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-exception 6 // 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 "src/__support/macros/config.h" 15 #include "src/errno/libc_errno.h" 16 #include <stdint.h> // For uint64_t. 17 #include <sys/syscall.h> // For syscall numbers. 18 19 namespace LIBC_NAMESPACE_DECL { 20 21 LLVM_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_DECL 48