1 | /* |
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2 | * Concatenate strings with dynamic memory allocation. |
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3 | * |
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4 | * Usage: |
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5 | * |
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6 | * string = concat(string1, string2, ..., (char *) 0); |
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7 | * path = concatpath(base, name); |
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8 | * |
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9 | * Dynamically allocates (using xmalloc) sufficient memory to hold all of the |
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10 | * strings given and then concatenates them together into that allocated |
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11 | * memory, returning a pointer to it. Caller is responsible for freeing. |
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12 | * Assumes xmalloc is available. The last argument must be a null pointer (to |
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13 | * a char *, if you actually find a platform where it matters). |
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14 | * |
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15 | * concatpath is similar, except that it only takes two arguments. If the |
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16 | * second argument begins with / or ./, a copy of it is returned; otherwise, |
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17 | * the first argument, a slash, and the second argument are concatenated |
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18 | * together and returned. This is useful for building file names where names |
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19 | * that aren't fully qualified are qualified with some particular directory. |
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20 | * |
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21 | * Written by Russ Allbery <rra@stanford.edu> |
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22 | * This work is hereby placed in the public domain by its author. |
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23 | */ |
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24 | |
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25 | #include <config.h> |
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26 | #include <portable/system.h> |
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27 | |
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28 | #include <util/util.h> |
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29 | |
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30 | /* Abbreviation for cleaner code. */ |
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31 | #define VA_NEXT(var, type) ((var) = (type) va_arg(args, type)) |
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32 | |
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33 | |
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34 | /* |
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35 | * Concatenate all of the arguments into a newly allocated string. ANSI C |
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36 | * requires at least one named parameter, but it's not treated any different |
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37 | * than the rest. |
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38 | */ |
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39 | char * |
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40 | concat(const char *first, ...) |
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41 | { |
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42 | va_list args; |
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43 | char *result, *p; |
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44 | const char *string; |
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45 | size_t length = 0; |
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46 | |
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47 | /* Find the total memory required. */ |
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48 | va_start(args, first); |
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49 | for (string = first; string != NULL; VA_NEXT(string, const char *)) |
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50 | length += strlen(string); |
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51 | va_end(args); |
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52 | length++; |
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53 | |
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54 | /* |
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55 | * Create the string. Doing the copy ourselves avoids useless string |
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56 | * traversals of result, if using strcat, or string, if using strlen to |
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57 | * increment a pointer into result, at the cost of losing the native |
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58 | * optimization of strcat if any. |
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59 | */ |
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60 | result = xmalloc(length); |
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61 | p = result; |
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62 | va_start(args, first); |
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63 | for (string = first; string != NULL; VA_NEXT(string, const char *)) |
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64 | while (*string != '\0') |
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65 | *p++ = *string++; |
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66 | va_end(args); |
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67 | *p = '\0'; |
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68 | |
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69 | return result; |
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70 | } |
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71 | |
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72 | |
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73 | /* |
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74 | * Concatenate name with base, unless name begins with / or ./. Return the |
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75 | * new string in newly allocated memory. |
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76 | */ |
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77 | char * |
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78 | concatpath(const char *base, const char *name) |
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79 | { |
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80 | if (name[0] == '/' || (name[0] == '.' && name[1] == '/')) |
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81 | return xstrdup(name); |
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82 | else |
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83 | return concat(base != NULL ? base : ".", "/", name, (char *) 0); |
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84 | } |
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