Add QUtil::make_shared_cstr

Replace most of the calls to QUtil::copy_string with this instead.

ChangeLog

@@ -1,5 +1,8 @@
 2022-01-22  Jay Berkenbilt  <ejb@ql.org>
 
+	* Add QUtil::make_shared_cstr to return a std::shared_ptr<char>
+	instead of a char* like QUtil::copy_string
+
 	* JSON: for (qpdf-specific, not official) "schema" checking, add
 	the ability to treat missing fields as optional. Also ensure that
 	values in the schema are dictionary, array, or string.

include/qpdf/QUtil.hh

@@ -30,6 +30,7 @@
 #include <vector>
 #include <stdexcept>
 #include <functional>
+#include <memory>
 #include <stdio.h>
 #include <time.h>
 
@@ -151,9 +152,15 @@ namespace QUtil
     QPDF_DLL
     std::string path_basename(std::string const& filename);
 
+    // Returns a dynamically allocated copy of a string that the
+    // caller has to delete with delete[].
     QPDF_DLL
     char* copy_string(std::string const&);
 
+    // Returns a shared_ptr<char> with the correct deleter.
+    QPDF_DLL
+    std::shared_ptr<char> make_shared_cstr(std::string const&);
+
     // Returns lower-case hex-encoded version of the string, treating
     // each character in the input string as unsigned.  The output
     // string will be twice as long as the input string.

libqpdf/QPDFWriter.cc

@@ -1915,9 +1915,8 @@ QPDFWriter::unparseObject(QPDFObjectHandle object, int level,
 	    }
 	    else
 	    {
-		PointerHolder<char> tmp_ph =
-                    PointerHolder<char>(true, QUtil::copy_string(val));
-                char* tmp = tmp_ph.getPointer();
+		auto tmp_ph = QUtil::make_shared_cstr(val);
+                char* tmp = tmp_ph.get();
 		size_t vlen = val.length();
 		RC4 rc4(QUtil::unsigned_char_pointer(this->m->cur_data_key),
 			QIntC::to_int(this->m->cur_data_key.length()));

libqpdf/QPDF_encryption.cc

@@ -1211,10 +1211,10 @@ QPDF::decryptString(std::string& str, int objid, int generation)
 	    size_t vlen = str.length();
 	    // Using PointerHolder guarantees that tmp will
 	    // be freed even if rc4.process throws an exception.
-	    PointerHolder<char> tmp(true, QUtil::copy_string(str));
+	    auto tmp = QUtil::make_shared_cstr(str);
 	    RC4 rc4(QUtil::unsigned_char_pointer(key), toI(key.length()));
-	    rc4.process(QUtil::unsigned_char_pointer(tmp.getPointer()), vlen);
-	    str = std::string(tmp.getPointer(), vlen);
+	    rc4.process(QUtil::unsigned_char_pointer(tmp.get()), vlen);
+	    str = std::string(tmp.get(), vlen);
 	}
     }
     catch (QPDFExc&)

libqpdf/QUtil.cc

@@ -731,6 +731,18 @@ QUtil::copy_string(std::string const& str)
     return result;
 }
 
+std::shared_ptr<char>
+QUtil::make_shared_cstr(std::string const& str)
+{
+    auto result = std::shared_ptr<char>(
+        new char[str.length() + 1],
+        std::default_delete<char[]>());
+    // Use memcpy in case string contains nulls
+    result.get()[str.length()] = '\0';
+    memcpy(result.get(), str.c_str(), str.length());
+    return result;
+}
+
 std::string
 QUtil::hex_encode(std::string const& input)
 {
@@ -2625,7 +2637,7 @@ QUtil::call_main_from_wmain(int argc, wchar_t* argv[],
                              QIntC::to_uchar(codepoint & 0xff)));
         }
         std::string utf8 = QUtil::utf16_to_utf8(utf16);
-        utf8_argv.push_back(std::shared_ptr<char>(QUtil::copy_string(utf8.c_str()), std::default_delete<char[]>()));
+        utf8_argv.push_back(QUtil::make_shared_cstr(utf8));
     }
     auto utf8_argv_sp =
         std::shared_ptr<char*>(new char*[1+utf8_argv.size()], std::default_delete<char*[]>());

libtests/qtest/qutil/qutil.out

@@ -22,6 +22,7 @@
 one
 7
 compare okay
+compare okay
 -2147483648 to int: PASSED
 2147483647 to int: PASSED
 2147483648 to int threw (integer out of range converting 2147483648 from a 8-byte signed type to a 4-byte signed type): PASSED

libtests/qutil.cc

@@ -150,6 +150,16 @@ void string_conversion_test()
 	std::cout << "compare failed" << std::endl;
     }
     delete [] tmp;
+    // Also test with make_shared_cstr
+    auto tmp2 = QUtil::make_shared_cstr(embedded_null);
+    if (memcmp(tmp2.get(), embedded_null.c_str(), 7) == 0)
+    {
+	std::cout << "compare okay" << std::endl;
+    }
+    else
+    {
+	std::cout << "compare failed" << std::endl;
+    }
 
     std::string int_max_str = QUtil::int_to_string(INT_MAX);
     std::string int_min_str = QUtil::int_to_string(INT_MIN);
@@ -407,8 +417,8 @@ void transcoding_test()
 
 void print_whoami(char const* str)
 {
-    PointerHolder<char> dup(true, QUtil::copy_string(str));
-    std::cout << QUtil::getWhoami(dup.getPointer()) << std::endl;
+    auto dup = QUtil::make_shared_cstr(str);
+    std::cout << QUtil::getWhoami(dup.get()) << std::endl;
 }
 
 void get_whoami_test()