String to Integer Implementation

The logic for doing String to Integer implementation is rather simple. Mostly handling the corner cases is what one needs to be care full about. The code should be followed by unit tests to check the validity will help to establish credibility for the code.

	/*
	* strtointeger.cpp
	*
	* Created on: Feb 20, 2015
	* Author: prasadnair
	*/
	#include <stdio.h>
	#include <stdlib.h>
	int strToInteger(char *temp)
	{
	int i=0,val=0,sign=1;
	printf("string value transferred : %s \n", temp);
	if(temp == NULL)
	{
	printf("Error: String cannot be null");
	return NULL;
	}
	while(temp[i] == ' ')
	{
	i++;
	}
	if(temp[i] == '-' | temp[i]=='+')
	{
	if(temp[i]=='-') sign = -1;
	if(temp[i]=='+') sign = 1;
	i++;
	}
	while(temp[i] != '\0')
	{
	if(temp[i] < '0' | temp[i] > '9')
	{
	printf("Error: Non integer value in the string");
	return NULL;
	}
	val = val*10 + (temp[i++] - '0');
	}
	return val*sign;
	}
	int main(int argc, char* argv[])
	{
	printf("value : %d \n", strToInteger("123"));
	printf("value : %d \n", strToInteger(" -0123"));
	printf("value : %d \n", strToInteger(" +0123"));
	printf("value : %d \n", strToInteger(" 456678"));
	printf("value : %d \n", strToInteger("1a23"));
	printf("value : %d \n", strToInteger(NULL));
	return 0;
	}

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