1 files changed, 123 insertions, 0 deletions
diff --git a/llvm/lib/DebugInfo/PDB/Native/StringTableStreamBuilder.cpp b/llvm/lib/DebugInfo/PDB/Native/StringTableStreamBuilder.cpp
new file mode 100644
index 00000000000..b19440961bc
--- /dev/null
+++ b/llvm/lib/DebugInfo/PDB/Native/StringTableStreamBuilder.cpp
@@ -0,0 +1,123 @@
+//===- StringTableStreamBuilder.cpp - PDB String Table ----------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/DebugInfo/PDB/Native/StringTableStreamBuilder.h"
+#include "llvm/ADT/ArrayRef.h"
+#include "llvm/DebugInfo/PDB/Native/Hash.h"
+#include "llvm/DebugInfo/PDB/Native/RawTypes.h"
+#include "llvm/Support/BinaryStreamWriter.h"
+#include "llvm/Support/Endian.h"
+
+using namespace llvm;
+using namespace llvm::support;
+using namespace llvm::support::endian;
+using namespace llvm::pdb;
+
+uint32_t StringTableStreamBuilder::insert(StringRef S) {
+  return Strings.insert(S);
+}
+
+static uint32_t computeBucketCount(uint32_t NumStrings) {
+  // The /names stream is basically an on-disk open-addressing hash table.
+  // Hash collisions are resolved by linear probing. We cannot make
+  // utilization 100% because it will make the linear probing extremely
+  // slow. But lower utilization wastes disk space. As a reasonable
+  // load factor, we choose 80%. We need +1 because slot 0 is reserved.
+  return (NumStrings + 1) * 1.25;
+}
+
+uint32_t StringTableStreamBuilder::hashTableSize() const {
+  uint32_t Size = sizeof(uint32_t); // Hash table begins with 4-byte size field.
+
+  Size += computeBucketCount(Strings.size()) * sizeof(uint32_t);
+  return Size;
+}
+
+uint32_t StringTableStreamBuilder::calculateSerializedSize() const {
+  uint32_t Size = 0;
+  Size += sizeof(StringTableHeader);
+  Size += Strings.calculateSerializedSize();
+  Size += hashTableSize();
+  Size += sizeof(uint32_t); // The table ends with the number of strings.
+  return Size;
+}
+
+Error StringTableStreamBuilder::writeHeader(BinaryStreamWriter &Writer) const {
+  // Write a header
+  StringTableHeader H;
+  H.Signature = StringTableSignature;
+  H.HashVersion = 1;
+  H.ByteSize = Strings.calculateSerializedSize();
+  if (auto EC = Writer.writeObject(H))
+    return EC;
+
+  assert(Writer.bytesRemaining() == 0);
+  return Error::success();
+}
+
+Error StringTableStreamBuilder::writeStrings(BinaryStreamWriter &Writer) const {
+  if (auto EC = Strings.commit(Writer))
+    return EC;
+
+  assert(Writer.bytesRemaining() == 0);
+  return Error::success();
+}
+
+Error StringTableStreamBuilder::writeHashTable(
+    BinaryStreamWriter &Writer) const {
+  // Write a hash table.
+  uint32_t BucketCount = computeBucketCount(Strings.size());
+  if (auto EC = Writer.writeInteger(BucketCount))
+    return EC;
+
+  std::vector<ulittle32_t> Buckets(BucketCount);
+
+  for (auto &Pair : Strings) {
+    StringRef S = Pair.getKey();
+    uint32_t Offset = Pair.getValue();
+    uint32_t Hash = hashStringV1(S);
+
+    for (uint32_t I = 0; I != BucketCount; ++I) {
+      uint32_t Slot = (Hash + I) % BucketCount;
+      if (Slot == 0)
+        continue; // Skip reserved slot
+      if (Buckets[Slot] != 0)
+        continue;
+      Buckets[Slot] = Offset;
+      break;
+    }
+  }
+
+  if (auto EC = Writer.writeArray(makeArrayRef(Buckets)))
+    return EC;
+  assert(Writer.bytesRemaining() == 0);
+  return Error::success();
+}
+
+Error StringTableStreamBuilder::commit(BinaryStreamWriter &Writer) const {
+  BinaryStreamWriter Section;
+
+  std::tie(Section, Writer) = Writer.split(sizeof(StringTableHeader));
+  if (auto EC = writeHeader(Section))
+    return EC;
+
+  std::tie(Section, Writer) = Writer.split(Strings.calculateSerializedSize());
+  if (auto EC = writeStrings(Section))
+    return EC;
+
+  std::tie(Section, Writer) = Writer.split(hashTableSize());
+  if (auto EC = writeHashTable(Section))
+    return EC;
+
+  if (auto EC = Writer.writeInteger<uint32_t>(Strings.size()))
+    return EC;
+
+  assert(Writer.bytesRemaining() == 0);
+  return Error::success();
+}