diff options
author | Explorer09 <explorer09@gmail.com> | 2016-08-11 10:49:35 +0800 |
---|---|---|
committer | Explorer09 <explorer09@gmail.com> | 2016-08-11 10:49:35 +0800 |
commit | bf35921abb2ad863b3f49b37c2559600304e451e (patch) | |
tree | aa805f4b034262f515352863a943c87fcc0954bf /linux/Battery.c | |
parent | b269eb24b09d48cbbcdbb7a68e122d49cb39d0f1 (diff) |
Optimize Strings_startWith()
Use strncmp() combined with a strlen() will give better performance
than a strstr in worst case. Especially when the match prefix is a
constant and not a variable.
While we are at it, replace the match() function in linux/Battery.c,
which uses a naive algorithm, with a macro that does better job by
utilizing Strings_startWith().
$ gcc --version | head -n 1
gcc (Ubuntu 4.8.4-2ubuntu1~14.04.3) 4.8.4
$ uname -m
x86_64
$ size htop.old htop.new
text data bss dec hex filename
137929 15112 3776 156817 26491 htop.old
137784 15104 3776 156664 263f8 htop.new
Signed-off-by: Kang-Che Sung <explorer09 @ gmail.com>
Diffstat (limited to 'linux/Battery.c')
-rw-r--r-- | linux/Battery.c | 22 |
1 files changed, 3 insertions, 19 deletions
diff --git a/linux/Battery.c b/linux/Battery.c index 10681844..b7a004ba 100644 --- a/linux/Battery.c +++ b/linux/Battery.c @@ -179,25 +179,6 @@ static inline ssize_t xread(int fd, void *buf, size_t count) { } } -/** - * Returns a pointer to the suffix of `str` if its beginning matches `prefix`. - * Returns NULL if the prefix does not match. - * Examples: - * match("hello world", "hello "); -> "world" - * match("hello world", "goodbye "); -> NULL - */ -static inline const char* match(const char* str, const char* prefix) { - for (;;) { - if (*prefix == '\0') { - return str; - } - if (*prefix != *str) { - return NULL; - } - prefix++; str++; - } -} - static void Battery_getSysData(double* level, ACPresence* isOnAC) { *level = 0; @@ -240,6 +221,8 @@ static void Battery_getSysData(double* level, ACPresence* isOnAC) { bool full = false; bool now = false; while ((line = strsep(&buf, "\n")) != NULL) { + #define match(str,prefix) \ + (String_startsWith(str,prefix) ? (str) + strlen(prefix) : NULL) const char* ps = match(line, "POWER_SUPPLY_"); if (!ps) { continue; @@ -266,6 +249,7 @@ static void Battery_getSysData(double* level, ACPresence* isOnAC) { continue; } } + #undef match } else if (entryName[0] == 'A') { if (*isOnAC != AC_ERROR) { continue; |