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	Refactor swap.c to use getline() instead of buf-filling - slstatus - status mon…
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	---
	commit a18439af114b98ab026921b0cac61164f7a4eea8
	parent 5d6415608b37ebed185e00eae01eb743edb555e5
	Author: Laslo Hunhold <[email protected]>
	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:
	M 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\…
	+ 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);
	}