[Asterisk-Dev] fun with valgrind

[Gilad Ben-Yossef]

Matthew Boehm wrote:

> /* substitute strings \t and \n into the apropriate characters */
> tmpread = tmpwrite = emailbody;
> while ((tmpwrite = strchr(tmpread,'\\'))) {
>     int len = strlen("\n");
>     switch (tmpwrite[1]) {
>         case 'n':
>             strncpy(tmpwrite+len,tmpwrite+2,strlen(tmpwrite+2)+1); <=== line
> 5545
>             strncpy(tmpwrite,"\n",len);
>             break;
>         case 't':
>             strncpy(tmpwrite+len,tmpwrite+2,strlen(tmpwrite+2)+1); <=== line
> 5549
>             strncpy(tmpwrite,"\t",len);
>             break;
>         default:
>             ast_log(LOG_NOTICE, "Substitution routine does not support this
> character: %c\n",tmpwrite[1]);
>     }
>     tmpread = tmpwrite+len;
> }
> 
> Could somebody explain what is going on there? It seems as if the code is
> replacing "\n" with "\n" and "\t" with "\t".
> 

That is exactly what it is doing - except that it replaces the literal 
characters '\' and 't', for example, with the ASCII code for tab, which 
in C is written '\t'.

In other words, the code in Asterisk that replcaes the characters "\t" 
with the ASCII value for a tab works thanks to the fact that  the C 
compiler does exactly the same thing in a kind of recursive way that 
reminds me of Scheme programs... :-)

Gilad

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