Implement BASE64 decoding of locations given by dictionary index

2 files changed, 39 insertions, 0 deletions

diff --git a/src/util/base64.cc b/src/util/base64.cc
new file mode 100644
index 0000000..4e8d0a4
--- /dev/null
+++ b/src/util/base64.cc
@@ -0,0 +1,29 @@
+#include "base64.h"
+
+#include <vector>
+#include <stdexcept>
+
+namespace dictzip {
+
+std::size_t base64_decode(const std::string& encoded) {
+	std::vector<std::int8_t> map(256,-1);
+
+    for ( int i = 0; i < 64; ++i ) {
+		map["ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"[i]] = i;
+	}
+
+	std::size_t value = 0;
+
+    for ( std::uint8_t c : encoded ) {
+        if ( map[c] == -1 ) {
+			throw std::invalid_argument("Invalid character in BASE64 string.");
+		} else {
+			value *= 64;
+			value += map[c];
+		}
+    }
+
+    return value;
+}
+
+}
diff --git a/src/util/base64.h b/src/util/base64.h
new file mode 100644
index 0000000..448609d
--- /dev/null
+++ b/src/util/base64.h
@@ -0,0 +1,10 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+
+namespace dictzip {
+
+std::size_t base64_decode(const std::string& encoded);
+
+}