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/*
* Copyright (C) 2017 The Android Open Source Project
*
* 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
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* 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.
*/
#ifndef NETUTILS_SLICE_H
#define NETUTILS_SLICE_H
#include <algorithm>
#include <array>
#include <cstring>
#include <ostream>
#include <tuple>
#include <vector>
namespace android {
namespace netdutils {
// Immutable wrapper for a linear region of unowned bytes.
// Slice represents memory as a half-closed interval [base, limit).
//
// Note that without manually invoking the Slice() constructor, it is
// impossible to increase the size of a slice. This guarantees that
// applications that properly use the slice API will never access
// memory outside of a slice.
//
// Note that const Slice still wraps mutable memory, however copy
// assignment and move assignment to slice are disabled.
class Slice {
public:
Slice() = default;
// Create a slice beginning at base and continuing to but not including limit
Slice(void* base, void* limit) : mBase(toUint8(base)), mLimit(toUint8(limit)) {}
// Create a slice beginning at base and continuing for size bytes
Slice(void* base, size_t size) : Slice(base, toUint8(base) + size) {}
// Return the address of the first byte in this slice
uint8_t* base() const { return mBase; }
// Return the address of the first byte following this slice
uint8_t* limit() const { return mLimit; }
// Return the size of this slice in bytes
size_t size() const { return limit() - base(); }
// Return true if size() == 0
bool empty() const { return base() == limit(); }
private:
static uint8_t* toUint8(void* ptr) { return reinterpret_cast<uint8_t*>(ptr); }
uint8_t* mBase = nullptr;
uint8_t* mLimit = nullptr;
};
// Return slice representation of ref which must be a POD type
template <typename T>
inline const Slice makeSlice(const T& ref) {
static_assert(std::is_pod<T>::value, "value must be a POD type");
static_assert(!std::is_pointer<T>::value, "value must not be a pointer type");
return {const_cast<T*>(&ref), sizeof(ref)};
}
// Return slice representation of string data()
inline const Slice makeSlice(const std::string& s) {
using ValueT = std::string::value_type;
return {const_cast<ValueT*>(s.data()), s.size() * sizeof(ValueT)};
}
// Return slice representation of vector data()
template <typename T>
inline const Slice makeSlice(const std::vector<T>& v) {
return {const_cast<T*>(v.data()), v.size() * sizeof(T)};
}
// Return slice representation of array data()
template <typename U, size_t V>
inline const Slice makeSlice(const std::array<U, V>& a) {
return {const_cast<U*>(a.data()), a.size() * sizeof(U)};
}
// Return prefix and suffix of Slice s ending and starting at position cut
inline std::pair<const Slice, const Slice> split(const Slice s, size_t cut) {
const size_t tmp = std::min(cut, s.size());
return {{s.base(), s.base() + tmp}, {s.base() + tmp, s.limit()}};
}
// Return prefix of Slice s ending at position cut
inline const Slice take(const Slice s, size_t cut) {
return std::get<0>(split(s, cut));
}
// Return suffix of Slice s starting at position cut
inline const Slice drop(const Slice s, size_t cut) {
return std::get<1>(split(s, cut));
}
// Copy from src into dst. Bytes copied is the lesser of dst.size() and src.size()
inline size_t copy(const Slice dst, const Slice src) {
const auto min = std::min(dst.size(), src.size());
memcpy(dst.base(), src.base(), min);
return min;
}
// Base case for variadic extract below
template <typename Head>
inline size_t extract(const Slice src, Head& head) {
return copy(makeSlice(head), src);
}
// Copy from src into one or more pointers to POD data. If src.size()
// is less than the sum of all data pointers a suffix of data will be
// left unmodified. Return the number of bytes copied.
template <typename Head, typename... Tail>
inline size_t extract(const Slice src, Head& head, Tail&... tail) {
const auto extracted = extract(src, head);
return extracted + extract(drop(src, extracted), tail...);
}
// Return a string containing a copy of the contents of s
std::string toString(const Slice s);
// Return a string containing a hexadecimal representation of the contents of s.
// This function inserts a newline into its output every wrap bytes.
std::string toHex(const Slice s, int wrap = INT_MAX);
inline bool operator==(const Slice& lhs, const Slice& rhs) {
return (lhs.base() == rhs.base()) && (lhs.limit() == rhs.limit());
}
inline bool operator!=(const Slice& lhs, const Slice& rhs) {
return !(lhs == rhs);
}
std::ostream& operator<<(std::ostream& os, const Slice& slice);
// Return suffix of Slice s starting at the first match of byte c. If no matched
// byte, return an empty Slice.
inline const Slice findFirstMatching(const Slice s, uint8_t c) {
uint8_t* match = (uint8_t*)memchr(s.base(), c, s.size());
if (!match) return Slice();
return drop(s, match - s.base());
}
} // namespace netdutils
} // namespace android
#endif /* NETUTILS_SLICE_H */