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 37ee85cb5bf3859da7605ed9384eb2829a36ff12..1958eefa5773934f13e0a6476f590faaa7244f02 100644 (file)
--- a/components/swap.c
+++ b/components/swap.c
@@ -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);
        }
@@ -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;
                }
 
@@ -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);
        }
@@ -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);
        }