simple_mmap - Memory-Mapped Files for Eiffel

Overview

simple_mmap provides SCOOP-compatible memory-mapped file operations for Eiffel applications. It wraps the Win32 file mapping API through a clean C interface, enabling efficient file I/O and shared memory without threading complications.

The library supports file-backed mappings, anonymous mappings, and shared memory segments for inter-process communication, with type-safe read/write operations for bytes, integers, strings, and raw byte arrays.

Part of the simple_* ecosystem of focused, single-purpose Eiffel libraries.

Quick Start

Installation

<library name="simple_mmap" location="$SIMPLE_EIFFEL/simple_mmap/simple_mmap.ecf"/>

File Mapping

local
    mmap: SIMPLE_MMAP
do
    -- Map an existing file
    create mmap.make_from_file ("data.bin", mmap.Access_read_write)

    if mmap.is_valid then
        -- Read/write at specific offsets
        mmap.write_string (0, "Hello, World!")
        print (mmap.read_string (0))
        mmap.close
    end
end

Anonymous Mapping

local
    mmap: SIMPLE_MMAP
do
    -- Create memory-only mapping (no file)
    create mmap.make_anonymous (4096)  -- 4KB

    if mmap.is_valid then
        mmap.write_integer (0, 42)
        print (mmap.read_integer (0))  -- 42
        mmap.close
    end
end

Shared Memory (IPC)

local
    mmap: SIMPLE_MMAP
do
    -- Create named shared memory accessible from other processes
    create mmap.make_shared ("MySharedMem", 1024)

    if mmap.is_valid then
        mmap.write_string (0, "Shared data")
        mmap.close
    end
end

Features

File Mapping

Map entire files or file regions into memory

Anonymous Mapping

Create memory-backed mappings without files

Shared Memory

Named mappings for inter-process communication

Type-Safe I/O

Read/write bytes, integers, strings, and byte arrays

Access Modes

Mode	Description
`Access_read`	Read-only access
`Access_read_write`	Read and write access

API Reference

Creation

Feature	Description
`make_from_file (path, access)`	Create mapping from file
`make_anonymous (size)`	Create memory-only mapping
`make_shared (name, size)`	Create named shared memory

Reading Data

Feature	Description
`read_byte (offset)`	Read single byte at offset
`read_integer (offset)`	Read 32-bit integer at offset
`read_string (offset)`	Read null-terminated string
`read_bytes (offset, count)`	Read array of bytes

Writing Data

Feature	Description
`write_byte (offset, value)`	Write single byte
`write_integer (offset, value)`	Write 32-bit integer
`write_string (offset, value)`	Write null-terminated string
`write_bytes (offset, bytes)`	Write array of bytes

Status

Feature	Description
`is_valid`	Is the mapping valid?
`size`	Size of mapped region in bytes
`close`	Unmap and release resources