C code for reading a CSV file

The world definitely needs another implementation of this.

There are a lot of places where it might be better (more efficient) to keep an extra copy of a value rather looking it up in the struct. I was originally writing this for someone else though and thought it was easier to understand as it is. Maybe I am wrong. Suggestions for improvement are always welcome.

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

typedef struct {
  int columns;
  int rows;

  double* data;
} Matrix;

void freeMatrix(Matrix* aMatrix)
{
  if (aMatrix) {
    free(aMatrix->data);
    free(aMatrix);
  }
}

int countChar(const char* str, char c)
{
  int count = 0;
  while (*str) {
    if (*str == c) {
      ++count;
    }
    ++str;
  }
  return count;
}

#define MAX_LINE 2000

/**
 * input -- a stream of comma-separated numbers, rows terminated
 * by new lines. The number of rows is determined from
 * the first line read.
 * naValue -- the value that will be used to replace
 * fields left blank.
 *
 * Returns NULL if there is a problem reading from the stream.
 * Check errno for details.
 */
Matrix* readCsv(FILE* input, double naValue) {
  Matrix* result = 0;
  char buffer[MAX_LINE];
  char* line = fgets(buffer, MAX_LINE, input);

  if (!line) {
    return 0;
  }
  else {
    result = malloc(sizeof(Matrix));
    int total = 0;
    int capacity = 0;

    result->rows = 0;
    result->columns = countChar(line, ',') + 1;
    capacity = result->columns * 20;

    result->data = malloc(sizeof(double) * capacity);
   
    do {
      int i;

      if ((total + result->columns) > capacity) {
 capacity *= 2;
 result->data = realloc(result->data,
                                  sizeof(double) * capacity);
      }

      for (i = 0; i < result->columns; ++i) {
 if (!line || ',' == line[0]
             || '\n' == line[0] || '\r' == line[0]) {
   result->data[total] = naValue;
 }
 else {
   double value;
   
   if (sscanf(line, "%lf", &value) == 1) {
     result->data[total] = value;
   }
   else {
     freeMatrix(result);
     return 0;
   }
 }
 ++total;

 if (line) {
   line = index(line, ',');
   if (line) {
     ++line;
   }
 }
      }

      ++(result->rows);
      line = fgets(buffer, MAX_LINE, input);
    } while (line && ('\n' != line[0])
                     && ('\r' != line[0]));
  }
  
  return result;
}

void printMatrix(FILE* out, const Matrix* aMatrix)
{
  int i;
  for (i = 0; i < aMatrix->rows; ++i) {
    int j;
    const int offset = i * aMatrix->columns;
    for (j = 0; j < aMatrix->columns; ++j) {
      fprintf(out, "%f ", aMatrix->data[offset + j]);
    }
    fprintf(out, "\n");
  }
}

int main(int argc, char** argv)
{
  if (argc == 2) {
    FILE* in = fopen(argv[1], "r");
    Matrix* m = readCsv(in, -HUGE_VAL);
    fclose(in);

    if (m) {
      printMatrix(stdout, m);
      freeMatrix(m);
    }
    else {
      printf("problem reading %s\n", argv[1]);
    }
  }
  
  return 0;
}

What is with Blogger clipping wide posts? Very helpful! As is inserting BR tags into a textarea. Use some of that magic DHTML to let people fold the sidebar out of the way. (Well, I suppose it's possible for me to add this myself. As newbie I shouldn't be complaining. But I think I am talking to myself now anyway. Hello, you, me!)