safestrap-functions.c

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <limits.h>
#include <paths.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>

#include <ctype.h>
#include "cutils/misc.h"
#include "cutils/properties.h"
#include <dirent.h>
#include <getopt.h>
#include <linux/input.h>
#include <signal.h>
#include <sys/limits.h>
#include <termios.h>
#include <time.h>
#include <sys/vfs.h>

#include "safestrap-functions.h"


// Search/Replace function pulled from StackOverflow user: Brandin

// str_replace(haystack, haystacksize, oldneedle, newneedle) --
//  Search haystack and replace all occurences of oldneedle with newneedle.
//  Resulting haystack contains no more than haystacksize characters (including the '\0').
//  If haystacksize is too small to make the replacements, do not modify haystack at all.
//
// RETURN VALUES
// str_replace() returns haystack on success and NULL on failure. 
// Failure means there was not enough room to replace all occurences of oldneedle.
// Success is returned otherwise, even if no replacement is made.
char *str_replace(char *haystack, size_t haystacksize, const char *oldneedle, const char *newneedle);

// ------------------------------------------------------------------
// Implementation of function
// ------------------------------------------------------------------
#define SUCCESS (char *)haystack
#define FAILURE (void *)NULL

char *str_replace(char *haystack, size_t haystacksize, const char *oldneedle, const char *newneedle) {   
    size_t oldneedle_len = strlen(oldneedle);
    size_t newneedle_len = strlen(newneedle);
    char *oldneedle_ptr;    // locates occurences of oldneedle
    char *read_ptr;         // where to read in the haystack
    char *write_ptr;        // where to write in the haystack
    const char *oldneedle_last =  // the last character in oldneedle
        oldneedle +             
        oldneedle_len - 1;      

    // Case 0: oldneedle is empty
    if (oldneedle_len == 0)
        return SUCCESS;     // nothing to do; define as success

    // Case 1: newneedle is not longer than oldneedle
    if (newneedle_len <= oldneedle_len) {       
        // Pass 1: Perform copy/replace using read_ptr and write_ptr
        for (oldneedle_ptr = (char *)oldneedle,
            read_ptr = haystack, write_ptr = haystack; 
            *read_ptr != '\0';
            read_ptr++, write_ptr++)
        {
            *write_ptr = *read_ptr;         
            bool found = locate_forward(&oldneedle_ptr, read_ptr,
                        oldneedle, oldneedle_last);
            if (found)  {   
                // then perform update
                write_ptr -= oldneedle_len;
                memcpy(write_ptr+1, newneedle, newneedle_len);
                write_ptr += newneedle_len;
            }               
        } 
        *write_ptr = '\0';
        return SUCCESS;
    }

    // Case 2: newneedle is longer than oldneedle
    else {
        size_t diff_len =       // the amount of extra space needed 
            newneedle_len -     // to replace oldneedle with newneedle
            oldneedle_len;      // in the expanded haystack

        // Pass 1: Perform forward scan, updating write_ptr along the way
        for (oldneedle_ptr = (char *)oldneedle,
            read_ptr = haystack, write_ptr = haystack;
            *read_ptr != '\0';
            read_ptr++, write_ptr++)
        {
            bool found = locate_forward(&oldneedle_ptr, read_ptr, 
                        oldneedle, oldneedle_last);
            if (found) {    
                // then advance write_ptr
                write_ptr += diff_len;
            }
            if (write_ptr >= haystack+haystacksize)
                return FAILURE; // no more room in haystack
        }

        // Pass 2: Walk backwards through haystack, performing copy/replace
        for (oldneedle_ptr = (char *)oldneedle_last;
            write_ptr >= haystack;
            write_ptr--, read_ptr--)
        {
            *write_ptr = *read_ptr;
            bool found = locate_backward(&oldneedle_ptr, read_ptr, 
                        oldneedle, oldneedle_last);
            if (found) {    
                // then perform replacement
                write_ptr -= diff_len;
                memcpy(write_ptr, newneedle, newneedle_len);
            }   
        }
        return SUCCESS;
    }
}

// locate_forward: compare needle_ptr and read_ptr to see if a match occured
// needle_ptr is updated as appropriate for the next call
// return true if match occured, false otherwise
bool locate_forward(char **needle_ptr, char *read_ptr, const char *needle, const char *needle_last) {
    if (**needle_ptr == *read_ptr) {
        (*needle_ptr)++;
        if (*needle_ptr > needle_last) {
            *needle_ptr = (char *)needle;
            return true;
        }
    }
    else 
        *needle_ptr = (char *)needle;
    return false;
}

// locate_backward: compare needle_ptr and read_ptr to see if a match occured
// needle_ptr is updated as appropriate for the next call
// return true if match occured, false otherwise
bool locate_backward(char **needle_ptr, char *read_ptr, const char *needle, const char *needle_last) {
    if (**needle_ptr == *read_ptr) {
        (*needle_ptr)--;
        if (*needle_ptr < needle) {
            *needle_ptr = (char *)needle_last;
            return true;
        }
    }
    else 
        *needle_ptr = (char *)needle_last;
    return false;
}


void ProcessSafestrapTranslations(char *buf, int bufLen) {
    fprintf(stderr, "Loaded ProcessSafestrapTranslations\n");
/*
** Functions:
** Load from /ss/safestrap/translate
** Format "source=new_value" (repeat)
** Process buf for any source values and replace w/ new_value
*/

    FILE *fp;
    char line[2048];
    char* find_str;
    char* replace_str;

    fp = fopen("/ss/safestrap/translate", "rt");
    if (fp != NULL) {
        while (fgets(line, sizeof(line), fp) != NULL) {
            find_str = strtok(line, "=");
            replace_str = strtok(NULL, "\n");
            if ((find_str != NULL) && (replace_str != NULL)) {
	        fprintf(stderr, "ProcessTranslation [%s = %s]\n", find_str, replace_str);
                if (str_replace(buf, bufLen, find_str, replace_str) == NULL) {
                    fprintf(stderr, "ProcessTranslation [FAIL]\n");
                }
                else {
                    fprintf(stderr, "ProcessTranslation [SUCCESS]\n");
                }
            }
        }
    }
    fclose(fp);
    fprintf(stderr, "ProcessTranslation RESULT:\n%s", buf);
}