Move StringToOffsetTable into the TableGen include directory so I can use it in clang.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@189567 91177308-0d34-0410-b5e6-96231b3b80d8

include/llvm/TableGen/StringToOffsetTable.h

@@ -0,0 +1,83 @@
+//===- StringToOffsetTable.h - Emit a big concatenated string ---*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef TBLGEN_STRING_TO_OFFSET_TABLE_H
+#define TBLGEN_STRING_TO_OFFSET_TABLE_H
+
+#include "llvm/ADT/SmallString.h"
+#include "llvm/ADT/StringExtras.h"
+#include "llvm/ADT/StringMap.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cctype>
+
+namespace llvm {
+
+/// StringToOffsetTable - This class uniques a bunch of nul-terminated strings
+/// and keeps track of their offset in a massive contiguous string allocation.
+/// It can then output this string blob and use indexes into the string to
+/// reference each piece.
+class StringToOffsetTable {
+  StringMap<unsigned> StringOffset;
+  std::string AggregateString;
+public:
+  
+  unsigned GetOrAddStringOffset(StringRef Str, bool appendZero = true) {
+    StringMapEntry<unsigned> &Entry = StringOffset.GetOrCreateValue(Str, -1U);
+    if (Entry.getValue() == -1U) {
+      // Add the string to the aggregate if this is the first time found.
+      Entry.setValue(AggregateString.size());
+      AggregateString.append(Str.begin(), Str.end());
+      if (appendZero)
+        AggregateString += '\0';
+    }
+    
+    return Entry.getValue();
+  }
+  
+  void EmitString(raw_ostream &O) {
+    // Escape the string.
+    SmallString<256> Str;
+    raw_svector_ostream(Str).write_escaped(AggregateString);
+    AggregateString = Str.str();
+
+    O << "    \"";
+    unsigned CharsPrinted = 0;
+    for (unsigned i = 0, e = AggregateString.size(); i != e; ++i) {
+      if (CharsPrinted > 70) {
+        O << "\"\n    \"";
+        CharsPrinted = 0;
+      }
+      O << AggregateString[i];
+      ++CharsPrinted;
+      
+      // Print escape sequences all together.
+      if (AggregateString[i] != '\\')
+        continue;
+      
+      assert(i+1 < AggregateString.size() && "Incomplete escape sequence!");
+      if (isdigit(AggregateString[i+1])) {
+        assert(isdigit(AggregateString[i+2]) && 
+               isdigit(AggregateString[i+3]) &&
+               "Expected 3 digit octal escape!");
+        O << AggregateString[++i];
+        O << AggregateString[++i];
+        O << AggregateString[++i];
+        CharsPrinted += 3;
+      } else {
+        O << AggregateString[++i];
+        ++CharsPrinted;
+      }
+    }
+    O << "\"";
+  }
+};
+
+} // end namespace llvm
+
+#endif