escape strings_and_characters, C (clang)

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//clang 3.8.0
#include <stdio.h>
#include <stdlib.h>
#include <math.h>
#include <inttypes.h>
#include <string.h>
#include <time.h>
#include <sys/timeb.h>

char *
str_escape(char str[])
{
    char chr[3];
    char *buffer = malloc(sizeof(char));
    unsigned int len = 1, blk_size;

while (*str != '\0') {
        blk_size = 2;
        switch (*str) {
            case '\n':
                strcpy(chr, "\\n");
                break;
            case '\t':
                strcpy(chr, "\\t");
                break;
            case '\v':
                strcpy(chr, "\\v");
                break;
            case '\f':
                strcpy(chr, "\\f");
                break;
            case '\a':
                strcpy(chr, "\\a");
                break;
            case '\b':
                strcpy(chr, "\\b");
                break;
            case '\r':
                strcpy(chr, "\\r");
                break;
            default:
                sprintf(chr, "%c", *str);
                blk_size = 1;
                break;
        }
        len += blk_size;
        buffer = realloc(buffer, len * sizeof(char));
        strcat(buffer, chr);
        ++str;
    }
    return buffer;
}

int main(void)
{
    char x = '\t';        //character
    char x2[256];         //temp character
    sprintf(x2, "%c", x); //write to temp character
    puts(str_escape(x2)); //escape this...
    
    
    puts(str_escape("\tAnbms\n"));
    puts(str_escape("\tA\v\fZ\a"));
    puts(str_escape("txt \t\n\r\f\a\v 1 \t\n\r\f\a\v tt"));
    puts(str_escape("dhsjdsdjhs hjd hjds "));
    puts(str_escape(""));
    puts(str_escape("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ!\"#$%&\'()*+,-./:;<=>?@[\\]^_`{|}~ \t\n\r\f\a\v"));
    puts(str_escape("\x0b\x0c\t\n\r\f\a\v"));
    puts(str_escape("\x01\x02\x03\x04\x05\x06\x07\x08\t\n\x0b\x0c\r\x0e\x0f\x10\x11\x12\x13\x14"));
}

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Compilation time: 0.24 sec, absolute running time: 0.24 sec, cpu time: 0.17 sec, memory peak: 3 Mb, absolute service time: 0,49 sec