blob: 597dea54b6cc22505a702d82281d30bc38ba3fe4 [file] [log] [blame]
// Copyright 2021 The Pigweed Authors
// Licensed under the Apache License, Version 2.0 (the "License"); you may not
// use this file except in compliance with the License. You may obtain a copy of
// the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations under
// the License.
// Defines functions for implementing seeking in a stream.
#pragma once
#include <cstddef>
#include "pw_stream/stream.h"
namespace pw::stream {
// Adds a seek offset to the specified origin.
constexpr ptrdiff_t ResolveSeekOffset(ptrdiff_t offset,
Stream::Whence origin,
size_t end_position,
size_t current_position) {
switch (origin) {
case Stream::kBeginning:
return offset;
case Stream::kCurrent:
return static_cast<ptrdiff_t>(current_position) + offset;
case Stream::kEnd:
return static_cast<ptrdiff_t>(end_position) + offset;
// Implements seek for a class that supports absolute position changes. The
// new position is calculated and assigned to the provided position variable.
// Returns OUT_OF_RANGE for seeks to a negative position or past the end.
constexpr Status CalculateSeek(ptrdiff_t offset,
Stream::Whence origin,
size_t end_position,
size_t& current_position) {
const ptrdiff_t new_position =
ResolveSeekOffset(offset, origin, end_position, current_position);
if (new_position < 0 || static_cast<size_t>(new_position) > end_position) {
return Status::OutOfRange();
current_position = static_cast<size_t>(new_position);
return OkStatus();
} // namespace pw::stream