newstr.c

   1 /*
   2  * Copyright 1993, 1995 Christopher Seiwald.
   3  *
   4  * This file is part of Jam - see jam.c for Copyright information.
   5  */
   6
   7 /*
   8  * newstr.c - string manipulation routines
   9  *
  10  * To minimize string copying, string creation, copying, and freeing
  11  * is done through newstr.
  12  *
  13  * External functions:
  14  *
  15  *    newstr() - return a malloc'ed copy of a string
  16  *    copystr() - return a copy of a string previously returned by newstr()
  17  *    freestr() - free a string returned by newstr() or copystr()
  18  *    donestr() - free string tables
  19  *
  20  * Once a string is passed to newstr(), the returned string is readonly.
  21  *
  22  * This implementation builds a hash table of all strings, so that multiple
  23  * calls of newstr() on the same string allocate memory for the string once.
  24  * Strings are never actually freed.
  25  *
  26  * 11/04/02 (seiwald) - const-ing for string literals
  27  */
  28
  29 # include "jam.h"
  30 # include "newstr.h"
  31 # include "hash.h"
  32
  33 typedef const char *STRING;
  34
  35 static struct hash *strhash = 0;
  36 static int strtotal = 0;
  37
  38
  39 /*
  40  * newstr() - return a malloc'ed copy of a string
  41  */
  42 const char *newstr (const char *string) {
  43   STRING str, *s = &str;
  44
  45   if (!strhash) strhash = hashinit(sizeof(STRING), "strings");
  46   *s = string;
  47   if (hashenter(strhash, (HASHDATA **)&s)) {
  48     int l = strlen(string);
  49     char *m = (char *)malloc(l+1);
  50
  51     if (DEBUG_MEM) printf("newstr: allocating %d bytes\n", l+1);
  52     strtotal += l+1;
  53     memcpy(m, string, l+1);
  54     *s = m;
  55   }
  56   return *s;
  57 }
  58
  59
  60 /*
  61  * copystr() - return a copy of a string previously returned by newstr()
  62  */
  63 const char *copystr (const char *s) {
  64   return s;
  65 }
  66
  67
  68 /*
  69  * freestr() - free a string returned by newstr() or copystr()
  70  */
  71 void freestr (const char *s) {
  72 }
  73
  74
  75 /*
  76  * donestr() - free string tables
  77  */
  78 void donestr (void) {
  79   hashdone(strhash);
  80   if (DEBUG_MEM) printf("%dK in strings\n", strtotal/1024);
  81 }