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4349 | Serge | 1 | /* |
2 | FUNCTION |
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3 | < |
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4 | |||
5 | INDEX |
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6 | strncat |
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7 | |||
8 | ANSI_SYNOPSIS |
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9 | #include |
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10 | char *strncat(char *<[dst]>, const char *<[src]>, size_t <[length]>); |
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11 | |||
12 | TRAD_SYNOPSIS |
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13 | #include |
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14 | char *strncat(<[dst]>, <[src]>, <[length]>) |
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15 | char *<[dst]>; |
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16 | char *<[src]>; |
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17 | size_t <[length]>; |
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18 | |||
19 | DESCRIPTION |
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20 | < |
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21 | the string pointed to by <[src]> (including the terminating |
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22 | null character) to the end of the string pointed to by |
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23 | <[dst]>. The initial character of <[src]> overwrites the null |
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24 | character at the end of <[dst]>. A terminating null character |
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25 | is always appended to the result |
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26 | |||
27 | WARNINGS |
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28 | Note that a null is always appended, so that if the copy is |
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29 | limited by the <[length]> argument, the number of characters |
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30 | appended to <[dst]> is < |
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31 | |||
32 | RETURNS |
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33 | This function returns the initial value of <[dst]> |
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34 | |||
35 | PORTABILITY |
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36 | < |
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37 | |||
38 | < |
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39 | |||
40 | QUICKREF |
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41 | strncat ansi pure |
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42 | */ |
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43 | |||
44 | #include |
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45 | #include |
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46 | |||
47 | /* Nonzero if X is aligned on a "long" boundary. */ |
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48 | #define ALIGNED(X) \ |
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49 | (((long)X & (sizeof (long) - 1)) == 0) |
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50 | |||
51 | #if LONG_MAX == 2147483647L |
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52 | #define DETECTNULL(X) (((X) - 0x01010101) & ~(X) & 0x80808080) |
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53 | #else |
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54 | #if LONG_MAX == 9223372036854775807L |
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55 | /* Nonzero if X (a long int) contains a NULL byte. */ |
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56 | #define DETECTNULL(X) (((X) - 0x0101010101010101) & ~(X) & 0x8080808080808080) |
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57 | #else |
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58 | #error long int is not a 32bit or 64bit type. |
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59 | #endif |
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60 | #endif |
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61 | |||
62 | #ifndef DETECTNULL |
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63 | #error long int is not a 32bit or 64bit byte |
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64 | #endif |
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65 | |||
66 | char * |
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67 | _DEFUN (strncat, (s1, s2, n), |
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68 | char *s1 _AND |
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69 | _CONST char *s2 _AND |
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70 | size_t n) |
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71 | { |
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72 | #if defined(PREFER_SIZE_OVER_SPEED) || defined(__OPTIMIZE_SIZE__) |
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73 | char *s = s1; |
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74 | |||
75 | while (*s1) |
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76 | s1++; |
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77 | while (n-- != 0 && (*s1++ = *s2++)) |
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78 | { |
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79 | if (n == 0) |
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80 | *s1 = '\0'; |
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81 | } |
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82 | |||
83 | return s; |
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84 | #else |
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85 | char *s = s1; |
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86 | |||
87 | /* Skip over the data in s1 as quickly as possible. */ |
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88 | if (ALIGNED (s1)) |
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89 | { |
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90 | unsigned long *aligned_s1 = (unsigned long *)s1; |
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91 | while (!DETECTNULL (*aligned_s1)) |
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92 | aligned_s1++; |
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93 | |||
94 | s1 = (char *)aligned_s1; |
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95 | } |
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96 | |||
97 | while (*s1) |
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98 | s1++; |
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99 | |||
100 | /* s1 now points to the its trailing null character, now copy |
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101 | up to N bytes from S2 into S1 stopping if a NULL is encountered |
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102 | in S2. |
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103 | |||
104 | It is not safe to use strncpy here since it copies EXACTLY N |
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105 | characters, NULL padding if necessary. */ |
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106 | while (n-- != 0 && (*s1++ = *s2++)) |
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107 | { |
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108 | if (n == 0) |
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109 | *s1 = '\0'; |
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110 | } |
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111 | |||
112 | return s; |
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113 | #endif /* not PREFER_SIZE_OVER_SPEED */ |
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114 | } |