Re: Standard function to convert "\t" to '\t' (etc.)?

Gordon Burditt wrote:

In BSD there are non-standard functions strunvis(), strunvisx(),
strvis(), and strvisx() which translate strings from and to a visual
representation of the string. There are several visual representations,
one of them being C-style, and another being octal escapes. strunvis()
decodes all these escapes back into a string. The strvis*() forms
have many options as to what to encode.

It isn't that I didn't already have my own code for this (see below my signature, includes not shown, it needs limits.h). I just wanted to know if there might not be a function always present in the C library that would do this.

Thanks,

David Mathog

/* Convert text form for special characters in a string to the
corresponding (unsigned) character. Handles:
Some C escape sequences: \\, \a,\b,\f,\t,\r, and \n.
ASCII control characters like ^J (masks the 2nd character
retaining only the lowest 6 bits)
For a lone "^" use "/^".
Numerically specified character values as \###,\o###,\x## (3,3,
and 2 digits, as shown, ONLY)
Range is 0-255.
Returns 1 on success, 0 on error
*/
int convert_escape(char *string){
unsigned char *parsed;
unsigned char *scan;
#define NORMAL 0
#define ESCAPE 1
#define CONTROL 2
#define DNUMERIC 3
#define ONUMERIC 4
#define XNUMERIC 5
int state = NORMAL;
int sum = 0;
int count = 0;
int status = 1;
int ok = 1;
for(scan = parsed = (unsigned char *) string; ok; scan++){
switch(state){
case NORMAL:
switch(*scan){
case '\\':
state=ESCAPE;
break;
case '^':
state=CONTROL;
break;
case '\0':
*parsed = *scan; ok = 0;
break;
default:
*parsed=*scan; parsed++;
}
break;
case ESCAPE:
switch(*scan){
case '\\':
state=NORMAL; *parsed=*scan; parsed++;
break;
case 'a':
state=NORMAL; *parsed='\a'; parsed++;
break;
case 'b':
state=NORMAL; *parsed='\b'; parsed++;
break;
case 'f':
state=NORMAL; *parsed='\f'; parsed++;
break;
case 't':
state=NORMAL; *parsed='\t'; parsed++;
break;
case 'r':
state=NORMAL; *parsed='\r'; parsed++;
break;
case 'n':
state=NORMAL; *parsed='\n'; parsed++;
break;
case 'd':
state=DNUMERIC; sum=0; count=0;
break;
case 'o':
state=ONUMERIC; sum=0; count=0;
break;
case 'x':
state=XNUMERIC; sum=0; count=0;
break;
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
state=DNUMERIC; sum = *scan - '0'; count=1;
break;
case '\0':
ok = status = 0;
break;
default:
state=NORMAL; *parsed=*scan; parsed++;
}
break;
case CONTROL:
if(*scan=='\0'){
ok = status = 0;
}
else {
state=NORMAL; *parsed = *scan & 31; parsed++;
}
break;
case DNUMERIC:
switch(*scan){
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
sum=(10*sum) + (*scan - '0');
if(++count == 3){ /* There must be exactly 3 digits */
if(sum > UCHAR_MAX){
ok = status = 0;
}
else {
state = NORMAL; *parsed=sum; parsed++;
}
}
break;
default:
ok = status = 0;
}
break;
case ONUMERIC:
switch(*scan){
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
sum= (8*sum) + (*scan - '0');
if(++count == 3){ /* There must be exactly 3 digits */
if(sum > UCHAR_MAX){
ok = status = 0;
}
else {
state = NORMAL; *parsed=sum; parsed++;
}
}
break;
default:
ok = status = 0;
}
break;
case XNUMERIC:
switch(*scan){
case '0':
case '1':
case '2':
case '3':
case '4':
case '5':
case '6':
case '7':
case '8':
case '9':
sum=(16*sum) + (*scan - '0');
if(++count == 2){ /* There must be exactly 2 digits */
state = NORMAL; *parsed=sum; parsed++;
}
break;
case 'A':
case 'B':
case 'C':
case 'D':
case 'E':
case 'F':
sum=(16*sum) + (10 + *scan - 'A');
if(++count == 2){ /* There must be exactly 2 digits */
state = NORMAL; *parsed=sum; parsed++;
}
break;
case 'a':
case 'b':
case 'c':
case 'd':
case 'e':
case 'f':
sum=(16*sum) + (10 + *scan - 'a');
if(++count == 2){ /* There must be exactly 2 digits */
state = NORMAL; *parsed=sum; parsed++;
}
break;
default:
ok = status = 0;
}
break;
default: /* catch what should be an impossible state */
ok = status = 0;
}
}
return(status);
}
.

Relevant Pages

  • RfD: Escaped Strings version 4
    ... the S" string can only contain printable characters, ... the S" string cannot contain the '"' character, ... as an escape character for the entry of characters that cannot be ... \b BS (backspace, ASCII 8) ...
    (comp.lang.forth)
  • RfD: Escaped Strings version 4
    ... the S" string can only contain printable characters, ... the S" string cannot contain the '"' character, ... as an escape character for the entry of characters that cannot be ... \b BS (backspace, ASCII 8) ...
    (comp.lang.forth)
  • Re: problems with opening files due to files path
    ... GUI or it is a console app. ... of what an escape character and escape sequence is. ... character) inside a string specially, it makes the character after the ...
    (comp.lang.python)
  • Re: html_entity_decode + regex = profit?
    ... I've got an incoming string with a caret that's been escaped to ... The caret isn't a legal character where it's going (a text ... You can also use preg_quoteto escape metacharacters in a string. ...
    (comp.lang.php)
  • RE: DTS How to parse a varcharfield
    ... Nick Barclay created a UDF function that parses a varchar field. ... It returns the position of the character AFTER the nth(i.e. ... you know the positions you could update the varchar string by substituting ... returns int ...
    (microsoft.public.sqlserver.dts)
Loading