From 38483fe7a7933049ec353744a3aa961fb608b214 Mon Sep 17 00:00:00 2001
From: Vladislav Sovrasov <sovrasov.vlad@gmail.com>
Date: Tue, 1 Nov 2016 12:24:30 +0300
Subject: [PATCH 1/2] Skip UTF-8 BOM in FileStorage

---
 modules/core/src/persistence.cpp | 17 +++++++++++++++--
 modules/core/test/test_io.cpp    | 22 ++++++++++++++++++++++
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/modules/core/src/persistence.cpp b/modules/core/src/persistence.cpp
index a1c843dc52..8cb7ec2aba 100644
--- a/modules/core/src/persistence.cpp
+++ b/modules/core/src/persistence.cpp
@@ -96,6 +96,15 @@ static inline bool cv_isspace(char c)
     return (9 <= c && c <= 13) || c == ' ';
 }
 
+static inline char* cv_skip_BOM(char* ptr)
+{
+    if((uchar)ptr[0] == 0xef && (uchar)ptr[1] == 0xbb && (uchar)ptr[2] == 0xbf) //UTF-8 BOM
+    {
+      return ptr + 3;
+    }
+    return ptr;
+}
+
 static char* icv_itoa( int _val, char* buffer, int /*radix*/ )
 {
     const int radix = 10;
@@ -4399,10 +4408,13 @@ cvOpenFileStorage( const char* query, CvMemStorage* dststorage, int flags, const
         const char* json_signature = "{";
         char buf[16];
         icvGets( fs, buf, sizeof(buf)-2 );
+        char* bufPtr = cv_skip_BOM(buf);
+        size_t bufOffset = bufPtr - buf;
+
         fs->fmt
-            = strncmp( buf, yaml_signature, strlen(yaml_signature) ) == 0
+            = strncmp( bufPtr, yaml_signature, strlen(yaml_signature) ) == 0
             ? CV_STORAGE_FORMAT_YAML
-            : strncmp( buf, json_signature, strlen(json_signature) ) == 0
+            : strncmp( bufPtr, json_signature, strlen(json_signature) ) == 0
             ? CV_STORAGE_FORMAT_JSON
             : CV_STORAGE_FORMAT_XML
             ;
@@ -4420,6 +4432,7 @@ cvOpenFileStorage( const char* query, CvMemStorage* dststorage, int flags, const
             buf_size = MAX( buf_size, (size_t)(CV_FS_MAX_LEN*2 + 1024) );
         }
         icvRewind(fs);
+        fs->strbufpos = bufOffset;
 
         fs->str_hash = cvCreateMap( 0, sizeof(CvStringHash),
                         sizeof(CvStringHashNode), fs->memstorage, 256 );
diff --git a/modules/core/test/test_io.cpp b/modules/core/test/test_io.cpp
index 75953e10ac..34915cc6ef 100644
--- a/modules/core/test/test_io.cpp
+++ b/modules/core/test/test_io.cpp
@@ -928,3 +928,25 @@ TEST(Core_InputOutput, filestorage_json_comment)
 
     EXPECT_EQ(str, String("value"));
 }
+
+TEST(Core_InputOutput, filestorage_utf8_bom)
+{
+    EXPECT_NO_THROW(
+    {
+        String content ="\xEF\xBB\xBF<?xml version=\"1.0\"?>\n<opencv_storage>\n</opencv_storage>\n";
+        cv::FileStorage fs(content, cv::FileStorage::READ | cv::FileStorage::MEMORY);
+        fs.release();
+    });
+    EXPECT_NO_THROW(
+    {
+        String content ="\xEF\xBB\xBF%YAML:1.0\n";
+        cv::FileStorage fs(content, cv::FileStorage::READ | cv::FileStorage::MEMORY);
+        fs.release();
+    });
+    EXPECT_NO_THROW(
+    {
+        String content ="\xEF\xBB\xBF{\n}\n";
+        cv::FileStorage fs(content, cv::FileStorage::READ | cv::FileStorage::MEMORY);
+        fs.release();
+    });
+}

From e955d17c51b0b7375739e57fcf83b90f2f400d4f Mon Sep 17 00:00:00 2001
From: Vladislav Sovrasov <sovrasov.vlad@gmail.com>
Date: Wed, 2 Nov 2016 14:53:04 +0300
Subject: [PATCH 2/2] Add new error messages

---
 modules/core/src/persistence.cpp | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/modules/core/src/persistence.cpp b/modules/core/src/persistence.cpp
index 8cb7ec2aba..eacdcc5ef5 100644
--- a/modules/core/src/persistence.cpp
+++ b/modules/core/src/persistence.cpp
@@ -4406,18 +4406,22 @@ cvOpenFileStorage( const char* query, CvMemStorage* dststorage, int flags, const
         size_t buf_size = 1 << 20;
         const char* yaml_signature = "%YAML";
         const char* json_signature = "{";
+        const char* xml_signature  = "<?xml";
         char buf[16];
         icvGets( fs, buf, sizeof(buf)-2 );
         char* bufPtr = cv_skip_BOM(buf);
         size_t bufOffset = bufPtr - buf;
 
-        fs->fmt
-            = strncmp( bufPtr, yaml_signature, strlen(yaml_signature) ) == 0
-            ? CV_STORAGE_FORMAT_YAML
-            : strncmp( bufPtr, json_signature, strlen(json_signature) ) == 0
-            ? CV_STORAGE_FORMAT_JSON
-            : CV_STORAGE_FORMAT_XML
-            ;
+        if(strncmp( bufPtr, yaml_signature, strlen(yaml_signature) ) == 0)
+            fs->fmt = CV_STORAGE_FORMAT_YAML;
+        else if(strncmp( bufPtr, json_signature, strlen(json_signature) ) == 0)
+            fs->fmt = CV_STORAGE_FORMAT_JSON;
+        else if(strncmp( bufPtr, xml_signature, strlen(xml_signature) ) == 0)
+            fs->fmt = CV_STORAGE_FORMAT_XML;
+        else if(fs->strbufsize  == bufOffset)
+            CV_Error(CV_BADARG_ERR, "Input file is empty");
+        else
+            CV_Error(CV_BADARG_ERR, "Unsupported file storage format");
 
         if( !isGZ )
         {