Linking the functions in pi-md5.h

[Robert Cahn]

I need to write a little program that computes an md5 checksum.  In
/usr/include there is a nice header file that includes the functions

void MD5Init(struct MD5Context *context);
void MD5Update(struct MD5Context *context, UINT8 const *buf, unsigned len);
void MD5Final(unsigned char digest[16], struct MD5Context *context);
void MD5Transform(UINT32 buf[4], UINT32 const in[16]);

void byteSwap(UINT32 * buf, unsigned words);

When I do 

#include "
pi-md5.h" the code compiles but the linker can't find the function.  Does anybody know what library contains the code?

/Bob Cahn