Mac Hash Table

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115

#include <stdio.h> #include <stdint.h> #include <string.h> #include <stdlib.h> static unsigned char PseudoRandomHash[256] = { 1, 87, 49, 12, 176, 178, 102, 166, 121, 193, 6, 84, 249, 230, 44, 163, 14, 197, 213, 181, 161, 85, 218, 80, 64, 239, 24, 226, 236, 142, 38, 200, 110, 177, 104, 103, 141, 253, 255, 50, 77, 101, 81, 18, 45, 96, 31, 222, 25, 107, 190, 70, 86, 237, 240, 34, 72, 242, 20, 214, 244, 227, 149, 235, 97, 234, 57, 22, 60, 250, 82, 175, 208, 5, 127, 199, 111, 62, 135, 248, 174, 169, 211, 58, 66, 154, 106, 195, 245, 171, 17, 187, 182, 179, 0, 243, 132, 56, 148, 75, 128, 133, 158, 100, 130, 126, 91, 13, 153, 246, 216, 219, 119, 68, 223, 78, 83, 88, 201, 99, 122, 11, 92, 32, 136, 114, 52, 10, 138, 30, 48, 183, 156, 35, 61, 26, 143, 74, 251, 94, 129, 162, 63, 152, 170, 7, 115, 167, 241, 206, 3, 150, 55, 59, 151, 220, 90, 53, 23, 131, 125, 173, 15, 238, 79, 95, 89, 16, 105, 137, 225, 224, 217, 160, 37, 123, 118, 73, 2, 157, 46, 116, 9, 145, 134, 228, 207, 212, 202, 215, 69, 229, 27, 188, 67, 124, 168, 252, 42, 4, 29, 108, 21, 247, 19, 205, 39, 203, 233, 40, 186, 147, 198, 192, 155, 33, 164, 191, 98, 204, 165, 180, 117, 76, 140, 36, 210, 172, 41, 54, 159, 8, 185, 232, 113, 196, 231, 47, 146, 120, 51, 65, 28, 144, 254, 221, 93, 189, 194, 139, 112, 43, 71, 109, 184, 209}; #define N 256 int PearsonHash(uint64_t macAddr) { int i; uint8_t h[sizeof(uint64_t)]; int result; bzero(h, sizeof(h)); for(i=1; i<sizeof(h); i++) { uint8_t byte = (uint8_t)(macAddr & 0xff); h[i] = PseudoRandomHash[(h[i-1] ^ byte) & 0xFF]; macAddr >>= 8; result = h[i]; } return result; } typedef struct { uint64_t macAddr; int aid; } RecordT; RecordT* buildHashTable(int sz) { RecordT *p = calloc(sz, sizeof(RecordT)); return p; } void addRecord(RecordT* table, RecordT* rec) { int slot = PearsonHash(rec->macAddr); table[slot].macAddr = rec->macAddr; table[slot].aid = rec->aid; } RecordT* findRecord(RecordT *table, uint64_t mac) { int slot = PearsonHash(mac); return &table[slot]; } int main() { int i; int n; const uint64_t MacBase = 0x000011BABEBEEF00ULL; uint64_t macTable[N]; for(i=0; i<N; i++) { printf(" %03u ", PseudoRandomHash[i]); if ((i+1)%16 == 0) printf("\n"); } RecordT *hashTable = buildHashTable(N); for(i=0; i<N; i++) { uint64_t mac; macTable[i] = mac = MacBase + i; } for(i=0; i<N; ++i) { RecordT rec; rec.macAddr = macTable[i]; rec.aid = N-i; addRecord(hashTable, &rec); } for(i=0; i<N; i++) { printf("%d\t %08lX: \tSlot=%u\n", i, macTable[i], PearsonHash(macTable[i])); } for(int k=0; k<N; ++k) { uint64_t mac = macTable[k]; RecordT *p = findRecord(hashTable, mac); printf("mac[%d]=%08lX \trec(%08lX,%d)\n", k, macTable[k], p->macAddr, p->aid); } free(hashTable); }

Raspberry PI 3 Model B Rev 1.2 Power Wattage

My order of USB power meter arrived a few days ago, but only today I could put it into use by plugging it in between the power supply adapter and my RPI.

The way I test the max power consumed is by creating a small C program to do infinite loop such as:

int main()
{
   while (1) {}
}

I executed it in four separate processes (open four terminals, and run the program in each one). This way I could exhaust the whole four cores in the CPU.  I also GUI desktop on the machine (LXDE).

Here what is shown by "top":




My USB power meter shows 1.17 WH, meaning in each hour it consumes 2.37 Watt or 0.00237 KWh.  If the price per kWh charged by Utility company is 12.01 cent ($0.1201/KWH), in a day I'd pay 0.00237 KWh* $0.1201/KWh * 24 hours = $‭0.006831288‬ or about $0.0068 per day.  In a month I'd pay about $0.2 minimum.

After I killed all those four infinite loop processes, the wattage did not drop.  Instead I saw it climbed to almost 2 Watt-hour.  I think over time it probably would drop back to around 2 W (idling time).

What Coronavirus Symptoms Look Like, Day By Day

https://www.youtube.com/embed/OOJqHPfG7pA

Windows Application Development on Linux

Make sure you have installed MinGW on Linux:

sudo apt install mingw-w64 gdb-mingw-w64

Optionally, for testing purpose, install also WINE:

wine-stable wine-development wine64 wine64-development

FYI, with my recent mingw32 installation, the location for needed DLL files are in :

/usr/lib/gcc/x86_64-w64-mingw32/7.3-posix/

ll /usr/lib/gcc/x86_64-w64-mingw32/7.3-posix/*.dll
-rwxr-xr-x 1 root root   482339 Mar 12  2018 /usr/lib/gcc/x86_64-w64-mingw32/7.3-posix/libatomic-1.dll*
-rwxr-xr-x 1 root root  1190750 Mar 12  2018 /usr/lib/gcc/x86_64-w64-mingw32/7.3-posix/libgcc_s_seh-1.dll*
-rwxr-xr-x 1 root root  1523015 Mar 12  2018 /usr/lib/gcc/x86_64-w64-mingw32/7.3-posix/libgomp-1.dll*
-rwxr-xr-x 1 root root  1393636 Mar 12  2018 /usr/lib/gcc/x86_64-w64-mingw32/7.3-posix/libquadmath-0.dll*
-rwxr-xr-x 1 root root   387526 Mar 12  2018 /usr/lib/gcc/x86_64-w64-mingw32/7.3-posix/libssp-0.dll*
-rwxr-xr-x 1 root root 16229690 Mar 12  2018 /usr/lib/gcc/x86_64-w64-mingw32/7.3-posix/libstdc++-6.dll*

(this path should be added into PATH to make wine able to run our compiled EXE)

Example of Makefile:


APP=MyGUI
CC=x86_64-w64-mingw32-g++
WRC=x86_64-w64-mingw32-windres

$(APP).exe : $(APP).o $(APP).res
$(CC) -mwindows $(APP).o $(APP).res -o $@

$(APP).o: $(APP).c
$(CC) -mwindows -c -o $@ $<

$(APP).res : resource.rc resource.h
$(WRC) $< -O coff -o $@

clean:
rm *.res *.o $(APP).exe



The Source code:

/*-------------------------------------------------*/
/* MyGUI.c - gui hello world                    */
/* build: gcc -mwindows MyGUI.c -o MyGUI.exe */
/*-------------------------------------------------*/
#include <windows.h>

char glpszText[1024];

LRESULT CALLBACK WndProc(HWND, UINT, WPARAM, LPARAM);

/******************************************************************************
* Main entry
******************************************************************************/
int APIENTRY WinMain(HINSTANCE hInstance, 
     HINSTANCE hPrevInstance,
     LPSTR lpCmdLine,
     int nCmdShow)
{
 wsprintf(glpszText, 
   "Hello World\nGetCommandLine(): [%s]\n"
   "WinMain lpCmdLine: [%s]\n",
   lpCmdLine, GetCommandLine() );

 WNDCLASSEX wcex; 
              
  wcex.cbSize = sizeof(wcex);
 wcex.style = CS_HREDRAW | CS_VREDRAW;
 wcex.lpfnWndProc = WndProc; /* set the callback */
 wcex.cbClsExtra = 0;
 wcex.cbWndExtra = 0;
 wcex.hInstance = hInstance;
 wcex.hIcon = LoadIcon(NULL, IDI_APPLICATION);
 wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
 wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
 wcex.lpszMenuName = NULL;
 wcex.lpszClassName = "MYGUI";
 wcex.hIconSm = NULL;

 if (!RegisterClassEx(&wcex))
  return FALSE; 

 HWND hWnd;
 hWnd = CreateWindow("MYGUI", "MyGUI", WS_OVERLAPPEDWINDOW,
      CW_USEDEFAULT, CW_USEDEFAULT, CW_USEDEFAULT, 
      CW_USEDEFAULT, NULL, NULL, hInstance, NULL);

 if (!hWnd)
  return FALSE;

 ShowWindow(hWnd, nCmdShow);
 UpdateWindow(hWnd);

 MSG msg;
 /* main loop */
 while (GetMessage(&msg, NULL, 0, 0)) 
 {
  /* we can intercept keystrokes here too if we want */
  TranslateMessage(&msg);
  DispatchMessage(&msg);
 }

 return msg.wParam;
}


/******************************************************************************
* Main callback
******************************************************************************/
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
 PAINTSTRUCT ps;
 HDC hdc;
                                                 
 switch (message) 
 {
  case WM_PAINT:
   hdc = BeginPaint(hWnd, &ps);
   RECT rt;
   GetClientRect(hWnd, &rt);
   DrawText(hdc, glpszText, strlen(glpszText), &rt, DT_TOP | DT_LEFT);
   EndPaint(hWnd, &ps);
   break;

  case WM_DESTROY:
   PostQuitMessage(0);
   break;
    
  default:
   /* for everything else unhandled, do this */
   return DefWindowProc(hWnd, message, wParam, lParam);
   
 }
   
 return 0;
   
}

To run:

wine64 MyGUI.exe

If we find issue that WINE could not find some MinGW's *.dll, create soft links in WINE's system directory to the MinGW's dll:

pushd ~/.wine/drive_c/windows/system
cp -s /usr/lib/gcc/i686-w64-mingw32/7.3-win32/*.dll .
popd



To debug the EXE:

i686-w64-mingw32-gdb <EXE code>

To list (dir command) file names sorted by their name's length

Suppose we want to list certain files (or all files in a directory), but sorted ascending by their filename's length.

The following small script meets the purpose:

First, create a PowerShell script, say, dirnamesize.ps1 with its content as below:

param (
   [string]$dirpath = "."
)

gci $dirpath | select-object name, @{Name="Nlength";Expression={$_.Name.Length}} | sort-object Nlength


Second, create a normal DOS shell file to call that PowerShell (so we don't need to open PowerShell), say, dirnamesize.cmd with the content:

set DIRPATH=%*

@if "%DIRPATH%"=="" (
    powershell dirnamesize.ps1
) else (
    powershell dirnamesize.ps1 -dirpath %DIRPATH%
)


Example:

C:\Windows>dirname *.xml

Name                        Nlength
----                        -------
Education.xml                    13
ServerRdsh.xml                   14
Enterprise.xml                   14
Professional.xml                 16
ProfessionalEducation.xml        25
ProfessionalWorkstation.xml      27

Example of Intrusive Singly Linked List

#include <stdio.h>
#include <stdlib.h>
#include <stddef.h>



typedef struct list_item {
    int val;
    void *next;
} list_item;


typedef struct List {
    list_item *head;
    list_item *prev;
} List;


list_item *create_list_item(int val)
{
    list_item *p = (list_item *)malloc(sizeof(list_item));
    if (p)
    {
        p->val = val;
        p->next = NULL;
    }
    return p;
}


void add_list_item_into_node(List *list, int val)
{
    list_item *newlist_item = create_list_item(val);
    if (list->prev != NULL)
    {
        list->prev->next = newlist_item;
        list->prev = newlist_item;
    }
    else
    {
        list->head = newlist_item;
        list->prev = newlist_item;
        printf("FIRST! head==prev ? %d, %p\n", list->head==list->prev, list->head);
    }

    printf("%p added; head=%p, prev=%p\n", newlist_item, list->head, list->prev);
}


void init_list(List *l)
{
    l->head = l->prev = NULL;
}


void clear_list(List *l)
{
    list_item *p = l->head;
    while (p != NULL)
    {
        list_item *pn = (list_item *)p->next; 
        printf("Freeing %p, next p is=%p\n", p, pn);
        free(p);
        p = pn;
    }
    l->head = l->prev = NULL;
}


typedef void (*callback_t)(list_item *);

void print(list_item *p)
{
    printf("p=%p: val=%d\n", p, p->val);
}

void iterate(List *list, callback_t cbk)
{
    list_item *p = list->head;
    while (p)
    {
        cbk(p);
        p = p->next;
    }
}

int main()
{
    List mylist;
    init_list(&mylist);

    for(int i=0; i<10; ++i)
    {
        add_list_item_into_node(&mylist, i*2+1);
    }

   iterate(&mylist, print);

    // cleanup; starting from head
    printf("Cleaning up!\n");
    clear_list(&mylist);
    iterate(&mylist, print);

    printf("head = %p, prev=%p\n", mylist.head, mylist.prev);
}