Implementation:Ollama Ollama Llama Base64

Knowledge Sources	Ollama
Domains	Encoding, Utilities
Last Updated	2025-02-15 00:00 GMT

Overview

Header-only Base64 encoding and decoding utility library used for binary data conversion within the llama.cpp common library.

Description

Provides a base64 class with static template methods for encoding binary data to Base64 strings and decoding Base64 strings back to binary. Supports multiple alphabet variants (standard and URL-safe) via an alphabet enum, and configurable decoding behavior (moderate vs. loose). Throws base64_error (derived from std::runtime_error) on invalid input during decoding. The library is public domain (Unlicense).

Usage

Use this when encoding or decoding binary data (such as image data for multimodal models) to and from Base64 format within the llama.cpp ecosystem.

Code Reference

Source Location

• Repository: Ollama
• File: llama/llama.cpp/common/base64.hpp
• Lines: 1-392

Signature

class base64_error : public std::runtime_error {
public:
    using std::runtime_error::runtime_error;
};

class base64 {
public:
    enum class alphabet { auto_, standard, url_filename_safe };
    enum class decoding_behavior { moderate, loose };

    template<typename Input_iterator, typename Output_iterator>
    static Output_iterator encode(Input_iterator in_begin, Input_iterator in_end,
                                  Output_iterator out, alphabet alphabet = alphabet::standard);

    static std::string encode(const std::string& str, alphabet alphabet = alphabet::standard);
    static std::string encode(const char* buffer, std::size_t size, alphabet alphabet = alphabet::standard);

    template<typename Input_iterator, typename Output_iterator>
    static Output_iterator decode(Input_iterator in_begin, Input_iterator in_end,
                                  Output_iterator out,
                                  alphabet alphabet = alphabet::auto_,
                                  decoding_behavior behavior = decoding_behavior::moderate);

    static std::string decode(const std::string& str,
                              alphabet alphabet = alphabet::auto_,
                              decoding_behavior behavior = decoding_behavior::moderate);

    static std::size_t required_encode_size(std::size_t size);
    static std::size_t required_decode_size(std::size_t size);
};

Import

#include "base64.hpp"

I/O Contract

Inputs

Name	Type	Required	Description
in_begin	Input_iterator	Yes	Iterator to the beginning of source data
in_end	Input_iterator	Yes	Iterator to the end of source data
alphabet	base64::alphabet	No	Which Base64 alphabet to use (default: standard for encode, auto for decode)
behavior	base64::decoding_behavior	No	How to handle padding/errors during decoding

Outputs

Name	Type	Description
result	std::string	Encoded or decoded string result
out	Output_iterator	Iterator past the last written element (template version)

Usage Examples

#include "base64.hpp"

// Encode a string to Base64
std::string encoded = base64::encode("Hello, World!");

// Decode a Base64 string
std::string decoded = base64::decode(encoded);

// URL-safe encoding
std::string url_safe = base64::encode("binary\xFFdata", base64::alphabet::url_filename_safe);

// Check required buffer size
std::size_t needed = base64::required_encode_size(input.size());

Related Pages

• Principle:Ollama_Ollama_Llama_Cpp_Common_Library