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commit a18439af114b98ab026921b0cac61164f7a4eea8
parent 5d6415608b37ebed185e00eae01eb743edb555e5
Author: Laslo Hunhold <dev@frign.de>
Date:   Mon, 28 May 2018 21:16:02 +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.

Diffstat:
components/swap.c | 123++++++++++++++++++++++++++++++++-----------------------------------------------
1 file changed, 50 insertions(+), 73 deletions(-)

diff --git 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); }