Source code for a string builder class

This one is a string class. I should really call it string builder, but that name is just too long. At some point I am going to explain how each part of the code works, but I really don't feel like writing right now. I am including the full source code here just so I can refer to it later. None of these code files are really that good, they are just some quick stuff that I made without much thought.

#ifndef TYPESTRING_H
#define TYPESTRING_H

#include <stdlib.h>

#define STRING_MIN     1
#define STRING_MAX     4096

typedef struct
  {
  unsigned long Capacity;
  unsigned long Length;
  char*         Data;
  } typeString;

long stringCreate(typeString* str,unsigned long capacity);
long stringGetCString(typeString* str,char* buffer,unsigned long buffersize);
long stringSetLength(typeString* str,unsigned long length);
long stringSetCapacity(typeString* str,unsigned long capacity);
long stringReverse(typeString* str);
long stringReverseRange(typeString* str,unsigned long start,unsigned long length);
long stringAppendCharacter(typeString* str,char value);
long stringAppendCString(typeString* str,const char* value);
long stringAppendString(typeString* str,typeString* value);
long stringAppendInt64(typeString* str,unsigned long long value,long base);
long stringDestroy(typeString* str);

long stringCreate(typeString* str,unsigned long capacity)
  {
  char*  buffer;

  if (capacity < STRING_MIN)
    capacity = STRING_MIN;

  buffer = (char*)malloc(capacity);

  if (buffer == 0)
    return 0;

  str->Capacity = capacity;
  str->Length   = 0;
  str->Data     = buffer;

  return 1;
  }

long stringGetCString(typeString* str,char* buffer,unsigned long buffersize)
  {
  unsigned long I;

  I = 0;
  while ((I < str->Length) && (I < buffersize-1))
    {
    buffer[I] = str->Data[I];
    buffer[I+1] = 0;
    I++;
    }

  return 1;
  }

long stringSetLength(typeString* str,unsigned long length)
  {
  if (length > str->Capacity)
    return 0;

  str->Length = length;

  return 1;
  }

long stringSetCapacity(typeString* str,unsigned long capacity)
  {
  unsigned long I;
  char*         buffer;

  if (capacity == str->Capacity)
    return 1;

  if (capacity < STRING_MIN)
    capacity = STRING_MIN;

  buffer = (char*)malloc(capacity);

  if (buffer == 0)
    return 0;

  I = 0;
  while (I < capacity)
    {
    if (I < str->Length)
      buffer[I] = str->Data[I];
    else
      buffer[I] = 0;
    }

  free(str->Data);

  if (str->Length > capacity)
    str->Length = capacity;

  str->Capacity = capacity;
  str->Data     = buffer;

  return 1;
  }

long stringReverse(typeString* str)
  {
  unsigned long I,J;
  char          temp;
  I = 0;
  J = str->Length - 1;

  while (I < J)
    {
    temp = str->Data[I];
    str->Data[I] = str->Data[J];
    str->Data[J] = temp;

    I++;
    J--;
    }

  return 1;
  }

long stringReverseRange(typeString* str,unsigned long start,unsigned long length)
  {
  unsigned long I,J;
  char          temp;

  I = start;
  J = start + length - 1;

  if ((I < 0) || (J > str->Length))
    return 0;

  while (I < J)
    {
    temp = str->Data[I];
    str->Data[I] = str->Data[J];
    str->Data[J] = temp;

    I++;
    J--;
    }

  return 1;
  }

long stringAppendCharacter(typeString* str,char value)
  {
  if (str->Length >= str->Capacity)
    return 0;

  str->Data[str->Length] = value;

  str->Length++;

  return 1;
  }

long stringAppendCString(typeString* str,const char* value)
  {
  unsigned long I,J;

  I = str->Length;
  J = 0;
  while ((value[J] != 0) &&
         (J < STRING_MAX) &&
         (I < str->Capacity))
    {
    str->Data[I] = value[J];

    I++;
    J++;
    }

  str->Length = I;

  return 1;
  }

long stringAppendString(typeString* str,typeString* value)
  {
  unsigned long I,J;

  I = str->Length;
  J = 0;
  while ((I < str->Capacity) && (J < value->Length))
    {
    str->Data[I] = value->Data[J];

    I++;
    J++;
    }

  str->Length = I;

  return 1;
  }

long stringAppendInt64(typeString* str,unsigned long long value,long base)
  {
  static const char digits[] = "0123456789ABCDEFGHIGKLMNOPQRSTUVWXYZabcdefghigklmnopqrstuvwxyz-_";
  unsigned long     start,length;

  if ((base < 2) || (base > 64))
    return 0;

  start = str->Length;

  do
    {
    stringAppendCharacter(str,digits[value % base]);

    value = value/base;
    }
  while (value != 0);

  length = str->Length - start;

  stringReverseRange(str,start,length);

  return 1;
  }

long stringDestroy(typeString* str)
  {
  free(str->Data);

  return 1;
  }

#endif // TYPESTRING_H