Add charset conversion library

1 files changed, 89 insertions, 0 deletions

diff --git a/lib/charset/charset.h b/lib/charset/charset.h
new file mode 100644
index 0000000..6ff19bc
--- /dev/null
+++ b/lib/charset/charset.h
@@ -0,0 +1,89 @@
+/*
+    Copyright (C) 2015 Matthias P. Braendli (http://opendigitalradio.org)
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+/*!
+    \file charset.h
+    \brief Define the EBU charset according to ETSI TS 101 756v1.8.1 for DLS encoding
+
+    \author Matthias P. Braendli <matthias@mpb.li>
+    \author Lindsay Cornell
+*/
+
+#ifndef __CHARSET_H_
+#define __CHARSET_H_
+
+#include "utf8.h"
+#include <cstdint>
+#include <string>
+#include <vector>
+#include <algorithm>
+
+#define CHARSET_TABLE_OFFSET 1 // NUL at index 0 cannot be represented
+#define CHARSET_TABLE_ENTRIES (256 - CHARSET_TABLE_OFFSET)
+extern const char* utf8_encoded_EBU_Latin[CHARSET_TABLE_ENTRIES];
+
+class CharsetConverter
+{
+    public:
+        CharsetConverter() {
+            /*! Build the converstion table that contains the known code points,
+             * at the indices corresponding to the EBU Latin table
+             */
+            using namespace std;
+            for (size_t i = 0; i < CHARSET_TABLE_ENTRIES; i++) {
+                string table_entry(utf8_encoded_EBU_Latin[i]);
+                string::iterator it = table_entry.begin();
+                uint32_t code_point = utf8::next(it, table_entry.end());
+                m_conversion_table.push_back(code_point);
+            }
+        }
+
+        /*! Convert a UTF-8 encoded text line into an EBU Latin encoded byte stream
+         */
+        std::string convert(std::string line_utf8) {
+            using namespace std;
+
+            // check for invalid utf-8, we only convert up to the first error
+            string::iterator end_it = utf8::find_invalid(line_utf8.begin(), line_utf8.end());
+
+            // Convert it to utf-32
+            vector<uint32_t> utf32line;
+            utf8::utf8to32(line_utf8.begin(), end_it, back_inserter(utf32line));
+
+            string encoded_line(utf32line.size(), '0');
+
+            // Try to convert each codepoint
+            for (size_t i = 0; i < utf32line.size(); i++) {
+                vector<uint32_t>::iterator iter = find(m_conversion_table.begin(),
+                        m_conversion_table.end(), utf32line[i]);
+                if (iter != m_conversion_table.end()) {
+                    size_t index = std::distance(m_conversion_table.begin(), iter);
+
+                    encoded_line[i] = (char)(index + CHARSET_TABLE_OFFSET);
+                }
+                else {
+                    encoded_line[i] = ' ';
+                }
+            }
+            return encoded_line;
+        }
+
+    private:
+
+        std::vector<uint32_t> m_conversion_table;
+};
+
+#endif