From 5745fbce1674b29f4dce6b6e31556c4c1e83dc89 Mon Sep 17 00:00:00 2001 From: Benjamin Kramer Date: Tue, 22 Nov 2011 12:31:53 +0000 Subject: Add configure checking for pread(2) and use it to save a syscall when reading files. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@145061 91177308-0d34-0410-b5e6-96231b3b80d8 --- lib/Support/MemoryBuffer.cpp | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'lib/Support/MemoryBuffer.cpp') diff --git a/lib/Support/MemoryBuffer.cpp b/lib/Support/MemoryBuffer.cpp index 580338117b..1a409720c0 100644 --- a/lib/Support/MemoryBuffer.cpp +++ b/lib/Support/MemoryBuffer.cpp @@ -14,6 +14,7 @@ #include "llvm/Support/MemoryBuffer.h" #include "llvm/ADT/OwningPtr.h" #include "llvm/ADT/SmallString.h" +#include "llvm/Config/config.h" #include "llvm/Support/MathExtras.h" #include "llvm/Support/Errno.h" #include "llvm/Support/Path.h" @@ -320,11 +321,17 @@ error_code MemoryBuffer::getOpenFile(int FD, const char *Filename, char *BufPtr = const_cast(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; -- cgit v1.2.3