#include <stdint.h>
#include "base64_encode.h"

int base64encode(const void* data_buf, size_t dataLength, char* result,
                 size_t resultSize) {
  const char base64chars[] =
      "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
  const uint8_t *data = (const uint8_t *) data_buf;
  size_t resultIndex = 0;
  size_t x;
  uint32_t n = 0;
  int padCount = dataLength % 3;
  uint8_t n0, n1, n2, n3;

  /* increment over the length of the string, three characters at a time */
  for (x = 0; x < dataLength; x += 3) {
    /* these three 8-bit (ASCII) characters become one 24-bit number */
    n = ((uint32_t) data[x]) << 16;  //parenthesis needed, compiler depending on flags can do the shifting before conversion to uint32_t, resulting to 0

    if ((x + 1) < dataLength)
      n += ((uint32_t) data[x + 1]) << 8;  //parenthesis needed, compiler depending on flags can do the shifting before conversion to uint32_t, resulting to 0

    if ((x + 2) < dataLength)
      n += data[x + 2];

    /* this 24-bit number gets separated into four 6-bit numbers */
    n0 = (uint8_t) (n >> 18) & 63;
    n1 = (uint8_t) (n >> 12) & 63;
    n2 = (uint8_t) (n >> 6) & 63;
    n3 = (uint8_t) n & 63;

    /*
     * if we have one byte available, then its encoding is spread
     * out over two characters
     */
    if (resultIndex >= resultSize)
      return 1; /* indicate failure: buffer too small */
    result[resultIndex++] = base64chars[n0];
    if (resultIndex >= resultSize)
      return 1; /* indicate failure: buffer too small */
    result[resultIndex++] = base64chars[n1];

    /*
     * if we have only two bytes available, then their encoding is
     * spread out over three chars
     */
    if ((x + 1) < dataLength) {
      if (resultIndex >= resultSize)
        return 1; /* indicate failure: buffer too small */
      result[resultIndex++] = base64chars[n2];
    }

    /*
     * if we have all three bytes available, then their encoding is spread
     * out over four characters
     */
    if ((x + 2) < dataLength) {
      if (resultIndex >= resultSize)
        return 1; /* indicate failure: buffer too small */
      result[resultIndex++] = base64chars[n3];
    }
  }

  /*
   * create and add padding that is required if we did not have a multiple of 3
   * number of characters available
   */
  if (padCount > 0) {
    for (; padCount < 3; padCount++) {
      if (resultIndex >= resultSize)
        return 1; /* indicate failure: buffer too small */
      result[resultIndex++] = '=';
    }
  }
  if (resultIndex >= resultSize)
    return 1; /* indicate failure: buffer too small */
  result[resultIndex] = 0;
  return 0; /* indicate success */
}