Add standard Base64 encoding support

[ Merge of http://go/wvgerrit/16550 ]

This is in addition to Web safe Base64 encode/decode support by core.

Change-Id: I9ed51721b138a7f15fb4d216796deadd5d5b31a2

libwvdrmengine/cdm/core/src/string_conversions.cpp

@@ -10,6 +10,7 @@
 #include <iostream>
 #include <vector>
 
+#include <modp_b64.h>
 #include <modp_b64w.h>
 
 #include "log.h"
@@ -78,6 +79,26 @@ std::string b2a_hex(const std::string& byte) {
                    byte.length());
 }
 
+// Encode for standard base64 encoding (RFC4648).
+std::string Base64Encode(const std::vector<uint8_t>& bin_input) {
+  if (bin_input.empty()) {
+    return std::string();
+  }
+
+  int in_size = bin_input.size();
+  std::string b64_output(modp_b64_encode_len(in_size), 0);
+
+  int out_size = modp_b64_encode(
+      &b64_output[0], reinterpret_cast<const char*>(&bin_input[0]), in_size);
+  if (out_size == -1) {
+    LOGE("Base64Encode failed");
+    return std::string();
+  }
+
+  b64_output.resize(out_size);
+  return b64_output;
+}
+
 // Filename-friendly base64 encoding (RFC4648), commonly referred to
 // as Base64WebSafeEncode.
 //
@@ -111,6 +132,25 @@ std::string Base64SafeEncodeNoPad(const std::vector<uint8_t>& bin_input) {
   return b64_output;
 }
 
+// Decode for standard base64 encoding (RFC4648).
+std::vector<uint8_t> Base64Decode(const std::string& b64_input) {
+  if (b64_input.empty()) {
+    return std::vector<uint8_t>();
+  }
+
+  int in_size = b64_input.size();
+  std::vector<uint8_t> bin_output(modp_b64_decode_len(in_size), 0);
+  int out_size = modp_b64_decode(reinterpret_cast<char*>(&bin_output[0]),
+                                 b64_input.data(), in_size);
+  if (out_size == -1) {
+    LOGE("Base64Decode failed");
+    return std::vector<uint8_t>(0);
+  }
+
+  bin_output.resize(out_size);
+  return bin_output;
+}
+
 // Decode for Filename-friendly base64 encoding (RFC4648), commonly referred
 // as Base64WebSafeDecode.
 std::vector<uint8_t> Base64SafeDecode(const std::string& b64_input) {