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authorJulian Andres Klode <jak@debian.org>2016-01-07 19:14:21 +0100
committerJulian Andres Klode <jak@debian.org>2016-01-07 19:59:08 +0100
commitfe7fa47c1141066c89ab3382c318a4b9d00fe249 (patch)
treeebce4698872ee71336c3e30376b1b3fbb6217f8e
parent4fcff7ed46aec6c0147abe855c13dd537277273e (diff)
Introduce internal APT::StringView class
The class APT::StringView implements a drop-in replacement for a subset of C++17 std::string_view() features. It will be dropped at a later point and may not be used in public interfaces.
-rw-r--r--apt-pkg/contrib/string_view.h112
1 files changed, 112 insertions, 0 deletions
diff --git a/apt-pkg/contrib/string_view.h b/apt-pkg/contrib/string_view.h
new file mode 100644
index 000000000..b4ce0431c
--- /dev/null
+++ b/apt-pkg/contrib/string_view.h
@@ -0,0 +1,112 @@
+/*
+ * Basic implementation of string_view
+ *
+ * (C) 2015 Julian Andres Klode <jak@debian.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ */
+
+#if !defined(APT_STRINGVIEW_H) && defined(APT_PKG_EXPOSE_STRING_VIEW)
+#define APT_STRINGVIEW_H
+#include <string.h>
+#include <string>
+
+namespace APT {
+
+/**
+ * \brief Simple subset of std::string_view from C++17
+ *
+ * This is an internal implementation of the subset of std::string_view
+ * used by APT. It is not meant to be used in programs, only inside the
+ * library for performance critical paths.
+ */
+class StringView {
+ const char *data_;
+ size_t size_;
+
+public:
+ static constexpr size_t npos = static_cast<size_t>(-1);
+
+ /* Constructors */
+ constexpr StringView() : data_(""), size_(0) {}
+ constexpr StringView(const char *data, size_t size) : data_(data), size_(size) {}
+
+ StringView(const char *data) : data_(data), size_(strlen(data)) {}
+ StringView(std::string const & str): data_(str.data()), size_(str.size()) {}
+
+
+ /* Viewers */
+ constexpr StringView substr(size_t pos, size_t n = npos) const {
+ return StringView(data_ + pos, n > (size_ - pos) ? (size_ - pos) : n);
+ }
+
+ size_t find(int c, size_t pos=0) const {
+ if (pos != 0)
+ return substr(pos).find(c);
+
+ const char *found = static_cast<const char*>(memchr(data_, c, size_));
+
+ if (found == NULL)
+ return npos;
+
+ return found - data_;
+ }
+
+ size_t rfind(int c, size_t pos=0) const {
+ if (pos != 0)
+ return substr(pos).find(c);
+
+ const char *found = static_cast<const char*>(memrchr(data_, c, size_));
+
+ if (found == NULL)
+ return npos;
+
+ return found - data_;
+ }
+
+ /* Conversions */
+ std::string to_string() const {
+ return std::string(data_, size_);
+ }
+
+ /* Comparisons */
+ int compare(size_t pos, size_t n, StringView other) const {
+ return substr(pos, n).compare(other);
+ }
+
+ int compare(StringView other) const {
+ int res;
+
+ res = memcmp(data_, other.data_, std::min(size_, other.size_));
+ if (res != 0)
+ return res;
+ if (size_ == other.size_)
+ return res;
+
+ return (size_ > other.size_) ? 1 : -1;
+ }
+
+ /* Optimization: If size not equal, string cannot be equal */
+ bool operator ==(StringView other) const { return size_ == other.size_ && compare(other) == 0; }
+ bool operator !=(StringView other) const { return !(*this == other); }
+
+ /* Accessors */
+ constexpr bool empty() const { return size_ == 0; }
+ constexpr const char* data() const { return data_; }
+ constexpr const char* begin() const { return data_; }
+ constexpr const char* end() const { return data_ + size_; }
+ constexpr char operator [](size_t i) const { return data_[i]; }
+ constexpr size_t size() const { return size_; }
+ constexpr size_t length() const { return size_; }
+};
+
+
+}
+
+inline bool operator ==(const char *other, APT::StringView that);
+inline bool operator ==(const char *other, APT::StringView that) { return that.compare(other) == 0; }
+
+#endif