1 | /* |
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2 | FUNCTION |
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3 | <<strcat>>---concatenate strings |
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4 | |
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5 | INDEX |
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6 | strcat |
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7 | |
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8 | SYNOPSIS |
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9 | #include <string.h> |
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10 | char *strcat(char *restrict <[dst]>, const char *restrict <[src]>); |
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11 | |
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12 | DESCRIPTION |
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13 | <<strcat>> appends a copy of the string pointed to by <[src]> |
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14 | (including the terminating null character) to the end of the |
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15 | string pointed to by <[dst]>. The initial character of |
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16 | <[src]> overwrites the null character at the end of <[dst]>. |
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17 | |
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18 | RETURNS |
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19 | This function returns the initial value of <[dst]> |
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20 | |
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21 | PORTABILITY |
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22 | <<strcat>> is ANSI C. |
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23 | |
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24 | <<strcat>> requires no supporting OS subroutines. |
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25 | |
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26 | QUICKREF |
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27 | strcat ansi pure |
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28 | */ |
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29 | |
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30 | #include <string.h> |
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31 | #include <limits.h> |
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32 | |
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33 | /* Nonzero if X is aligned on a "long" boundary. */ |
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34 | #define ALIGNED(X) \ |
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35 | (((long)X & (sizeof (long) - 1)) == 0) |
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36 | |
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37 | #if LONG_MAX == 2147483647L |
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38 | #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080) |
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39 | #else |
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40 | #if LONG_MAX == 9223372036854775807L |
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41 | /* Nonzero if X (a long int) contains a NULL byte. */ |
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42 | #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080) |
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43 | #else |
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44 | #error long int is not a 32bit or 64bit type. |
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45 | #endif |
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46 | #endif |
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47 | |
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48 | #ifndef DETECTNULL |
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49 | #error long int is not a 32bit or 64bit byte |
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50 | #endif |
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51 | |
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52 | |
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53 | /*SUPPRESS 560*/ |
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54 | /*SUPPRESS 530*/ |
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55 | |
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56 | char * |
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57 | strcat (char *__restrict s1, |
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58 | const char *__restrict s2) |
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59 | { |
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60 | #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) |
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61 | char *s = s1; |
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62 | |
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63 | while (*s1) |
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64 | s1++; |
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65 | |
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66 | while (*s1++ = *s2++) |
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67 | ; |
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68 | return s; |
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69 | #else |
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70 | char *s = s1; |
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71 | |
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72 | |
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73 | /* Skip over the data in s1 as quickly as possible. */ |
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74 | if (ALIGNED (s1)) |
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75 | { |
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76 | unsigned long *aligned_s1 = (unsigned long *)s1; |
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77 | while (!DETECTNULL (*aligned_s1)) |
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78 | aligned_s1++; |
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79 | |
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80 | s1 = (char *)aligned_s1; |
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81 | } |
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82 | |
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83 | while (*s1) |
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84 | s1++; |
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85 | |
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86 | /* s1 now points to the its trailing null character, we can |
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87 | just use strcpy to do the work for us now. |
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88 | |
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89 | ?!? We might want to just include strcpy here. |
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90 | Also, this will cause many more unaligned string copies because |
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91 | s1 is much less likely to be aligned. I don't know if its worth |
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92 | tweaking strcpy to handle this better. */ |
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93 | strcpy (s1, s2); |
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94 | |
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95 | return s; |
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96 | #endif /* not PREFER_SIZE_OVER_SPEED */ |
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97 | } |
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