Implementation:Ollama Ollama Readline Buffer

Knowledge Sources	Ollama
Domains	CLI, Terminal UI
Last Updated	2025-02-15 00:00 GMT

Overview

Implements the text editing buffer for the readline interactive input system, providing cursor movement, text insertion, deletion, and display management.

Description

The Buffer struct wraps an array list of runes with cursor position tracking (both logical position and display position to handle wide characters). Provides methods for cursor movement (left/right by character or word, start/end of line), text manipulation (add, delete, backspace, kill line, transpose, yank), and display rendering with line wrapping. Handles wide Unicode characters via runewidth for correct cursor positioning. Uses ANSI escape sequences to update the terminal display efficiently.

Usage

Core component of the interactive CLI prompt, managing the editable text area where users type prompts for the ollama run command.

Code Reference

Source Location

• Repository: Ollama
• File: readline/buffer.go
• Lines: 1-527

Signature

type Buffer struct {
    DisplayPos   int
    Pos          int
    Buf          *arraylist.List[rune]
    LineHasSpace *arraylist.List[bool]
    Prompt       *Prompt
    LineWidth    int
    Width        int
    Height       int
}

func NewBuffer(prompt *Prompt) (*Buffer, error)
func (b *Buffer) MoveLeft()
func (b *Buffer) MoveRight()
func (b *Buffer) MoveLeftWord()
func (b *Buffer) MoveRightWord()
func (b *Buffer) MoveToStart()
func (b *Buffer) MoveToEnd()
func (b *Buffer) Add(r rune)
func (b *Buffer) Delete()
func (b *Buffer) String() string

Import

import "github.com/ollama/ollama/readline"

I/O Contract

Inputs

Name	Type	Required	Description
prompt	*Prompt	Yes	Prompt configuration for display width calculation

Outputs

Name	Type	Description
*Buffer	*Buffer	Initialized buffer with terminal dimensions
error	error	Non-nil if terminal size cannot be determined

Usage Examples

prompt := &readline.Prompt{Prompt: ">>> "}
buf, err := readline.NewBuffer(prompt)
if err != nil {
    log.Fatal(err)
}

buf.Add('H')
buf.Add('i')
fmt.Println(buf.String()) // "Hi"
buf.MoveToStart()
buf.Delete()
fmt.Println(buf.String()) // "i"

Related Pages

• Principle:Ollama_Ollama_CLIArchitecture