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Factor out the Unix-specific parts of canonPathInner

This prepares the code to also support Windows paths in the next commit.
This commit is contained in:
John Ericson 2024-01-29 17:16:18 -05:00
parent 60936f28e5
commit 4531585275
3 changed files with 45 additions and 11 deletions

View file

@ -10,6 +10,39 @@
namespace nix {
/**
* Unix-style path primives.
*
* Nix'result own "logical" paths are always Unix-style. So this is always
* used for that, and additionally used for native paths on Unix.
*/
struct UnixPathTrait
{
using CharT = char;
using String = std::string;
using StringView = std::string_view;
constexpr static char preferredSep = '/';
static inline bool isPathSep(char c)
{
return c == '/';
}
static inline size_t findPathSep(StringView path, size_t from = 0)
{
return path.find('/', from);
}
static inline size_t rfindPathSep(StringView path, size_t from = StringView::npos)
{
return path.rfind('/', from);
}
};
/**
* Core pure path canonicalization algorithm.
*
@ -24,25 +57,26 @@ namespace nix {
* This is a chance to modify those two paths in arbitrary way, e.g. if
* "result" points to a symlink.
*/
typename std::string canonPathInner(
std::string_view remaining,
template<class PathDict>
typename PathDict::String canonPathInner(
typename PathDict::StringView remaining,
auto && hookComponent)
{
assert(remaining != "");
std::string result;
typename PathDict::String result;
result.reserve(256);
while (true) {
/* Skip slashes. */
while (!remaining.empty() && remaining[0] == '/')
while (!remaining.empty() && PathDict::isPathSep(remaining[0]))
remaining.remove_prefix(1);
if (remaining.empty()) break;
auto nextComp = ({
auto nextPathSep = remaining.find('/');
auto nextPathSep = PathDict::findPathSep(remaining);
nextPathSep == remaining.npos ? remaining : remaining.substr(0, nextPathSep);
});
@ -53,14 +87,14 @@ typename std::string canonPathInner(
/* If `..', delete the last component. */
else if (nextComp == "..")
{
if (!result.empty()) result.erase(result.rfind('/'));
if (!result.empty()) result.erase(PathDict::rfindPathSep(result));
remaining.remove_prefix(2);
}
/* Normal component; copy it. */
else {
result += '/';
if (const auto slash = remaining.find('/'); slash == result.npos) {
result += PathDict::preferredSep;
if (const auto slash = PathDict::findPathSep(remaining); slash == result.npos) {
result += remaining;
remaining = {};
} else {
@ -73,7 +107,7 @@ typename std::string canonPathInner(
}
if (result.empty())
result = "/";
result = typename PathDict::String { PathDict::preferredSep };
return result;
}