         << "}");
         }
 
-        status = maybePadTo(&elemFound, newIdx);
+        status = maybePadTo(&elemFound, *newIdx);
         if (!status.isOK()) {
             return status;
         }