Ultra Fast Standard C Program to Add a Line Feed to CSV files to Transpose from All Columns to All Rows

main.c

#include <string>  
#include <stdlib.h>
#include <stdio.h>

void GetLen(FILE * fp, int &len);
void ReadAll(char * &buf, int len, FILE * fp);
void ChangeExtension(char *fname, char *newExt);
int StrReplace(char *target, const char *needle, const char *replacement, int len);

int main(int c, char**v)
{
	FILE *fp = NULL;
	int len = 0;
	char *buf = NULL;
	char fname[256];

	if (c < 2)
	{
		puts("I need a filename, jackass");
		return 0;
	}
	
	for (int i = 1; i  < c; i++)
	{ 
		fopen_s(&fp, v[i], "r");
		GetLen(fp, len);
		buf = (char*)calloc(1, len * 2);
		if (!buf)
		{
			puts("Wow! That file's too big for me. Out of memory!");
			return -1;
		}

		fread(buf, len, 1, fp);
		fclose(fp);
		int result = StrReplace(buf, ",", ",\n", len*2);
		if(result)
		{
			puts("Something went wrong. I have to quit!");
			return -1;
		}
		strcpy(fname, v[i]);
		ChangeExtension(fname, "csv");
		fopen_s(&fp, fname, "w");
		fwrite(buf, strlen(buf), 1, fp);
		fclose(fp);
	}

    return 0;
}

void ReadAll(char * &buf, int len, FILE * fp)
{
	buf = (char*)calloc(1, len * 2);
	fread(buf, len, 1, fp);
	fclose(fp);
}

void GetLen(FILE * fp, int &len)
{
	fseek(fp, 0L, SEEK_END);
	len = ftell(fp);
	rewind(fp);
}

void ChangeExtension(char *fname, char *newExt)
{
#define EVAL_MAX_LEN (300)

	size_t nLen;
	char szOut[EVAL_MAX_LEN] = { 0 };
	char szPath[EVAL_MAX_LEN];
	strcpy(szPath, fname);
	nLen = strlen(szPath);
	if ((nLen > 0) && (nLen < EVAL_MAX_LEN))
	{

		while (nLen)
		{
			if (szPath[nLen] == '.')
			{
				szPath[nLen] = '\0';
				break;
			}
			nLen--;
		}
		sprintf(szOut, "%s.%s", szPath, newExt);
		strcpy(fname, szOut);
	}
	return;
}

int StrReplace(char *target, const char *needle, const char *replacement, int len)
{
	char *buffer = (char*)calloc(1, len);
	if (!buffer)
	{
		puts("Wow! That file's too big for me. Out of memory!");
		return -1;
	}
	
	char *insert_point = &buffer[0];
	const char *tmp = target;
	size_t needle_len = strlen(needle);
	size_t repl_len = strlen(replacement);

	while (1) 
	{
		const char *p = strstr(tmp, needle);
		if (p == NULL) 
		{
			strcpy(insert_point, tmp);
			break;
		}
		memcpy(insert_point, tmp, p - tmp);
		insert_point += p - tmp;
		memcpy(insert_point, replacement, repl_len);
		insert_point += repl_len;
		tmp = p + needle_len;
	}
	strcpy(target, buffer);
	return 0;
}