[hackers] [slstatus] Refactor swap.c to use getline() instead of buf-filling || Laslo Hunhold

From: <git_AT_suckless.org>
Date: Mon, 28 May 2018 22:22:13 +0200 (CEST)

commit a18439af114b98ab026921b0cac61164f7a4eea8
Author: Laslo Hunhold <dev_AT_frign.de>
AuthorDate: Mon May 28 21:16:02 2018 +0200
Commit: Aaron Marcher <me_AT_drkhsh.at>
CommitDate: Mon May 28 22:21:34 2018 +0200

    Refactor swap.c to use getline() instead of buf-filling
    
    This drops a lot of code and even though we are using a common function,
    the specification of only the needed things keeps it very efficient and
    even more efficient in memory and time than the previous solution.

diff --git a/components/swap.c b/components/swap.c
index 37ee85c..1958eef 100644
--- a/components/swap.c
+++ b/components/swap.c
_AT_@ -1,52 +1,71 @@
 /* See LICENSE file for copyright and license details. */
 #include <errno.h>
+#include <stdint.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #include "../util.h"
 
 #if defined(__linux__)
- static size_t
- pread(const char *path, char *buf, size_t bufsiz)
+ static int
+ get_swap_info(long *s_total, long *s_free, long *s_cached)
         {
                 FILE *fp;
- size_t bytes_read;
-
- if (!(fp = fopen(path, "r"))) {
- warn("fopen '%s':", path);
- return 0;
- }
- if (!(bytes_read = fread(buf, sizeof(char), bufsiz, fp))) {
- warn("fread '%s':", path);
- fclose(fp);
- return 0;
+ struct {
+ const char *name;
+ const size_t len;
+ long *var;
+ } ent[] = {
+ { "SwapTotal", sizeof("SwapTotal") - 1, s_total },
+ { "SwapFree", sizeof("SwapFree") - 1, s_free },
+ { "SwapCached", sizeof("SwapCached") - 1, s_cached },
+ };
+ size_t line_len = 0, i, left;
+ char *line = NULL;
+
+ /* get number of fields we want to extract */
+ for (i = 0, left = 0; i < LEN(ent); i++) {
+ if (ent[i].var) {
+ left++;
+ }
+ }
+
+ if (!(fp = fopen("/proc/meminfo", "r"))) {
+ warn("fopen '/proc/meminfo':");
+ return 1;
                 }
- fclose(fp);
 
- buf[bytes_read] = '\0';
+ /* read file line by line and extract field information */
+ while (left > 0 && getline(&line, &line_len, fp) >= 0) {
+ for (i = 0; i < LEN(ent); i++) {
+ if (ent[i].var &&
+ !strncmp(line, ent[i].name, ent[i].len)) {
+ sscanf(line + ent[i].len + 1, "%ld kB\n",
+ ent[i].var);
+ left--;
+ break;
+ }
+ }
+ }
+ free(line);
+ if (ferror(fp)) {
+ warn("getline '/proc/meminfo':");
+ return 1;
+ }
 
- return bytes_read;
+ fclose(fp);
+ return 0;
         }
 
         const char *
         swap_free(void)
         {
- long total, free;
- char *match;
-
- if (!pread("/proc/meminfo", buf, sizeof(buf) - 1)) {
- return NULL;
- }
-
- if (!(match = strstr(buf, "SwapTotal"))) {
- return NULL;
- }
- sscanf(match, "SwapTotal: %ld kB\n", &total);
+ long free;
 
- if (!(match = strstr(buf, "SwapFree"))) {
+ if (get_swap_info(NULL, &free, NULL)) {
                         return NULL;
                 }
- sscanf(match, "SwapFree: %ld kB\n", &free);
 
                 return fmt_human(free * 1024, 1024);
         }
_AT_@ -55,28 +74,8 @@
         swap_perc(void)
         {
                 long total, free, cached;
- char *match;
-
- if (!pread("/proc/meminfo", buf, sizeof(buf) - 1)) {
- return NULL;
- }
-
- if (!(match = strstr(buf, "SwapTotal"))) {
- return NULL;
- }
- sscanf(match, "SwapTotal: %ld kB\n", &total);
-
- if (!(match = strstr(buf, "SwapCached"))) {
- return NULL;
- }
- sscanf(match, "SwapCached: %ld kB\n", &cached);
-
- if (!(match = strstr(buf, "SwapFree"))) {
- return NULL;
- }
- sscanf(match, "SwapFree: %ld kB\n", &free);
 
- if (total == 0) {
+ if (get_swap_info(&total, &free, &cached) || total == 0) {
                         return NULL;
                 }
 
_AT_@ -87,16 +86,10 @@
         swap_total(void)
         {
                 long total;
- char *match;
-
- if (!pread("/proc/meminfo", buf, sizeof(buf) - 1)) {
- return NULL;
- }
 
- if (!(match = strstr(buf, "SwapTotal"))) {
+ if (get_swap_info(&total, NULL, NULL)) {
                         return NULL;
                 }
- sscanf(match, "SwapTotal: %ld kB\n", &total);
 
                 return fmt_human(total * 1024, 1024);
         }
_AT_@ -105,26 +98,10 @@
         swap_used(void)
         {
                 long total, free, cached;
- char *match;
-
- if (!pread("/proc/meminfo", buf, sizeof(buf) - 1)) {
- return NULL;
- }
-
- if (!(match = strstr(buf, "SwapTotal"))) {
- return NULL;
- }
- sscanf(match, "SwapTotal: %ld kB\n", &total);
-
- if (!(match = strstr(buf, "SwapCached"))) {
- return NULL;
- }
- sscanf(match, "SwapCached: %ld kB\n", &cached);
 
- if (!(match = strstr(buf, "SwapFree"))) {
+ if (get_swap_info(&total, &free, &cached)) {
                         return NULL;
                 }
- sscanf(match, "SwapFree: %ld kB\n", &free);
 
                 return fmt_human((total - free - cached) * 1024, 1024);
         }
Received on Mon May 28 2018 - 22:22:13 CEST