standard c library for escaping a string

Question

Is there a standard C library function to escape C-strings?

For example, if I had the C string:

char example[] = \"first line\\nsecond line: \\\"inne         


        

Answer 1

#include     
/* int c_quote(const char* src, char* dest, int maxlen)
 *
 * Quotes the string given so that it will be parseable by a c compiler.
 * Return the number of chars copied to the resulting string (including any nulls)
 *
 * if dest is NULL, no copying is performed, but the number of chars required to 
 * copy will be returned.
 *
 * maxlen characters are copied. If maxlen is negative, 
 * strlen is used to find the length of the source string, and the whole string
 * including the NULL-terminator is copied.
 *
 * Note that this function will not null-terminate the string in dest.
 * If the string in src is not null-terminated, or maxlen is specified to not
 * include the whole src, remember to null-terminate dest afterwards.
 *
 */
int c_quote(const char* src, char* dest, int maxlen) {
    int count = 0;
    if(maxlen < 0) {
        maxlen = strlen(src)+1;      /* add 1 for NULL-terminator */
    }

    while(src  && maxlen > 0) {
        switch(*src) {

            /* these normal, printable chars just need a slash appended */
            case '\\':
            case '\"':
            case '\'':
                if(dest) {
                    *dest++ = '\\';
                    *dest++ = *src;
                }
                count += 2;
                break; 

            /* newlines/tabs and unprintable characters need a special code.
             * Use the macro CASE_CHAR defined below.
             * The first arg for the macro is the char to compare to,
             * the 2nd arg is the char to put in the result string, after the '\' */
#define CASE_CHAR(c, d) case c:\
    if(dest) {\
        *dest++ = '\\'; *dest++ = (d);\
        }\
count += 2;\
break;
            /* --------------  */
            CASE_CHAR('\n', 'n');
            CASE_CHAR('\t', 't');
            CASE_CHAR('\b', 'b');
            /*  ------------- */

#undef CASE_CHAR


            /* by default, just copy the char over */
            default:
                if(dest) {
                    *dest++ = *src;
                }
                count++;
        }

        ++src;
        --maxlen;
    }
    return count;
}