438 lines
14 KiB
C++
438 lines
14 KiB
C++
//===--- MemoryBuffer.cpp - Memory Buffer implementation ------------------===//
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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 MemoryBuffer interface.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/Support/MemoryBuffer.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/Config/config.h"
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#include "llvm/Support/Errc.h"
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#include "llvm/Support/Errno.h"
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#include "llvm/Support/FileSystem.h"
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#include "llvm/Support/MathExtras.h"
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#include "llvm/Support/Path.h"
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#include "llvm/Support/Process.h"
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#include "llvm/Support/Program.h"
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#include <cassert>
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#include <cerrno>
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#include <cstring>
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#include <new>
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#include <sys/types.h>
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#include <system_error>
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#if !defined(_MSC_VER) && !defined(__MINGW32__)
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#include <unistd.h>
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#else
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#include <io.h>
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#endif
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using namespace llvm;
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//===----------------------------------------------------------------------===//
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// MemoryBuffer implementation itself.
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//===----------------------------------------------------------------------===//
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MemoryBuffer::~MemoryBuffer() { }
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/// init - Initialize this MemoryBuffer as a reference to externally allocated
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/// memory, memory that we know is already null terminated.
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void MemoryBuffer::init(const char *BufStart, const char *BufEnd,
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bool RequiresNullTerminator) {
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assert((!RequiresNullTerminator || BufEnd[0] == 0) &&
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"Buffer is not null terminated!");
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BufferStart = BufStart;
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BufferEnd = BufEnd;
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}
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//===----------------------------------------------------------------------===//
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// MemoryBufferMem implementation.
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//===----------------------------------------------------------------------===//
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/// CopyStringRef - Copies contents of a StringRef into a block of memory and
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/// null-terminates it.
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static void CopyStringRef(char *Memory, StringRef Data) {
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if (!Data.empty())
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memcpy(Memory, Data.data(), Data.size());
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Memory[Data.size()] = 0; // Null terminate string.
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}
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namespace {
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struct NamedBufferAlloc {
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const Twine &Name;
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NamedBufferAlloc(const Twine &Name) : Name(Name) {}
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};
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}
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void *operator new(size_t N, const NamedBufferAlloc &Alloc) {
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SmallString<256> NameBuf;
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StringRef NameRef = Alloc.Name.toStringRef(NameBuf);
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char *Mem = static_cast<char *>(operator new(N + NameRef.size() + 1));
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CopyStringRef(Mem + N, NameRef);
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return Mem;
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}
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namespace {
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/// MemoryBufferMem - Named MemoryBuffer pointing to a block of memory.
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class MemoryBufferMem : public MemoryBuffer {
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public:
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MemoryBufferMem(StringRef InputData, bool RequiresNullTerminator) {
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init(InputData.begin(), InputData.end(), RequiresNullTerminator);
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}
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const char *getBufferIdentifier() const override {
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// The name is stored after the class itself.
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return reinterpret_cast<const char*>(this + 1);
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}
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BufferKind getBufferKind() const override {
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return MemoryBuffer_Malloc;
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}
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};
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}
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static ErrorOr<std::unique_ptr<MemoryBuffer>>
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getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
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uint64_t Offset, bool RequiresNullTerminator, bool IsVolatileSize);
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std::unique_ptr<MemoryBuffer>
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MemoryBuffer::getMemBuffer(StringRef InputData, StringRef BufferName,
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bool RequiresNullTerminator) {
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auto *Ret = new (NamedBufferAlloc(BufferName))
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MemoryBufferMem(InputData, RequiresNullTerminator);
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return std::unique_ptr<MemoryBuffer>(Ret);
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}
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std::unique_ptr<MemoryBuffer>
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MemoryBuffer::getMemBuffer(MemoryBufferRef Ref, bool RequiresNullTerminator) {
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return std::unique_ptr<MemoryBuffer>(getMemBuffer(
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Ref.getBuffer(), Ref.getBufferIdentifier(), RequiresNullTerminator));
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}
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std::unique_ptr<MemoryBuffer>
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MemoryBuffer::getMemBufferCopy(StringRef InputData, const Twine &BufferName) {
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std::unique_ptr<MemoryBuffer> Buf =
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getNewUninitMemBuffer(InputData.size(), BufferName);
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if (!Buf)
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return nullptr;
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memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
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InputData.size());
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return Buf;
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}
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std::unique_ptr<MemoryBuffer>
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MemoryBuffer::getNewUninitMemBuffer(size_t Size, const Twine &BufferName) {
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// Allocate space for the MemoryBuffer, the data and the name. It is important
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// that MemoryBuffer and data are aligned so PointerIntPair works with them.
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// TODO: Is 16-byte alignment enough? We copy small object files with large
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// alignment expectations into this buffer.
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SmallString<256> NameBuf;
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StringRef NameRef = BufferName.toStringRef(NameBuf);
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size_t AlignedStringLen =
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RoundUpToAlignment(sizeof(MemoryBufferMem) + NameRef.size() + 1, 16);
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size_t RealLen = AlignedStringLen + Size + 1;
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char *Mem = static_cast<char*>(operator new(RealLen, std::nothrow));
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if (!Mem)
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return nullptr;
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// The name is stored after the class itself.
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CopyStringRef(Mem + sizeof(MemoryBufferMem), NameRef);
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// The buffer begins after the name and must be aligned.
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char *Buf = Mem + AlignedStringLen;
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Buf[Size] = 0; // Null terminate buffer.
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auto *Ret = new (Mem) MemoryBufferMem(StringRef(Buf, Size), true);
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return std::unique_ptr<MemoryBuffer>(Ret);
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}
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std::unique_ptr<MemoryBuffer>
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MemoryBuffer::getNewMemBuffer(size_t Size, StringRef BufferName) {
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std::unique_ptr<MemoryBuffer> SB = getNewUninitMemBuffer(Size, BufferName);
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if (!SB)
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return nullptr;
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memset(const_cast<char*>(SB->getBufferStart()), 0, Size);
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return SB;
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}
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ErrorOr<std::unique_ptr<MemoryBuffer>>
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MemoryBuffer::getFileOrSTDIN(const Twine &Filename, int64_t FileSize,
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bool RequiresNullTerminator) {
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SmallString<256> NameBuf;
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StringRef NameRef = Filename.toStringRef(NameBuf);
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if (NameRef == "-")
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return getSTDIN();
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return getFile(Filename, FileSize, RequiresNullTerminator);
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}
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ErrorOr<std::unique_ptr<MemoryBuffer>>
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MemoryBuffer::getFileSlice(const Twine &FilePath, uint64_t MapSize,
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uint64_t Offset) {
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return getFileAux(FilePath, -1, MapSize, Offset, false, false);
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}
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//===----------------------------------------------------------------------===//
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// MemoryBuffer::getFile implementation.
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//===----------------------------------------------------------------------===//
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namespace {
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/// \brief Memory maps a file descriptor using sys::fs::mapped_file_region.
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///
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/// This handles converting the offset into a legal offset on the platform.
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class MemoryBufferMMapFile : public MemoryBuffer {
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sys::fs::mapped_file_region MFR;
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static uint64_t getLegalMapOffset(uint64_t Offset) {
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return Offset & ~(sys::fs::mapped_file_region::alignment() - 1);
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}
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static uint64_t getLegalMapSize(uint64_t Len, uint64_t Offset) {
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return Len + (Offset - getLegalMapOffset(Offset));
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}
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const char *getStart(uint64_t Len, uint64_t Offset) {
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return MFR.const_data() + (Offset - getLegalMapOffset(Offset));
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}
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public:
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MemoryBufferMMapFile(bool RequiresNullTerminator, int FD, uint64_t Len,
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uint64_t Offset, std::error_code &EC)
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: MFR(FD, sys::fs::mapped_file_region::readonly,
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getLegalMapSize(Len, Offset), getLegalMapOffset(Offset), EC) {
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if (!EC) {
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const char *Start = getStart(Len, Offset);
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init(Start, Start + Len, RequiresNullTerminator);
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}
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}
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const char *getBufferIdentifier() const override {
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// The name is stored after the class itself.
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return reinterpret_cast<const char *>(this + 1);
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}
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BufferKind getBufferKind() const override {
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return MemoryBuffer_MMap;
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}
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};
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}
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static ErrorOr<std::unique_ptr<MemoryBuffer>>
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getMemoryBufferForStream(int FD, const Twine &BufferName) {
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const ssize_t ChunkSize = 4096*4;
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SmallString<ChunkSize> Buffer;
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ssize_t ReadBytes;
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// Read into Buffer until we hit EOF.
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do {
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Buffer.reserve(Buffer.size() + ChunkSize);
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ReadBytes = read(FD, Buffer.end(), ChunkSize);
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if (ReadBytes == -1) {
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if (errno == EINTR) continue;
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return std::error_code(errno, std::generic_category());
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}
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Buffer.set_size(Buffer.size() + ReadBytes);
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} while (ReadBytes != 0);
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return MemoryBuffer::getMemBufferCopy(Buffer, BufferName);
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}
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ErrorOr<std::unique_ptr<MemoryBuffer>>
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MemoryBuffer::getFile(const Twine &Filename, int64_t FileSize,
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bool RequiresNullTerminator, bool IsVolatileSize) {
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return getFileAux(Filename, FileSize, FileSize, 0,
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RequiresNullTerminator, IsVolatileSize);
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}
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static ErrorOr<std::unique_ptr<MemoryBuffer>>
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getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,
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uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
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bool IsVolatileSize);
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static ErrorOr<std::unique_ptr<MemoryBuffer>>
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getFileAux(const Twine &Filename, int64_t FileSize, uint64_t MapSize,
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uint64_t Offset, bool RequiresNullTerminator, bool IsVolatileSize) {
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int FD;
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std::error_code EC = sys::fs::openFileForRead(Filename, FD);
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if (EC)
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return EC;
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ErrorOr<std::unique_ptr<MemoryBuffer>> Ret =
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getOpenFileImpl(FD, Filename, FileSize, MapSize, Offset,
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RequiresNullTerminator, IsVolatileSize);
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close(FD);
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return Ret;
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}
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static bool shouldUseMmap(int FD,
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size_t FileSize,
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size_t MapSize,
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off_t Offset,
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bool RequiresNullTerminator,
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int PageSize,
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bool IsVolatileSize) {
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// mmap may leave the buffer without null terminator if the file size changed
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// by the time the last page is mapped in, so avoid it if the file size is
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// likely to change.
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if (IsVolatileSize)
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return false;
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// We don't use mmap for small files because this can severely fragment our
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// address space.
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if (MapSize < 4 * 4096 || MapSize < (unsigned)PageSize)
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return false;
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if (!RequiresNullTerminator)
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return true;
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// If we don't know the file size, use fstat to find out. fstat on an open
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// file descriptor is cheaper than stat on a random path.
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// FIXME: this chunk of code is duplicated, but it avoids a fstat when
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// RequiresNullTerminator = false and MapSize != -1.
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if (FileSize == size_t(-1)) {
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sys::fs::file_status Status;
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if (sys::fs::status(FD, Status))
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return false;
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FileSize = Status.getSize();
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}
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// If we need a null terminator and the end of the map is inside the file,
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// we cannot use mmap.
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size_t End = Offset + MapSize;
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assert(End <= FileSize);
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if (End != FileSize)
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return false;
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// Don't try to map files that are exactly a multiple of the system page size
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// if we need a null terminator.
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if ((FileSize & (PageSize -1)) == 0)
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return false;
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#if defined(__CYGWIN__)
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// Don't try to map files that are exactly a multiple of the physical page size
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// if we need a null terminator.
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// FIXME: We should reorganize again getPageSize() on Win32.
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if ((FileSize & (4096 - 1)) == 0)
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return false;
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#endif
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return true;
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}
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static ErrorOr<std::unique_ptr<MemoryBuffer>>
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getOpenFileImpl(int FD, const Twine &Filename, uint64_t FileSize,
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uint64_t MapSize, int64_t Offset, bool RequiresNullTerminator,
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bool IsVolatileSize) {
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static int PageSize = sys::Process::getPageSize();
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// Default is to map the full file.
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if (MapSize == uint64_t(-1)) {
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// If we don't know the file size, use fstat to find out. fstat on an open
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// file descriptor is cheaper than stat on a random path.
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if (FileSize == uint64_t(-1)) {
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sys::fs::file_status Status;
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std::error_code EC = sys::fs::status(FD, Status);
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if (EC)
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return EC;
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// If this not a file or a block device (e.g. it's a named pipe
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// or character device), we can't trust the size. Create the memory
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// buffer by copying off the stream.
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sys::fs::file_type Type = Status.type();
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if (Type != sys::fs::file_type::regular_file &&
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Type != sys::fs::file_type::block_file)
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return getMemoryBufferForStream(FD, Filename);
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FileSize = Status.getSize();
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}
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MapSize = FileSize;
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}
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if (shouldUseMmap(FD, FileSize, MapSize, Offset, RequiresNullTerminator,
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PageSize, IsVolatileSize)) {
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std::error_code EC;
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std::unique_ptr<MemoryBuffer> Result(
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new (NamedBufferAlloc(Filename))
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MemoryBufferMMapFile(RequiresNullTerminator, FD, MapSize, Offset, EC));
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if (!EC)
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return std::move(Result);
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}
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std::unique_ptr<MemoryBuffer> Buf =
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MemoryBuffer::getNewUninitMemBuffer(MapSize, Filename);
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if (!Buf) {
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// Failed to create a buffer. The only way it can fail is if
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// new(std::nothrow) returns 0.
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return make_error_code(errc::not_enough_memory);
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}
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char *BufPtr = const_cast<char *>(Buf->getBufferStart());
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size_t BytesLeft = MapSize;
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#ifndef HAVE_PREAD
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if (lseek(FD, Offset, SEEK_SET) == -1)
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return std::error_code(errno, std::generic_category());
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#endif
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while (BytesLeft) {
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#ifdef HAVE_PREAD
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ssize_t NumRead = ::pread(FD, BufPtr, BytesLeft, MapSize-BytesLeft+Offset);
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#else
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ssize_t NumRead = ::read(FD, BufPtr, BytesLeft);
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#endif
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if (NumRead == -1) {
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if (errno == EINTR)
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continue;
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// Error while reading.
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return std::error_code(errno, std::generic_category());
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}
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if (NumRead == 0) {
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memset(BufPtr, 0, BytesLeft); // zero-initialize rest of the buffer.
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break;
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}
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BytesLeft -= NumRead;
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BufPtr += NumRead;
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}
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return std::move(Buf);
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}
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ErrorOr<std::unique_ptr<MemoryBuffer>>
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MemoryBuffer::getOpenFile(int FD, const Twine &Filename, uint64_t FileSize,
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bool RequiresNullTerminator, bool IsVolatileSize) {
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return getOpenFileImpl(FD, Filename, FileSize, FileSize, 0,
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RequiresNullTerminator, IsVolatileSize);
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}
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ErrorOr<std::unique_ptr<MemoryBuffer>>
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MemoryBuffer::getOpenFileSlice(int FD, const Twine &Filename, uint64_t MapSize,
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int64_t Offset) {
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assert(MapSize != uint64_t(-1));
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return getOpenFileImpl(FD, Filename, -1, MapSize, Offset, false,
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/*IsVolatileSize*/ false);
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}
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ErrorOr<std::unique_ptr<MemoryBuffer>> MemoryBuffer::getSTDIN() {
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// Read in all of the data from stdin, we cannot mmap stdin.
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//
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// FIXME: That isn't necessarily true, we should try to mmap stdin and
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// fallback if it fails.
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sys::ChangeStdinToBinary();
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return getMemoryBufferForStream(0, "<stdin>");
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}
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MemoryBufferRef MemoryBuffer::getMemBufferRef() const {
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StringRef Data = getBuffer();
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StringRef Identifier = getBufferIdentifier();
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return MemoryBufferRef(Data, Identifier);
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}
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