Estou tentando implementar as funções de desinflar e inflar zlib.h para compactar e descompactar uma matriz de caracteres (não um arquivo

Gostaria de saber se a seguinte sintaxe está correta? Estou faltando alguma coisa ou defini algo incorretamente?

char a[50] = "Hello World!";
char b[50];
char c[50];

// deflate
// zlib struct
z_stream defstream;
defstream.zalloc = Z_NULL;
defstream.zfree = Z_NULL;
defstream.opaque = Z_NULL;
defstream.avail_in = (uInt)sizeof(a); // size of input
defstream.next_in = (Bytef *)a; // input char array
defstream.avail_out = (uInt)sizeof(b); // size of output
defstream.next_out = (Bytef *)b; // output char array

deflateInit(&defstream, Z_DEFAULT_COMPRESSION);
deflate(&defstream, Z_FINISH);
deflateEnd(&defstream);

printf("Deflate:\n%lu\n%s\n", strlen(b), b);

// inflate
// zlib struct
z_stream infstream;
infstream.zalloc = Z_NULL;
infstream.zfree = Z_NULL;
infstream.opaque = Z_NULL;
infstream.avail_in = (uInt)sizeof(b); // size of input
infstream.next_in = (Bytef *)b; // input char array
infstream.avail_out = (uInt)sizeof(c); // size of output
infstream.next_out = (Bytef *)c; // output char array

inflateInit(&infstream);
inflate(&infstream, Z_NO_FLUSH);
inflateEnd(&infstream);

printf("Inflate:\n%lu\n%s\n", strlen(c), c);