| // Copyright 2020 The Fuchsia Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. |
| |
| #include <string.h> |
| |
| template <typename T> |
| size_t WritePaddedInternal(T* buffer, const void* msg, size_t length) { |
| size_t needs_padding = (length % sizeof(T)) > 0; |
| size_t padding = sizeof(T) - (length % sizeof(T)); |
| // Multiply by needs_padding to set padding to 0 if no padding |
| // is necessary. This avoids unnecessary branching. |
| padding *= needs_padding; |
| // If we added padding -- zero the padding bytes in a single write operation |
| size_t is_nonzero_length = length != 0; |
| size_t eof_in_bytes = length + padding; |
| size_t eof_in_words = eof_in_bytes / sizeof(T); |
| size_t last_word = eof_in_words - is_nonzero_length; |
| // Set the last word in the buffer to zero before writing |
| // the data to it if we added padding. If we didn't add padding, |
| // multiply by 1 which ends up writing back the current contents of that word |
| // resulting in a NOP. |
| buffer[last_word] *= !needs_padding; |
| memcpy(buffer, msg, length); |
| return (length + padding) / sizeof(T); |
| } |
