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+/*
+ * Copyright (c) 2022 Apple Inc. All rights reserved.
+ *
+ * @APPLE_LICENSE_HEADER_START@
+ *
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ *
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ *
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+#ifndef common_CString_h
+#define common_CString_h
+
+#include <string_view>
+#include <span>
+#include <string>
+#include <assert.h>
+
+// commmon
+#include "Defines.h"
+
+/*!
+ * @class CString
+ *
+ * @abstract
+ * A type safe wrapper of a null-terminated string. It is based on std::string\_view, so it inherits string\_view's methods and can be used interchangeably with it.
+ *
+ * string\_view methods that operate on the string bounds still return string\_view objects. This is the behaviour we need, since the new string\_view might no longer point to a null-terminated string.
+ * For this reason it's good to specialize certain methods where null-terminators can still be guaranteed.
+ * An example of such API specialization is the `substr(size_type pos)` method, where we know the end pointer won't change.
+ *
+ * CString is also compatible with POSIX APIs that require null-terminated strings, unlike string\_view where there's no such guarantee.
+ * Compatibility with C strings isn't totally transparent and there are some limitations:
+ * - The type is only explicitly convertible to `const char*`. Implicit conversion could be supported, but it would require explicit implementation of existing string_view operators.
+ * - CString can't be used interchangeably with `const char*` in variadic APIs, such as `printf`. Instead we use `c_str` method or an explicit cast.
+ * Variadic functions don't have explicit types, so the type won't be converted to `const char*`, even if we'd have an implicit conversion operator.
+ * Compiler also warns about functions such as `printf` when trying to use CString object with the `%s` format.
+ */
+struct VIS_HIDDEN CString: public std::string_view
+{
+
+ constexpr CString(): std::string_view() {}
+ constexpr CString(const char* cstr): std::string_view(cstr ? std::string_view(cstr) : std::string_view()) {}
+ CString(const std::string& str): std::string_view(str) {}
+ CString(const char* str, size_t len): std::string_view(str, len) {}
+
+ // Allow std::string_view conversion only in a compile time context.
+ // Runtime casting should be done only explicitly using ::fromSV API.
+ consteval CString(std::string_view str): std::string_view(std::move(str)) {
+ assert(str.data() == nullptr || *(str.data() + str.size()) == 0);
+ }
+
+ static constexpr CString fromSV(std::string_view str)
+ {
+ return CString(str, UnsafeSVCastTag());
+ }
+
+ constexpr const char* c_str() const { return std::string_view::data(); }
+ explicit constexpr operator const char*() const { return c_str(); }
+
+ static CString dup(std::string_view str)
+ {
+ char* buffer = (char*)malloc(str.size() + 1);
+ memcpy(buffer, str.data(), str.size());
+ buffer[str.size()] = 0;
+ return fromSV(std::string_view(buffer, str.size()));
+ }
+
+ CString dup() const { return CString::dup(*this); }
+
+ CString strcpy(char* dst) const
+ {
+ size_t size = this->size();
+ memcpy(dst, c_str(), size);
+ *(dst + size) = '\0';
+ return CString(std::string_view(dst, size), UnsafeSVCastTag());
+ }
+
+ static CString strcpy(std::string_view src, char* dst)
+ {
+ memcpy(dst, src.data(), src.size());
+ *(dst + src.size()) = '\0';
+ return CString(std::string_view(dst, src.size()), UnsafeSVCastTag());
+ }
+
+ // Substring from an offset will still be a valid C string, as the end pointer doesn't change.
+ CString substr(size_type pos) const
+ {
+ return fromSV(this->std::__1::string_view::substr(pos));
+ }
+
+ std::string_view substr(size_type pos, size_type n) const
+ {
+ return this->std::string_view::substr(pos, n);
+ }
+
+ CString dupSubstr(size_type pos, size_type n) const { return dup(substr(pos, n)); }
+
+ // string_view::contains() was added in c++23, but we still build with c++20
+ constexpr bool contains(std::string_view str) const {
+ return (this->find(str) != std::string_view::npos);
+ }
+
+ static constexpr CString concat(std::span<const std::string_view> strs)
+ {
+ size_t length = 0;
+ for (std::string_view s : strs) {
+ length += s.size();
+ }
+
+ char* buffer = (char*)malloc(length + 1);
+ char* ptr = buffer;
+
+ for (std::string_view s : strs) {
+ memcpy(ptr, s.data(), s.size());
+ ptr += s.size();
+ }
+
+ *ptr = 0;
+ return fromSV(std::string_view(buffer, length));
+ }
+
+ const char* data() const = delete;
+
+ const CString leafName() const
+ {
+ size_t pos = this->rfind('/');
+ if ( pos == npos )
+ return *this;
+ return substr(pos+1);
+ }
+
+private:
+ // Dummy type to support a private std::string_view -> CString constructor.
+ struct UnsafeSVCastTag {};
+
+ constexpr CString(std::string_view str, UnsafeSVCastTag): std::string_view(str)
+ {
+ assert(str.data() == nullptr || *(str.data() + str.size()) == 0);
+ }
+};
+
+namespace std
+{
+
+template<>
+struct hash<CString>
+{
+ uint64_t operator()(CString str) const { return std::hash<std::string_view>{}(str); }
+};
+}
+
+#endif // common_CString_h