Add date module

premake5.lua

@@ -3,7 +3,10 @@ workspace "custos"
     kind "ConsoleApp"
     language "C"
     cdialect "C11"
-    defines { "_POSIX_C_SOURCE=200112L" }
+    defines {
+        "_POSIX_C_SOURCE=200112L",
+        "_XOPEN_SOURCE",
+    }
     warnings "Extra"
 
     filter "configurations:debug"

src/date.c

+#include "date.h"
+
+#include <errno.h>
+#include <stdio.h>
+
+#include <time.h>
+
+#include "utils.h"
+
+#define DATE_FMT "%Y-%m-%dT%H:%M:%S"
+#define DATE_SIZE sizeof("YYYY-MM-DDTHH:MM:SS")
+
+struct tz {
+    const char *name, *id;
+};
+
+static struct tz tzs[] = {
+    {.name = "P ", .id = "US/Pacific"},
+    {.name = "E ", .id = "US/Eastern"},
+    {.name = "BR", .id = "America/Sao_Paulo"},
+    {.name = "CE", .id = "Europe/Prague"},
+};
+
+static bool init_tzs(long *v);
+static bool restore_tz(const char *tz);
+
+void *date_init(void) {
+    long *const v = calloc(ARRAY_SIZE(tzs), sizeof(*v));
+    if(!v)
+        return LOG_ERRNO("calloc"), NULL;
+    const char *const tz = getenv("TZ");
+    if(!init_tzs(v) || !restore_tz(tz)) {
+        free(v);
+        return NULL;
+    }
+    return v;
+}
+
+bool init_tzs(long *v) {
+    time_t t = {0};
+    if(time(&t) == -1)
+        return LOG_ERRNO("time"), false;
+    for(size_t i = 0; i != ARRAY_SIZE(tzs); ++i) {
+        if(setenv("TZ", tzs[i].id, 1) == -1)
+            return LOG_ERRNO("setenv"), false;
+        tzset();
+        struct tm tm = {0};
+        if(!localtime_r(&t, &tm))
+            return LOG_ERRNO("localtime_r"), false;
+        tm.tm_isdst = 0;
+        time_t t_tz = mktime(&tm);
+        if(t_tz == -1)
+            return LOG_ERRNO("mktime"), false;
+        v[i] = t - t_tz + timezone;
+    }
+    return true;
+}
+
+static bool restore_tz(const char *tz) {
+    if(tz) {
+        if(setenv("TZ", tz, 1) == -1)
+            return LOG_ERRNO("setenv"), false;
+    } else
+        if(unsetenv("TZ") == -1)
+            return LOG_ERRNO("unsetenv"), false;
+    tzset();
+    return true;
+}
+
+bool date_destroy(void *d) {
+    free(d);
+    return true;
+}
+
+bool date_update(void *d) {
+    const long *const v = d;
+    puts("date");
+    time_t t = {0};
+    if(time(&t) == -1)
+        return LOG_ERRNO("time"), false;
+    for(size_t i = 0; i != ARRAY_SIZE(tzs); ++i) {
+        const time_t t_tz = t - v[i];
+        struct tm tm = {0};
+        if(!gmtime_r(&t_tz, &tm))
+            return LOG_ERRNO("gmtime_r"), false;
+        char str[DATE_SIZE] = {0};
+        if(strftime(str, sizeof(str), DATE_FMT, &tm) != sizeof(str) - 1)
+            return LOG_ERR("strftime failed\n"), false;
+        printf("  %s %s\n", tzs[i].name, str);
+    }
+    return true;
+}

src/date.h

+#ifndef CUSTOS_DATE_H
+#define CUSTOS_DATE_H
+
+#include <stdbool.h>
+
+void *date_init(void);
+bool date_destroy(void *d);
+bool date_update(void *d);
+
+#endif

src/main.c

@@ -10,6 +10,7 @@
 #include <signal.h>
 #include <time.h>
 
+#include "date.h"
 #include "load.h"
 #include "test.h"
 #include "thermal.h"
@@ -57,6 +58,11 @@ static struct module modules[] = {{
     .init = thermal_init,
     .destroy = thermal_destroy,
     .update = thermal_update,
+}, {
+    .name = "date",
+    .init = date_init,
+    .destroy = date_destroy,
+    .update = date_update,
 }};
 
 static void sigint_handler(int s) {

src/premake5.lua

 project "custos"
     files {
+        "date.h",
+        "date.c",
         "load.c",
         "load.h",
         "main.c",