initial index codes for access97 general collation order

git-svn-id: https://svn.code.sf.net/p/jackcess/code/jackcess/branches/a97_indexes@1304 f203690c-595d-4dc9-a70b-905162fa7fd2

1 files changed, 127 insertions, 0 deletions

diff --git a/src/main/java/com/healthmarketscience/jackcess/impl/General97IndexCodes.java b/src/main/java/com/healthmarketscience/jackcess/impl/General97IndexCodes.java
new file mode 100644
index 0000000..432a0a9
--- /dev/null
+++ b/src/main/java/com/healthmarketscience/jackcess/impl/General97IndexCodes.java
@@ -0,0 +1,127 @@
+/*
+Copyright (c) 2019 James Ahlborn
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package com.healthmarketscience.jackcess.impl;
+
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+
+import static com.healthmarketscience.jackcess.impl.ByteUtil.ByteStream;
+
+/**
+ * Various constants used for creating "general" (access 1997) sort order
+ * text index entries.
+ *
+ * @author James Ahlborn
+ */
+public class General97IndexCodes extends GeneralLegacyIndexCodes
+{
+  // stash the codes in some resource files
+  private static final String CODES_FILE =
+    DatabaseImpl.RESOURCE_PATH + "index_codes_gen_97.txt";
+  private static final String EXT_MAPPINGS_FILE =
+    DatabaseImpl.RESOURCE_PATH + "index_mappings_ext_gen_97.txt";
+
+  private static final class Codes
+  {
+    /** handlers for the first 256 chars.  use nested class to lazy load the
+        handlers */
+    private static final CharHandler[] _values = loadCodes(
+        CODES_FILE, FIRST_CHAR, LAST_CHAR);
+  }
+
+  private static final class ExtMappings
+  {
+    /** mappings for the rest of the chars in BMP 0.  use nested class to lazy
+        load the handlers.  since these codes are for single byte encodings,
+        you would think you wou;dn't need any ext codes.  however, some chars
+        in the extended range have corollaries in the single byte range. this
+        array holds the mappings from the ext range to the single byte range.
+        chars without mappings go to 0. */
+    private static final short[] _values = loadMappings(
+        EXT_MAPPINGS_FILE, FIRST_EXT_CHAR, LAST_EXT_CHAR);
+  }
+
+  static final General97IndexCodes GEN_97_INSTANCE = new General97IndexCodes();
+
+  General97IndexCodes() {}
+
+  /**
+   * Returns the CharHandler for the given character.
+   */
+  @Override
+  CharHandler getCharHandler(char c)
+  {
+    if(c <= LAST_CHAR) {
+      return Codes._values[c];
+    }
+
+    // some ext chars are equivalent to single byte chars.  most chars have no
+    // equivalent, and they map to 0 (which is an "ignored" char, so it all
+    // works out)
+    int extOffset = asUnsignedChar(c) - asUnsignedChar(FIRST_EXT_CHAR);
+    return Codes._values[ExtMappings._values[extOffset]];
+  }
+
+  @Override
+  void writeNonNullIndexTextValue(
+      Object value, ByteStream bout, boolean isAscending)
+    throws IOException
+  {
+    // use simplified format for 97 encoding
+    writeNonNull97IndexTextValue(value, bout, isAscending);
+  }
+
+  static short[] loadMappings(String mappingsFilePath,
+                              char firstChar, char lastChar)
+  {
+    int firstCharCode = asUnsignedChar(firstChar);
+    int numMappings = (asUnsignedChar(lastChar) - firstCharCode) + 1;
+    short[] values = new short[numMappings];
+
+    BufferedReader reader = null;
+    try {
+
+      reader = new BufferedReader(
+          new InputStreamReader(
+              DatabaseImpl.getResourceAsStream(mappingsFilePath), "US-ASCII"));
+
+      // this is a sparse file with entries like <fromCode>,<toCode>
+      String mappingLine = null;
+      while((mappingLine = reader.readLine()) != null) {
+        mappingLine = mappingLine.trim();
+        if(mappingLine.length() == 0) {
+          continue;
+        }
+
+        String[] mappings = mappingLine.split(",");
+        int fromCode = Integer.parseInt(mappings[0]);
+        int toCode = Integer.parseInt(mappings[1]);
+
+        values[fromCode - firstCharCode] = (short)toCode;
+      }
+
+    } catch(IOException e) {
+      throw new RuntimeException("failed loading index mappings file " +
+                                 mappingsFilePath, e);
+    } finally {
+      ByteUtil.closeQuietly(reader);
+    }
+
+    return values;
+  }
+}