fish-shell/src/enum_map.h
2021-10-01 03:39:43 -07:00

52 lines
1.6 KiB
C++

#ifndef FISH_ENUM_MAP_H
#define FISH_ENUM_MAP_H
#include "config.h" // IWYU pragma: keep
#include <cwchar>
/// Used for constructing mappings between enums and strings. The resulting array must be sorted
/// according to the `str` member since str_to_enum() does a binary search. Also the last entry must
/// have NULL for the `str` member and the default value for `val` to be returned if the string
/// isn't found.
template <typename T>
struct enum_map {
T val;
const wchar_t *const str;
};
/// Given a string return the matching enum. Return the sentinel enum if no match is made. The map
/// must be sorted by the `str` member. A binary search is twice as fast as a linear search with 16
/// elements in the map.
template <typename T>
T str_to_enum(const wchar_t *name, const enum_map<T> map[], int len) {
// Ignore the sentinel value when searching as it is the "not found" value.
size_t left = 0, right = len - 1;
while (left < right) {
size_t mid = left + (right - left) / 2;
int cmp = std::wcscmp(name, map[mid].str);
if (cmp < 0) {
right = mid; // name was smaller than mid
} else if (cmp > 0) {
left = mid + 1; // name was larger than mid
} else {
return map[mid].val; // found it
}
}
return map[len - 1].val; // return the sentinel value
}
/// Given an enum return the matching string.
template <typename T>
const wchar_t *enum_to_str(T enum_val, const enum_map<T> map[]) {
for (const enum_map<T> *entry = map; entry->str; entry++) {
if (enum_val == entry->val) {
return entry->str;
}
}
return nullptr;
};
#endif