Nettle is a cryptographic library that is designed to fit easily in more or less any context: in crypto toolkits for object-oriented languages (c++, python, pike, ...), in applications like lsh or gnupg, or even in kernel space.

it tries to solve a problem of providing a common set of cryptographic algorithms for higher-level applications by implementing a context-independent set of cryptographic algorithms. in that light, nettle doesn't do any memory allocation or i/o, it simply provides the cryptographic algorithms for the application to use in any environment and in any way it needs.