From 7deb187736b09aa0805b7d9902f499e41feefccc Mon Sep 17 00:00:00 2001 From: Rafael Espindola Date: Thu, 10 Mar 2011 16:10:30 +0000 Subject: [PATCH] Add support for MemoryBuffers that are not null terminated and add support for creating buffers that cover only a part of a file. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@127409 91177308-0d34-0410-b5e6-96231b3b80d8 --- include/llvm/Support/MemoryBuffer.h | 8 ++- include/llvm/Support/PathV1.h | 5 +- lib/Support/MemoryBuffer.cpp | 99 +++++++++++++++++++++-------- lib/Support/Unix/Path.inc | 6 +- 4 files changed, 86 insertions(+), 32 deletions(-) diff --git a/include/llvm/Support/MemoryBuffer.h b/include/llvm/Support/MemoryBuffer.h index b6243b7b10d..a52dc11cffa 100644 --- a/include/llvm/Support/MemoryBuffer.h +++ b/include/llvm/Support/MemoryBuffer.h @@ -40,7 +40,8 @@ class MemoryBuffer { MemoryBuffer &operator=(const MemoryBuffer &); // DO NOT IMPLEMENT protected: MemoryBuffer() {} - void init(const char *BufStart, const char *BufEnd); + void init(const char *BufStart, const char *BufEnd, + bool RequiresNullTerminator); public: virtual ~MemoryBuffer(); @@ -72,7 +73,10 @@ public: /// return a MemoryBuffer. static error_code getOpenFile(int FD, const char *Filename, OwningPtr &result, - int64_t FileSize = -1); + size_t FileSize = -1, + size_t MapSize = -1, + off_t Offset = 0, + bool RequiresNullTerminator = true); /// getMemBuffer - Open the specified memory range as a MemoryBuffer. Note /// that InputData must be null terminated. diff --git a/include/llvm/Support/PathV1.h b/include/llvm/Support/PathV1.h index d7753a3e71e..024bb39cedc 100644 --- a/include/llvm/Support/PathV1.h +++ b/include/llvm/Support/PathV1.h @@ -608,14 +608,15 @@ namespace sys { /// /// This API is not intended for general use, clients should use /// MemoryBuffer::getFile instead. - static const char *MapInFilePages(int FD, uint64_t FileSize); + static const char *MapInFilePages(int FD, size_t FileSize, + off_t Offset); /// UnMapFilePages - Free pages mapped into the current process by /// MapInFilePages. /// /// This API is not intended for general use, clients should use /// MemoryBuffer::getFile instead. - static void UnMapFilePages(const char *Base, uint64_t FileSize); + static void UnMapFilePages(const char *Base, size_t FileSize); /// @} /// @name Data diff --git a/lib/Support/MemoryBuffer.cpp b/lib/Support/MemoryBuffer.cpp index a0c650d6820..80d556cbf5b 100644 --- a/lib/Support/MemoryBuffer.cpp +++ b/lib/Support/MemoryBuffer.cpp @@ -46,8 +46,10 @@ MemoryBuffer::~MemoryBuffer() { } /// init - Initialize this MemoryBuffer as a reference to externally allocated /// memory, memory that we know is already null terminated. -void MemoryBuffer::init(const char *BufStart, const char *BufEnd) { - assert(BufEnd[0] == 0 && "Buffer is not null terminated!"); +void MemoryBuffer::init(const char *BufStart, const char *BufEnd, + bool RequiresNullTerminator) { + assert((BufEnd[0] == 0 || !RequiresNullTerminator) && + "Buffer is not null terminated!"); BufferStart = BufStart; BufferEnd = BufEnd; } @@ -65,18 +67,19 @@ static void CopyStringRef(char *Memory, StringRef Data) { /// GetNamedBuffer - Allocates a new MemoryBuffer with Name copied after it. template -static T* GetNamedBuffer(StringRef Buffer, StringRef Name) { +static T* GetNamedBuffer(StringRef Buffer, StringRef Name, + bool RequiresNullTerminator) { char *Mem = static_cast(operator new(sizeof(T) + Name.size() + 1)); CopyStringRef(Mem + sizeof(T), Name); - return new (Mem) T(Buffer); + return new (Mem) T(Buffer, RequiresNullTerminator); } namespace { /// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory. class MemoryBufferMem : public MemoryBuffer { public: - MemoryBufferMem(StringRef InputData) { - init(InputData.begin(), InputData.end()); + MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) { + init(InputData.begin(), InputData.end(), RequiresNullTerminator); } virtual const char *getBufferIdentifier() const { @@ -90,7 +93,7 @@ public: /// that EndPtr[0] must be a null byte and be accessible! MemoryBuffer *MemoryBuffer::getMemBuffer(StringRef InputData, StringRef BufferName) { - return GetNamedBuffer(InputData, BufferName); + return GetNamedBuffer(InputData, BufferName, true); } /// getMemBufferCopy - Open the specified memory range as a MemoryBuffer, @@ -127,7 +130,7 @@ MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(size_t Size, char *Buf = Mem + AlignedStringLen; Buf[Size] = 0; // Null terminate buffer. - return new (Mem) MemoryBufferMem(StringRef(Buf, Size)); + return new (Mem) MemoryBufferMem(StringRef(Buf, Size), true); } /// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that @@ -172,11 +175,19 @@ namespace { /// sys::Path::UnMapFilePages method. class MemoryBufferMMapFile : public MemoryBufferMem { public: - MemoryBufferMMapFile(StringRef Buffer) - : MemoryBufferMem(Buffer) { } + MemoryBufferMMapFile(StringRef Buffer, bool RequiresNullTerminator) + : MemoryBufferMem(Buffer, RequiresNullTerminator) { } ~MemoryBufferMMapFile() { - sys::Path::UnMapFilePages(getBufferStart(), getBufferSize()); + static int PageSize = sys::Process::GetPageSize(); + + uintptr_t Start = reinterpret_cast(getBufferStart()); + size_t Size = getBufferSize(); + uintptr_t RealStart = Start & ~(PageSize - 1); + size_t RealSize = Size + (Start - RealStart); + + sys::Path::UnMapFilePages(reinterpret_cast(RealStart), + RealSize); } }; } @@ -205,12 +216,44 @@ error_code MemoryBuffer::getFile(const char *Filename, return ret; } +static bool shouldUseMmap(size_t FileSize, + size_t MapSize, + off_t Offset, + bool RequiresNullTerminator, + int PageSize) { + // We don't use mmap for small files because this can severely fragment our + // address space. + if (MapSize < 4096*4) + return false; + + if (!RequiresNullTerminator) + return true; + + // If we need a null terminator and the end of the map is inside the file, + // we cannot use mmap. + size_t End = Offset + MapSize; + assert(End <= FileSize); + if (End != FileSize) + return false; + + // Don't try to map files that are exactly a multiple of the system page size + // if we need a null terminator. + if ((FileSize & (PageSize -1)) == 0) + return false; + + return true; +} + error_code MemoryBuffer::getOpenFile(int FD, const char *Filename, OwningPtr &result, - int64_t FileSize) { + size_t FileSize, size_t MapSize, + off_t Offset, + bool RequiresNullTerminator) { + static int PageSize = sys::Process::GetPageSize(); + // If we don't know the file size, use fstat to find out. fstat on an open // file descriptor is cheaper than stat on a random path. - if (FileSize == -1) { + if (FileSize == size_t(-1)) { struct stat FileInfo; // TODO: This should use fstat64 when available. if (fstat(FD, &FileInfo) == -1) { @@ -219,23 +262,26 @@ error_code MemoryBuffer::getOpenFile(int FD, const char *Filename, FileSize = FileInfo.st_size; } + // Default is to map the full file. + if (MapSize == size_t(-1)) + MapSize = FileSize; - // If the file is large, try to use mmap to read it in. We don't use mmap - // for small files, because this can severely fragment our address space. Also - // don't try to map files that are exactly a multiple of the system page size, - // as the file would not have the required null terminator. - // - // FIXME: Can we just mmap an extra page in the latter case? - if (FileSize >= 4096*4 && - (FileSize & (sys::Process::GetPageSize()-1)) != 0) { - if (const char *Pages = sys::Path::MapInFilePages(FD, FileSize)) { + if (shouldUseMmap(FileSize, MapSize, Offset, RequiresNullTerminator, + PageSize)) { + off_t RealMapOffset = Offset & ~(PageSize - 1); + off_t Delta = Offset - RealMapOffset; + size_t RealMapSize = MapSize + Delta; + + if (const char *Pages = sys::Path::MapInFilePages(FD, + RealMapSize, + RealMapOffset)) { result.reset(GetNamedBuffer( - StringRef(Pages, FileSize), Filename)); + StringRef(Pages + Delta, MapSize), Filename, RequiresNullTerminator)); return success; } } - MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(FileSize, Filename); + MemoryBuffer *Buf = MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename); if (!Buf) { // Failed to create a buffer. The only way it can fail is if // new(std::nothrow) returns 0. @@ -245,7 +291,10 @@ error_code MemoryBuffer::getOpenFile(int FD, const char *Filename, OwningPtr SB(Buf); char *BufPtr = const_cast(SB->getBufferStart()); - size_t BytesLeft = FileSize; + size_t BytesLeft = MapSize; + if (lseek(FD, Offset, SEEK_SET) == -1) + return error_code(errno, posix_category()); + while (BytesLeft) { ssize_t NumRead = ::read(FD, BufPtr, BytesLeft); if (NumRead == -1) { diff --git a/lib/Support/Unix/Path.inc b/lib/Support/Unix/Path.inc index 0f6e800505e..430cf2ed8e8 100644 --- a/lib/Support/Unix/Path.inc +++ b/lib/Support/Unix/Path.inc @@ -869,18 +869,18 @@ Path::makeUnique(bool reuse_current, std::string* ErrMsg) { return false; } -const char *Path::MapInFilePages(int FD, uint64_t FileSize) { +const char *Path::MapInFilePages(int FD, size_t FileSize, off_t Offset) { int Flags = MAP_PRIVATE; #ifdef MAP_FILE Flags |= MAP_FILE; #endif - void *BasePtr = ::mmap(0, FileSize, PROT_READ, Flags, FD, 0); + void *BasePtr = ::mmap(0, FileSize, PROT_READ, Flags, FD, Offset); if (BasePtr == MAP_FAILED) return 0; return (const char*)BasePtr; } -void Path::UnMapFilePages(const char *BasePtr, uint64_t FileSize) { +void Path::UnMapFilePages(const char *BasePtr, size_t FileSize) { ::munmap((void*)BasePtr, FileSize); }