48 lines · cpp
1//===-- Linux implementation of pwrite ------------------------------------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#include "src/unistd/pwrite.h"10 11#include "src/__support/OSUtil/syscall.h" // For internal syscall function.12#include "src/__support/common.h"13 14#include "hdr/stdint_proxy.h" // For uint64_t.15#include "src/__support/libc_errno.h"16#include "src/__support/macros/config.h"17#include <sys/syscall.h> // For syscall numbers.18 19namespace LIBC_NAMESPACE_DECL {20 21LLVM_LIBC_FUNCTION(ssize_t, pwrite,22 (int fd, const void *buf, size_t count, off_t offset)) {23 24 ssize_t ret;25 if constexpr (sizeof(long) == sizeof(uint32_t) &&26 sizeof(off_t) == sizeof(uint64_t)) {27 // This is a 32-bit system with a 64-bit offset, offset must be split.28 const uint64_t bits = cpp::bit_cast<uint64_t>(offset);29 const uint32_t lo = bits & UINT32_MAX;30 const uint32_t hi = bits >> 32;31 const long offset_low = cpp::bit_cast<long>(static_cast<long>(lo));32 const long offset_high = cpp::bit_cast<long>(static_cast<long>(hi));33 ret = LIBC_NAMESPACE::syscall_impl<ssize_t>(SYS_pwrite64, fd, buf, count,34 offset_low, offset_high);35 } else {36 ret = LIBC_NAMESPACE::syscall_impl<ssize_t>(SYS_pwrite64, fd, buf, count,37 offset);38 }39 40 if (ret < 0) {41 libc_errno = static_cast<int>(-ret);42 return -1;43 }44 return ret;45}46 47} // namespace LIBC_NAMESPACE_DECL48