llvm-6502/lib/Support/MemoryBuffer.cpp
Rafael Espindola 70c7e48545 Split getOpenFile into getOpenFile and getOpenFileSlice.
The main observation is that we never need both the filesize and the map size.
When mapping a slice of a file, it doesn't make sense to request a null
terminator and that would be the only case where the filesize would be used.

There are other cleanups that should be done in this area:

* A client should not have to pass the size (even an explicit -1) to say if
  it wants a null terminator or not, so we should probably swap the argument
  order.
* The default should be to not require a null terminator. Very few clients
  require this, but many end up asking for it just because it is the default.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@186984 91177308-0d34-0410-b5e6-96231b3b80d8
2013-07-23 20:25:01 +00:00

420 lines
15 KiB
C++

//===--- 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 for use in getOpenFile.
#ifndef S_ISREG
#define S_ISREG(x) (1)
#endif
#ifndef S_ISBLK
#define S_ISBLK(x) (0)
#endif
#endif
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.
}
namespace {
struct NamedBufferAlloc {
StringRef Name;
NamedBufferAlloc(StringRef Name) : Name(Name) {}
};
}
void *operator new(size_t N, const NamedBufferAlloc &Alloc) {
char *Mem = static_cast<char *>(operator new(N + Alloc.Name.size() + 1));
CopyStringRef(Mem + N, Alloc.Name);
return Mem;
}
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 new (NamedBufferAlloc(BufferName))
MemoryBufferMem(InputData, 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);
}
//===----------------------------------------------------------------------===//
// MemoryBuffer::getFile implementation.
//===----------------------------------------------------------------------===//
namespace {
/// \brief Memorry maps a file descriptor using sys::fs::mapped_file_region.
///
/// This handles converting the offset into a legal offset on the platform.
class MemoryBufferMMapFile : public MemoryBuffer {
sys::fs::mapped_file_region MFR;
static uint64_t getLegalMapOffset(uint64_t Offset) {
return Offset & ~(sys::fs::mapped_file_region::alignment() - 1);
}
static uint64_t getLegalMapSize(uint64_t Len, uint64_t Offset) {
return Len + (Offset - getLegalMapOffset(Offset));
}
const char *getStart(uint64_t Len, uint64_t Offset) {
return MFR.const_data() + (Offset - getLegalMapOffset(Offset));
}
public:
MemoryBufferMMapFile(bool RequiresNullTerminator, int FD, uint64_t Len,
uint64_t Offset, error_code EC)
: MFR(FD, false, sys::fs::mapped_file_region::readonly,
getLegalMapSize(Len, Offset), getLegalMapOffset(Offset), EC) {
if (!EC) {
const char *Start = getStart(Len, Offset);
init(Start, Start + Len, 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_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);
}
static error_code getOpenFileImpl(int FD, const char *Filename,
OwningPtr<MemoryBuffer> &Result,
uint64_t FileSize, uint64_t MapSize,
int64_t Offset, bool RequiresNullTerminator);
error_code MemoryBuffer::getFile(const char *Filename,
OwningPtr<MemoryBuffer> &result,
int64_t FileSize,
bool RequiresNullTerminator) {
int FD;
error_code EC = sys::fs::openFileForRead(Filename, FD);
if (EC)
return EC;
error_code ret = getOpenFileImpl(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)) {
sys::fs::file_status Status;
error_code EC = sys::fs::status(FD, Status);
if (EC)
return EC;
FileSize = Status.getSize();
}
// 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;
}
static error_code getOpenFileImpl(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)) {
sys::fs::file_status Status;
error_code EC = sys::fs::status(FD, Status);
if (EC)
return EC;
// 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.
sys::fs::file_type Type = Status.type();
if (Type != sys::fs::file_type::regular_file &&
Type != sys::fs::file_type::block_file)
return getMemoryBufferForStream(FD, Filename, result);
FileSize = Status.getSize();
}
MapSize = FileSize;
}
if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
PageSize)) {
error_code EC;
result.reset(new (NamedBufferAlloc(Filename)) MemoryBufferMMapFile(
RequiresNullTerminator, FD, MapSize, Offset, EC));
if (!EC)
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();
}
error_code MemoryBuffer::getOpenFile(int FD, const char *Filename,
OwningPtr<MemoryBuffer> &Result,
uint64_t FileSize,
bool RequiresNullTerminator) {
return getOpenFileImpl(FD, Filename, Result, FileSize, FileSize, 0,
RequiresNullTerminator);
}
error_code MemoryBuffer::getOpenFileSlice(int FD, const char *Filename,
OwningPtr<MemoryBuffer> &Result,
uint64_t MapSize, int64_t Offset) {
return getOpenFileImpl(FD, Filename, Result, -1, MapSize, Offset, false);
}
//===----------------------------------------------------------------------===//
// 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::ChangeStdinToBinary();
return getMemoryBufferForStream(0, "<stdin>", result);
}