v0.40: Create exercises. Challenge the community.

memmove

Your mission

Implement gm_memmove, your own memmove, which copies n bytes from src to dst and returns dst, producing the correct result even when the two regions overlap.

See it in action

gm_memmove(buf, "git rebase", 11)

Expected result

git rebase.

Your checklist

For your own tracking. Tests grade your code.

Copy exactly n raw bytes from src to dst. Treat the data as bytes, not as a string: there is no terminator, and an embedded \0 must be copied like any other byte.
The regions may overlap. If you copy front-to-back while dst sits ahead of src, you overwrite source bytes before reading them and corrupt the result. This is the whole difference from memcpy.
When dst is greater than src, copy back-to-front (from the last byte to the first). Otherwise copy front-to-back.
If n is 0, copy nothing and leave both buffers untouched.
Always return dst.

More examples

gm_memmove(buf + 2, buf, 5)  // buf = "0123456789"

Expected result

0101234789

Constraints

Expected files

memmove.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

libc

Standard C library

Implements the contract of a function from the standard C library.

memmove

Bytes and raw memory

Your mission

Implement gm_memmove, your own memmove, which copies n bytes from src to dst and returns dst, producing the correct result even when the two regions overlap.

See it in action

gm_memmove(buf, "git rebase", 11)

Expected result

git rebase.

Your checklist

For your own tracking. Tests grade your code.

Copy exactly n raw bytes from src to dst. Treat the data as bytes, not as a string: there is no terminator, and an embedded \0 must be copied like any other byte.
The regions may overlap. If you copy front-to-back while dst sits ahead of src, you overwrite source bytes before reading them and corrupt the result. This is the whole difference from memcpy.
When dst is greater than src, copy back-to-front (from the last byte to the first). Otherwise copy front-to-back.
If n is 0, copy nothing and leave both buffers untouched.
Always return dst.

More examples

gm_memmove(buf + 2, buf, 5)  // buf = "0123456789"

Expected result

0101234789

Constraints

Expected files

memmove.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

libc

Standard C library

Implements the contract of a function from the standard C library.

Tests

Run the tests to grade your code

Build your code, then check each test here. Open a result to inspect its output.

Build

01Non-overlapping copyWaiting

02Forward overlap (dst ahead of src)Waiting

03Backward overlap (dst behind src)Waiting

04Zero bytes copiedWaiting

05Embedded NUL copied verbatimWaiting

06Single byteWaiting

07dst equals srcWaiting

08Returns dstWaiting

memmove

Your mission

Implement gm_memmove, your own memmove, which copies n bytes from src to dst and returns dst, producing the correct result even when the two regions overlap.

See it in action

gm_memmove(buf, "git rebase", 11)

Expected result

git rebase.

Your checklist

For your own tracking. Tests grade your code.

Copy exactly n raw bytes from src to dst. Treat the data as bytes, not as a string: there is no terminator, and an embedded \0 must be copied like any other byte.
The regions may overlap. If you copy front-to-back while dst sits ahead of src, you overwrite source bytes before reading them and corrupt the result. This is the whole difference from memcpy.
When dst is greater than src, copy back-to-front (from the last byte to the first). Otherwise copy front-to-back.
If n is 0, copy nothing and leave both buffers untouched.
Always return dst.

More examples

gm_memmove(buf + 2, buf, 5)  // buf = "0123456789"

Expected result

0101234789

Constraints

Expected files

memmove.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

libc

Standard C library

Implements the contract of a function from the standard C library.

v0.40: Create exercises. Challenge the community.

Meet Studio →

memmove

Bytes and raw memory

Your mission

Implement gm_memmove, your own memmove, which copies n bytes from src to dst and returns dst, producing the correct result even when the two regions overlap.

See it in action

gm_memmove(buf, "git rebase", 11)

Expected result

git rebase.

Your checklist

For your own tracking. Tests grade your code.

Copy exactly n raw bytes from src to dst. Treat the data as bytes, not as a string: there is no terminator, and an embedded \0 must be copied like any other byte.
The regions may overlap. If you copy front-to-back while dst sits ahead of src, you overwrite source bytes before reading them and corrupt the result. This is the whole difference from memcpy.
When dst is greater than src, copy back-to-front (from the last byte to the first). Otherwise copy front-to-back.
If n is 0, copy nothing and leave both buffers untouched.
Always return dst.

More examples

gm_memmove(buf + 2, buf, 5)  // buf = "0123456789"

Expected result

0101234789

Constraints

Expected files

memmove.c

Allowed functions

None. Write every helper yourself.

Allowed headers

<stddef.h>defines size_t

libc

Standard C library

Implements the contract of a function from the standard C library.

Tests

Run the tests to grade your code

Build your code, then check each test here. Open a result to inspect its output.

Build

01Non-overlapping copyWaiting

02Forward overlap (dst ahead of src)Waiting

03Backward overlap (dst behind src)Waiting

04Zero bytes copiedWaiting

05Embedded NUL copied verbatimWaiting

06Single byteWaiting

07dst equals srcWaiting

08Returns dstWaiting