242 lines
8.7 KiB
C++
242 lines
8.7 KiB
C++
//===--- HeaderMap.cpp - A file that acts like dir of symlinks ------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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//
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// This file implements the HeaderMap interface.
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//
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//===----------------------------------------------------------------------===//
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#include "clang/Lex/HeaderMap.h"
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#include "clang/Basic/CharInfo.h"
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#include "clang/Basic/FileManager.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/Support/DataTypes.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Support/MemoryBuffer.h"
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#include <cstdio>
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#include <memory>
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using namespace clang;
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//===----------------------------------------------------------------------===//
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// Data Structures and Manifest Constants
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//===----------------------------------------------------------------------===//
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enum {
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HMAP_HeaderMagicNumber = ('h' << 24) | ('m' << 16) | ('a' << 8) | 'p',
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HMAP_HeaderVersion = 1,
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HMAP_EmptyBucketKey = 0
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};
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namespace clang {
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struct HMapBucket {
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uint32_t Key; // Offset (into strings) of key.
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uint32_t Prefix; // Offset (into strings) of value prefix.
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uint32_t Suffix; // Offset (into strings) of value suffix.
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};
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struct HMapHeader {
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uint32_t Magic; // Magic word, also indicates byte order.
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uint16_t Version; // Version number -- currently 1.
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uint16_t Reserved; // Reserved for future use - zero for now.
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uint32_t StringsOffset; // Offset to start of string pool.
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uint32_t NumEntries; // Number of entries in the string table.
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uint32_t NumBuckets; // Number of buckets (always a power of 2).
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uint32_t MaxValueLength; // Length of longest result path (excluding nul).
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// An array of 'NumBuckets' HMapBucket objects follows this header.
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// Strings follow the buckets, at StringsOffset.
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};
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} // end namespace clang.
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/// HashHMapKey - This is the 'well known' hash function required by the file
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/// format, used to look up keys in the hash table. The hash table uses simple
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/// linear probing based on this function.
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static inline unsigned HashHMapKey(StringRef Str) {
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unsigned Result = 0;
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const char *S = Str.begin(), *End = Str.end();
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for (; S != End; S++)
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Result += toLowercase(*S) * 13;
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return Result;
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}
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//===----------------------------------------------------------------------===//
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// Verification and Construction
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//===----------------------------------------------------------------------===//
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/// HeaderMap::Create - This attempts to load the specified file as a header
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/// map. If it doesn't look like a HeaderMap, it gives up and returns null.
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/// If it looks like a HeaderMap but is obviously corrupted, it puts a reason
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/// into the string error argument and returns null.
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const HeaderMap *HeaderMap::Create(const FileEntry *FE, FileManager &FM) {
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// If the file is too small to be a header map, ignore it.
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unsigned FileSize = FE->getSize();
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if (FileSize <= sizeof(HMapHeader)) return nullptr;
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std::unique_ptr<const llvm::MemoryBuffer> FileBuffer(FM.getBufferForFile(FE));
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if (!FileBuffer) return nullptr; // Unreadable file?
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const char *FileStart = FileBuffer->getBufferStart();
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// We know the file is at least as big as the header, check it now.
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const HMapHeader *Header = reinterpret_cast<const HMapHeader*>(FileStart);
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// Sniff it to see if it's a headermap by checking the magic number and
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// version.
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bool NeedsByteSwap;
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if (Header->Magic == HMAP_HeaderMagicNumber &&
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Header->Version == HMAP_HeaderVersion)
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NeedsByteSwap = false;
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else if (Header->Magic == llvm::ByteSwap_32(HMAP_HeaderMagicNumber) &&
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Header->Version == llvm::ByteSwap_16(HMAP_HeaderVersion))
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NeedsByteSwap = true; // Mixed endianness headermap.
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else
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return nullptr; // Not a header map.
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if (Header->Reserved != 0) return nullptr;
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// Okay, everything looks good, create the header map.
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return new HeaderMap(FileBuffer.release(), NeedsByteSwap);
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}
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HeaderMap::~HeaderMap() {
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delete FileBuffer;
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}
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//===----------------------------------------------------------------------===//
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// Utility Methods
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//===----------------------------------------------------------------------===//
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/// getFileName - Return the filename of the headermap.
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const char *HeaderMap::getFileName() const {
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return FileBuffer->getBufferIdentifier();
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}
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unsigned HeaderMap::getEndianAdjustedWord(unsigned X) const {
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if (!NeedsBSwap) return X;
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return llvm::ByteSwap_32(X);
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}
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/// getHeader - Return a reference to the file header, in unbyte-swapped form.
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/// This method cannot fail.
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const HMapHeader &HeaderMap::getHeader() const {
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// We know the file is at least as big as the header. Return it.
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return *reinterpret_cast<const HMapHeader*>(FileBuffer->getBufferStart());
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}
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/// getBucket - Return the specified hash table bucket from the header map,
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/// bswap'ing its fields as appropriate. If the bucket number is not valid,
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/// this return a bucket with an empty key (0).
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HMapBucket HeaderMap::getBucket(unsigned BucketNo) const {
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HMapBucket Result;
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Result.Key = HMAP_EmptyBucketKey;
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const HMapBucket *BucketArray =
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reinterpret_cast<const HMapBucket*>(FileBuffer->getBufferStart() +
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sizeof(HMapHeader));
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const HMapBucket *BucketPtr = BucketArray+BucketNo;
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if ((const char*)(BucketPtr+1) > FileBuffer->getBufferEnd()) {
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Result.Prefix = 0;
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Result.Suffix = 0;
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return Result; // Invalid buffer, corrupt hmap.
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}
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// Otherwise, the bucket is valid. Load the values, bswapping as needed.
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Result.Key = getEndianAdjustedWord(BucketPtr->Key);
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Result.Prefix = getEndianAdjustedWord(BucketPtr->Prefix);
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Result.Suffix = getEndianAdjustedWord(BucketPtr->Suffix);
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return Result;
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}
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/// getString - Look up the specified string in the string table. If the string
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/// index is not valid, it returns an empty string.
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const char *HeaderMap::getString(unsigned StrTabIdx) const {
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// Add the start of the string table to the idx.
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StrTabIdx += getEndianAdjustedWord(getHeader().StringsOffset);
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// Check for invalid index.
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if (StrTabIdx >= FileBuffer->getBufferSize())
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return nullptr;
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// Otherwise, we have a valid pointer into the file. Just return it. We know
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// that the "string" can not overrun the end of the file, because the buffer
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// is nul terminated by virtue of being a MemoryBuffer.
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return FileBuffer->getBufferStart()+StrTabIdx;
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}
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//===----------------------------------------------------------------------===//
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// The Main Drivers
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//===----------------------------------------------------------------------===//
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/// dump - Print the contents of this headermap to stderr.
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void HeaderMap::dump() const {
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const HMapHeader &Hdr = getHeader();
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unsigned NumBuckets = getEndianAdjustedWord(Hdr.NumBuckets);
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fprintf(stderr, "Header Map %s:\n %d buckets, %d entries\n",
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getFileName(), NumBuckets,
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getEndianAdjustedWord(Hdr.NumEntries));
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for (unsigned i = 0; i != NumBuckets; ++i) {
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HMapBucket B = getBucket(i);
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if (B.Key == HMAP_EmptyBucketKey) continue;
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const char *Key = getString(B.Key);
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const char *Prefix = getString(B.Prefix);
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const char *Suffix = getString(B.Suffix);
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fprintf(stderr, " %d. %s -> '%s' '%s'\n", i, Key, Prefix, Suffix);
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}
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}
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/// LookupFile - Check to see if the specified relative filename is located in
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/// this HeaderMap. If so, open it and return its FileEntry.
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const FileEntry *HeaderMap::LookupFile(
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StringRef Filename, FileManager &FM) const {
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SmallString<1024> Path;
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StringRef Dest = lookupFilename(Filename, Path);
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if (Dest.empty())
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return nullptr;
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return FM.getFile(Dest);
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}
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StringRef HeaderMap::lookupFilename(StringRef Filename,
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SmallVectorImpl<char> &DestPath) const {
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const HMapHeader &Hdr = getHeader();
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unsigned NumBuckets = getEndianAdjustedWord(Hdr.NumBuckets);
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// If the number of buckets is not a power of two, the headermap is corrupt.
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// Don't probe infinitely.
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if (NumBuckets & (NumBuckets-1))
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return StringRef();
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// Linearly probe the hash table.
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for (unsigned Bucket = HashHMapKey(Filename);; ++Bucket) {
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HMapBucket B = getBucket(Bucket & (NumBuckets-1));
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if (B.Key == HMAP_EmptyBucketKey) return StringRef(); // Hash miss.
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// See if the key matches. If not, probe on.
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if (!Filename.equals_lower(getString(B.Key)))
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continue;
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// If so, we have a match in the hash table. Construct the destination
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// path.
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StringRef Prefix = getString(B.Prefix);
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StringRef Suffix = getString(B.Suffix);
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DestPath.clear();
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DestPath.append(Prefix.begin(), Prefix.end());
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DestPath.append(Suffix.begin(), Suffix.end());
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return StringRef(DestPath.begin(), DestPath.size());
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}
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}
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