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Shell: Cache PATH for faster tab completion

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This patch reduces the O(n) tab completion to something like O(log(n)).
The cache is just a sorted vector of strings and we binary search it to
get a string matching our input, and then check the surrounding strings
to see if we need to remove any characters. Also we no longer stat each
file every time.

Also added an #include in BinarySearch since it was using size_t. Oops.

If `export` is called, we recache. Need to implement the `hash` builtin
for when an executable has been added to a directory in PATH.
This commit is contained in:
William McPherson 2019-12-03 17:36:46 +11:00 • committed by Andreas Kling
parent 431abc8846
commit aa8b40dce6
4 changed files with 58 additions and 30 deletions
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70
Shell/LineEditor.cpp
View file

@ -37,58 +37,70 @@ void LineEditor::append(const String& string)
m_cursor = m_buffer.size();
}
void LineEditor::tab_complete_first_token()
void LineEditor::cache_path()
{
auto input = String::copy(m_buffer);
if (!m_path.is_empty())
m_path.clear_with_capacity();
String path = getenv("PATH");
if (path.is_empty())
return;
auto directories = path.split(':');
String match;
// Go through the files in PATH.
for (const auto& directory : directories) {
CDirIterator programs(directory.characters(), CDirIterator::SkipDots);
while (programs.has_next()) {
String program = programs.next_path();
if (!program.starts_with(input))
continue;
auto program = programs.next_path();
// Check that the file is an executable program.
struct stat program_status;
StringBuilder program_path;
program_path.append(directory.characters());
program_path.append('/');
program_path.append(program.characters());
struct stat program_status;
int stat_error = stat(program_path.to_string().characters(), &program_status);
if (stat_error || !(program_status.st_mode & S_IXUSR))
continue;
// Set `match` to the first one that starts with `input`.
if (match.is_empty()) {
match = program;
} else {
// Remove characters from the end of `match` if they're
// different from another `program` starting with `input`.
int i = input.length();
while (i < match.length() && i < program.length() && match[i] == program[i])
++i;
match = match.substring(0, i);
}
if (match.length() == input.length())
return;
m_path.append(program.characters());
}
}
if (match.is_empty())
quick_sort(m_path.begin(), m_path.end(), AK::is_less_than<String>);
}
void LineEditor::cut_mismatching_chars(String& completion, const String& program, int token_length)
{
int i = token_length;
while (i < completion.length() && i < program.length() && completion[i] == program[i])
++i;
completion = completion.substring(0, i);
}
void LineEditor::tab_complete_first_token()
{
String token = String::copy(m_buffer);
auto match = binary_search(m_path.data(), m_path.size(), token, [](const String& token, const String& program) -> int {
return strncmp(token.characters(), program.characters(), token.length());
});
if (!match)
return;
// Then append `match` to the buffer, excluding the `input` part which is
// already in the buffer.
append(match.substring(input.length(), match.length() - input.length()).characters());
String completion = *match;
// Now that we have a program name starting with our token, we look at
// other program names starting with our token and cut off any mismatching
// characters.
int index = match - m_path.data();
for (int i = index - 1; i >= 0 && m_path[i].starts_with(token); --i)
cut_mismatching_chars(completion, m_path[i], token.length());
for (int i = index + 1; i < m_path.size() && m_path[i].starts_with(token); ++i)
cut_mismatching_chars(completion, m_path[i], token.length());
if (token.length() == completion.length())
return;
append(completion.substring(token.length(), completion.length() - token.length()).characters());
}
String LineEditor::get_line(const String& prompt)