3 Ways to stitch the "C Language Learning Notes" string.

Last night and @buptpatriot discussed the question of the function return pointer (malloc generated), referring to string concatenation, to make a summary.

[CPP]View Plaincopyprint?

2. #include <stdio.h>
4. #include <stdlib.h>
6. #include <string.h>
10. Char *join1 (char *, char*);
12. void Join2 (char *, char *);
14. Char *join3 (char *, char*);
18. int main (void) {
20. char a[4] = "abc"; //char *a = "abc"
22. char b[4] = "Def"; //Char *b = "def"
26. char *c = Join3 (A, b);
28. printf ("concatenated String is%s\n", c);
32. Free (c);
34. c = NULL;
38. return 0;
40. }
44. /* Method One, do not change the string A, B, by malloc, generate a third string C, return the local pointer variable */
46. Char *join1 (char *a, char *b) {
48. char *c = (char *) malloc (strlen (a) + strlen (b) + 1); //local variables, requesting memory with malloc
50. if (c = = NULL) exit (1);
52. char *TEMPC = c; //Save the first address
54. While (*a! = ')} {
56. *c++ = *a++;
58. }
60. While ((*c++ = *b++)! = ' + ' ) {
62. ;
64. }
66. //Note that at this point the pointer C has pointed to the end of the string after stitching!
68. return TEMPC; The //return value is a pointer variable for the local malloc request, which is required after the function call ends
70. }
76. /* Method Two, get rid of the string directly a,*/
78. void Join2 (char *a, char *b) {
80. //Note that if a A, B in the main function defines a string constant (as follows):
82. //char *a = "abc";
84. //char *b = "Def";
86. //Then the join2 is not feasible.
88. //must be defined like this:
90. //char a[4] = "ABC";
92. //char B[4] = "Def";
94. While (*a! = ')} {
96. a++;
98. }
100. While ((*a++ = *b++)! = ' + ' ) {
102. ;
104. }
106. }
110. /* Method Three, call C library function, */
112. char* join3 (char *s1, char *s2)
114. {
116. char *result = malloc (strlen (S1) +strlen (S2) +1); //+1 for the Zero-terminator
118. //in Real code would check for errors on malloc here
120. if (result = = NULL) exit (1);
124. strcpy (result, S1);
126. strcat (result, S2);
130. return result;
132. }

3 Ways to stitch the "C Language Learning Notes" string.