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llvm-mirror/lib/Support/MemoryBuffer.cpp
Argyrios Kyrtzidis 697931fd3d In llvm::MemoryBuffer::getFile() remove an unnecessary stat call check. 
The sys::fs::is_directory() check is unnecessary because, if the filename is
a directory, the function will fail anyway with the same error code returned.
Remove the check to avoid an unnecessary stat call.

Someone needs to review on windows and see if the check is necessary there or not.

llvm-svn: 176386
2013-03-01 22:48:51 +00:00

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//===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements the MemoryBuffer interface.
//
//===----------------------------------------------------------------------===//
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/Config/config.h"
#include "llvm/Support/Errno.h"
#include "llvm/Support/FileSystem.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/Process.h"
#include "llvm/Support/Program.h"
#include "llvm/Support/system_error.h"
#include <cassert>
#include <cerrno>
#include <cstdio>
#include <cstring>
#include <new>
#include <sys/stat.h>
#include <sys/types.h>
#if !defined(_MSC_VER) && !defined(__MINGW32__)
#include <unistd.h>
#else
#include <io.h>
// Simplistic definitinos of these macros to allow files to be read with
// MapInFilePages.
#ifndef S_ISREG
#define S_ISREG(x) (1)
#endif
#ifndef S_ISBLK
#define S_ISBLK(x) (0)
#endif
#endif
#include <fcntl.h>
using namespace llvm;
//===----------------------------------------------------------------------===//
// MemoryBuffer implementation itself.
//===----------------------------------------------------------------------===//
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,
bool RequiresNullTerminator) {
assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
"Buffer is not null terminated!");
BufferStart = BufStart;
BufferEnd = BufEnd;
}
//===----------------------------------------------------------------------===//
// MemoryBufferMem implementation.
//===----------------------------------------------------------------------===//
/// CopyStringRef - Copies contents of a StringRef into a block of memory and
/// null-terminates it.
static void CopyStringRef(char *Memory, StringRef Data) {
memcpy(Memory, Data.data(), Data.size());
Memory[Data.size()] = 0; // Null terminate string.
}
/// GetNamedBuffer - Allocates a new MemoryBuffer with Name copied after it.
template <typename T>
static T *GetNamedBuffer(StringRef Buffer, StringRef Name,
bool RequiresNullTerminator) {
char *Mem = static_cast<char*>(operator new(sizeof(T) + Name.size() + 1));
CopyStringRef(Mem + sizeof(T), Name);
return new (Mem) T(Buffer, RequiresNullTerminator);
}
namespace {
/// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
class MemoryBufferMem : public MemoryBuffer {
public:
MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
init(InputData.begin(), InputData.end(), RequiresNullTerminator);
}
virtual const char *getBufferIdentifier() const LLVM_OVERRIDE {
// The name is stored after the class itself.
return reinterpret_cast<const char*>(this + 1);
}
virtual BufferKind getBufferKind() const LLVM_OVERRIDE {
return MemoryBuffer_Malloc;
}
};
}
/// getMemBuffer - Open the specified memory range as a MemoryBuffer. Note
/// that InputData must be a null terminated if RequiresNullTerminator is true!
MemoryBuffer *MemoryBuffer::getMemBuffer(StringRef InputData,
StringRef BufferName,
bool RequiresNullTerminator) {
return GetNamedBuffer<MemoryBufferMem>(InputData, BufferName,
RequiresNullTerminator);
}
/// getMemBufferCopy - Open the specified memory range as a MemoryBuffer,
/// copying the contents and taking ownership of it. This has no requirements
/// on EndPtr[0].
MemoryBuffer *MemoryBuffer::getMemBufferCopy(StringRef InputData,
StringRef BufferName) {
MemoryBuffer *Buf = getNewUninitMemBuffer(InputData.size(), BufferName);
if (!Buf) return 0;
memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
InputData.size());
return Buf;
}
/// getNewUninitMemBuffer - Allocate a new MemoryBuffer of the specified size
/// that is not initialized. Note that the caller should initialize the
/// memory allocated by this method. The memory is owned by the MemoryBuffer
/// object.
MemoryBuffer *MemoryBuffer::getNewUninitMemBuffer(size_t Size,
StringRef BufferName) {
// Allocate space for the MemoryBuffer, the data and the name. It is important
// that MemoryBuffer and data are aligned so PointerIntPair works with them.
size_t AlignedStringLen =
RoundUpToAlignment(sizeof(MemoryBufferMem) + BufferName.size() + 1,
sizeof(void*)); // TODO: Is sizeof(void*) enough?
size_t RealLen = AlignedStringLen + Size + 1;
char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
if (!Mem) return 0;
// The name is stored after the class itself.
CopyStringRef(Mem + sizeof(MemoryBufferMem), BufferName);
// The buffer begins after the name and must be aligned.
char *Buf = Mem + AlignedStringLen;
Buf[Size] = 0; // Null terminate buffer.
return new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);
}
/// getNewMemBuffer - Allocate a new MemoryBuffer of the specified size that
/// is completely initialized to zeros. Note that the caller should
/// initialize the memory allocated by this method. The memory is owned by
/// the MemoryBuffer object.
MemoryBuffer *MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {
MemoryBuffer *SB = getNewUninitMemBuffer(Size, BufferName);
if (!SB) return 0;
memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
return SB;
}
/// getFileOrSTDIN - Open the specified file as a MemoryBuffer, or open stdin
/// if the Filename is "-". If an error occurs, this returns null and fills
/// in *ErrStr with a reason. If stdin is empty, this API (unlike getSTDIN)
/// returns an empty buffer.
error_code MemoryBuffer::getFileOrSTDIN(StringRef Filename,
OwningPtr<MemoryBuffer> &result,
int64_t FileSize) {
if (Filename == "-")
return getSTDIN(result);
return getFile(Filename, result, FileSize);
}
error_code MemoryBuffer::getFileOrSTDIN(const char *Filename,
OwningPtr<MemoryBuffer> &result,
int64_t FileSize) {
if (strcmp(Filename, "-") == 0)
return getSTDIN(result);
return getFile(Filename, result, FileSize);
}
//===----------------------------------------------------------------------===//
// MemoryBuffer::getFile implementation.
//===----------------------------------------------------------------------===//
namespace {
/// MemoryBufferMMapFile - This represents a file that was mapped in with the
/// sys::Path::MapInFilePages method. When destroyed, it calls the
/// sys::Path::UnMapFilePages method.
class MemoryBufferMMapFile : public MemoryBufferMem {
public:
MemoryBufferMMapFile(StringRef Buffer, bool RequiresNullTerminator)
: MemoryBufferMem(Buffer, RequiresNullTerminator) { }
~MemoryBufferMMapFile() {
static int PageSize = sys::process::get_self()->page_size();
uintptr_t Start = reinterpret_cast<uintptr_t>(getBufferStart());
size_t Size = getBufferSize();
uintptr_t RealStart = Start & ~(PageSize - 1);
size_t RealSize = Size + (Start - RealStart);
sys::Path::UnMapFilePages(reinterpret_cast<const char*>(RealStart),
RealSize);
}
virtual BufferKind getBufferKind() const LLVM_OVERRIDE {
return MemoryBuffer_MMap;
}
};
}
static error_code getMemoryBufferForStream(int FD,
StringRef BufferName,
OwningPtr<MemoryBuffer> &result) {
const ssize_t ChunkSize = 4096*4;
SmallString<ChunkSize> Buffer;
ssize_t ReadBytes;
// Read into Buffer until we hit EOF.
do {
Buffer.reserve(Buffer.size() + ChunkSize);
ReadBytes = read(FD, Buffer.end(), ChunkSize);
if (ReadBytes == -1) {
if (errno == EINTR) continue;
return error_code(errno, posix_category());
}
Buffer.set_size(Buffer.size() + ReadBytes);
} while (ReadBytes != 0);
result.reset(MemoryBuffer::getMemBufferCopy(Buffer, BufferName));
return error_code::success();
}
error_code MemoryBuffer::getFile(StringRef Filename,
OwningPtr<MemoryBuffer> &result,
int64_t FileSize,
bool RequiresNullTerminator) {
// Ensure the path is null terminated.
SmallString<256> PathBuf(Filename.begin(), Filename.end());
return MemoryBuffer::getFile(PathBuf.c_str(), result, FileSize,
RequiresNullTerminator);
}
error_code MemoryBuffer::getFile(const char *Filename,
OwningPtr<MemoryBuffer> &result,
int64_t FileSize,
bool RequiresNullTerminator) {
// FIXME: Review if this check is unnecessary on windows as well.
#ifdef LLVM_ON_WIN32
// First check that the "file" is not a directory
bool is_dir = false;
error_code err = sys::fs::is_directory(Filename, is_dir);
if (err)
return err;
if (is_dir)
return make_error_code(errc::is_a_directory);
#endif
int OpenFlags = O_RDONLY;
#ifdef O_BINARY
OpenFlags |= O_BINARY; // Open input file in binary mode on win32.
#endif
int FD = ::open(Filename, OpenFlags);
if (FD == -1)
return error_code(errno, posix_category());
error_code ret = getOpenFile(FD, Filename, result, FileSize, FileSize,
0, RequiresNullTerminator);
close(FD);
return ret;
}
static bool shouldUseMmap(int FD,
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 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.
// FIXME: this chunk of code is duplicated, but it avoids a fstat when
// RequiresNullTerminator = false and MapSize != -1.
if (FileSize == size_t(-1)) {
struct stat FileInfo;
// TODO: This should use fstat64 when available.
if (fstat(FD, &FileInfo) == -1) {
return error_code(errno, posix_category());
}
FileSize = FileInfo.st_size;
}
// 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<MemoryBuffer> &result,
uint64_t FileSize, uint64_t MapSize,
int64_t Offset,
bool RequiresNullTerminator) {
static int PageSize = sys::process::get_self()->page_size();
// Default is to map the full file.
if (MapSize == uint64_t(-1)) {
// 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 == uint64_t(-1)) {
struct stat FileInfo;
// TODO: This should use fstat64 when available.
if (fstat(FD, &FileInfo) == -1) {
return error_code(errno, posix_category());
}
// If this not a file or a block device (e.g. it's a named pipe
// or character device), we can't trust the size. Create the memory
// buffer by copying off the stream.
if (!S_ISREG(FileInfo.st_mode) && !S_ISBLK(FileInfo.st_mode)) {
return getMemoryBufferForStream(FD, Filename, result);
}
FileSize = FileInfo.st_size;
}
MapSize = FileSize;
}
if (shouldUseMmap(FD, 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<MemoryBufferMMapFile>(
StringRef(Pages + Delta, MapSize), Filename, RequiresNullTerminator));
return error_code::success();
}
}
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.
return make_error_code(errc::not_enough_memory);
}
OwningPtr<MemoryBuffer> SB(Buf);
char *BufPtr = const_cast<char*>(SB->getBufferStart());
size_t BytesLeft = MapSize;
#ifndef HAVE_PREAD
if (lseek(FD, Offset, SEEK_SET) == -1)
return error_code(errno, posix_category());
#endif
while (BytesLeft) {
#ifdef HAVE_PREAD
ssize_t NumRead = ::pread(FD, BufPtr, BytesLeft, MapSize-BytesLeft+Offset);
#else
ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
#endif
if (NumRead == -1) {
if (errno == EINTR)
continue;
// Error while reading.
return error_code(errno, posix_category());
}
if (NumRead == 0) {
assert(0 && "We got inaccurate FileSize value or fstat reported an "
"invalid file size.");
*BufPtr = '\0'; // null-terminate at the actual size.
break;
}
BytesLeft -= NumRead;
BufPtr += NumRead;
}
result.swap(SB);
return error_code::success();
}
//===----------------------------------------------------------------------===//
// MemoryBuffer::getSTDIN implementation.
//===----------------------------------------------------------------------===//
error_code MemoryBuffer::getSTDIN(OwningPtr<MemoryBuffer> &result) {
// Read in all of the data from stdin, we cannot mmap stdin.
//
// FIXME: That isn't necessarily true, we should try to mmap stdin and
// fallback if it fails.
sys::Program::ChangeStdinToBinary();
return getMemoryBufferForStream(0, "<stdin>", result);
}
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