implement enough helper functions to successfully dump out the

contents of the header map.  Look ma, no assumptions about input data
here (aka, corrupt header maps can't crash the compiler - crazy thought).

llvm-svn: 45122

2 files changed, 116 insertions, 7 deletions

diff --git a/clang/Lex/HeaderMap.cpp b/clang/Lex/HeaderMap.cpp
index abd1f9ee0c8..177821e0cf6 100644
--- a/clang/Lex/HeaderMap.cpp
+++ b/clang/Lex/HeaderMap.cpp
@@ -19,9 +19,23 @@
 #include "llvm/Support/MemoryBuffer.h"
 using namespace clang;
 
+//===----------------------------------------------------------------------===//
+// Data Structures and Manifest Constants
+//===----------------------------------------------------------------------===//
+
 enum {
-  HeaderMagicNumber = ('h' << 24) | ('m' << 16) | ('a' << 8) | 'p',
-  HeaderVersion = 1
+  HMAP_HeaderMagicNumber = ('h' << 24) | ('m' << 16) | ('a' << 8) | 'p',
+  HMAP_HeaderVersion = 1,
+  
+  HMAP_EmptyBucketKey = 0 
+};
+
+namespace clang {
+struct HMapBucket {
+  uint32_t Key;          // Offset (into strings) of key.
+
+  uint32_t Prefix;     // Offset (into strings) of value prefix.
+  uint32_t Suffix;     // Offset (into strings) of value suffix.
 };
 
 struct HMapHeader {
@@ -29,12 +43,17 @@ struct HMapHeader {
   uint16_t Version;         // Version number -- currently 1.
   uint16_t Reserved;        // Reserved for future use - zero for now.
   uint32_t StringsOffset;   // Offset to start of string pool.
-  uint32_t Count;           // Number of entries in the string table.
-  uint32_t Capacity;        // Number of buckets (always a power of 2).
+  uint32_t NumEntries;      // Number of entries in the string table.
+  uint32_t NumBuckets;      // Number of buckets (always a power of 2).
   uint32_t MaxValueLength;  // Length of longest result path (excluding nul).
+  // An array of 'NumBuckets' HMapBucket objects follows this header.
   // Strings follow the buckets, at StringsOffset.
 };
+} // end namespace clang.
 
+//===----------------------------------------------------------------------===//
+// Verification and Construction
+//===----------------------------------------------------------------------===//
 
 /// HeaderMap::Create - This attempts to load the specified file as a header
 /// map.  If it doesn't look like a HeaderMap, it gives up and returns null.
@@ -57,10 +76,11 @@ const HeaderMap *HeaderMap::Create(const FileEntry *FE) {
   // Sniff it to see if it's a headermap by checking the magic number and
   // version.
   bool NeedsByteSwap;
-  if (Header->Magic == HeaderMagicNumber && Header->Version == HeaderVersion)
+  if (Header->Magic == HMAP_HeaderMagicNumber && 
+      Header->Version == HMAP_HeaderVersion)
     NeedsByteSwap = false;
-  else if (Header->Magic == llvm::ByteSwap_32(HeaderMagicNumber) &&
-           Header->Version == llvm::ByteSwap_16(HeaderVersion))
+  else if (Header->Magic == llvm::ByteSwap_32(HMAP_HeaderMagicNumber) &&
+           Header->Version == llvm::ByteSwap_16(HMAP_HeaderVersion))
     NeedsByteSwap = true;  // Mixed endianness headermap.
   else 
     return 0;  // Not a header map.
@@ -75,12 +95,90 @@ HeaderMap::~HeaderMap() {
   delete FileBuffer;
 }
 
+//===----------------------------------------------------------------------===//
+//  Utility Methods
+//===----------------------------------------------------------------------===//
+
 
 /// getFileName - Return the filename of the headermap.
 const char *HeaderMap::getFileName() const {
   return FileBuffer->getBufferIdentifier();
 }
 
+unsigned HeaderMap::getEndianAdjustedWord(unsigned X) const {
+  if (!NeedsBSwap) return X;
+  return llvm::ByteSwap_32(X);
+}
+
+/// getHeader - Return a reference to the file header, in unbyte-swapped form.
+/// This method cannot fail.
+const HMapHeader &HeaderMap::getHeader() const {
+  // We know the file is at least as big as the header.  Return it.
+  return *reinterpret_cast<const HMapHeader*>(FileBuffer->getBufferStart());
+}
+
+/// getBucket - Return the specified hash table bucket from the header map,
+/// bswap'ing its fields as appropriate.  If the bucket number is not valid,
+/// this return a bucket with an empty key (0).
+HMapBucket HeaderMap::getBucket(unsigned BucketNo) const {
+  HMapBucket Result;
+  Result.Key = HMAP_EmptyBucketKey;
+  
+  const HMapBucket *BucketArray = 
+    reinterpret_cast<const HMapBucket*>(FileBuffer->getBufferStart() +
+                                        sizeof(HMapHeader));
+  
+  const HMapBucket *BucketPtr = BucketArray+BucketNo;
+  if ((char*)(BucketPtr+1) > FileBuffer->getBufferEnd())
+    return Result;  // Invalid buffer, corrupt hmap.
+
+  // Otherwise, the bucket is valid.  Load the values, bswapping as needed.
+  Result.Key    = getEndianAdjustedWord(BucketPtr->Key);
+  Result.Prefix = getEndianAdjustedWord(BucketPtr->Prefix);
+  Result.Suffix = getEndianAdjustedWord(BucketPtr->Suffix);
+  return Result;
+}
+
+/// getString - Look up the specified string in the string table.  If the string
+/// index is not valid, it returns an empty string.
+const char *HeaderMap::getString(unsigned StrTabIdx) const {
+  // Add the start of the string table to the idx.
+  StrTabIdx += getEndianAdjustedWord(getHeader().StringsOffset);
+  
+  // Check for invalid index.
+  if (StrTabIdx >= FileBuffer->getBufferSize())
+    return 0;
+  
+  // Otherwise, we have a valid pointer into the file.  Just return it.  We know
+  // that the "string" can not overrun the end of the file, because the buffer
+  // is nul terminated by virtue of being a MemoryBuffer.
+  return FileBuffer->getBufferStart()+StrTabIdx;
+}
+
+//===----------------------------------------------------------------------===//
+// The Main Drivers
+//===----------------------------------------------------------------------===//
+
+/// dump - Print the contents of this headermap to stderr.
+void HeaderMap::dump() const {
+  const HMapHeader &Hdr = getHeader();
+  unsigned NumBuckets = getEndianAdjustedWord(Hdr.NumBuckets);
+  
+  fprintf(stderr, "Header Map %s:\n  %d buckets, %d entries\n", 
+          getFileName(), NumBuckets,
+          getEndianAdjustedWord(Hdr.NumEntries));
+  
+  for (unsigned i = 0; i != NumBuckets; ++i) {
+    HMapBucket B = getBucket(i);
+    if (B.Key == HMAP_EmptyBucketKey) continue;
+    
+    const char *Key    = getString(B.Key);
+    const char *Prefix = getString(B.Prefix);
+    const char *Suffix = getString(B.Suffix);
+    fprintf(stderr, "  %d. %s -> '%s' '%s'\n", i, Key, Prefix, Suffix);
+  }
+}
+
 /// LookupFile - Check to see if the specified relative filename is located in
 /// this HeaderMap.  If so, open it and return its FileEntry.
 const FileEntry *HeaderMap::LookupFile(const char *FilenameStart,
diff --git a/clang/include/clang/Lex/HeaderMap.h b/clang/include/clang/Lex/HeaderMap.h
index 973cf10a861..3bc0acf70fc 100644
--- a/clang/include/clang/Lex/HeaderMap.h
+++ b/clang/include/clang/Lex/HeaderMap.h
@@ -20,6 +20,8 @@ namespace llvm {
 namespace clang {
   class FileEntry;
   class FileManager;
+  struct HMapBucket;
+  struct HMapHeader;
 
 /// This class represents an Apple concept known as a 'header map'.  To the
 /// #include file resolution process, it basically acts like a directory of
@@ -49,6 +51,15 @@ public:
   
   /// getFileName - Return the filename of the headermap.
   const char *getFileName() const;
+  
+  /// dump - Print the contents of this headermap to stderr.
+  void dump() const;
+  
+private:
+  unsigned getEndianAdjustedWord(unsigned X) const;
+  const HMapHeader &getHeader() const;
+  HMapBucket getBucket(unsigned BucketNo) const;
+  const char *getString(unsigned StrTabIdx) const;
 };
 
 } // end namespace clang.