Avoid a data copy decoding base64 data.

Use an out parameter to avoid a buffer alloc/copy/free cycle
when returning base64-decoded data.

simgear/io/SVNReportParser.cxx

@@ -165,7 +165,7 @@ namespace {
          _ptr = p;
      }
   
-    bool apply(std::vector<char>& output, std::istream& source)
+    bool apply(std::vector<unsigned char>& output, std::istream& source)
     {
         unsigned char* pEnd = _ptr + instructionLength;
         unsigned char* newData = pEnd;
@@ -330,11 +330,12 @@ public:
   }
   
   bool decodeTextDelta(const SGPath& outputPath)
-  {    
+  {
-    string decoded = strutils::decodeBase64(txDeltaData);
+      std::vector<unsigned char> output, decoded;
+    strutils::decodeBase64(txDeltaData, decoded);
     size_t bytesToDecode = decoded.size();
-    std::vector<char> output;      
+         
-    unsigned char* p = (unsigned char*) decoded.data();
+    unsigned char* p = decoded.data();
     if (memcmp(p, "SVN\0", DELTA_HEADER_SIZE) != 0) {
         return false; // bad header
     }
@@ -346,9 +347,9 @@ public:
     
     while (bytesToDecode > 0) {  
         if (!SVNDeltaWindow::isWindowComplete(p, bytesToDecode)) {
-	  SG_LOG(SG_IO, SG_WARN, "SVN txdelta broken window");
+            SG_LOG(SG_IO, SG_WARN, "SVN txdelta broken window");
-	  return false;
+            return false;
-	}
+        }
 	
         SVNDeltaWindow window(p);      
         assert(bytesToDecode >= window.size());
@@ -362,7 +363,7 @@ public:
     std::ofstream f;
     f.open(outputPath.c_str(), 
       std::ios::out | std::ios::trunc | std::ios::binary);
-    f.write(output.data(), output.size());
+    f.write((char*) output.data(), output.size());
 
     // compute MD5 while we have the file in memory
     memset(&md5Context, 0, sizeof(SG_MD5_CTX));

simgear/misc/strutils.cxx

@@ -370,14 +370,13 @@ static bool is_whitespace(unsigned char c) {
     return ((c == ' ') || (c == '\r') || (c == '\n'));
 }
 
-std::string decodeBase64(const std::string& encoded_string)
+void decodeBase64(const std::string& encoded_string, std::vector<unsigned char>& ret)
 {
   int in_len = encoded_string.size();
   int i = 0;
   int j = 0;
   int in_ = 0;
   unsigned char char_array_4[4], char_array_3[3];
-  std::string ret;
   
   while (in_len-- && ( encoded_string[in_] != '=')) {
     if (is_whitespace( encoded_string[in_])) {
@@ -399,7 +398,7 @@ std::string decodeBase64(const std::string& encoded_string)
       char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
       
       for (i = 0; (i < 3); i++)
-        ret += char_array_3[i];
+        ret.push_back(char_array_3[i]);
       i = 0;
     }
   }
@@ -415,10 +414,8 @@ std::string decodeBase64(const std::string& encoded_string)
     char_array_3[1] = ((char_array_4[1] & 0xf) << 4) + ((char_array_4[2] & 0x3c) >> 2);
     char_array_3[2] = ((char_array_4[2] & 0x3) << 6) + char_array_4[3];
     
-    for (j = 0; (j < i - 1); j++) ret += char_array_3[j];
+    for (j = 0; (j < i - 1); j++) ret.push_back(char_array_3[j]);
   }
-  
-  return ret;
 }  
 
 const char hexChar[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};

simgear/misc/strutils.hxx

@@ -160,7 +160,7 @@ namespace simgear {
      * NULs). Throws an exception if input data is not base64, or is
      * malformed
      */
-    std::string decodeBase64(const std::string& a);
+      void decodeBase64(const std::string& a, std::vector<unsigned char>& output);
     
     /**
      * convert bytes to hexadecimal equivalent