Expose getLocationLineAndColumn() as a public API

Allows better use of the offset data returned by getStructuredErrors()

Author: martinduffy1

include/json/reader.h

@@ -395,6 +395,15 @@ bool JSON_API parseFromStream(CharReader::Factory const&, IStream&, Value* root,
  */
 JSON_API IStream& operator>>(IStream&, Value&);
 
+struct LineAndColumn {
+ int line;
+ int column;
+};
+
+/** Get the line and column of a character within a string.
+ */
+LineAndColumn JSON_API getLocationLineAndColumn(char const* beginDoc, char const* endDoc,
+                                       size_t location);
 } // namespace Json
 
 #pragma pack(pop)

src/lib_json/json_reader.cpp

@@ -767,24 +767,12 @@ Reader::Char Reader::getNextChar() {
 
 void Reader::getLocationLineAndColumn(Location location, int& line,
                                       int& column) const {
-  Location current = begin_;
-  Location lastLineStart = current;
-  line = 0;
-  while (current < location && current != end_) {
-    Char c = *current++;
-    if (c == '\r') {
-      if (*current == '\n')
-        ++current;
-      lastLineStart = current;
-      ++line;
-    } else if (c == '\n') {
-      lastLineStart = current;
-      ++line;
-    }
-  }
-  // column & line start at 1
-  column = int(location - lastLineStart) + 1;
-  ++line;
+  Json::LineAndColumn lineAndColumn =
+    Json::getLocationLineAndColumn(document_.data(),
+                                 document_.data() + document_.length(),
+                                 location - document_.data());
+  line = lineAndColumn.line;
+  column = lineAndColumn.column;
 }
 
 String Reader::getLocationLineAndColumn(Location location) const {
@@ -1991,6 +1979,31 @@ bool parseFromStream(CharReader::Factory const& fact, IStream& sin, Value* root,
   return reader->parse(begin, end, root, errs);
 }
 
+Json::LineAndColumn getLocationLineAndColumn(char const* beginDoc, char const* endDoc,
+                              size_t location) {
+  Json::LineAndColumn lineAndColumn;
+  char const* current = beginDoc;
+  char const* lastLineStart = current;
+  int line = 0;
+  while (current < beginDoc + location && current < endDoc) {
+    char c = *current++;
+    if (c == '\r') {
+      if (*current == '\n')
+        ++current;
+      lastLineStart = current;
+      ++line;
+    } else if (c == '\n') {
+      lastLineStart = current;
+      ++line;
+    }
+  }
+  // column & line start at 1
+  lineAndColumn.column = int(beginDoc + location - lastLineStart) + 1;
+  lineAndColumn.line=++line;
+
+  return lineAndColumn;
+}
+
 IStream& operator>>(IStream& sin, Value& root) {
   CharReaderBuilder b;
   String errs;

src/test_lib_json/main.cpp

@@ -3903,6 +3903,38 @@ JSONTEST_FIXTURE_LOCAL(FuzzTest, fuzzDoesntCrash) {
                              example.size()));
 }
 
+struct GetLocationLineAndColumnTest : JsonTest::TestCase {
+  void testLineAndColumn(const std::string& doc, ptrdiff_t location, int row,
+                         int column) {
+    Json::LineAndColumn actualLocation =
+      Json::getLocationLineAndColumn(doc.data(), doc.data() + doc.length(),
+                                     location);
+    JSONTEST_ASSERT_EQUAL(row, actualLocation.line);
+    JSONTEST_ASSERT_EQUAL(column, actualLocation.column);
+  }
+};
+
+JSONTEST_FIXTURE_LOCAL(GetLocationLineAndColumnTest, test) {
+  const std::string example = "line 1\nline 2\r\nline 3\rline 4";
+  size_t found_l = -1;
+  size_t found_i = -1;
+  size_t found_n = -1;
+  size_t found_e = -1;
+  size_t found_space = -1;
+  for (int row = 1; row <= 4; ++row) {
+    found_l = example.find('l', found_l+1);
+    found_i = example.find('i', found_i+1);
+    found_n = example.find('n', found_n+1);
+    found_e = example.find('e', found_e+1);
+    found_space = example.find(' ', found_space+1);
+    testLineAndColumn(example, found_l, row, 1);
+    testLineAndColumn(example, found_i, row, 2);
+    testLineAndColumn(example, found_n, row, 3);
+    testLineAndColumn(example, found_e, row, 4);
+    testLineAndColumn(example, found_space, row, 5);
+  }
+}
+
 int main(int argc, const char* argv[]) {
   JsonTest::Runner runner;