// g++ cpp-attribute-packed.cpp -o a.out
#include <iostream>
using namespace std;

struct CharChar      { char c; char c2; };
struct CharCharInt   { char c; char c2; int i; };
struct IntCharChar   { int i;  char c;  char c2; };
struct CharIntChar   { char c; int i;   char c2; };
struct CharShortChar { char c; short s; char c2; };

int main() {
    cout << "sizeof(CharChar)      " << sizeof(CharChar) << '\n';
    cout << "sizeof(CharCharInt)   " << sizeof(CharCharInt) << '\n';
    cout << "sizeof(IntCharChar)   " << sizeof(IntCharChar) << '\n';
    cout << "sizeof(CharIntChar)   " << sizeof(CharIntChar) << '\n';
    cout << "sizeof(CharShortChar) " << sizeof(CharShortChar) << '\n';

    return 0;
}

// g++ cpp-attribute-packed2.cpp -o a.out
#include <iostream>
using namespace std;

struct __attribute__((__packed__)) CharChar {
    char c;
    char c2;
};

struct __attribute__((__packed__)) CharCharInt {
    char c;
    char c2;
    int i;
};

struct IntCharChar {
    int i;
    char c;
    char c2;
} __attribute__((__packed__));

struct CharIntChar {
    char c;
    int i;
    char c2;
} __attribute__((__packed__)) charintchar;

typedef struct CharShortChar {
    char c;
    short s;
    char c2;
} __attribute__((__packed__)) CharShortChar_t;

int main() {
    charintchar.i = 123;
    CharShortChar_t charshortchar;
    cout << "sizeof(CharChar)       " << sizeof(CharChar) << '\n';
    cout << "sizeof(CharCharInt)    " << sizeof(CharCharInt) << '\n';
    cout << "sizeof(IntCharChar)    " << sizeof(IntCharChar) << '\n';
    cout << "sizeof(CharIntChar)    " << sizeof(CharIntChar) << '\n';
    cout << "sizeof(CharShortChar)  " << sizeof(CharShortChar) << '\n';

    return 0;
}

#define AID_ROOT             0  /* traditional unix root user */
#define AID_SYSTEM        1000  /* system server */
#define AID_RADIO         1001  /* telephony subsystem, RIL */
#define AID_BLUETOOTH     1002  /* bluetooth subsystem */
#define AID_GRAPHICS      1003  /* graphics devices */
#define AID_INPUT         1004  /* input devices */
#define AID_AUDIO         1005  /* audio devices */
#define AID_CAMERA        1006  /* camera devices */
#define AID_LOG           1007  /* log devices */
#define AID_COMPASS       1008  /* compass device */
#define AID_MOUNT         1009  /* mountd socket */
#define AID_WIFI          1010  /* wifi subsystem */
#define AID_ADB           1011  /* android debug bridge (adbd) */
#define AID_INSTALL       1012  /* group for installing packages */
#define AID_MEDIA         1013  /* mediaserver process */
#define AID_DHCP          1014  /* dhcp client */
#define AID_SHELL         2000  /* adb and debug shell user */
#define AID_CACHE         2001  /* cache access */
#define AID_DIAG          2002  /* access to diagnostic resources */
/* The 3000 series are intended for use as supplemental group id's only.
 * They indicate special Android capabilities that the kernel is aware of. */
#define AID_NET_BT_ADMIN  3001  /* bluetooth: create any socket */
#define AID_NET_BT        3002  /* bluetooth: create sco, rfcomm or l2cap sockets */
#define AID_INET          3003  /* can create AF_INET and AF_INET6 sockets */
#define AID_NET_RAW       3004  /* can create raw INET sockets */
#define AID_MISC          9998  /* access to misc storage */
#define AID_NOBODY        9999
#define AID_APP          10000 /* first app user */

struct android_id_info {
    const char *name;
    unsigned aid;
};

static struct android_id_info android_ids[] = {
    { "root",      AID_ROOT, },
    { "system",    AID_SYSTEM, },
    { "radio",     AID_RADIO, },
    { "bluetooth", AID_BLUETOOTH, },
    { "graphics",  AID_GRAPHICS, },
    { "input",     AID_INPUT, },
    { "audio",     AID_AUDIO, },
    { "camera",    AID_CAMERA, },
    { "log",       AID_LOG, },
    { "compass",   AID_COMPASS, },
    { "mount",     AID_MOUNT, },
    { "wifi",      AID_WIFI, },
    { "dhcp",      AID_DHCP, },
    { "adb",       AID_ADB, },
    { "install",   AID_INSTALL, },
    { "media",     AID_MEDIA, },
    { "shell",     AID_SHELL, },
    { "cache",     AID_CACHE, },
    { "diag",      AID_DIAG, },
    { "net_bt_admin", AID_NET_BT_ADMIN, },
    { "net_bt",    AID_NET_BT, },
    { "inet",      AID_INET, }, 
    { "net_raw",   AID_NET_RAW, },
    { "misc",      AID_MISC, },
    { "nobody",    AID_NOBODY, },
};

#define android_id_count \
    (sizeof(android_ids) / sizeof(android_ids[0]))

#define AID_ROOT 0 /* traditional unix root user */
/* The following are for LTP and should only be used for testing */
#define AID_DAEMON 1 /* traditional unix daemon owner */
#define AID_BIN 2    /* traditional unix binaries owner */
#define AID_SYSTEM 1000 /* system server */
#define AID_RADIO 1001           /* telephony subsystem, RIL */
#define AID_BLUETOOTH 1002       /* bluetooth subsystem */
#define AID_GRAPHICS 1003        /* graphics devices */
#define AID_INPUT 1004           /* input devices */
#define AID_AUDIO 1005           /* audio devices */
#define AID_CAMERA 1006          /* camera devices */
#define AID_LOG 1007             /* log devices */
#define AID_COMPASS 1008         /* compass device */
#define AID_MOUNT 1009           /* mountd socket */
#define AID_WIFI 1010            /* wifi subsystem */
#define AID_ADB 1011             /* android debug bridge (adbd) */
#define AID_INSTALL 1012         /* group for installing packages */
#define AID_MEDIA 1013           /* mediaserver process */
#define AID_DHCP 1014            /* dhcp client */
#define AID_SDCARD_RW 1015       /* external storage write access */
#define AID_VPN 1016             /* vpn system */
#define AID_KEYSTORE 1017        /* keystore subsystem */
#define AID_USB 1018             /* USB devices */
#define AID_DRM 1019             /* DRM server */
#define AID_MDNSR 1020           /* MulticastDNSResponder (service discovery) */
#define AID_GPS 1021             /* GPS daemon */
#define AID_UNUSED1 1022         /* deprecated, DO NOT USE */
#define AID_MEDIA_RW 1023        /* internal media storage write access */
#define AID_MTP 1024             /* MTP USB driver access */
#define AID_UNUSED2 1025         /* deprecated, DO NOT USE */
#define AID_DRMRPC 1026          /* group for drm rpc */
#define AID_NFC 1027             /* nfc subsystem */
#define AID_SDCARD_R 1028        /* external storage read access */
#define AID_CLAT 1029            /* clat part of nat464 */
#define AID_LOOP_RADIO 1030      /* loop radio devices */
#define AID_MEDIA_DRM 1031       /* MediaDrm plugins */
#define AID_PACKAGE_INFO 1032    /* access to installed package details */
#define AID_SDCARD_PICS 1033     /* external storage photos access */
#define AID_SDCARD_AV 1034       /* external storage audio/video access */
#define AID_SDCARD_ALL 1035      /* access all users external storage */
#define AID_LOGD 1036            /* log daemon */
#define AID_SHARED_RELRO 1037    /* creator of shared GNU RELRO files */
#define AID_DBUS 1038            /* dbus-daemon IPC broker process */
#define AID_TLSDATE 1039         /* tlsdate unprivileged user */
#define AID_MEDIA_EX 1040        /* mediaextractor process */
#define AID_AUDIOSERVER 1041     /* audioserver process */
#define AID_METRICS_COLL 1042    /* metrics_collector process */
#define AID_METRICSD 1043        /* metricsd process */
#define AID_WEBSERV 1044         /* webservd process */
#define AID_DEBUGGERD 1045       /* debuggerd unprivileged user */
#define AID_MEDIA_CODEC 1046     /* mediacodec process */
#define AID_CAMERASERVER 1047    /* cameraserver process */
#define AID_FIREWALL 1048        /* firewalld process */
#define AID_TRUNKS 1049          /* trunksd process (TPM daemon) */
#define AID_NVRAM 1050           /* Access-controlled NVRAM */
#define AID_DNS 1051             /* DNS resolution daemon (system: netd) */
#define AID_DNS_TETHER 1052      /* DNS resolution daemon (tether: dnsmasq) */
#define AID_WEBVIEW_ZYGOTE 1053  /* WebView zygote process */
#define AID_VEHICLE_NETWORK 1054 /* Vehicle network service */
#define AID_MEDIA_AUDIO 1055     /* GID for audio files on internal media storage */
#define AID_MEDIA_VIDEO 1056     /* GID for video files on internal media storage */
#define AID_MEDIA_IMAGE 1057     /* GID for image files on internal media storage */
#define AID_TOMBSTONED 1058      /* tombstoned user */
#define AID_MEDIA_OBB 1059       /* GID for OBB files on internal media storage */
#define AID_ESE 1060             /* embedded secure element (eSE) subsystem */
#define AID_OTA_UPDATE 1061      /* resource tracking UID for OTA updates */
#define AID_AUTOMOTIVE_EVS 1062  /* Automotive rear and surround view system */
#define AID_LOWPAN 1063          /* LoWPAN subsystem */
#define AID_HSM 1064             /* hardware security module subsystem */
#define AID_RESERVED_DISK 1065   /* GID that has access to reserved disk space */
#define AID_STATSD 1066          /* statsd daemon */
#define AID_INCIDENTD 1067       /* incidentd daemon */
#define AID_SECURE_ELEMENT 1068  /* secure element subsystem */
#define AID_LMKD 1069            /* low memory killer daemon */
#define AID_LLKD 1070            /* live lock daemon */
#define AID_IORAPD 1071          /* input/output readahead and pin daemon */
#define AID_GPU_SERVICE 1072     /* GPU service daemon */
#define AID_NETWORK_STACK 1073   /* network stack service */
#define AID_GSID 1074            /* GSI service daemon */
/* Changes to this file must be made in AOSP, *not* in internal branches. */
#define AID_SHELL 2000 /* adb and debug shell user */
#define AID_CACHE 2001 /* cache access */
#define AID_DIAG 2002  /* access to diagnostic resources */
/* The range 2900-2999 is reserved for OEM, and must never be
 * used here */
#define AID_OEM_RESERVED_START 2900
#define AID_OEM_RESERVED_END 2999
/* The 3000 series are intended for use as supplemental group id's only.
 * They indicate special Android capabilities that the kernel is aware of. */
#define AID_NET_BT_ADMIN 3001 /* bluetooth: create any socket */
#define AID_NET_BT 3002       /* bluetooth: create sco, rfcomm or l2cap sockets */
#define AID_INET 3003         /* can create AF_INET and AF_INET6 sockets */
#define AID_NET_RAW 3004      /* can create raw INET sockets */
#define AID_NET_ADMIN 3005    /* can configure interfaces and routing tables. */
#define AID_NET_BW_STATS 3006 /* read bandwidth statistics */
#define AID_NET_BW_ACCT 3007  /* change bandwidth statistics accounting */
#define AID_READPROC 3009     /* Allow /proc read access */
#define AID_WAKELOCK 3010     /* Allow system wakelock read/write access */
#define AID_UHID 3011         /* Allow read/write to /dev/uhid node */
/* The range 5000-5999 is also reserved for OEM, and must never be used here. */
#define AID_OEM_RESERVED_2_START 5000
#define AID_OEM_RESERVED_2_END 5999
#define AID_EVERYBODY 9997 /* shared between all apps in the same profile */
#define AID_MISC 9998      /* access to misc storage */
#define AID_NOBODY 9999
#define AID_APP 10000       /* TODO: switch users over to AID_APP_START */
#define AID_APP_START 10000 /* first app user */
#define AID_APP_END 19999   /* last app user */
#define AID_CACHE_GID_START 20000 /* start of gids for apps to mark cached data */
#define AID_CACHE_GID_END 29999   /* end of gids for apps to mark cached data */
#define AID_EXT_GID_START 30000 /* start of gids for apps to mark external data */
#define AID_EXT_GID_END 39999   /* end of gids for apps to mark external data */
#define AID_EXT_CACHE_GID_START 40000 /* start of gids for apps to mark external cached data */
#define AID_EXT_CACHE_GID_END 49999   /* end of gids for apps to mark external cached data */
#define AID_SHARED_GID_START 50000 /* start of gids for apps in each user to share */
#define AID_SHARED_GID_END 59999   /* end of gids for apps in each user to share */
/*
 * This is a magic number in the kernel and not something that was picked
 * arbitrarily. This value is returned whenever a uid that has no mapping in the
 * user namespace is returned to userspace:
 * https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/include/linux/highuid.h?h=v4.4#n40
 */
#define AID_OVERFLOWUID 65534 /* unmapped user in the user namespace */
/* use the ranges below to determine whether a process is isolated */
#define AID_ISOLATED_START 90000 /* start of uids for fully isolated sandboxed processes */
#define AID_ISOLATED_END 99999   /* end of uids for fully isolated sandboxed processes */
#define AID_USER 100000        /* TODO: switch users over to AID_USER_OFFSET */
#define AID_USER_OFFSET 100000 /* offset for uid ranges for each user */

size_t strlen(const char * str);

// g++ cpp-strlen.cpp -o a.out
#include <stdio.h>
#include <string.h>

int main() {
    char arr[] = "hello";

    printf("Length of string is: %d\n", (int)strlen(arr)); 

    return 0;
}

// g++ cpp-strlen2.cpp -o a.out
#include <stdio.h>
#include <string.h>

int main() {
    char arr[] = {'h', 'e', 'l', 'l', 'o', '\0'};

    printf("Length of string is: %d\n", (int)strlen(arr)); 

    return 0;
}

// g++ cpp-strlen3.cpp -o a.out
#include <stdio.h>
#include <string.h>

int main() {
    const char *arr = "hello";

    printf("Length of string is: %d\n", (int)strlen(arr)); 

    return 0;
}

// g++ cpp-strlen4.cpp -o a.out
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

int main() {
    char *arr = NULL;
    arr = (char *)malloc(sizeof(char) * 64);
    strcpy(arr, "hello");

    printf("Length of string is: %d\n", (int)strlen(arr)); 
    free(arr);
    return 0;
}

// g++ cpp-strlen5.cpp -o a.out
#include <stdio.h>
#include <string.h>

int main() {
    char arr[128] = {0};
    // gets(arr); // unsafe
    fgets(arr, 128, stdin);
    int len = (int)strlen(arr);
    if (arr[len-1] == '\n') // remove '\n'
        arr[len-1] = '\0';

    printf("Input: %s\n", arr); 
    printf("Length of string is: %d\n", (int)strlen(arr)); 
    return 0;
}

int snprintf(char * buffer, size_t n, const char * format, ...);

// g++ cpp-snprintf.cpp -o a.out
#include <stdio.h>

int main() {
    char buf[128] = {0};
    const char str[] = "hello world";
    char c = 'a';
    int num = 123;
    float f = 5.4321f;

    snprintf(buf, 128, "string: %s\n", str);
    printf("%s", buf);

    snprintf(buf, 128, "character: %c\n", c);
    printf("%s", buf);

    snprintf(buf, 128, "integer: %d\n", num);
    printf("%s", buf);

    snprintf(buf, 128, "float: %f\n", f);
    printf("%s", buf);

    return 0;
}

// g++ cpp-snprintf2.cpp -o a.out
#include <stdio.h>
#include <string.h>

int main() {
    char hex[] = {0x01, 0x02, 0x03, 0x1a, 0x2b, 0x3c};
    char tmp[128] = {0};
    char buf[128] = {0};

    for (int i = 0; i < sizeof(hex); i++) {
        snprintf(tmp, sizeof(tmp), "0x%02x, ", hex[i]);
        strcat(buf, tmp);
    }
    printf("hex : %s\n", buf);

    return 0;
}