Четверг 02 Сентябрь 2004 22:41, Kim Woelders написал:
> > 1. The allocation on the stack around 16 kilobytes is not a god idea,
> > because stack was invented for function calls and recursion , but not for
> > storing data. And this could theoretically lead to a problem in general
> > case, if system cannot allocate such a big chunk on the stack.
>
> We may be using a bit more stack space than necessary, but I doubt this
> causes any problems in E in real life. This construction is used
> throughout E's parsing code and recursion is never very deep.
> It is also vastly faster and less error prone than allocating memory
> dynamically.
> I don't agree with the "storing data" issue. The stack is the perfect
> place to store (moderate amounts of) data temporarily.
>
Point taken. But i hope if i continue to write malloced code, it will be not
count as an act of disobeying :-)
> > hopefully nothing, but still this two functions word and fword are not
> > safe, scanf("%<num>n") is better, but it is not an easy tool for string
> > parsing. If somebody protected eesh from buffer smashing, then it is
> > fine, but still i'm suspicious in using word and fword anyway (and of
> > course i believe there is no suid binaries in disributions :-)).
>
> If word() or fword() are broken they should be fixed. The solution is
> not to introduce yet another string parsing function.
>
Agreed, but getword already there.
I will look at this functions, hopefully do something.
>
> Finally, in case you haven't been discouraged entirely, one more thing.
> Please do not use C++ style "//" comments. I believe there are still
> compilers out there which don't like that.
>
> /Kim
>
So then i regenerate my patch, here it is:
--- ./etalon/e16/e/src/E.h 2004-08-31 21:24:39.000000000 +0400
+++ ./hacked/e16/e/src/E.h 2004-09-07 11:26:12.433520592 +0400
@@ -2083,7 +2110,7 @@
char *usershell(int uid);
const char *atword(const char *s, int num);
const char *atchar(const char *s, char c);
-char *getword(char *s, int num);
+char *getword(char *s,int num) ;
void word(const char *s, int num, char *wd);
int canread(const char *s);
int canwrite(const char *s);
--- ./etalon/e16/e/src/file.c 2004-07-13 03:33:15.000000000 +0400
+++ file.c 2004-09-07 11:38:43.320368440 +0400
@@ -510,74 +510,155 @@
EDBUG_RETURN(NULL);
}
-char *
-getword(char *s, int num)
-{
+/**
+ * Search for a [num]-th word in a string s and return it in
+ * allocated buffer.
+ *
+ * Parameters :
+ * s - pointer to a null terminating string.
+ * Punctuation signs treats as whitespaces.
+ * num - number of a token to search.
+ *
+ * Return value :
+ * NULL - if (num < 1) or (num > number of tokens in s)
+ * or if s contained unquoted symbols other than
+ * spaces, digits and symbols.
+ * Otherwise, pointer to null terminated string returned.
+ * WARNING : Caller must free the buffer.
+ *
+ * Example : " {..\" Alice \" wants more \"cookies4 grandma \""
+ * Token 1 = Alice
+ * Token 2 = wants
+ * Token 3 = more
+ * Token 4 = cookies4 grandma
+ */
+char *
+getword(const char *s, int num)
+{
+ int cnt = 1 ;
+
+ ptrdiff_t char_count = 0 ;
+
+ char *start = NULL ;
+ char *word = NULL ;
+ char *tmp_copy = NULL ;
- /* *********FIXME**************
- * This function is broken but it isn't in use so I'll fix it later
- * (DO NOT USE UNTIL FIXED
- */
- int cnt, i;
- char *start, *finish, *ss, *w;
- char *wd = NULL;
+ const char quota_sym = '"' ;
+
+ EDBUG(9,"getword") ;
- EDBUG(9, "getword");
if (!s)
- EDBUG_RETURN(NULL);
- if (!wd)
- EDBUG_RETURN(NULL);
+ {
+ goto fail ;
+ }
+
+ /*counting from 1, negative index is mistake */
if (num <= 0)
- {
- *wd = 0;
- EDBUG_RETURN(NULL);
- }
- cnt = 0;
- i = 0;
- start = NULL;
- finish = NULL;
- ss = NULL;
- w = wd;
-
- while (s[i])
- {
- if ((cnt == num) && ((s[i] == ' ') || (s[i] == '\t')))
- {
- finish = &s[i];
- break;
- }
- if ((s[i] != ' ') && (s[i] != '\t'))
- {
- if (i == 0)
- {
- cnt++;
- if (cnt == num)
- start = &s[i];
- }
- else if ((s[i - 1] == ' ') || (s[i - 1] == '\t'))
- {
- cnt++;
- if (cnt == num)
- start = &s[i];
- }
- }
- i++;
- }
- if (cnt == num)
- {
- if ((start) && (finish))
- {
- for (ss = start; ss < finish; ss++)
- *wd++ = *ss;
- }
- else if (start)
- {
- for (ss = start; *ss != 0; ss++)
- *wd++ = *ss;
- }
- *wd = 0;
- }
- EDBUG_RETURN(wd);
+ {
+ goto fail ;
+ }
+
+ /*skip all whitespaces at first */
+ /*except double quotas since they are meaningful*/
+ /*also let us ignore other garbage */
+ while(!isalnum(*s) && quota_sym != *s)
+ {
+ s++ ;
+ }
+
+ /*main cycle till the end */
+ while ('\0'!=*s)
+ {
+ /*we are standing at the start of quotes */
+ if (quota_sym == *s)
+ {
+ /*step over quota */
+ s++ ;
+ /*save start in case of word */
+ if(cnt == num)
+ {
+ start = s ;
+ }
+ /*it is possible to write inside quotes any trash*/
+ /*even bells and whistles :-) */
+ while (quota_sym != *s)
+ {
+ /*only one quote sign */
+ if ('\0' == *s)
+ {
+ goto fail ;
+ }
+ s++ ;
+ }
+
+ if (cnt == num)
+ {
+ char_count = s - start ;
+ /*so far we have start offset and char count*/
+ break ;
+ }
+ /*quotation ended */
+ cnt++ ;
+ } else if (isalnum(*s))
+ {
+ if(cnt == num)
+ {
+ start = s ;
+ }
+ /*go through word */
+ while (isalnum(*s))
+ {
+ s++ ;
+ }
+ /*we found word */
+ /*note: it can be followed by any crap*/
+ if (cnt == num)
+ {
+ char_count = s - start ;
+ break ;
+ }
+
+ /*word must be followed by space */
+ if (!isspace(*s) && !ispunct(*s))
+ {
+ goto fail ;
+ }
+ /*word ended */
+ cnt++ ;
+ /*return at the end of the word */
+ s-- ;
+ } else if (isspace(*s) || ispunct(*s))
+ {
+ /*just ignoring spaces */
+ } else
+ {
+ goto fail ;
+ }
+ s++ ;
+ }
+
+ if (start==NULL)
+ {
+ /*avoid allocation */
+ goto fail ;
+ }
+ /*at this point we found the WORD */
+ tmp_copy = word = (unsigned char *)Emalloc((sizeof(char)*char_count) + 1);
+ if(NULL==tmp_copy)
+ {
+ goto fail ;
+ }
+ while (0<= --char_count)
+ {
+ *tmp_copy++ = *start++ ;
+ }
+ *(tmp_copy++) = '\0' ;
+ goto success ;
+
+success :
+ EDBUG_RETURN(word) ;
+fail :
+ EDBUG_RETURN(NULL) ;
}
void
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