Memcpy structure single pointer
In this section, you are going to learn
How to do memcpy with structure single pointer ?
Topics in this section,
Two Arrays copy : One structure at a time with array indexing : Loop
Two Arrays copy : One structure at a time with array indexing (pointer notation): Loop
Two Arrays copy : One structure at a time with pointers indexing : Loop
Two Arrays copy : One structure at a time with pointers incrementing : Loop
Two Arrays copy : memcpy using Array Names : Relative position copy
Single array : Change contents of Single array using a Single pointer
Custom memcpy with single pointer : Pass single pointer to a function : Call by Value
Custom memcpy with single pointer : Pass single pointer to a function : Call by Reference
Step 1 : Define two structure variables
struct ABC {
int x;
int y;
int z;
};
struct ABC a = { .x = 10, .y = 20, .z = 30 };
struct ABC b;
Step 2 : Do structure copy
b = a;
Step 3 : Print structures
printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
See full program below
1#include <stdio.h>
2
3struct ABC {
4 int x;
5 int y;
6 int z;
7};
8
9int main(void)
10{
11 struct ABC a = { .x = 10, .y = 20, .z = 30 };
12 struct ABC b;
13
14 b = a;
15
16 printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
17
18 return 0;
19}
Output is as below
a.x = 10, a.y = 20, a.z = 30
Step 1 : Define two structure variables
struct ABC {
int x;
int y;
int z;
};
struct ABC a = { .x = 10, .y = 20, .z = 30 };
struct ABC b;
Step 2 : Do structure copy
memcpy(&b, &a, sizeof(struct ABC));
Step 3 : Print structures
printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
See full program below
1#include <stdio.h>
2#include <string.h>
3
4struct ABC {
5 int x;
6 int y;
7 int z;
8};
9
10int main(void)
11{
12 struct ABC a = { .x = 10, .y = 20, .z = 30 };
13
14 struct ABC b;
15
16 memcpy(&b, &a, sizeof(struct ABC));
17
18 printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
19
20 return 0;
21}
Output is as below
a.x = 10, a.y = 20, a.z = 30
Step 1 : Define two structure variables
struct ABC {
int x;
int y;
int z;
};
struct ABC a = { .x = 10, .y = 20, .z = 30 };
struct ABC b;
Step 2 : Define two pointers
struct ABC *p;
struct ABC *q;
p = &a;
q = &b;
Step 3 : Do structure copy
*q = *p;
Step 4 : Print structures
printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
See full program below
1#include <stdio.h>
2
3struct ABC {
4 int x;
5 int y;
6 int z;
7};
8
9int main(void)
10{
11 struct ABC a = { .x = 10, .y = 20, .z = 30 };
12
13 struct ABC b;
14
15 struct ABC *p;
16
17 struct ABC *q;
18
19 p = &a;
20
21 q = &b;
22
23 *q = *p;
24
25 printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
26
27 return 0;
28}
Output is as below
a.x = 10, a.y = 20, a.z = 30
Step 1 : Define two structure variables
struct ABC {
int x;
int y;
int z;
};
struct ABC a = { .x = 10, .y = 20, .z = 30 };
struct ABC b;
Step 2 : Define two pointers
struct ABC *p;
struct ABC *q;
p = &a;
q = &b;
Step 3 : Do structure copy using memcpy
memcpy(q, p, sizeof(struct ABC));
Step 4 : Print structures
printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
See full program below
1#include <stdio.h>
2#include <string.h>
3
4struct ABC {
5 int x;
6 int y;
7 int z;
8};
9
10int main(void)
11{
12 struct ABC a = { .x = 10, .y = 20, .z = 30 };
13
14 struct ABC b;
15
16 struct ABC *p;
17
18 struct ABC *q;
19
20 p = &a;
21 q = &b;
22
23 memcpy(q, p, sizeof(struct ABC));
24
25 printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
26
27 return 0;
28}
Output is as below
a.x = 10, a.y = 20, a.z = 30
Step 1 : Define two structure variables
struct ABC {
int x;
int y;
int z;
};
struct ABC a = { .x = 10, .y = 20, .z = 30 };
struct ABC b;
Step 2 : Define two pointers
struct ABC *p;
struct ABC *q;
p = &a;
q = &b;
Step 3 : Do structure copy using memcpy
for (int i = 0; i < sizeof(struct ABC); i += sizeof(struct ABC))
{
q[i] = p[i];
}
Step 4 : Print structures
printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
See full program below
1#include <stdio.h>
2
3struct ABC {
4 int x;
5 int y;
6 int z;
7};
8
9struct ABC a = { .x = 10, .y = 20, .z = 30 };
10
11struct ABC b;
12
13int main(void)
14{
15 struct ABC *p;
16 struct ABC *q;
17
18 p = &a;
19 q = &b;
20
21 for (int i = 0; i < sizeof(struct ABC); i += sizeof(struct ABC))
22 {
23 q[i] = p[i];
24 }
25
26 printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
27
28 return 0;
29}
Output is as below
a.x = 10, a.y = 20, a.z = 30
Step 1 : Define two structure variables
struct ABC {
int x;
int y;
int z;
};
struct ABC a = { .x = 10, .y = 20, .z = 30 };
struct ABC b;
Step 2 : Define two pointers
struct ABC *p;
struct ABC *q;
p = &a;
q = &b;
Step 3 : Do structure copy using memcpy
for (int i = 0; i < sizeof(struct ABC); i += sizeof(struct ABC) )
{
*q++ = *p++;
}
Step 4 : Print structures
printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
See full program below
1#include <stdio.h>
2
3struct ABC {
4 int x;
5 int y;
6 int z;
7};
8
9int main(void)
10{
11 struct ABC a = { .x = 10, .y = 20, .z = 30 };
12 struct ABC b;
13
14 struct ABC *p;
15 struct ABC *q;
16
17 p = &a;
18 q = &b;
19
20 for (int i = 0; i < sizeof(struct ABC); i += sizeof(struct ABC) )
21 {
22 *q++ = *p++;
23 }
24
25 printf("a.x = %d, a.y = %d, a.z = %d\n", a.x, a.y, a.z );
26
27 return 0;
28}
Output is as below
a.x = 10, a.y = 20, a.z = 30
Step 1 : Define two arrays
struct ABC {
int x;
int y;
int z;
};
struct ABC a[2] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
};
struct ABC b[2];
Step 2 : Do copy
for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
{
b[i] = a[i];
}
Step 3 : Print destination array
for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
{
printf("b[%d].x = %d ", i, b[i].x );
printf("b[%d].y = %d ", i, b[i].y );
printf("b[%d].z = %d ", i, b[i].z );
printf("\n");
}
See full program below
1#include <stdio.h>
2
3struct ABC {
4 int x;
5 int y;
6 int z;
7};
8
9int main(void)
10{
11 struct ABC a[2] = {
12 { .x = 1, .y = 2, .z = 3},
13 { .x = 10, .y = 20, .z = 30},
14 };
15
16 struct ABC b[2];
17
18 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
19 {
20 b[i] = a[i];
21 }
22
23 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
24 {
25 printf("b[%d].x = %d ", i, b[i].x );
26 printf("b[%d].y = %d ", i, b[i].y );
27 printf("b[%d].z = %d ", i, b[i].z );
28 printf("\n");
29 }
30
31 printf("\n");
32
33 return 0;
34}
Output is as below
b[0].x = 1 b[0].y = 2 b[0].z = 3
b[1].x = 10 b[1].y = 20 b[1].z = 30
Step 1 : Define two arrays
struct ABC {
int x;
int y;
int z;
};
struct ABC a[2] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
};
struct ABC b[2];
Step 2 : Do copy
for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
{
*(b + i) = *(a + i);
}
Step 3 : Print destination array
for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
{
printf("*(b + %d).x = %d ", i, (*(b + i)).x );
printf("*(b + %d).y = %d ", i, (*(b + i)).y );
printf("*(b + %d).z = %d ", i, (*(b + i)).z );
printf("\n");
}
See full program below
1#include <stdio.h>
2
3struct ABC {
4 int x;
5 int y;
6 int z;
7};
8
9int main(void)
10{
11 struct ABC a[2] = {
12 { .x = 1, .y = 2, .z = 3},
13 { .x = 10, .y = 20, .z = 30},
14 };
15
16 struct ABC b[2];
17
18 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
19 {
20 *(b + i) = *(a + i);
21 }
22
23 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
24 {
25 printf("*(b + %d).x = %d ", i, (*(b + i)).x );
26 printf("*(b + %d).y = %d ", i, (*(b + i)).y );
27 printf("*(b + %d).z = %d ", i, (*(b + i)).z );
28 printf("\n");
29 }
30
31 printf("\n");
32
33 return 0;
34}
Output is as below
*(b + 0).x = 1 *(b + 0).y = 2 *(b + 0).z = 3
*(b + 1).x = 10 *(b + 1).y = 20 *(b + 1).z = 30
Step 1 : Define two arrays
struct ABC {
int x;
int y;
int z;
};
struct ABC a[2] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
};
struct ABC b[2];
Step 2 : Define two pointers
struct ABC *p;
struct ABC *q;
p = a;
q = b;
Step 3 : Do copy
for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
{
q[i] = p[i];
}
See full program below
1#include <stdio.h>
2
3struct ABC {
4 int x;
5 int y;
6 int z;
7};
8
9int main(void)
10{
11 struct ABC a[2] = {
12 { .x = 1, .y = 2, .z = 3},
13 { .x = 10, .y = 20, .z = 30},
14 };
15
16 struct ABC b[2];
17
18 struct ABC *p;
19 struct ABC *q;
20
21 p = a;
22 q = b;
23
24 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
25 {
26 q[i] = p[i];
27 }
28
29 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
30 {
31 printf("b[%d].x = %d ", i, b[i].x );
32 printf("b[%d].y = %d ", i, b[i].y );
33 printf("b[%d].z = %d ", i, b[i].z );
34 printf("\n");
35 }
36
37 printf("\n");
38
39 return 0;
40}
Output is as below
b[0].x = 1 b[0].y = 2 b[0].z = 3
b[1].x = 10 b[1].y = 20 b[1].z = 30
Step 1 : Define two arrays
struct ABC {
int x;
int y;
int z;
};
struct ABC a[2] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
};
struct ABC b[2];
Step 2 : Define two pointers
struct ABC *p;
struct ABC *q;
p = a;
q = b;
Step 3 : Do copy
for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
{
*q++ = *p++;
}
See full program below
1#include <stdio.h>
2
3struct ABC {
4 int x;
5 int y;
6 int z;
7};
8
9int main(void)
10{
11 struct ABC a[2] = {
12 { .x = 1, .y = 2, .z = 3},
13 { .x = 10, .y = 20, .z = 30},
14 };
15
16 struct ABC b[2];
17
18 struct ABC *p;
19 struct ABC *q;
20
21 p = a;
22 q = b;
23
24 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
25 {
26 *q++ = *p++;
27 }
28
29 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
30 {
31 printf("b[%d].x = %d ", i, b[i].x );
32 printf("b[%d].y = %d ", i, b[i].y );
33 printf("b[%d].z = %d ", i, b[i].z );
34 printf("\n");
35 }
36
37 printf("\n");
38
39 return 0;
40}
Output is as below
b[0].x = 1 b[0].y = 2 b[0].z = 3
b[1].x = 10 b[1].y = 20 b[1].z = 30
Step 1 : Define two arrays
struct ABC {
int x;
int y;
int z;
};
struct ABC a[2] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
};
struct ABC b[2];
Step 2 : Do copy
memcpy(b, a, sizeof(b));
See full program below
1#include <stdio.h>
2#include <string.h>
3
4struct ABC {
5 int x;
6 int y;
7 int z;
8};
9
10int main(void)
11{
12 struct ABC a[2] = {
13 { .x = 1, .y = 2, .z = 3},
14 { .x = 10, .y = 20, .z = 30},
15 };
16
17 struct ABC b[2];
18
19 memcpy(b, a, sizeof(b));
20
21 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
22 {
23 printf("b[%d].x = %d ", i, b[i].x );
24 printf("b[%d].y = %d ", i, b[i].y );
25 printf("b[%d].z = %d ", i, b[i].z );
26 printf("\n");
27 }
28
29 printf("\n");
30
31 return 0;
32}
Output is as below
b[0].x = 1 b[0].y = 2 b[0].z = 3
b[1].x = 10 b[1].y = 20 b[1].z = 30
Step 1 : Define two arrays
struct ABC {
int x;
int y;
int z;
};
struct ABC a[2] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
};
struct ABC b[2];
Step 2 : Define Pointers
struct ABC *p;
struct ABC *q;
p = a;
q = b;
Step 3 : Do copy
memcpy(q, p, sizeof(b));
See full program below
1#include <stdio.h>
2#include <string.h>
3
4struct ABC {
5 int x;
6 int y;
7 int z;
8};
9
10int main(void)
11{
12 struct ABC a[2] = {
13 { .x = 1, .y = 2, .z = 3},
14 { .x = 10, .y = 20, .z = 30},
15 };
16
17 struct ABC b[2];
18
19 struct ABC *p;
20 struct ABC *q;
21
22 p = a;
23 q = b;
24
25 memcpy(q, p, sizeof(b));
26
27 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
28 {
29 printf("b[%d].x = %d ", i, b[i].x );
30 printf("b[%d].y = %d ", i, b[i].y );
31 printf("b[%d].z = %d ", i, b[i].z );
32 printf("\n");
33 }
34
35 printf("\n");
36
37 return 0;
38 }
Output is as below
b[0].x = 1 b[0].y = 2 b[0].z = 3
b[1].x = 10 b[1].y = 20 b[1].z = 30
Step 1 : Define two arrays
struct ABC {
int x;
int y;
int z;
};
struct ABC a[4] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
{ .x = 100, .y = 200, .z = 300},
{ .x = 1000, .y = 2000, .z = 3000},
};
struct ABC b[4];
Step 2 : Use first 2 structures in array “b”
b[0].x = 11; b[0].y = 22; b[0].z = 33;
b[1].x = 44; b[1].y = 55; b[1].z = 66;
Step 3 : Use remainig 2 structures in array “b” to copy contents from array “a”
memcpy(b + 2, a + 2, sizeof(b) - (2 * sizeof(struct ABC)) );
Step 4 : Print the contents of array “b”
for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
{
printf("b[%d].x = %d ", i, b[i].x );
printf("b[%d].y = %d ", i, b[i].y );
printf("b[%d].z = %d ", i, b[i].z );
printf("\n");
}
See full program below
1#include <stdio.h>
2#include <string.h>
3
4struct ABC {
5 int x;
6 int y;
7 int z;
8};
9
10int main(void)
11{
12 struct ABC a[4] = {
13 { .x = 1, .y = 2, .z = 3},
14 { .x = 10, .y = 20, .z = 30},
15 { .x = 100, .y = 200, .z = 300},
16 { .x = 1000, .y = 2000, .z = 3000},
17 };
18
19 struct ABC b[4];
20
21 // Clear garbage contents in array "b"
22 memset(b, 0, sizeof(b));
23
24 b[0].x = 11; b[0].y = 22; b[0].z = 33;
25 b[1].x = 44; b[1].y = 55; b[1].z = 66;
26
27 memcpy(b + 2, a + 2, sizeof(b) - (2 * sizeof(struct ABC)) );
28
29 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
30 {
31 printf("b[%d].x = %d ", i, b[i].x );
32 printf("b[%d].y = %d ", i, b[i].y );
33 printf("b[%d].z = %d ", i, b[i].z );
34 printf("\n");
35 }
36
37 printf("\n");
38
39 return 0;
40}
Output is as below
b[0].x = 11 b[0].y = 22 b[0].z = 33
b[1].x = 44 b[1].y = 55 b[1].z = 66
b[2].x = 100 b[2].y = 200 b[2].z = 300
b[3].x = 1000 b[3].y = 2000 b[3].z = 3000
Step 1 : Define two arrays
struct ABC {
int x;
int y;
int z;
};
struct ABC a[4] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
{ .x = 100, .y = 200, .z = 300},
{ .x = 1000, .y = 2000, .z = 3000},
};
struct ABC b[4];
Step 2 : Define two pointers
struct ABC *p;
struct ABC *q;
Step 3 : Extract part of data from array “a” into array “b”
p = a + 1;
q = a + 2;
for (int i = 0; p <= q; i++)
{
b[i] = *p;
p++;
}
Step 4 : Print the contents of array “b”
for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
{
printf("b[%d].x = %d ", i, b[i].x );
printf("b[%d].y = %d ", i, b[i].y );
printf("b[%d].z = %d ", i, b[i].z );
printf("\n");
}
See full program below
1#include <stdio.h>
2#include <string.h>
3
4struct ABC {
5 int x;
6 int y;
7 int z;
8};
9
10int main(void)
11{
12 struct ABC a[4] = {
13 { .x = 1, .y = 2, .z = 3},
14 { .x = 10, .y = 20, .z = 30},
15 { .x = 100, .y = 200, .z = 300},
16 { .x = 1000, .y = 2000, .z = 3000},
17 };
18
19 struct ABC b[4];
20
21 struct ABC *p;
22 struct ABC *q;
23
24 // Clear garbage contents in array "b"
25 memset(b, 0, sizeof(b));
26
27 // Extract part of data from array "a" into array "b"
28 p = a + 1;
29 q = a + 2;
30
31 for (int i = 0; p <= q; i++)
32 {
33 b[i] = *p;
34 p++;
35 }
36
37 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
38 {
39 printf("b[%d].x = %d ", i, b[i].x );
40 printf("b[%d].y = %d ", i, b[i].y );
41 printf("b[%d].z = %d ", i, b[i].z );
42 printf("\n");
43 }
44
45 printf("\n");
46
47 return 0;
48}
Output is as below
b[0].x = 10 b[0].y = 20 b[0].z = 30
b[1].x = 100 b[1].y = 200 b[1].z = 300
b[2].x = 0 b[2].y = 0 b[2].z = 0
b[3].x = 0 b[3].y = 0 b[3].z = 0
Step 1 : Define a Single Dimension array
struct ABC {
int x;
int y;
int z;
};
struct ABC a[4] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
{ .x = 100, .y = 200, .z = 300},
{ .x = 1000, .y = 2000, .z = 3000},
};
Step 2 : Define a Single pointer
struct ABC *p;
Step 3 : Change part of the array using a single pointer
p = a + 2;
// p[0] is equal to a[2]
p[0].x = 11;
p[0].y = 22;
p[0].z = 33;
// p[1] is equal to a[3]
p[1].x = 44;
p[1].y = 55;
p[1].z = 66;
Step 4 : Print the contents of array “a”
for (int i = 0; i < sizeof(a) / sizeof(a[0]); i++)
{
printf("a[%d].x = %d ", i, a[i].x );
printf("a[%d].y = %d ", i, a[i].y );
printf("a[%d].z = %d ", i, a[i].z );
printf("\n");
}
See full program below
1#include <stdio.h>
2
3struct ABC {
4 int x;
5 int y;
6 int z;
7};
8
9int main(void)
10{
11 struct ABC a[4] = {
12 { .x = 1, .y = 2, .z = 3},
13 { .x = 10, .y = 20, .z = 30},
14 { .x = 100, .y = 200, .z = 300},
15 { .x = 1000, .y = 2000, .z = 3000},
16 };
17
18 struct ABC *p;
19
20 // Change part of the array using a single pointer
21 p = a + 2;
22
23 // p[0] is equal to a[2]
24 p[0].x = 11;
25 p[0].y = 22;
26 p[0].z = 33;
27
28 // p[1] is equal to a[3]
29 p[1].x = 44;
30 p[1].y = 55;
31 p[1].z = 66;
32
33 for (int i = 0; i < sizeof(a) / sizeof(a[0]); i++)
34 {
35 printf("a[%d].x = %d ", i, a[i].x );
36 printf("a[%d].y = %d ", i, a[i].y );
37 printf("a[%d].z = %d ", i, a[i].z );
38 printf("\n");
39 }
40
41 printf("\n");
42
43 return 0;
44}
Output is as below
a[0].x = 1 a[0].y = 2 a[0].z = 3
a[1].x = 10 a[1].y = 20 a[1].z = 30
a[2].x = 11 a[2].y = 22 a[2].z = 33
a[3].x = 44 a[3].y = 55 a[3].z = 66
Step 1 : Define two arrays
struct ABC {
int x;
int y;
int z;
};
struct ABC a[4] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
{ .x = 100, .y = 200, .z = 300},
{ .x = 1000, .y = 2000, .z = 3000},
};
struct ABC b[4] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 11, .y = 22, .z = 33},
{ .x = 44, .y = 55, .z = 66},
{ .x = 77, .y = 88, .z = 99},
};
Step 2 : Change part of array “a” by copying contents from array “b”
memcpy(a + 1, b + 1, 3 * sizeof(struct ABC));
Step 3 : Print the contents of array “a”
for (int i = 0; i < sizeof(a) / sizeof(a[0]); i++)
{
printf("a[%d].x = %d ", i, a[i].x );
printf("a[%d].y = %d ", i, a[i].y );
printf("a[%d].z = %d ", i, a[i].z );
printf("\n");
}
See full program below
1#include <stdio.h>
2#include <string.h>
3
4struct ABC {
5 int x;
6 int y;
7 int z;
8};
9
10
11int main(void)
12{
13 struct ABC a[4] = {
14 { .x = 1, .y = 2, .z = 3},
15 { .x = 10, .y = 20, .z = 30},
16 { .x = 100, .y = 200, .z = 300},
17 { .x = 1000, .y = 2000, .z = 3000},
18 };
19
20 struct ABC b[4] = {
21 { .x = 1, .y = 2, .z = 3},
22 { .x = 11, .y = 22, .z = 33},
23 { .x = 44, .y = 55, .z = 66},
24 { .x = 77, .y = 88, .z = 99},
25 };
26
27 // Change part of array "a" by copying contents from array "b"
28 memcpy(a + 1, b + 1, 3 * sizeof(struct ABC));
29
30 // Print the contents of array "a"
31 for (int i = 0; i < sizeof(a) / sizeof(a[0]); i++)
32 {
33 printf("a[%d].x = %d ", i, a[i].x );
34 printf("a[%d].y = %d ", i, a[i].y );
35 printf("a[%d].z = %d ", i, a[i].z );
36 printf("\n");
37 }
38
39 printf("\n");
40
41 return 0;
42}
Output is as below
a[0].x = 1 a[0].y = 2 a[0].z = 3
a[1].x = 11 a[1].y = 22 a[1].z = 33
a[2].x = 44 a[2].y = 55 a[2].z = 66
a[3].x = 77 a[3].y = 88 a[3].z = 99
Step 1 : Define an array and a pointer
struct ABC {
int x;
int y;
int z;
};
struct ABC a[4] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
{ .x = 100, .y = 200, .z = 300},
{ .x = 1000, .y = 2000, .z = 3000},
};
struct ABC *q;
Step 2 : Allocate heap memory to pointer
q = malloc(4 * sizeof(struct ABC));
Step 3 : Clear garbage contents of allocated heap memory
memset(q, 0, 4 * sizeof(struct ABC));
Step 4 : Use standard “memcpy” on heap memory
memcpy(q, a, 4 * sizeof(struct ABC));
Step 5 : Free heap memory after use
free(q);
See full program below
1#include <stdio.h>
2#include <stdlib.h>
3#include <string.h>
4
5struct ABC {
6 int x;
7 int y;
8 int z;
9};
10
11int main(void)
12{
13 struct ABC a[4] = {
14 { .x = 1, .y = 2, .z = 3},
15 { .x = 10, .y = 20, .z = 30},
16 { .x = 100, .y = 200, .z = 300},
17 { .x = 1000, .y = 2000, .z = 3000},
18 };
19
20 struct ABC *q;
21
22 // Allocate 10 bytes memory in heap. Let "q" point to it
23 q = malloc(4 * sizeof(struct ABC));
24
25 // Clear garbage contents of allocated heap memory
26 memset(q, 0, 4 * sizeof(struct ABC));
27
28 // Use standard "memcpy" to copy contents into heap memory pointed by "q"
29 memcpy(q, a, 4 * sizeof(struct ABC));
30
31 // Use "%d" to print contents heap memory pointed by "q"
32 for (int i = 0; i < sizeof(a) / sizeof(a[0]); i++)
33 {
34 printf("q[%d].x = %d ", i, q[i].x );
35 printf("q[%d].y = %d ", i, q[i].y );
36 printf("q[%d].z = %d ", i, q[i].z );
37 printf("\n");
38 }
39
40 printf("\n");
41
42 free(q);
43}
Output is as below
q[0].x = 1 q[0].y = 2 q[0].z = 3
q[1].x = 10 q[1].y = 20 q[1].z = 30
q[2].x = 100 q[2].y = 200 q[2].z = 300
q[3].x = 1000 q[3].y = 2000 q[3].z = 3000
Step 1 : Define two arrays
struct ABC {
int x;
int y;
int z;
};
struct ABC a[4] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
{ .x = 100, .y = 200, .z = 300},
{ .x = 1000, .y = 2000, .z = 3000},
};
struct ABC b[4];
Step 2 : Define two pointers
struct ABC *p;
struct ABC *q;
p = a;
q = b;
Step 3 : Pass single pointer to a function : Call by Value
my_memcpy_1(q, p, sizeof(b));
Step 4 : Define my_memcpy_1 function
void my_memcpy_1(struct ABC *dest, struct ABC *src, int size)
{
memcpy(dest, src, size);
}
See full program below
1#include <stdio.h>
2#include <string.h>
3
4struct ABC {
5 int x;
6 int y;
7 int z;
8};
9
10void my_memcpy_1(struct ABC *dest, struct ABC *src, int size)
11{
12 memcpy(dest, src, size);
13}
14
15int main(void)
16{
17 struct ABC a[4] = {
18 { .x = 1, .y = 2, .z = 3},
19 { .x = 10, .y = 20, .z = 30},
20 { .x = 100, .y = 200, .z = 300},
21 { .x = 1000, .y = 2000, .z = 3000},
22 };
23
24 struct ABC b[4];
25
26 struct ABC *p;
27 struct ABC *q;
28
29 p = a;
30 q = b;
31
32 memset(b, 0, sizeof(b));
33
34 my_memcpy_1(q, p, sizeof(b));
35
36 // Use "%d" to print contents heap memory pointed by "q"
37 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
38 {
39 printf("b[%d].x = %d ", i, b[i].x );
40 printf("b[%d].y = %d ", i, b[i].y );
41 printf("b[%d].z = %d ", i, b[i].z );
42 printf("\n");
43 }
44
45 printf("\n");
46
47 return 0;
48}
Output is as below
b[0].x = 1 b[0].y = 2 b[0].z = 3
b[1].x = 10 b[1].y = 20 b[1].z = 30
b[2].x = 100 b[2].y = 200 b[2].z = 300
b[3].x = 1000 b[3].y = 2000 b[3].z = 3000
Step 1 : Define two arrays
struct ABC {
int x;
int y;
int z;
};
struct ABC a[4] = {
{ .x = 1, .y = 2, .z = 3},
{ .x = 10, .y = 20, .z = 30},
{ .x = 100, .y = 200, .z = 300},
{ .x = 1000, .y = 2000, .z = 3000},
};
struct ABC b[4];
Step 2 : Define two pointers
struct ABC *p;
struct ABC *q;
p = a;
q = b;
Step 3 : Pass single pointer to a function : Call by Value
my_memcpy_2(q, p, sizeof(b));
Step 4 : Define my_memcpy_1 function
void my_memcpy_2(struct ABC **dest, struct ABC **src, int size)
{
memcpy(*dest, *src, size);
}
See full program below
1#include <stdio.h>
2#include <string.h>
3
4struct ABC {
5 int x;
6 int y;
7 int z;
8};
9
10void my_memcpy_2(struct ABC **dest, struct ABC **src, int size)
11{
12 memcpy(*dest, *src, size);
13}
14
15int main(void)
16{
17 struct ABC a[4] = {
18 { .x = 1, .y = 2, .z = 3},
19 { .x = 10, .y = 20, .z = 30},
20 { .x = 100, .y = 200, .z = 300},
21 { .x = 1000, .y = 2000, .z = 3000},
22 };
23
24 struct ABC b[4];
25
26 struct ABC *p;
27 struct ABC *q;
28
29 p = a;
30 q = b;
31
32 memset(b, 0, sizeof(b));
33
34 my_memcpy_2(&q, &p, sizeof(b));
35
36 // Use "%d" to print contents heap memory pointed by "q"
37 for (int i = 0; i < sizeof(b) / sizeof(b[0]); i++)
38 {
39 printf("b[%d].x = %d ", i, b[i].x );
40 printf("b[%d].y = %d ", i, b[i].y );
41 printf("b[%d].z = %d ", i, b[i].z );
42 printf("\n");
43 }
44
45 printf("\n");
46
47 return 0;
48}
Output is as below
b[0].x = 1 b[0].y = 2 b[0].z = 3
b[1].x = 10 b[1].y = 20 b[1].z = 30
b[2].x = 100 b[2].y = 200 b[2].z = 300
b[3].x = 1000 b[3].y = 2000 b[3].z = 3000
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