From 478af5f01eca9e3ffdd05988943fabf46e187f2c Mon Sep 17 00:00:00 2001
From: James Turner <zakalawe@mac.com>
Date: Sun, 9 Jun 2013 19:17:37 +0100
Subject: [PATCH] Base64 and hex helpers for strings

---
 simgear/misc/strutils.cxx | 94 ++++++++++++++++++++++++++++++++++++++-
 simgear/misc/strutils.hxx | 13 ++++++
 2 files changed, 106 insertions(+), 1 deletion(-)

diff --git a/simgear/misc/strutils.cxx b/simgear/misc/strutils.cxx
index c6687158..d064ed6b 100644
--- a/simgear/misc/strutils.cxx
+++ b/simgear/misc/strutils.cxx
@@ -334,6 +334,98 @@ std::string convertWindowsLocal8BitToUtf8(const std::string& a)
 #endif
 }
 
-    } // end namespace strutils
+static const std::string base64_chars =
+"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
+"abcdefghijklmnopqrstuvwxyz"
+"0123456789+/";
+
+
+static inline bool is_base64(unsigned char c) {
+  return (isalnum(c) || (c == '+') || (c == '/'));
+}
+
+static bool is_whitespace(unsigned char c) {
+    return ((c == ' ') || (c == '\r') || (c == '\n'));
+}
+
+std::string decodeBase64(const std::string& encoded_string)
+{
+  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_])) {
+        in_++; 
+        continue;
+    }
+    
+    if (!is_base64(encoded_string[in_])) {
+        break;
+    }
+    
+    char_array_4[i++] = encoded_string[in_]; in_++;
+    if (i ==4) {
+      for (i = 0; i <4; i++)
+        char_array_4[i] = base64_chars.find(char_array_4[i]);
+      
+      char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
+      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 (i = 0; (i < 3); i++)
+        ret += char_array_3[i];
+      i = 0;
+    }
+  }
+  
+  if (i) {
+    for (j = i; j <4; j++)
+      char_array_4[j] = 0;
+    
+    for (j = 0; j <4; j++)
+      char_array_4[j] = base64_chars.find(char_array_4[j]);
+    
+    char_array_3[0] = (char_array_4[0] << 2) + ((char_array_4[1] & 0x30) >> 4);
+    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];
+  }
+  
+  return ret;
+}  
+
+const char hexChar[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+
+std::string encodeHex(const std::string& bytes)
+{
+  std::string hex;
+  size_t count = bytes.size();
+  for (unsigned int i=0; i<count;++i) {
+      unsigned char c = bytes[i];
+      hex.push_back(hexChar[c >> 4]);
+      hex.push_back(hexChar[c & 0x0f]);
+  }
+  
+  return hex;
+}
+
+std::string encodeHex(const unsigned char* rawBytes, unsigned int length)
+{
+  std::string hex;
+  for (unsigned int i=0; i<length;++i) {
+      unsigned char c = *rawBytes++;
+      hex.push_back(hexChar[c >> 4]);
+      hex.push_back(hexChar[c & 0x0f]);
+  }
+  
+  return hex;
+}
+
+} // end namespace strutils
     
 } // end namespace simgear
diff --git a/simgear/misc/strutils.hxx b/simgear/misc/strutils.hxx
index c9aa525c..d2c8a3e8 100644
--- a/simgear/misc/strutils.hxx
+++ b/simgear/misc/strutils.hxx
@@ -155,6 +155,19 @@ namespace simgear {
      */
     std::string convertWindowsLocal8BitToUtf8(const std::string& a);
 
+    /**
+     * convert base-64 encoded data to raw bytes (possibly with embedded
+     * NULs). Throws an exception if input data is not base64, or is
+     * malformed
+     */
+    std::string decodeBase64(const std::string& a);
+    
+    /**
+     * convert bytes to hexadecimal equivalent
+     */
+    std::string encodeHex(const std::string& bytes);
+    
+    std::string encodeHex(const unsigned char* rawBytes, unsigned int length);
   } // end namespace strutils
 } // end namespace simgear
 
-- 
2.39.5