DirectXShaderCompiler/lib/Support/MemoryBuffer.cpp at main · microsoft/DirectXShaderCompiler · GitHub

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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/SmallString.h"

#include "llvm/Config/config.h"

#include "llvm/Support/Errc.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 <cassert>

#include <cerrno>

#include <cstring>

#include <new>

#include <sys/types.h>

#include <system_error>

#if !defined(_MSC_VER) && !defined(__MINGW32__)

#include <unistd.h>

#else

#include <io.h>

#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) {

if (!Data.empty())

memcpy(Memory, Data.data(), Data.size());

Memory[Data.size()] = 0; // Null terminate string.

}

namespace {

struct NamedBufferAlloc {

const Twine &Name;

NamedBufferAlloc(const Twine &Name) : Name(Name) {}

};

}

void *operator new(size_t N, const NamedBufferAlloc &Alloc) {

SmallString<256> NameBuf;

StringRef NameRef = Alloc.Name.toStringRef(NameBuf);

char *Mem = static_cast<char *>(operator new(N + NameRef.size() + 1));

CopyStringRef(Mem + N, NameRef);

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);

}

// Disable sized deallocation for MemoryByfferMem, because it has

// tail-allocated data.

// (See llvm commit 21c303e9eadfbd2d685665176159f5f4738169b1)

void operator delete(void *p) { ::operator delete(p); }

const char *getBufferIdentifier() const override {

// The name is stored after the class itself.

return reinterpret_cast<const char*>(this + 1);

}

BufferKind getBufferKind() const override {

return MemoryBuffer_Malloc;

}

};

}

static ErrorOr<std::unique_ptr<MemoryBuffer>>

getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,

uint64_t Offset, bool RequiresNullTerminator, bool IsVolatileSize);

std::unique_ptr<MemoryBuffer>

MemoryBuffer::getMemBuffer(StringRef InputData, StringRef BufferName,

bool RequiresNullTerminator) {

auto *Ret = new (NamedBufferAlloc(BufferName))

MemoryBufferMem(InputData, RequiresNullTerminator);

return std::unique_ptr<MemoryBuffer>(Ret);

}

std::unique_ptr<MemoryBuffer>

MemoryBuffer::getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator) {

return std::unique_ptr<MemoryBuffer>(getMemBuffer(

Ref.getBuffer(), Ref.getBufferIdentifier(), RequiresNullTerminator));

}

std::unique_ptr<MemoryBuffer>

MemoryBuffer::getMemBufferCopy(StringRef InputData, const Twine &BufferName) {

std::unique_ptr<MemoryBuffer> Buf =

getNewUninitMemBuffer(InputData.size(), BufferName);

if (!Buf)

return nullptr;

if (InputData.size())

memcpy(const_cast<char *>(Buf->getBufferStart()), InputData.data(),

InputData.size());

return Buf;

}

std::unique_ptr<MemoryBuffer>

MemoryBuffer::getNewUninitMemBuffer(size_t Size, const Twine &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.

// TODO: Is 16-byte alignment enough? We copy small object files with large

// alignment expectations into this buffer.

SmallString<256> NameBuf;

StringRef NameRef = BufferName.toStringRef(NameBuf);

size_t AlignedStringLen =

RoundUpToAlignment(sizeof(MemoryBufferMem) + NameRef.size() + 1, 16);

size_t RealLen = AlignedStringLen + Size + 1;

char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));

if (!Mem)

return nullptr;

// The name is stored after the class itself.

CopyStringRef(Mem + sizeof(MemoryBufferMem), NameRef);

// The buffer begins after the name and must be aligned.

char *Buf = Mem + AlignedStringLen;

Buf[Size] = 0; // Null terminate buffer.

auto *Ret = new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);

return std::unique_ptr<MemoryBuffer>(Ret);

}

std::unique_ptr<MemoryBuffer>

MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {

std::unique_ptr<MemoryBuffer> SB = getNewUninitMemBuffer(Size, BufferName);

if (!SB)

return nullptr;

memset(const_cast<char*>(SB->getBufferStart()), 0, Size);

return SB;

}

ErrorOr<std::unique_ptr<MemoryBuffer>>

MemoryBuffer::getFileOrSTDIN(const Twine &Filename, int64_t FileSize) {

SmallString<256> NameBuf;

StringRef NameRef = Filename.toStringRef(NameBuf);

if (NameRef == "-")

return getSTDIN();

return getFile(Filename, FileSize);

}

ErrorOr<std::unique_ptr<MemoryBuffer>>

MemoryBuffer::getFileSlice(const Twine &FilePath, uint64_t MapSize,

uint64_t Offset) {

return getFileAux(FilePath, -1, MapSize, Offset, false, false);

}

//===----------------------------------------------------------------------===//

// MemoryBuffer::getFile implementation.

//===----------------------------------------------------------------------===//

namespace {

/// \brief Memory 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, std::error_code &EC)

: MFR(FD, 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);

}

// Disable sized deallocation for MemoryByfferMem, because it has

// tail-allocated data.

// (See llvm commit 21c303e9eadfbd2d685665176159f5f4738169b1)

void operator delete(void *p) { ::operator delete(p); }

const char *getBufferIdentifier() const override {

// The name is stored after the class itself.

return reinterpret_cast<const char *>(this + 1);

}

BufferKind getBufferKind() const override {

return MemoryBuffer_MMap;

}

};

}

static ErrorOr<std::unique_ptr<MemoryBuffer>>

getMemoryBufferForStream(int FD, const Twine &BufferName) {

const ssize_t ChunkSize = 4096*4;

const ssize_t InitialChunkSize = 4096*2; // HLSL Change - be more conservative on how much stack space we start with

SmallString<InitialChunkSize> Buffer;

ssize_t ReadBytes;

// Read into Buffer until we hit EOF.

do {

Buffer.reserve(Buffer.size() + ChunkSize);

ReadBytes = llvm::sys::fs::msf_read(FD, Buffer.end(), ChunkSize);

if (ReadBytes == -1) {

if (errno == EINTR) continue;

return std::error_code(errno, std::generic_category());

}

Buffer.set_size(Buffer.size() + ReadBytes);

} while (ReadBytes != 0);

return MemoryBuffer::getMemBufferCopy(Buffer, BufferName);

}

ErrorOr<std::unique_ptr<MemoryBuffer>>

MemoryBuffer::getFile(const Twine &Filename, int64_t FileSize,

bool RequiresNullTerminator, bool IsVolatileSize) {

return getFileAux(Filename, FileSize, FileSize, 0,

RequiresNullTerminator, IsVolatileSize);

}

static ErrorOr<std::unique_ptr<MemoryBuffer>>

getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,

uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,

bool IsVolatileSize);

static ErrorOr<std::unique_ptr<MemoryBuffer>>

getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,

uint64_t Offset, bool RequiresNullTerminator, bool IsVolatileSize) {

int FD;

std::error_code EC = sys::fs::openFileForRead(Filename, FD);

if (EC)

return EC;

ErrorOr<std::unique_ptr<MemoryBuffer>> Ret =

getOpenFileImpl(FD, Filename, FileSize, MapSize, Offset,

RequiresNullTerminator, IsVolatileSize);

llvm::sys::fs::msf_close(FD); // HLSL Change - use msf_close

return Ret;

}

static bool shouldUseMmap(int FD,

size_t FileSize,

size_t MapSize,

off_t Offset,

bool RequiresNullTerminator,

int PageSize,

bool IsVolatileSize) {

// mmap may leave the buffer without null terminator if the file size changed

// by the time the last page is mapped in, so avoid it if the file size is

// likely to change.

if (IsVolatileSize)

return false;

// We don't use mmap for small files because this can severely fragment our

// address space.

if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)

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;

if (sys::fs::status(FD, Status))

return false;

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;

#if defined(__CYGWIN__)

// Don't try to map files that are exactly a multiple of the physical page size

// if we need a null terminator.

// FIXME: We should reorganize again getPageSize() on Win32.

if ((FileSize & (4096 - 1)) == 0)

return false;

#endif

return true;

}

static ErrorOr<std::unique_ptr<MemoryBuffer>>

getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,

uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,

bool IsVolatileSize) {

static int PageSize = sys::Process::getPageSize();

// 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;

std::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);

FileSize = Status.getSize();

}

MapSize = FileSize;

}

if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,

PageSize, IsVolatileSize)) {

std::error_code EC;

std::unique_ptr<MemoryBuffer> Result(

new (NamedBufferAlloc(Filename))

MemoryBufferMMapFile(RequiresNullTerminator, FD, MapSize, Offset, EC));

if (!EC) {

return ErrorOr(

std::move(Result)); // HLSL Change - Fix redundant move warning.

}

std::unique_ptr<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);

}

char *BufPtr = const_cast<char *>(Buf->getBufferStart());

size_t BytesLeft = MapSize;

#undef HAVE_PREAD // HLSL Change - pread bypasses needed layers

#ifndef HAVE_PREAD

if (llvm::sys::fs::msf_lseek(FD, Offset, SEEK_SET) == -1) // HLSL Change - use msf_lseek

return std::error_code(errno, std::generic_category());

#endif

while (BytesLeft) {

#ifdef HAVE_PREAD

ssize_t NumRead = ::pread(FD, BufPtr, BytesLeft, MapSize-BytesLeft+Offset);

#else

ssize_t NumRead = ::llvm::sys::fs::msf_read(FD, BufPtr, BytesLeft);

#endif

if (NumRead == -1) {

if (errno == EINTR)

continue;

// Error while reading.

return std::error_code(errno, std::generic_category());

}

if (NumRead == 0) {

memset(BufPtr, 0, BytesLeft); // zero-initialize rest of the buffer.

break;

}

BytesLeft -= NumRead;

BufPtr += NumRead;

}

return ErrorOr(std::move(Buf)); // HLSL Change - Fix redundant move warning.

}

ErrorOr<std::unique_ptr<MemoryBuffer>>

MemoryBuffer::getOpenFile(int FD, const Twine &Filename, uint64_t FileSize,

bool RequiresNullTerminator, bool IsVolatileSize) {

return getOpenFileImpl(FD, Filename, FileSize, FileSize, 0,

RequiresNullTerminator, IsVolatileSize);

}

ErrorOr<std::unique_ptr<MemoryBuffer>>

MemoryBuffer::getOpenFileSlice(int FD, const Twine &Filename, uint64_t MapSize,

int64_t Offset) {

assert(MapSize != uint64_t(-1));

return getOpenFileImpl(FD, Filename, -1, MapSize, Offset, false,

/*IsVolatileSize*/ false);

}

ErrorOr<std::unique_ptr<MemoryBuffer>> MemoryBuffer::getSTDIN() {

// 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>");

}

MemoryBufferRef MemoryBuffer::getMemBufferRef() const {

StringRef Data = getBuffer();

StringRef Identifier = getBufferIdentifier();

return MemoryBufferRef(Data, Identifier);

}

DirectXShaderCompiler/lib/Support/MemoryBuffer.cpp at main · microsoft/DirectXShaderCompiler · GitHub

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