使用C中的X和Y值將緩沖區讀取為矩陣

Question

我有一個包含256個整數的緩沖區，因此創建了一個16x16的矩陣。 我要完成的工作是讀取存儲在緩沖區中的值，就像它是一個矩陣一樣。 因此，如果我給出5和3的坐標，則應該得到Y為5且Y為X的值。

例如，這是緩沖區的一小部分，但是在16x3的矩陣中以便於閱讀，請考慮將其作為起始索引0而不是1）

0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
7 8 9 1 2 3 4 5 6 7 8 9 1 2 3 4
4 5 6 7 8 9 1 0 2 3 4 5 6 7 8 9

因此，如果我嘗試獲得Y = 2和X = 5的值，則應該返回值9。

這是我已經有的一些代碼，但是我的數學關閉了。

unsigned char getTablevalue(int tableIndex, unsigned char *buffer) {
    return buffer[tableIndex];
}

void getInput(....) {
    int yValue = 2;
    int xValue = 5;
    int returnValue = 0;
    unsigned char *buffer = malloc(256 * sizeof (unsigned char));
    memset(buffer, 0, 256);

    ... Some code to fill buffer...
    returnValue = getTablevalue({what can I put here}, buffer); 

}

任何幫助，將不勝感激！ 先感謝您。

Answer 1

這演示了如何將緩沖區用作數組並將緩沖區“數組”復制到實際數組中。

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

int main()
{
    int n;
    int x, y;
    int arr[16][16];
    int xtest =2, ytest =12; //'random values to test that it works

    /* allocate space for a buffer of 256 values in the range 0 to 255) */
    unsigned char *buffer = malloc(256 * sizeof (unsigned char));

    /* fill the buffer with sequential values from 0 to 255 */
    for (n = 0; n < 256; n++) {
        buffer[n] = n;
    }

    /* just to check the fill was OK - print out the buffer contents */
    for (n = 0; n < 256; n++) {
        printf("%d .. ", buffer[n]);
    }
    printf("\n\n");

   /* fill a 16 * 16 array with values from the buffer
       that the buffer data is arranged in 16 groups of 16 values in a 
       single sequential buffer */
    for (x = 0; x < 16; x++) {
        for (y = 0; y < 16; y++) {
            arr[x][y] = buffer[(x * 16) + y];
        }
    }

    /* print out the array */
    for (x = 0; x < 16; x++) {
        for (y = 0; y < 16; y++) {
            printf("%d\t", arr[x][y]);
        }
        printf("\n");
    }
    printf("\n\n");

    /* just print a 'random' xy value from the matrix and from the buffer
       they will be the same (we hope) */
    printf("X=%d,Y=%d, Matrix[%d][%d] is: %d ... and Buffer %d,%d is %d\n",
            xtest, ytest, xtest, ytest, arr[xtest][ytest],
            xtest, ytest, buffer[(xtest * 16) + ytest]);
    if (arr[xtest][ytest] == buffer[(xtest * 16) + ytest]) {
        printf("Wow - they ARE the same\n");
        } else {
        printf("Oh No - they are different\n");
    }
}    

樣品輸出
X=2,Y=12, Matrix[2][12] is: 44 ... and Buffer 2,12 is 44 Wow - they ARE the same