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use binary search for enum map lookups

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Switch from a linear to a binary search when looking for a matching
string in an enum map. Testing shows this is a little more than twice as
fast when searching for keywords in the sixteen entry keyword_map array.
This speedup doesn't matter much when searching for subbcommands but any
slow down in the parser is unacceptable.
This commit is contained in:
Kurtis Rader 2016-11-11 15:26:16 -08:00
parent bd03c3fbc5
commit 5d6415b6bf
2 changed files with 35 additions and 19 deletions
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22
src/builtin.cpp
View file

@ -2172,19 +2172,21 @@ enum status_cmd_t {
STATUS_PRINT_STACK_TRACE,
STATUS_UNDEF
};
// Must be sorted by string, not enum or random.
const enum_map<status_cmd_t> status_enum_map[] = {
{STATUS_IS_LOGIN, L"is-login"},
{STATUS_IS_INTERACTIVE, L"is-interactive"},
{STATUS_CURRENT_FILENAME, L"current-filename"},
{STATUS_CURRENT_LINE_NUMBER, L"current-line-number"},
{STATUS_IS_BLOCK, L"is-block"},
{STATUS_IS_COMMAND_SUB, L"is-command-sub"},
{STATUS_IS_FULL_JOB_CTRL, L"is-full-job-control"},
{STATUS_IS_INTERACTIVE, L"is-interactive"},
{STATUS_IS_INTERACTIVE_JOB_CTRL, L"is-interactive-job-control"},
{STATUS_IS_LOGIN, L"is-login"},
{STATUS_IS_NO_JOB_CTRL, L"is-no-job-control"},
{STATUS_CURRENT_FILENAME, L"current-filename"},
{STATUS_CURRENT_LINE_NUMBER, L"current-line-number"},
{STATUS_SET_JOB_CONTROL, L"job-control"},
{STATUS_PRINT_STACK_TRACE, L"print-stack-trace"},
{STATUS_UNDEF, NULL}};
#define status_enum_map_len (sizeof status_enum_map / sizeof *status_enum_map)
/// Remember the status subcommand and disallow selecting more than one status subcommand.
static bool set_status_cmd(wchar_t *const cmd, status_cmd_t *status_cmd, status_cmd_t sub_cmd,
@ -2348,7 +2350,7 @@ static int builtin_status(parser_t &parser, io_streams_t &streams, wchar_t **arg
// If a status command hasn't already been specified via a flag check the first word.
// Note that this can be simplified after we eliminate allowing subcommands as flags.
if (w.woptind < argc) {
status_cmd_t subcmd = str_to_enum(argv[w.woptind], status_enum_map);
status_cmd_t subcmd = str_to_enum(argv[w.woptind], status_enum_map, status_enum_map_len);
if (subcmd != STATUS_UNDEF) {
if (!set_status_cmd(cmd, &status_cmd, subcmd, streams)) {
return STATUS_BUILTIN_ERROR;
@ -2947,9 +2949,11 @@ static int builtin_return(parser_t &parser, io_streams_t &streams, wchar_t **arg
}
enum hist_cmd_t { HIST_SEARCH = 1, HIST_DELETE, HIST_CLEAR, HIST_MERGE, HIST_SAVE, HIST_UNDEF };
const enum_map<hist_cmd_t> hist_enum_map[] = {{HIST_SEARCH, L"search"}, {HIST_DELETE, L"delete"},
{HIST_CLEAR, L"clear"}, {HIST_MERGE, L"merge"},
{HIST_SAVE, L"save"}, {HIST_UNDEF, NULL}};
// Must be sorted by string, not enum or random.
const enum_map<hist_cmd_t> hist_enum_map[] = {{HIST_CLEAR, L"clear"}, {HIST_DELETE, L"delete"},
{HIST_MERGE, L"merge"}, {HIST_SAVE, L"save"},
{HIST_SEARCH, L"search"}, {HIST_UNDEF, NULL}};
#define hist_enum_map_len (sizeof hist_enum_map / sizeof *hist_enum_map)
/// Remember the history subcommand and disallow selecting more than one history subcommand.
static bool set_hist_cmd(wchar_t *const cmd, hist_cmd_t *hist_cmd, hist_cmd_t sub_cmd,
@ -3129,7 +3133,7 @@ static int builtin_history(parser_t &parser, io_streams_t &streams, wchar_t **ar
// Note that this can be simplified after we eliminate allowing subcommands as flags.
// See the TODO above regarding the `long_options` array.
if (w.woptind < argc) {
hist_cmd_t subcmd = str_to_enum(argv[w.woptind], hist_enum_map);
hist_cmd_t subcmd = str_to_enum(argv[w.woptind], hist_enum_map, hist_enum_map_len);
if (subcmd != HIST_UNDEF) {
if (!set_hist_cmd(cmd, &hist_cmd, subcmd, streams)) {
return STATUS_BUILTIN_ERROR;

32
src/common.h
View file

@ -781,25 +781,37 @@ long convert_digit(wchar_t d, int base);
// Return true if the character is in a range reserved for fish's private use.
bool fish_reserved_codepoint(wchar_t c);
/// Used for constructing mappings between enums and strings.
/// 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 sentinal enum if no match is made.
/// Given a string return the matching enum. Return the sentinal 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>
static T str_to_enum(const wchar_t *enum_str, const enum_map<T> map[]) {
const enum_map<T> *entry = map;
while (entry->str) {
if (wcscmp(enum_str, entry->str) == 0) {
return entry->val;
static 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 = 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
}
entry++;
}
return entry->val; // return val of sentinel entry in the array
};
return map[len - 1].val; // return the sentinel value
}
/// Given an enum return the matching string.
template <typename T>